AN INVESTEGATEON 0F TEE RESPONDENT
CGNBIE‘EONABILITY OF THE
MEWLE EAR REFLEX

 

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MICHEGAN STATE UNIVEESE'EY

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This is to certify that the

thesis entitled

AN INVESTIGATION OF THE RESPONIEN T CONDITIONABEITY

OF THE MIDDIE EAR REFLEX
presented by

Susan H. Brainerd

has been accepted towards fulfillment
of the requirements for

Mdegree mm and
Speech Sciences

    

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ABSTRACT
AN INVESTIGATION OF Tm RESPONIENT CONDITIONABIIJTY
OF m MIDDLE EAR EFLEX

By
Susan H. Brainerd

Three experiments are reported which investigate the behavior of
the middle ear reflex. For the most part, the investigations are
concerned with determining the susceptibility of the middle ear reflex
to classical conditioning. Specifically, attempts to condition the
middle ear reflex both to a temporal interval and to a visual stimulus
are reported.

The focus of the first experiment was on temporal conditioning.

* Five normal hearing college age females were employed as subjects.

Each subject received a total of 100 conditioning trials and four test
trials. The unconditioned stimulus was a 1000 Hz tone presented 10 dB
above the subject's middle ear reflex threshold level for a duration of
1&5 seconds. .411 reflex responses were measured with an electre-acoustic
impedance bridge and the correlated voltage changes were pemanently
recorded. The data were independently scored by two judges in terms of
the number of conditioned reflexes which occurred during the test trials.
The results indicated that no conditioned responses were elicited from
any subject during any test trial. Therefore, temporal conditioning

of the middle ear reflex was not demonstrated.

The purpose of the second experiment was to investigate the
ability of a visual stimulus to elicit the middle ear reflex. The
chosen stimulus was a light with an effective illumination of 0.2 fc.

Susan H. Brainerd

Again, five normal hearing college age females served as subjects. Each
subject received a total of 50 experimental trials consisting of 25
presentations of the light and 25 empty intervals, randomly ordered.

The duration of each experimental trial was one second and the time
interval between successive trials was #5 seconds. All reflex responses
were measured with an electro-acoustic impedance bridge and the
correlated voltage changes were permanently recorded. Two judges
independently scored the data in terms of the number of reflexes which
were elicited during any of the experimental trials. The results
indicated that no reflexes were elicited from any of the subjects
during any of the 50 trials. ~ Therefore, since there was no difference
in the number of spontaneous reflexes elicited during the empty
intervals and the number of reflexes elicited by the light, it was
concluded that the experimental light did not normally elicit the

middle ear reflex.

In the third experiment an attempt was made to condition the
middle ear reflex to a neutral stimulus. Twenty normal hearing college
age females served as subjects. As in the first experiment, each subject
received a total of 100 conditioning trials and four test trials. The
unconditioned stimulus was a 1000 Hz tone presented 10 dB above the
subject's middle ear reflex threshold level for a duration of one second.
The conditioned stimulus was a light with an effective illumination of
0.2 fc. During each conditioning trial the onset of the conditioned
stimulus preceded the onset of the unconditioned stimulus. Moreover,
four interstimulus intervals were employed. Specifically, these were
0, 0.5, 1.5. and 2.5 seconds. Each of these interstimulus intervals
was randomly assigned to five different subjects. The termination of

 

 

Susan H. Brainerd

the stimuli presentations was simultaneous. The time intervals between

successive presentations of the unconditioned stimulus were varied

randomly at 30, 1+5, and 60 seconds. All reflex responses were measured

with an electro-acoustic impedance bridge and the correlated voltage

changes were permanently recorded. Two judges independently scored

the data in terms of the number of conditioned responses that occurred

during the test trials. The results indicated that no reflexes were

elicited from any subject during any of the test trials. Therefore,

neither simultaneous nor delayed conditioning were demonstrated.

Moreover, it was not demonstrated that the conditionability of the p < ‘
middle ear reflex varies with the interstimulus interval that is

employed.

  

Approved
Date \€//f/// 7,1

AN INVESTIGATION OF THE ESPONIENT CONDITIONABIIII’Y
OF THE MIDDLE EAR REFIEX

By

Susan Ell Brainerd

ATHESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements

for the degree of

IDCTOR OF PHILO$PHI

Department of Audiology and Speech Sciences
1971

PLEASE NOTE:

Some Pages have indistinct
print. Filmed as received.

UNIVERSITY MICROFILMS

0 7&3d2

ACKNOWIEDQEENTS

Preparation of the present thesis and the research reported herein
were supported by Rehabilitation Services of America Traineeship 2h5-T-71
which was granted to the author. The author also wishes to acknowledge
the many helpful comments and criticisms of the thesis committee: Daniel
S. Beasley, Chairman; S. Howard Bartley: William F. Rintelmann; and Oscar
Tosi. Special thanks are also due to Donald Riggs for his technical

assistance .

ii

TABLE OF CONTENTS

INTIDDUCTION

Physiological Basis of the Middle Ear Reflex
Acoustic Responses of the Middle Ear Muscles

Nonacoustic Responses of the Middle Ear Muscles

Conditioning the Middle Ear Reflex

Successful Attempts . .

Human Studies e e e e
Infrahuman Studies . .
Unsuccessful Attempts . . .
Human Studies a e e e
Infrahuman Studies . .
Sumery..........

EXPERIMENT It mm CONDITIONING
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Subjects

Design and Conditioning Procedure
InStrumentation.........

Stimulus Presentation
Heeponse Measurement .
Recording
Procedures

Results and Discussion . . . . .
EXPERDIENT II:

C O O O O C O

LIGHT AS AN UNOONDITIOIED STIMULUS

Metbd O O O O O O O O O O O O O O O O O O O 0

Subjects

Design and Experimental Procedure

Instrumentation o e e e e e
Stimulus Presentation
Response Measurement .
kcording

Procedures

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Results andDiscussion . . . . .

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Instmntation e e a e e
Stimulus Presentation
Response Measurement
Recording

Procedures

Results and Discussion . . . .
ENERAL DISCUSSION 0 e o e a e o 0
Conclusions and Implications .
LIST OF REFEMNCES

APPENDDC I: SUBJECT VARIABLES
APPENDIX II:
APPENDIX III: EQUIPMENT
APPENDIX IV:
APPENDIX V:

APPENDIX VI:
APPENDIX VII: mFOfMATION SHEET
APPENDIX VIII: INSTRUCTIONS
APPENDIX IX:
APPENDIX X:

APPENDIX XI:

Design and Conditioning Procedure

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NOISE IEVELS IN OCTAVE BANDS

STIMULUS AND IESPONSE RECORDINGS

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DESCRIPTION OF THE MADSEN BKEDCE .

SCHEMATIC WIRING DIAGRAMS OF TDIEIB

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SIMULTANEOUS AND IELAIED CONDITIONING

INTERTRIAL IN’JERVALS EMPLOYED IN EXPERIMENT III

STIMULUS SEQUENCE PRESENTATIONS IN EXPERIMENT II

INTERSTIMULUS INTERVAL-‘3 EMPLOYED IN EXPERIMENT III

 

 

 

 

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LIST OF TABLES

Table 1: Stimulus Presentations in Temporal Conditioning . . . . . 17

Table 2: Stimulus Presentations in Simultaneous and Delayed
Conditioning.......................36

Figure 1:
Figure 2:
Figure 3:
Figure 1}:
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Figure 6:
Figure 7:
Figure 8:
Figure 9:
Figure 10:

Figure 11:

Figure 12:

LIST OF FIGUES

Block Diagram of Experimental Situation for Temporal
Conditioning......................

Schematic Illustration of Instrumentation for Temporal
Conditioning......................

Spontaneous Reflexes Elicited Mg Temporal
Conditioning......................

Conditioned Reflexes Elicited During Temporal
Conditioning eeeeeeeeeeeeeeeeoeeeee

Block Diagram of Emerimental Situation for Determining
theueutrdityOfGVisudStmulus o e o o e e e e e e 0

Schematic Illustration of Instrumentation for
Determining the Neutrality of a Visual Stimulus . . . . .

Spontaneous Reflexes Elicited During the Determination
of the Neutrality of aVisual Stimulus . . . . . . . . .

Unconditioned Reflexes Elicited During the Determination
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Schematic Illustration of Instrumentation for
Simultaneous and Delayed Conditioning . . . . . . . . .

Conditioned Reflexes Elicited From All Subjects
hiring Simultaneous and Delayed Conditioning . . . . . .

Comparison of Conditioned Reflexes Elicited in each
Experimental Group wring Simultaneous and Delayed
Conditioning eeeeeeeeeeeeeeeeeeeeee

Schematic Diagram of Principal Components of the Madsen

mectro-Acoustic Impedance Bridge . . . . . . . . . . . .

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INTRODUCTION

Investigations of the middle ear reflex began in the late 1880's
and, since then, numerous clinical and experimental studies concerned
with the reflex have been carried out (Jepson, 1963). While some of
these investigations have been concerned with the properties of the
reflex itself, the majority of studies have employed the reflex as a
method for investigating the function of the auditory system (Dallas,
196»). Moreover, these applied investigations have focused on a wide 4?
variety of acoustic variables.

A number of investigators have demonstrated the importance of the
middle ear reflex as a clinical tool in the differential diagnosis of
auditory impairments. For example, Metz (1952) reported that the
intensity level of the reflex threshold could supplement the results of
loudness balancing for the determination of cochlear impairments.
Similarly, ICIockhoff (1961), Feldman (1961;) and Djupesland (1969) all
have reported success in using the reflex as an aid in the topical.
diagnosis of facial nerve lesions. Finally, Zwislocki and Feldman
(1970) demonstrated that the reflex could be used to identify the
location of disarticulation in cases of ossicular separation.

Other investigators have identified relationships between the
middle ear reflex and a variety of auditory phenomena. For example,
Ward (1961) and Gjaevenes and Vigran (1967) suggest that middle ear
reflex activity is an important variable in remote masking. Likewise,
Melnick (1965) and Ross (1968) contend that reflex activity is an
important variable in loudness judgments. In addition, several

1

investigators have demonstrated that middle ear reflex activity is
related to variability in speech discrimination scores (Liden, Nordlund
and Hawkins, 1963; Clubb. 1965; and Jauhianen, Hakkinen, Lindroos and
Raid, 1967). Finally, Sedlacek (1965) and Lawrence (1965) argue that
middle ear reflex activity has important implications for theories on
binaural hearing.

Even a cursory review of the studies, such as those noted above.
reveals that the middle ear reflex is becoming a prominent topic in
studies of the auditory system. However, although the reflex is being
used widely. a vast number of questions remain concerning its behavior.
In fact, Dallos (196+) commented that more questions concerning the
behavior of the middle ear reflex were unresolved than answered.

The most basic question concerning the behavior of the middle ear
reflex which has not yet been resolved is the question of its suscepti-
bility to conditioning procedures. The evaluation of such susceptibility
clearly is needed if we are to understand fully middle ear reflex
activity. In addition, such an evaluation would provide a means for
comparing the middle ear reflex with reflexes associated with other
sensory modalities. Finally, a well controlled investigation of the
conditionability of the middle ear reflex would provide a means of
assessing the validity of the empirical results of previous studies in
which the investigators did not control for possible conditioned reflexes
to incidental stimuli. In response to this need for determining the
conditionability of the middle ear reflex, the experiments presented
below were designed to investigate the susceptibility of the middle
ear reflex to a variety of classical conditioning paradigm.

Physiological Basis of the Middle Ear Reflex

Kobrak (1959). Polyak (1946), Never and Lawrence (199+). and
Zemlin (1968) have provided pertinent discussions on the anatomy and
physiology of the middle ear. Moreover, a review of the discussions
presented by each of the above authors reveals a great consistency in
their descriptions of the middle ear and its associated structures.
Therefore, the discussion presented below has been compiled from the
general consensus of the above authors.

The middle ear is a minute air-filled space in the part of the
temporal bone that foms the base of the skull. The cavity is located 3%
about one-third of the distance between the surface of the skull at the
entrance of the external meatus and the mid-sagittal plane. The diameter
of the middle ear varies from about 2 mm to 8 or 9 mm. Its vertical
direction measures up to 13 or 14 mm. The structures enclosed in the
middle ear include: (a) the ossicles and their ligaments, (b) the muscles
and their tendons, (c) the chorda tympani nerve, and (d) the tympanic
plexus of nerves.

Two muscles are housed in the middle ear: the stapedius and the
tensor tympani. These muscles are the smallest striated muscles in the
body. Moreover, since they are of the pennate type they have a great
capacity for exerting tension with little linear displacement.

The tensor tympani is the larger of the tympanic muscles. It is
a slender, spindle-shaped muscle, about 25 mm in length and 5.85 m2
in cross sectional area. The tensor tympani is located in the upper
compartment of the musculo-tubal canal of the Eustachian passage on the
anterior wall of the middle ear. It is separated from the Eustachian

tube by a bony partition. The muscle fibers of the tensor tympani
originate in the cartilaginous portion of the framework of the
musculo-tubal canal. The muscle then passes out of the canal over the
cochleariform process which serves as a pulley for the muscle tendon.
As the tendon passes over the cochleariform process it makes nearly a
right angle turn laterally and crosses the tympanic cavity. The tendon
inserts into the manubrium just below the neck of the malleus. Upon
contraction, the tensor tympani draws the malleus medially, inferiorly
and anteriorly. The force is almost at a right angle to the course of
the ossicular chain.

The stapedius muscle averages 6.3 mm in length. It has a. cross
sectional area of about 5 m2. It takes origin from a canal which
runs almost parallel to the facial nerve canal and is located on the
posterior wall. of the tympanic cavity. The muscle fibers take their
origin from the walls of the bony canal. The tendon of the muscle
emerges from an aperture at the apex of the pyramidal eminence. From
this point the tendon proceeds anteriorly to insert into the posterior
surface of the neck of the stapes. Contraction of the stapedius exerts
a force on the head of the stapes, drawing it posteriorly at a right
angle to the direction of movement of the ossicular chain.

An involuntary contraction of the two middle ear muscles to
effective stimulation constitutes the middle ear reflex. Moreover,
as in other body reflexes, a specific neural. pathway is followed in
the production of the response. Iorente do No (1935) and Rasmussen
(1946) have outlined the reflex are for the middle ear muscles. These
authors maintain that the cochlear nerve constitutes the afferent

(sensory) part of the reflex arc. The "reflex center“ is believed to

be in the pens, specifically in the superior olivary complex. The
efferent (motor) part of the reflex arc consists of various cranial
serves. The facial nerve is known to be the sole innervator of the
stapedius muscle. However, multiple neural connections have been
identified for the tensor tympani muscle. Specifically, the tensor
tympani is believed to be connected to the tympanic plexus of nerves
besides being innervated by the mandibular branch of the trigeminal
nerve (Lawrence, 1962).
Acoustic Respgnses of the Middle Ear Muscles

Luscher pioneered the investigation of the middle ear reflex in
humans (Jepson, 1963). During the 1920's and 1930's Luscher determined
that the response of the middle ear muscles to acoustic stimulation is a
consistent phenomenon in man. In addition, he demonstrated that
unilateral acoustic stimulation elicits a bilateral reflex contraction,
that the reflex depends upon the intensity of the stimulation, and that
the reflex threshold varies across stimulus frequencies with the mid-
frequencies providing the most sensitive reflex thresholds. This later
finding has been more recently confirmed by Jepson (1963) and Peterson,
Lamb and Hanson (1965) who demonstrated that the midfrequencies produce
the most sensitive and reliable reflex thresholds both within and across
subjects.

other investigators have studied the recovery time and the relaxa-
tion time of the middle ear muscles. Meta (1951) demonstrated that the
middle ear muscles do not require any recovery time between successive
contractions to independent stimuli. However, both Mats (1951) and
Dallos (1964) have demonstrated that the middle ear muscles do require

some time following the cessation of an auditory stimulus in order to

 

attain a relaxed state. Metz found that measureable activity could endure
in the muscles for more than one second following the cessation of an
auditory stimulus and Dallas demonstrated that in some instances the
muscles were not relaxed completely in less than two seconds following
cessation of an auditory stimulus. Neither Metz nor Dallos were able to
identify any consistency in the amount of relaxation time required across
subjects.

Several investigators have been concerned with identifying the
relative importance of each of the middle ear muscles in the middle ear
reflex. Studies employing infrahuman subjects have suggested that both
the stapedius muscle and the tensor tympani play active roles in the
acoustic reflex (Pollak, 1887; Kate, 1913; and Wersal, 1958). On the other
hand, investigators employing hman subjects unanimously contend that
only the stapedius muscle is involved in the middle ear reflex (Metz,
1946; Jepson, 1955: nockhoff, 1961: Salomon and Starr, 1963; and Feldman,
1967).

Nonacoustic Resmnses of the Middle Ear Muscles

Several investigators have demonstrated that the middle ear muscles
will contract in response to both cutaneous stimulation of the external
auditory meatus and to forceful contraction of the orbital muscles
(Klockhoff, 1961; Salomon and Starr, 1963: and Djupesland, 1965). In
addition, Salomon and Starr (1963) and Djupesland (1965) have recorded
muscle activity accompanying such voluntary motor activities as swallowing,
coughing, yaming, and head turning. Moreover, it has been demonstrated
also that middle ear muscle activity precedes vocalization (Salomon and
Starr, 1963: Shearer and Simmons, 1965: and Djupesland, 1965). Finally.
it has been determined that middle ear muscle contractions are one of

the motor components of a general startle response (Klockhoff and Anderson,
1959: Klockhoff, 1961: Salomon and Starr, 1963; and Djupesland, 1965).

Conditioning the Middle Ear Reflex

There have been relatively few attempts made to determine the
conditionability of the middle ear reflex. Moreover, the results of
such attempts have not demonstrated conclusively whether or not the
middle ear reflex is susceptible to classical conditioning procedures.
Successful Attempts

Human Studies. Luscher reportedly was successful in conditioning
the middle ear reflex during the 1920's (Jepson, 1963). In addition, '
Kobrak (1948) reports that "the patient may be 'conditioned' by
repetition and may show contractions due to expectation." However,

Isince both Luscher and Kobrak only visually observed the reflexes in
question, their conclusions need to be accepted cautiously. Without
either permanent records or reports of interjudge reliability the results
of both investigators are potentially open to significant experimenter
bias. In particular, the results may reflect expected rather than actual
observations.

Ioeb and Fletcher (1963) reported success in conditioning the
middle ear reflex to a temporal interval. In their investigation, the
authors compared the amounts of temporary threshold shift (TTS) acquired
by subjects who were exposed to five experimental presentations of either
continuous or intermittent noise. The continuous noise was presented at
110 dB SPL for a total of 50 minutes while the intermittent noise was
presented at 120 dB for an equivalent time period. The on- and off-times
of the intermittent noise were each one second. The results indicated

that subjects in the continuous group acquired a constant mount of TTS
at each of the five sessions. However, subjects in the intermittent
group tended to acquire less TTS at each successive session. The authors
concluded that the results demonstrated temporal conditioning of the
middle ear muscles. However, based on the work of Mats (1951) and
Dallas (1964) which has been cited above, it appears likely that Leah
and Fletcher did not allow sufficient time between stimulus presentations
for the middle ear muscles to relax completely. Therefore. Loeb and
Fletcher's results may be confounded by the fact that during the exper-
imental sessions the middle ear muscles of the subjects in the intermittent
noise group were in a state of continuous activity.

Mendelson, Fletcher and Loch (1965) reported observing tonic
contractions of the middle ear muscles in a group of subjects who were
exposed to a series of noise impulses with on-times of 300 msec and off-
times of 660 msec . The experimenters contended that the tonic contractions
were due to conditioning since the subjects were all in the military and
had ”chronic exposure to impulsive noise." Alternatively, the argmnent
could be made that the observed reflex activity was not a form of
conditioned response but merely the normal muscle activity which follows
the cessation of an auditory stimulus (Mots, 1951 and Dallas, 1964).
Moreover, since Mendelson et a1. did not report having pro-exposure
records on their subjects and they did not run a control group, any
conclusion of conditioning would be tenuous .

Mendelson et a1. (1963) also reported observing modified reflex
activity in one subject who was a "sonabuoy listener” and, therefore,
was required to make difficult auditory discriminations . Investigations

on the subject revealed that his reflex activity was increased during
some difficult listening situations. Therefore, the authors concluded
that this activity was a conditioned response which had developed
through the subject's experience as a "sonabuoy listener." However,
again Mendelson et a1. failed to obtain pre-exposure data or to run
control subjects. It is feasible that the subject may have had the
ability to vary the contractibility of his middle ear muscles prior
to the experience of being a "sonabuoy listener." Such ability has
been demonstrated by Reger (1960) in college students.

Brasher, Coles, Elwood and Ferres (1969) reported success in
eliciting middle ear muscle contractions in anticipation of gunfire
initiated by the subject himself. Brasher et al.'s subjects fired
pistol shots at regular intervals of about every 5 seconds. The peak
noise of each shot was between 1’45 and 155 dB. Middle ear muscle activity
was measured with the Madsen Bridge Model 2061. or Brasher et al.'s 16
subjects, nine showed impedance changes both before the shots were fired
and with misfire clicks, while two more subjects showed impedance changes
with misfire clicks only. Brasher et al. did not report how many condi-
tioning trials were employed. However, they did provide an example which
illustrated a slight anticipatory effect by the third shot and a marked
effect by the tenth shot.

Although the results by Brasher et al. appear to suggest condi-
tioning of the middle ear muscles, the results obtained in a similar
study by Djupesland (1965) suggest that Brasher et a1. were merely
recording one component of a general muscle contraction rather than an
isolated conditioned response of the middle ear muscles. In his

10

investigation, Djupesland presented a toy pistol to his subjects and
told them that the gun would produce a loud and unpleasant sound. Of
his 30 subjects, 21+ reacted to sight of the pistol with a general
muscular contraction. Moreover, in each case, the general muscle
contraction was accompanied by contractions of the middle ear muscles.
All of Djupesland's results were based on electro-myographic recordings.
Infrahuman Studies. Simone, Galambos, and Rupert (1959) have

 

presented the only report of successful conditioning of the middle ear
muscles in infrahumans. Specifically, Simmons et al. reported success

in conditioning the middle ear reflex in awake cats to a neutral stimulus ,
under three different conditioning procedures. In all. of their studies,
moreover, a. truck horn was employed as the unconditioned stimulus (U03)
and a light served as the conditioned stimulus (CS). (Unfortunately,
however, Simmons et a1. did not provide quantitative levels for any of
their stimuli.) In each of the three experiments the subjects were placed
in a dark, sound treated room during both the conditioning and the test
trials. All reflex resPonses were recorded as changes in cochlear
microphonics measured by electrodes which were permanently implanted

in the round window of each subject.

In their first experiment. Simone et a1. employed a photographic
flash unit for the CS. During the conditioning trials the flash was
followed immediately by a "blast“ from the U05 (the truck horn). Six
cats served as subjects and Simmons et al. reported that five of the six
cats were "well conditioned" in less than 30 trials. (A quantitative
definition of "well conditioned" was not provided.)

Simmons et al. reported, however, that there might have been a

confounding variable in their first experiment. Specifically, they

 

11

noted that due to intense levels of stimulation a form of pseudo-
conditioning might have occurred. Kimble (1961) reports that whenever
a noxious stimulus is employed nonessociative pseudoconditioning to the
general situation may occur rather than true conditioning to the specific
stimulus .

Therefore, in their second experiment, Simmons et al. employed a
6 volt light in place of the photoflash in an attempt to eliminate any
pseudoconditioning. The light bulb was placed "a few inches" from the
subject's head and as in the first experiment, a ”blast” from the horn
imediately followed each presentation of the light. Four cats were
employed as subjects in the second experiment and only one of the four
cats was successfully conditioned. Simone et al. concluded that this
proved conditionability of the middle ear reflex. However, statistically
this result would be of only questionable value based on the small number
of subjects that were conditioned. In addition, it could still be argued
that a form of pseudoconditioning occurred. For even though Simone et
a1. did not report the effective level of their light, the present author
measured the illumination produced by a 6 volt tungsten lamp and found
it to be 16 fc at approximately 3 inches from the bulb.1 Such a level is
sufficiently intense to produce an avoidance response .

In their third experiment, Simons et a1. reportedly demonstrated
differential conditioning. In this experiment both the light flash and
, the light bulb were presented to each subject. However, only the
presentation of the light bulb was reinforced with the horn. A 500 msec

 

1Throughout thiszmanuscript, 1 fc 1s taken to be approximately
equal to 10.7 lumens/m . .

12

delay was allowed between the cessation of the light and the horn "blast."
Three cats served as subjects and two of the three were successfully
conditioned. However, both of these animals required about 200 trials
before differentiation was complete.

In general, the results of the above three experiments need to be
viewed with caution since Simmons et a1. did not employ any control
groups. The only form of control that they employed was one recording
made from a single cat which showed no reaction to the photoflash being
presented by itself. The recording was reportedly made after tlm cat
had been "successfully conditioned" to the photoflash and the conditioned
response subsequently extinguished. However, since the authors did not
present a record of the cat's response to the photoflash prior to con-
ditioning, it could be argued that the subject originally produced a
startle reSponse to the photoflash but that after sufficient presentations
of the stimulus, the startle response was finally adapted. In this case,
Simmons et a1. were measuring a form of adaptation rather than a form of
conditioning.

Unsuccessful Attempts

Human Studies. Ward and Fleer (1961) reported an unsuccessful
attempt to condition the middle ear reflex temporally in an experiment
similar in design to that employed by Leah and Fletcher (1963). In their
experiment, Ward and Fleer measured the amount of TTS produced by exposure
to high intensity acoustic clicks (peak value of 155 dB SPL) with either
periodic (2J4 seconds) or aperiodic (1-5 seconds) interclick intervals.
Their results reflected no difference in the amount of TTS acquired by
the subjects in the two experimental groups. Therefore, based on the
assumption that a temporally conditioned reflex would have reduced the

 

13

amount of acquired TTS in the intermittent noise group, Ward and Fleer
concluded that the middle ear reflex is not susceptible to temporal
conditioning. There is a possibility, however, that Ward and Floor
suppressed conditioning by using such intense levels of stimulation.
Kimble (1961) reports that the use of noxious stimulation may reduce
or eliminate conditioned activity.

Infrahuman Studies. Simone (199+) reported an unsuccessful
attempt to condition the middle ear reflex in cats to a neutral
stimulus. Simons recorded muscular activity with cochlear microphonics.
A tone of variable frequency and intensity (range of 105-120 dB) served
as the U03. A second tone, also of variable frequency and intensity
(range of 140-70 dB) served as the CS. The UCS was presented for a
duration of 200 msec, while the duration of the (3 varied from 200-300
msec. A trace conditioning paradign was employed, with the presentation
of the CS stopping before the U08 presentation was initiated. It should
be noted, however, that although Simmons reported that he could not
consistently elicit reflex contractions without continually varying the
stimuli, it is very likely that such stimulus variations served to
eliminate conditioned reSponses.
m

A review of the investigations presented above reveals that studies
which have attempted to condition the middle ear reflex Suffer from
serious methodological deficits. For example, none of the investigators
provided a quantitative definition for a conditioned reflex. Likewise,
they neither employed a control group nor attempted to control for
incidental. reflexes which would be elicited by voluntary motor activities.
other additional methodological flaws included failure to control for

 

1h

relevant background variables (i.e. Mendenson et al., 1963; Brasher et al. ,
1969; and Simmons et al.. 1959). failure to control for the possible
elicitation of a general startle reSponse (i.e. Simmons et al.. 1959;
Ward and Fleer, 1961; and Brasher et al., 1969). and failure to allow
sufficient relaxation time for the middle ear muscles (Leah and Fletcher,
1963 and Mendelson at al., 1963).
Therefore, based upon a review of past investigations, there is
a clear need for a well controlled investigation of the conditionability
of the middle ear reflex. Such an investigation, moreover, is presented
below in the form of two experiments which attempt to condition the 1!
middle ear reflex both to a temporal interval and to a visual stimulus.
In addition, a third experiment determines the neutrality of the visual
stimulus. Specifically, the following questions are investigated:
1. Can the middle ear reflex be conditioned to a temporal
interval?
2. Does light serve as an unconditioned stimulus for the
middle ear reflex?
3. Can the middle ear reflex be conditioned to a neutral
visual stimulus?
1%. Is the middle ear reflex differentially sensitive to ‘
conditioning as a function of the interstimulus interval

employed?

EXPERIMENT I: meow. CONDITIONING

In the first experiment an initial attempt was made to classically
condition the middle ear reflex. The purpose of the experiment was to
determine whether or not time could serve as an effective CS.

Method

Subjects

Five normal hearing female volunteers who were students at Michigan
State University served as subjects. The subjects ranged in age between
20.8 years and 24.8 years with a mean of 22.1} years. All subjects had
normal pure tone thresholds, i.e. their air conduction thresholds were
bilaterally less than 25 dB ISO at all octaves from 250 Hz through 8000 Hz
and their bone conduction thresholds were within ‘5 5 dB of their air
conduction thresholds. In addition, all subjects had normal acoustic
impedance scores,1 ranging from 320 to 510 acoustic ohms, with a mean of
390 acoustic ohms. Finally, all subjects had a middle ear reflex which
could be measured with the Madsen Electra-Acoustic Impedance Bridge (Model
Z070). The reflex thresholds at 1000 Hz ranged from 90 to 100 dB with a.

2

mean of 93 dB. All testing was done in an experimental room which had an

 

1Acoustic impedance is defined as pressure [volume-velocity and it
refers to the amount of "resistance" offered by the middle ear to the
propagation of sound waves (Miller, 196+). Zwislocki and Feldman (1970)
reported that the impedance of the normal ear lies within a conservative
range of 280 to 630 acoustic ohms at 250 Hz.

2The rise and decay times of the 1000 Hz tone were 25 msec and 35
msec reSpectiveZLv.

15

16

ambient noise level of 50 dB as measured on the C scale of a Bruel and
Kjaer sound level meter (Model 2201+). (Octave band levels of the ambient
noise are presented in Appendix II.)
Basie and Conditiomg Procedure

As indicated above , a temporal conditioning paradim was employed
in the first experiment. Therefore, the erqaeriment was designed to
present the 008 by itself with constant time intervals between successive
presentations. The UCS was a 1000 Hz tone presented 10 dB above the
subject's reflex threshold for a durationeof 1 second (t .6 msec) and the
CS was a time interval of ’45 seconds (i 160 msec).1

Daring the experiment, each subject received the same number of
conditioning trials and test trials. (See Table 1.) Specifically,
each subject received a total of 100 conditioning trials and four test
trials within a 24 hour period.2 The conditioning trials were presented
in four groups of 25 trials with each block of conditioning trials being
followed by a test trial. In addition, three unreinforced trials were
presented immediately prior to each set of conditioning trials in order

 

1Stimulus values were not picked totally at random. The choice of
1000 Hz as the U08 frequency was based on the reports of Luscher and Jepson
(cited above) which indicate that the midfrequencies produce the most
sensitive and reliable measurements . In addition, the intensity of the
UCS was chosen as a compromise between obtaining consistent reflex responses
yet eliminating general startle reaponses. Finally, choice of the CS
interval was based on the reports of Meta and Dallas (cited above) con-
cerning relaxation time of the muscles and also on Morgan's (1965) finding
that humans are best able to discriminate time intervals between 30 and
60 seconds in length.

2One subject received a total of 123 trials. The extra block of

conditioning trials was presented because an instrumentation difficulty
disrupted the timed presentations of conditioning trials numbered 99 and
100 .

17

to establish a baseline of responding. Each subject was seen twice
within the 21+ hour period. At each of these experimental settings,
the subject received two blocks of conditioning trials (a total of 50
trials). In addition, the subject was given a 15 minute rest period
after the first 25 conditioning trials at each session.

 

 

Table 1
Stimulus Presentations in Temporal Conditioning

 

Trial Seguence
Conditioning or Reinforced Trial 1&5 Second Time Interval

1000 Hz Tone Presented for 1 Second
as Second Time Interval

Test or Unreinforced Trial #5 Second Time Interval
Tone Withheld for 1 Second
1+5 Second Time Interval

 

 

Instrumentationl

Stimulus Presentatign; As indicated above , the 008 was presented
for a duration of one second every lb 5 seconds during the conditioning
trials. A Beltane portable audiometer (Model 100) generated the 008 and
controlled its frequency and intensity. Two Hunter timers (Model 1000,

Series D and Model 111C, Series D) controlled and automated repetition of

 

1A complete listing of the equipment employed may be found in
Appendix III.

18

the UCS - time interval - UCS sequence. (A schematic wiring diagram
may be found in Appendix IV.) The first timer (T1) controlled the

UCS presentations and the second timer (T2) controlled the time interval
between successive presentations. T1 and T2 were wired together so that
when either timer finished its timed interval it activated the other
timer. In addition, T1 was wired to the audiometer so that when T1 was
activated (by the shut off of T2) the UCS was simultaneously turned off.
The automated sequence started when the experimenter manually turned on
T2 and stopped when the experimenter manually turned off the same timer.
The stimulus presentation switch on the audiometer was used to delete
the UCS during the test trials.

Resmnse Measurement. ReSponses to the stimuli were measured with
the Madsen Electra-Acoustic Impedance Bridge (Model 2070). (A complete
description of the Madsen Bridge may be found in Appendix v.) The
resPonses which took the form of impedance changes in the subject's ear
were correlated with voltage changes in the Madsen Bridge and appeared
as deflections on the balance meter of the bridge (Terkildsen and Nielson,
1960).

Recording. Recordings were made of both the stimulus and reoponse
signals utilizing a Brush graphic recorder. (Sample recordings may be
found in Appendix VI.) The recorded stimulus signal was correlated with
the CS and UCS presentations. The signal originated at T1 and was
amplified by the Brush DC amplifier before being recorded on the graphic
recorder. Two six volt batteries were employed to drive the needle of
the graphic recorder.

The recorded response signal was correlated with impedance changes

in the subject's ear canal as measured by the Madsen Bridge. The signal

19

from the Madsen Bridge was then amplified reSpectively by a Tektronix
amplifier (Type 2A63) and the Brush amplifier before it was recorded
by the Brush graphic recorder.

 

 

 

 

 

 

Stimulus and
Recording Equipment Si
rimenter I
Madsen
Bridge

 

 

 

1!!! Subject 1 - w

 

 

 

Figure 1. Block diagram of experimental situation for
temporal conditioning.

20

 

 

 

 

 

Amplifier

 

 

 

 

 

Amplifier

 

 

 

 

 

 

 

Figure 2.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Graphic
Recorder
Amplifier
T1 - T2
Subject Audiometer
Earphone

Schematic illustration of instrumentation
for temporal conditioning.

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-n.

 

 

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21

Procedures

The experimenter calibrated the Madsen Bridge and the Beltane
audiometer each day that a conditioning attempt was made. (A listing
of the equipment employed in the calibration may be found in Appendix
III.) The calibration of the Madsen Bridge consisted of insuring that
the indicator needle on the pressure gauge was at a 0 reading when no
pressure was being applied. Calibration of the audiometer consisted
of determining the SPL outputs at each octave frequency from 250 Hz
through 8000 Hz for air conduction and from 250 Hz through “000 Hz for
bone conduction. The SPL outputs were then compared with the air
conduction standards as published by the International Standards Organ-
ization (1961+) and the interim bone conduction standards as published
by the Hearing Aid Industry Conference (Lybarger, 1966). Compensations
for intensity norm deviations were made during testing.

At each subject's first experimental session, her name and age
were recorded on a standardized form. (A copy of this form may be found
in Appendix VII.) Following this formality, the criteria tests for
hearing were administered. The pure tone test was always administered
first followed by the impedance measurements. Pure tone thresholds were
determined by the Hughson-Westlake technique as described by Carhart and
Jerger (1959). This same technique was employed in determining the
middle ear reflex threshold level.1 Acoustic impedance values were
determined through use of the following expression which was provided in
the manual for the Madsen Bridge: zx = (Z1 1; 22) / (z1 - 22). The

1Lamb, Peterson and Hansen (1968) recommend emfloying the Carhart
and Jerger ascending technique for determining middle ear reflex thresholds.

required values were determined through the following steps. First the
pressure in the ear canal was increased to +200 mm water pressure and

the compliance control was adjusted as necessary to obtain a zero reading
on the balance meter when the meter was set for a sensitivity of -_I-_ 1 cc.
The correlated impedance reading represented the point of least compliance
of the middle ear system and this value was employed as 21 in the above
expression. The value of 22 was obtained by reducing the pressure in the
ear canal until the balance meter needle had reached its maximmn swing to
the left and the compliance control was subsequently adjusted to again
produce a zero reading on the balance meter. The correlated impedance
reading here represented the maximum compliance of the middle ear system.
Finally, the two impedance values were combined in the expression provided
above to determine the acoustic impedance in the plane of the eardrum (Zx).
A11 impedance measurements were made with the probe from the Madsen Bridge
fitted to the subject's right ear.

Prior to the experimental session, all of the equipment was warmed
up for a period of 10 minutes. During the hearing tests, however, the
Tektronix amplifier and its power supply and the Brush graphic recorder
were turned off. These instruments had been found to increase the ambient
noise in the room from 50 dB to 55 dB as measured on the C scale of a
Bruel and Kjaer sound level meter (Model 2204).

Following the administration of the criteria tests for hearing, all
of the equipment was again turned on. At this time, the instructions were
read to the subject. (A copy of these instructions may be found in
Appendix VIII.) A carbon copy of the instructions was given to the
subject so that she could follow along with the verbalization. After the

instructions were read, the experimenter answered any questions posed by

23

the subject. After all questions had been answered, the subject was
given a 3 minute period to adjust to the experimental situation, i.e.
an habituation period. Following this, the experimental trials were
administered as outlined above.

Results and Discussion

The data were independently analyzed by two judges employing
the following criteria.1 A middle ear reflex response was operationally
defined as a needle deflection on the graphic recorder of approximately
90° from the baseline with a minimum deflection magnitude corresponding :3
to a 20 mv change. During the conditioning trials, only reSponses which
occurred during the one second interval when the UCS was presented were
counted. During the baseline trials and the test trials, however, a
response meeting the operational definition was accepted if it occurred
anytime after the first four-fifths of the intertrial interval (ITI).2
The results of both judges' analyses were in perfect agreement and they
are summarized below in Figures 3 and ’4.

All subjects responded with an acceptable reflex on each of the
UCS conditioning presentations.3 However, inspection of Figure 3 reveals
that no spontaneous reflexes were elicited during the baseline trials

which preceded each block of conditioning trials. In addition,

1The experimenter served as one judge. The other judge was a
graduate student in English.

zMorgan (1965) reported that the normal error allowance in studies
of temporal discrimination is one-fifth of the time interval.

30m subject failed to respond with an accepted reflex to one UCS
presentation during her first block of conditioning trials. The given
response did not meet the magnitude criteria.

Mean Number of Reflexes

 

21+

 

 

Figure 3.

0 25 50 75
Number of Preceding Conditioning Trials

Spontaneous reflexes elicited during temporal conditioning.

 

Mean Number of Reflexes

25

 

 

 

25 50 75 100
Number of Preceding Conditioning Trials

Figure Ur. Conditioned reflexes elicited during temporal conditioning.

..
.
..

 

26

inspection of Figure 1+ reveals that there were no conditioned reflexes
(CRs) elicited during any of the test trials. Therefore, since there
was no difference in the baseline reSponse and in the number of CR5.
temporal conditioning of the middle ear reflex was not demonstrated.

This absence of temporally conditioned reSponses is consistent with
the results obtained by Ward and Fleer (1961). However, such a result is
incompatible with the conclusion drawn by Ioeb and Fletcher (1963) and
Mendelson et al. (1963). As indicated above, these later experimenters
reported success in conditioning the middle ear reflex to a time interval.

A cursory review of the literature, therefore, might suggest that
the conditionability of the middle ear reflex to time is an equivacal
question since two studies have reportedly demonstrated such conditioning
and two studies have failed to demonstrate such conditioning. A careful
review of the employed methodologies, however, reveals that in both of
the successful investigations ITIs were equal to or less than one second.
Moreover, according to the data presented above by Mats (1951) and Dallos
(196+) such ITIs may be too short to allow complete relaxation of the
middle ear muscles. Thus, the results obtained by Loeb and Fletcher (1963)
and Mendelson et al. (1963) possibly are confounded and, therefore,
cannot be interpreted. This suggests that based on present research, the
only conclusion that can be dram at this time is that the middle ear
reflex has not been shown to be susceptible to temporal conditioning.

 

 

 

 

 

 

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EXPERIMENT II: LIGHT AS AN UNCONDITIONED STIMULUS

In the second experiment an attempt was made to elicit the middle
ear reflex with visual stimulation. The purpose of the experiment was
to determine whether or not the chosen visual stimulus consistently

evoked the reflex reSponse.1

Method

subjects I
Five normal hearing female volunteers served as subjects. Four of
the subjects were students at Michigan State University and one subject
was an alumnus of the same institution. Subjects ranged in age between
20.9 years and 214.? years with a mean age of 22.8 years. All subjects
had normal pure tone thresholds of hearing under the criteria. outlined
in the first experiment. In addition, all subjects showed normal acoustic
impedance values, ranging from 350 to 540 acoustic ohms with a mean value
of l+20 acoustic ohms. Finally, all subjects had middle ear reflexes which
could be measured with the Madsen Electra-Acoustic Impedance Bridge (Model
2070). The reflex thresholds ranged from 80 to 95 dB with a mean of 88 dB.
All of the hearing criteria tests were administered in the experimental
room employed in the first experiment.

1The chosen visual stimulus was a 6 volt tungston lamp with an effective
illumination of 0.2 fc measured at the subject's eye. The light provided an
illumination of 16 fc measured approximately 3 inches from the bulb. The
illumination at the subject's eye provided by the room lights was 4 fc. All
illumination measurements were made with a Spectra Exposure Meter manufactured
by the Photo Research Corporation.

2?

28

Desigg and ggfimental Procedure
The second experiment was designed to determine if the light

evoked the middle ear reflex at a. greater than chance frequency. This
detemination was made by comparing the number of reflexes that occurred
during 25 one second time intervals when the light was presented with the
number of reflexes that occurred during 25 one second time intervals when
the light was withheld.

Testing was completed in one session with the subject receiving a
15 minute rest period halfway through the testing. The instrumentation
was automated to present the light for a duration of 1 second (1 6 msec)
every 1+5 seconds (1 160 msec). During the session a. total of 50 stimulus
presentations were originated. However, by means of a switch, the exper-
imenter deleted a random 50% of these presentations so that the subject
observed the light only 25 times. The same random pattern of presenta-
tions was used for all subjects. (This random sequence is presented in
Appendix DC).
Distrmnentation

Stimulus Presentation. A General Electric tungsten lamp (Model 51)
attached to an Electronic DC power supply (Model 1020) generated the
stimulus. The stimulus-time interval-stimulus sequence was automated and
controlled by two Hunter timers (Model 100C, Series D and Model 1110,
Series D). (A schematic wiring diagram may be found in Appendix IV.)
The wiring of the timers was the same as in experiment I except that in
the second experiment T1 was wired to the power Supply for the light
rather than to the audiemeter. In addition, the experimenter employed
a switch which was wired to the power supply of the light to delete

presentations of the light during appmpriate time intervals.

 

 

 

   

 

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29

Resmnse Measurement. As in the first experiment, the subject's
resPonse to the stimulus was measured by the Madsen Electro-Acoustic
Impedance Bridge (Model 2070).

Recording. The recording procedure for the second experiment was
the same as in the first experiment. The only difference was that the
recorded stimulus event in the second experiment was the interval
correlated with a light presentation or deletion rather than an interval

correlated with a tone presentation.

 

 

Stimulus and
Recording Equipment

 

 

 

 

Experimenter
Madsen

Bridge

 

 

 

1 m Subject 1 m ight

 

 

 

Figure 5. Block diagram of experimental situation for determining the
neutrality of a visual stimulus.

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Schematic illustration of instmmentation for
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31

Procedures

All of the procedures employed as precedents to administering
the experimental trials in experiment II were the same procedures as
employed in the first experiment. However, as indicated above, all of
the testing in the second experiment was completed in one session. In
addition. following the 50th trial in the second experiment, a reflex
response was elicited from each subject with a 100 dB stimulus at 1000 Hz
as confirmation that the probe from the Madsen Bridge had remained in

place during the entire session.
Results and Discussion 13}

The data were independently analyzed by the two judges employed in
the first experiment. Likewise, the data were objectively scored by
applying the operational definition of a reflex resPonse which was pre-
sented in the first experiment. In the second experiment, however,
only those reflexes were considered which occurred either during the
light presentations or during the empty intervals during which the light
was deleted. Again, the judges were in perfect agreement in their
analyses and the results are summarized below in Figures 7 and 8.

Inspection of Figure 7 reveals that no spontaneous reflexes were
elicited from any subject during any of the 25 empty intervals. Likewise,
inspection of Figure 8 reveals that no reflexes were elicited in response
to any of the 25 light presentations. Therefore, since there was no
difference in the number of spontaneous reflexes and the number of
unconditioned responses, it was concluded that the experimental light

is not an unconditioned stimulus for the middle ear reflex.

Mean Number of Reflexes

32

 

 

 

O 5 10 15 20 25

Eupty Intervals

Figure 7. Spontaneous reflexes elicited during the determination
of the neutrality of the visual stimulus.

V)

 

 

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Mean Number of Reflexes

33

 

 

 

O 5 10 15 20 25

Light Presentations

Figure 8. Unconditioned reflexes elicited during the determination
of the neutrality of the visual stimulus.

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EXPERJIENT III: SD’IULTANEOUS AND IELAIED CONDITIONING

The third experiment provided a final attempt to classically
condition the middle ear reflex. Specifically, the main purpose of the
experiment was to determine whether or not the middle ear reflex could
be conditioned to a neutral visual stimulus. The chosen stimulus was
the light which had been employed in experiment II. Moreover, since
prior conditioning studies on other modalities have demonstrated that
conditioning frequently depends upon an appropriate delay time between _.
the onset of the cs and the onset of the ucs (Kimble, 1947: Gerall and 7
Woodward, 1958; and Jones, 1962 among others), the present experiment
was also designed to determine if the conditionability of the middle
ear reflex varied with different interstimulus intervals (ISIS).

Method

Subjects
Twenty normal hearing female volunteers served assubjects. Fifteen

of the subjects were students at Michigan State University and five of the
subjects were alumni of the institution. Subjects ranged in age between
20.0 and 2h.6 years with a mean of 22.0 years. All subjects had normal
pure tone thresholds of hearing under the criteria outlined in the first
experiment. In addition, all subjects showed normal acoustic impedance
values, ranging from 290 to 560 acoustic ohms with a mean value of 400
acoustic ohms. Finally, all subjects had middle ear reflexes which could
be measured with the Madsen Electra-Acoustic Impedance Bridge (Model 2070).

34

 

 

 

 

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35

The reflex thresholds ranged from 80 to 100 dB with a: mean of 92 dB.
All screening was done in the experimental room employed in the first
two experiments.
Desigr and Conditioning Procedure

As indicated above, the purpose of the third experiment was to
determine if the middle ear reflex could be conditioned to a neutral
visual stimulus. The UCS was a 1000 Hz tone presented 10 dB above the
subject's middle ear reflex threshold for a duration of one second
(+/— six msec) and the CS was a tungsten lamp with an effective illumin-
ation of 0.2 fc. In order to avoid any possibility of temporal condi-
tioning, the time intervals between successive UCS presentations were
randomly varied at 30, 1+5 or 60 seconds. The same random order was
used for all subjects. (This random order may be found in Appendix 1:.)

The conditioning trials were presented in the same manner as they
were in the first experiment. That is, a total of 100 reinforced trials
were presented in two sessions within a 2L! hour period. A test trial
followed each block of 25 conditioning trials and the subject was given
a 15 minute rest period after the first test trial at each session.

Four experimental groups were employed in the third experiment.
The dependent variable of concern was the effect on conditioning of various
delay times between the onset of the CS and the UCS presentations. Four
delay times, varying from 0 delay to a 2.5 second delay were employed.
The stimulus presentation sequences for each experimental group are
presented in Table 2.

The experimental situation in the present experiment was the same
as in experiment II. A block diagram of this situation many be found

in Figure 5.

36

 

 

Table 2

Stimulus Presentations for Simultaneous and Delayed Conditioning.“

 

Group 1

Group 2

Simultaneous Conditioning Group

Reinforced Trial - CS and UCS presented concurrently for
a duration of one second. Intervals between UCS onsets
are randomly varied at 30, 45 or 60 seconds.

Test Trial - CS' and UCS off for an interval varying
randomly from 30 to 60 seconds. CS on for one second,
UCS remains off.

Del d Conditionin : ISI of 0. Seconds

Reinforced Trial - CS onset precedes UCS onset by 0.5
seconds. After UCS onset, both CS and UCS remain on
for one second. Intervals between UCS onsets are
randomly varied at 30, 1+5 or 60 seconds.

Test Trial - CS and UCS off for an interval varying
randomly from 29.5 to 59.5 seconds. CS on for 1.5
seconds, UCS remains off.

Del d Conditionin : 161 of 1. Seconds

Reinforced Trial - CS onset precedes UCS onset by 1.5
seconds. After UCS onset, both CS and UCS remain on
for one second. Intervals between UCS onsets are
randomly varied at 30, 1+5 or 60 seconds.

Test Trial - CS and UCS off for an interval varying
randomly from 28.5 to 58.5 seconds. CS on for 2.5
seconds, UCS remains off.

Del ed Conditionin : 181 of 2. Seconds

Reinforced Trial - CS onset precedes UCS onset by 2.5
seconds. After UCS onset, both CS and UCS remain on
for one second. Intervals between UCS onsets are
randomly varied at 30, 1+5 or 60 seconds.

Test Trial - CS and UCS off for an interval varying
randomly from 27.5 to 57.5 seconds. CS on for 3.5
seconds, UCS remains off

 

*Ranges and averages of the delay times in msec for each experimental
group are presented in Appendix XI.

 

 

 

 

   

 

 
     

 

 

 

 
 

 

 

 

 

   

   

 

 

   

   

 

 

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37

Instrumentation

Stimulus Presentation. A Beltane portable audiometer (Model 100)
generated the UCS and controlled its frequency and intensity. The CS
was generated by a General Electric tungsten lamp (Model 51) and an
Electronic DC power supply (Model 1020). Three Hunter timers (Model
1000 series D and 2 Model 1110 series D) controlled the UCS and CS
presentations for each conditioning trial. The first timer (T1)
initiated the onset of the CS. The second timer (T2) initiated the
UCS onset. Finally, the third timer (T3) set the delay interval between
the onset of the CS and the onset of the UCS. The random time intervals 31
were measured individually with a Dimco-Gray universal timer.

A manuale operated mercury relay was used as a switch to originate
each conditioning sequence. Whenever the relay was tilted out of the
vertical direction, it closed a switch on T3 thereby starting that timer.
Moreover, T3 was wired to T1 in such a way that when T3 was activated it
simultaneously turned on T1. In addition, T3 was wired to T2 in such a
manner that when T3 finished its timed interval it activated T2. T3
remained in its finished position until T2 completed its timed cycle.
When T2 finished its timed interval it acted to reset timers T3 and T1
thus also resetting itself.

Resmnse Measurement. As in the first experiments, the response
of the middle ear to the stimulus was measured with the Madsen Electro-
Acoustic Impedance Bridge (Model 2070).

Recording. Stimulus and response recordings for the third exper-
iment were the same as outlined in experiment II.

 

Graphic
Re co rde r

 

 

 

 

 

 

 

Amplifier

W

Amplifier

 

 

 

 

 

  
 
 

   

Subject . Audiometer \

 

 

Probe \\ ,, // Earphone

 

 

Figure 9. Schematic illustration of instrumentation for
simultaneous and delayed conditioning.

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mi

All. of the procedures employed as precedents to administering the
conditioning trials in experiment III were the same procedures as
employed in the first two experiments.

Results and Discussion

The data were independently analyzed by the two judges employed
in the first two experiments. Likewise, the data were objectively
scored by applying the operational definition of a reflex response which
was presented in the first experiment. In the third experiment, however, “4%
only those reflexes were considered which occurred while the CS was I
being presented. Again the judges were in perfect agreement in their
analyses and the results are summarized in Figures 10 and 11.

Criterion reflexes were elicited from all subjects in reaponse to
each UCS presentation during the conditioning trials. However, inspection
of Figure 10 reveals that no CRs were elicited from any subject in response
to the CS during the test trials. Likewise, inspection of Figure 11
reveals that there is no difference in the mean number of CRs obtained
from subjects across experimental groups. Therefore, the results
suggest that the middle ear reflex cannot be conditioned to a neutral
stimulus through either a simultaneous. conditioning paradigm or a
delayed conditioning paradigm in which various 1315 are employed.

The results of the present experiment were in agreement with the
results obtained by Simmons (196+). However, the results contradict
those obtained by Simmons et al. (1959), Mendelson et al. (1963) and
Brasher et al. (1969). Yet, as indicated above, a careful inspection
of the methodologies employed in each of these "successful" studies

1+0

. ;;éiee~ ‘-

~91

Mean Number of Reflexes
H ,

 

 

 

Test Trials

Figure 10. Conditioned reflexes elicited from all subjects
during simultaneous and delayed conditioning.

Mean Number of Reflexes

41

 

 

 

1 2 3 1+
Experimental Groups

Figure 11. Comparison of conditioned reflexes elicited in
each experimental group during simultaneous and
delayed conditioning.

a,

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42

reveals that all of the investigations contain significant methodological.
flaws. Specifically, all of the investigators failed to quantitatively
define a. conditioned reflex, failed to employ control groups, and failed
to control for voluntary motor activities which might elicit incidental
reflexes. In addition Simmons et al. (1959) and Brasher et al. (1969)
may have elicited startle responses from their subjects and thus con-
founded their results. (Alternatively, the present investigator quanti-
tatively defined the reflex response, made a determination of the
neutrality of the conditioned stimulus as a control procedure, reduced
voluntary motor activities through instructions to the subject and
reduced the possibility of startle responses by employing a stimulus
only 10 dB above the subject's reflex threshold.)

Thus, a careful review of the literature indicates that condi-
tioning of the middle ear reflex to a neutral stimulus has not yet been
demonstrated. Moreover, since Simmons (1961;) employed constantly
varying stimuli in his "unsuccessful” investigation of conditioning, the
present investigation of the conditionability of the middle ear reflex

is left as the most methodologica'lly sound study of this phenomenon.

   
  
    

 

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GENERAL DISCUSSION

In this section the nature of a CR remains to be considered lest
the present experiments be criticized at a later date for employing
excessively stringent criteria in defining a reflex contraction. The
implication of such a criticism could be that true CRs were overlooked
through the use of the chosen quantitative definition. Such a criticism
would be based on the assumption that CRs are never exactly the same
as their associated UCRs (Kimble, 1961). In point of fact, although
the form of the responses are generally similar, the magnitude of the
CR is decidedly reduced from that of the UCR. Indeed, inspection of
the "CBS" obtained by both Simmons et al. (1959) and Brasher et al.
(1969) reflects this similarity of form but reduction in magnitude of
the conditioned middle ear reflex.

In the present investigation the operational criteria were
developed under full awareness of the nature of the typical CR. In
fact, the criterion level magnitude proved to be less than one-fourth
of the typical UCR magnitude obtained from any subject in any of the
experimental groups. Nevertheless, an added precautionary measure was
taken to guard against the employment of excessively stringent criteria.
Specifically, a month after all of the criterion analyses were made,
the same judges again reviewed the data. During this final review no
criteria were employed and the judges were instructed merely to identify
any impedance changes that they even suspected could be related to the

presentation of the CS. Even under these instructions, however, no CR5

43

were identified. Therefore, it can be assumed that the criteria
employed in the present investigations to define a reflex contraction

were not excessively stringent.
Conclusions and Implications

Within the limits imposed by the instrumentation employed in the
present experiments and the subjects who participated, the following
conclusions seem warranted.

1. The middle ear reflex cannot be conditioned to a temporal

interval. a

2. Light does not serve as an unconditioned stimulus for the
middle ear reflex.

3. The middle ear reflex cannot be conditioned to a neutral
stimulus through either a simultaneous or a delayed
conditioning paradigm

1+. The conditionability of the middle ear reflex is not
differentially affected by the interstimulus interval
employed in a delayed conditioning paradigm.

Based on these conclusions, therefore, it appears that incidentally
conditioned reflexes do not serve as experimental sources of error.
Moreover, this implies a greater degree of validity may be assigned
to the results of past experiments which have investigated the role
of the middle ear reflex in auditory functioning. That is , based on
the present results, it does not appear likely that CRs confounded the
reported results.

Nevertheless, before conditioning is ignored as an experimental
variable, the results of the present experiments should be cross

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45

validated by other experiments. In particular, the following variables,
which have been proven to have significant effects on conditioning,
should be considered: age of subject, type of stimulation, and type
of instructions. Braun and Geislhart (1959), for example, demonstrated
that conditionability of the eyelid reflex decreases with age.
Moreover, Brackbill, Fitzgerald, and Lintz (1967) demonstrated differential
conditionability both as a function of the type of CS employed and as a
function of the age of the subject. Specifically, BrackbiJl, et al.
demonstrated that the pupillary reflex may be temporally conditioned in
infants but not in adults; yet the same reflex may be conditioned to an
auditory stimulus in adults but not in infants. Finally, Miller (1939)
illustrated the effects of various types of instructions on the rate of
acquisition and extinction of the conditioned eyelid response. He suggests
that the type of instruction may serve to either restrain or facilitate CRs.

The results of the present experiments also suggest that the middle
ear reflex may be grouped with reflexes such as the patellar reflex, the
abdominal reflex, the plantar reflex and the pupillary reflex, since all
of these reflexes are considered to be difficult to condition. Kimble
(1961) suggests, moreover, that any reflex which is resistant to condi-
tioning probably is only slightly involved in the processes of motivation
and reward. That is, these difficult to condition reflexes do not appear
to contain the same amount of drive reduction value as do easily con-
ditioned reflexes such as the eyelid reflex or salivation.

Finally, it could be argued that the middle ear reflex is not easily
conditioned because the middle ear muscle contractions are integral parts
of a general auditory processing system rather than isolated responses to

sufficiently intense auditory stimuli. Such an argument, moreover, would be

.llll'

 

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1.4 I

1+6

upheld by the results of several investigations which have been reviewed
above. In particular, the results reported by Sedlacek (1965) and
Lawrence (1965) suggest that the middle ear muscles are actively involved
in binaural hearing. Likewise, the results obtained by Liden et al.
(1963), Clubb (1965), and Jauhianen et al. (1967) suggest that middle
ear muscle activity is related to variations in speech discrimination.
Finally, the findings of Salomon and Starr (1963), Shearer and Simmons
(1965) and Djupesland (1965) all suggest that the middle ear muscles

are activated by motor control centers which initiate vocalization.
Therefore, if the middle ear muscles are assumed to be part of an
auditory processing system rather than isolated respondents, possibly
the total system would need to be involved before any conditioning
could be demonstrated.

LIST OF IEFEIENQS

 

emu-55:17:55: "ifl "3211.1

 

 

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BraSher, Po Fe, C0195, Re Re Ac. Elwodq Me An, and Farms. Ho Mo VThe
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Braun, H. W., and Geiselhart, R. Age differences in the acquisition and
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Carhart, R., and Jerger, J. Preferred method for clinical determination s
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’47

 

 

 

 

 

 

 

 

 

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... . . n. . ..
i - I.
I 1': ' ‘ . I n .-
5" " I. ;. . .'- . -
.- '.'. ' __ - u.' - _
I-- \~ ‘-—.I u... I h - l-‘lI-I I
v I I I' I I
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~ . . .
a ' - .. I o - "‘
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-. . _ . ‘ -.l '
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.-. '
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1+8

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(Whole No. 15 .

APPENDICES

 

SUBJECT VARIABLES

APPENDIZ.I

 

 

Subject Age in Impedance Reflex Sensation Hours Between
Number Years in KO Threshold Level of Experimental
in dB Threshold Sessions
Tepppral Conditioning Group
1 22.6 .32 95 90 21
2 20.8 .35 100 95 14
3 22.5 .43 90 85 21
4 24.8 .51 90 90 15
5 21 .4 .34. 90 90 14/20
Neutrality Determining Group
6 23.9 .42 90 85
7 22.2 .54 85 80
8 20.9 .38 90 90
9 24.7 .35 95 90
10 22.0 .43 80 75
Simultaneous and Delgypd Conditioning Groups
11 23.9 .44 95 90 24
12 24.3 .29 85 85 24
13 23.0 .33 100 90 21
14 24.6 .50 95 90 23
15 20.8 .45 95 85 18
16 20.5 .30 100 90 24
17 20.2 .56 85 85 20
18 20.8 .47 95 90 20
19 20.7 .35 90 90 23
20 24.1 .31 100 95 19
21 22.9 .42 85 80 21.
22 21 .0 .48 95 90 23

51

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ll-
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II 0'-
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52

Subject Variables , continued

 

 

Subject Age in Impedance Reflex Sensation I-burs Between
Number Years in Korma Thmshold Level of Experimental
in dB Threshold Sessions

23 21.8 .35 90 90 21

24 . 22.5 .ho 95 90 21"

25 21.1 .51 85 85 11+

26 20.0 .29 9O 90 15

27 23.1 .35 90 90 27

28 21.1 .37 85 85 21+

29 22.7 .4? 8O 80 18

30 22 .1» .1»? 100 95 20 i,

 

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APEENDIX II
NOISE DEVELS IN OCTIVE BENDS

 

 

Center dB levels, dB Levels,
Frequencies Equipment Equipmnt
in E! On Off
31 .5 51 50
63 no 38
125 #5 40
250 51 33
500 1&8 20
1000 #3 10
2000 #2 Less than 10
M00 1+1 Less than 10
8000 36 Less than 10
16000 22 Less than 10

53

n
w

 

APPENDIX III

EQUIPMENT
Temral Conditiom Grog
Screening
Portable Audiometer Beltane Model 10c (Calibrated to Leo)
Earphones ‘Ielephonics Model TDH 39 102

Earphone Cushions

Bone Oscillator

Ele ctro -Acoustic
Impedance Bridge

Calibration

Sound level Meter
Octave Band Filters
Microphones
Pistonpbone
Artificial Ear
Volt Meter
Artificial Mastoid
Amplifier
mectronic Counter
and Timer

Stimulus Presentation

Decade Timers (2)

Portable Audiometer
Earphone
Earphone Cushion

Response Measurement

Electm-Acoustic
Impedance Bridge

lbcording

Differential Amplifier
DC Power Supply

6 Volt Batteries (2)
Graphic Recorder

DC Amplifier

lblephonics Model nx ul/AR
Radioear B70A

Madsen Model 2070

Bruel 8: KJaer Type 2301}
Bruel & KJaer Type 1613
Bruel 8: Hear type 41M»
Bruel 8: Kjaer Type #220
Bruel & Kjaer Type 4152
Bruel & Kjaer Type 21509
Beltane Model HSA

Beltane Model M5A

Bckman Model 7370

Hunter Model 100C Series D

Hunter Model 1110 Series D

Beltane Model 10c (Calibrated to ISO)
Telephonics Model TDH 39 102
Telephonics Model 14x 41 [AR

Madsen Model 2070

Tektronix Type 2A63
Tektronix Type 129

Brush
Brush

 

 

 

 

 

 

 

 

 

-
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..
.
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55

Equipnent , continued
Neutralitz Detemi__n__ing Ggggp
Screening
Calibration
Stimulus Presentation
Decade Timers (2)

‘hngston Lamp
DC Power Supply

Reaponse Measurement

hoarding

Same as inexperimentI
Same as inexperimentI

Hunter Model 1000 Series D
HInter Model 1110 Series D
General Electric Model 51
Electronic Model 1020

Same as in eXperiment I
Same as in experiment I

Simultaneous and Balm“ d Conditioning Gmug

Screening

Calibration

Stimulus Presentation
Decade Timers (3)
Portable Audiometer
Earphones
Earphone Cushions
Mgston Lamp
DC Power Supply
Universal Timer

Response Measurement

Recording

Same as in experiment I
Same as in experiment I

Hunter Model 100C Series D (1)
Enter Model 1110 Series D (2)
Beltane Model 10c (Calibrated to ISO)
Telephonics Model TDH 39 102
Telephonics meal MX 41 IAR

General Electric Model 51

Electronic Model 1020

Dimco-Gray

Same as in experiment I
Same as in experiment I

 

 

 

 

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APPENDIX IV

SCHEMATIC WING DIAGRAM 0F TIMERS

Tamra]. Conditioning Groug and Neutralitz Dabemining Gnoug

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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General Notations:

Left Column
Center Column
Right Column

Open Relays
Common Relays
Closen Relays

56

INTERVAL TIMER

Relays 341+ Start Relays
Relays 15-26 Stop Relays

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continued

57

Simultaneous and Delmd Conditioning Groug

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APPENDIX V
IESCKEPTION OF THE MADSEN BRIDGE

The Madsen Electra-Acoustic Impedance Bridge was developed by
Terkildsen and Nielson (1960) for the dual purpose of measuring both
middle ear pressure and acoustic impedance. Moreover, construction of
the bridge (see Figure 12) reflects its dual purpose in that it contains
two separate measurement systems. However, both of these systems are
connected to the subject's ear via a single metal probe and rubber ear
tip.

The acoustic impedance section of the bridge consists of a loud-
speaker, a microphone, and a pure tone generator. The loudspeaker and
microphone are contained in a. metal case which is attached to a headband
worn by the subject. A 220 Hz oscillator generates a "probe tone" which
is applied to the loudspeaker and the resulting sound wave travels down
a rubber tube to one of three pipettes in the metal probe which is fitted
to the subject's ear. The microprnne, which is connected by a second
rubber tube to another of the probe pipettes, serves to monitor the SPL
of the probe tone in the ear canal by delivering the transduced voltage
through an amplifier to a bridge circuit and balance meter. The balance
meter is nulled by a SPL of exactly 95 dB in the ear canal. Moreover,
the SPL in the ear canal can be manually attenuated by compliance varia-
tions (a range of 0.2 to 5.0 so is provided).

The air pressure system of the Madsen Bridge consists of an electro-
manometer and a pump which are connected via. flexible tubing to the third

58

 

59

Madsen Bridge Description. continued

Oscillator "
220 Hz
Potentiometer‘
\

 
  
    

 

 

Manometer

 

 

 

Figure 12. Schematic diagram of principal components of the Madsen
electro-acoustic impedance bridge. (Jerger. 1970. P. 313)

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Hadsen Bridge Description, continued

probe pipe. The pump permits variations in air pressure in the ear
canal over a range of 1&00 mm (water pressure). The air pressure is

read on the electro-manometer. When the air pressure is set at +200 mm
the associated compliance reading is almost totally determined by the
ear canal space. However, when this artificial pressure is reduced, the
compliance increases and reaches a maadmm when the pressures in the ear
canal and middle ear are identical. i.e. when the ear drum is in the
midline position. In the present investigation. all measurements of the
middle ear reflex were made from the midline position.

Fl.—

 

 

 

 

 

APPENDIX VI
s'mmms AND WE ECORDINGS

Condit Trials 5 9 Eco

 

Top Graph: Response Signal
Bottom Graph: Stimulus Signal

61

Recordings , continued

Test Trials S 9 Race

 

Top Graph: Response Signal
Ettom Graph: Stimulus Signal

 

APPENDIX VII
INFORMATION SHEET

Name Subject Number
Age: Years Months
1st Session: Date Time

W

2nd Session: Date Time
Impedance Values:

200 mm (21) Midline (22)

m—

Plane (2):) where 21: = 21 x 22
21 - ZZ

 

Reflex Threshold Sensation Level

63

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APPENDIX VIII
INSTRUCTIONS

Tam rel Conditioning Greg

1. Your job in this experiment is to maintain a relaxed
attitude and remain quietly seated. During the exper-
iment you should keep the back of your head against
the cushion on the top of the chair and look at the
wall in front of you.

2. All head movements need to be kept at a minimum during
the experiment. In particular, whenever you hear a
tone in your left ear, do not swallow, blink your eyes
or make any other movements of your eyes, mouth or
throat. Remain perfectly still while the tone is on.

3. The tone will come on for short periods of time
throughout the entire experiment. The time intervals
between the tone onsets will be constant.

it. Do you have any questions?
5. The experiment has begun.

Neutralitz Detemining Greg

1 . Your Job in this experiment is to maintain a relaxed
attitude and remain quietly seated. During the exper-
iment you should keep the back of your head against
the cushion on the top of the chair, and look at the
light bulb in front of you.

2. All head movements and to be loept at a minimum during
the experiment. In particular, whenever you see the
bulb light up do not swallow, blink your eyes or make
any other movements of your eyes, mouth or throat.
Remain perfech still while the light is on.

3. The bulb will light up for short periods of time
throughout the entire experiment. The time intervals
between the light onsets will vary.

’4. Do you have any questions?

5. The experiment has begun.

6h

 

 

65

Simultaneous Conditioning Group

1.

3.

4.
5.

Your job in this experiment is to maintain a relaxed
attitude and remain quietly seated. During the exper-
iment you should keep the back of your head against
the cushion on the top of the chair, and look at the
light bulb in front of you.

All head movements need to be kept at a minimum during
the experiment. In particular, whenever you see the
bulb light up and you hear a tone in your left ear, do
not blink your eyes, swallow or make any other movements
of your eyes, mouth or throat. Remain perfectly still
while the light and the tone are on.

The light and the tone will come on together for slmrt
periods of time throughout the entire experiment. The
time intervals between the onsets of the light and tone
will vary.

Do you have any questions?

The experiment has begun.

Delmd Conditioning Group

1.

Your job in this experiment is to maintain a relaxed
attitude and remain quietly seated. During the exper-
iment you should keep the back of your head against
the cushion on the top of the chair, and look at the
light bulb in front of you.

All head movements need to be kept at a minimum during
the experiment. In particular, whenever you see the
bulb light up, do not blink your eyes, swallow or make
any other movements of your eyes, mouth or throat.
Remain perfectly still while tin light is on. A short
time after the light comes on you will hear a tone in
your left ear. The tone will go off at the same time
as the light.

The light, followed by a tone, will come on for short
periods of time througlbut the entire experiment. The
time intervals between the light onsets will vary.

Do you have any questions?

The experiment has begun.

APPENDIX DC

STIMULUS SEQUENCE PRESENTATIONS 1N EXPERIMENT H

 

 

Trial Stimulus Trial Stimulus
1 Light 26 Light
2 Light 27 Empty Interval
3 Light 28 Light
4 Light 29 Empty Interval
5 Empty Interval 30 Empty Interval
6 mnpty Interval 31 Light
7 Empty Interval 32 Empty Interval.
8 Empty Interval 33 Light
9 Empty Interval 3“ Light
10 Light 35 Light
11 Empty Interval 36 Light
12 Light 37 Empty Interval
13 Light 38 Empty Interval
14 Empty Interval 39 Empty Interval
15 Light ‘00 Light
16 Empty Interval 41 Empty InterVal
17 Empty Interval 42 Light
18 Empty Interval 1&3 Light
19 Light 154 Empty Interval
20 Light 45 Light
21 Empty Interval #6 Light
22 Empty Interval #7 Light
23 Empty Interval #8 Empty Interval
2“ Empty Interval 49 Empty Interval
25 Light 50 Light

66

APPENDH X
mERTRIAL HERVALS EMPLOYED IN EXPERJIENT III*

 

 

Trial Interval in Seconds Trial Interval in Seconds
1 30 20 1+5
2 1&5 21 60
3 1+5 22 60
u 30 23 60
5 #5 2’4 45
6 6O 25 30
7 30 26 3o
8 60 27 45
9 60 28 3o

10 6O 29 30
11 30 30 £15
12 1&5 31 60
13 30 32 45
1h . 30 33 us
15 #5 34 #5
16 45 35 30
1? 45 36 6O
18 30 3? 1&5
19 45 38 “5

 

*The interval values presented depict the intervals between
successive UCS presentations. For group 1 . this interval also
represents the time between successive CS presentations. Ibwever,
in the other experimental groups the exact interval between
successive CS presentations would be reduced by 0.5, 1.5. and 2.5
seconds respectively from the values presented.

67

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Intertrial Intervals , continued

 

 

Trial Interval in Seconds Trial Interval in Seconds
39 30 70 60
1+0 60 71 30
#1 30 72 60
#2 ‘ 6o 73 6o
43 60 7h 30
44 30 75 30
115 60 76 30
46 #5 77 60
h? 30 78 “5
48 30 79 60
49 30 80 30
50 us 81 us
51 3o 82 45

30 83 45
53 #5 84 30
5h 30 85 30
55 45 86 30
56 6o 87 30
57 60 88 30
58 30 89 45
59 60 90 #5
60 45 91 6o
61 60 92 3o
62 30 93 60
63 30 9h 30
61+ 30 95 60
65 1&5 96 115
66 30 9? 45
67 30 98 3o
68 60 99 30
69 #5 100 60

 

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APPENDIX XI
IN'IERSTMIIDS IN‘IERVALS EMPLOYED IN EXPERIMENT m

 

 

Experimental Group Average ISI Range of ISIS
in MSec in MSec
1 3 2 - 3
2 516 512 - 520
3 1502 1495 - 1507
a 21181 2h75 - M85

69

 

 

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