‘—v .

 

THE EFFECTS OF SPACENG OF TRAiNING
AND EXTIRPAHGN OF CEREBRAL
GANGUA ON THE flNCONDETiONED
RESPONSES OF EARHWORMS

Thesis {m- f'hc Degree 0? M. A.
MICHEGAN STATE BRE‘JERSET’Y
Donaici Geraid Stein
1962

73485293

 

THE EFFECTS OF SPACING OF IRAINING-AND EXIIRPAIIOH
OF CEREBRAL GANGLIA ON THE UNOONDITIONED
RESPONSES OF EARIHWORMS

By

Donald Gerald Stein

AN ABSTRACT

Submitted to
Michigan state University
in partial fulfillment of the requirements
fer the degree of

EASIER OF ARTS

Department of Psychology

1962

ABSTRACT

THE EFFECTS OF SPAOING OF TRAINING AND EXTIRPATIOR
OF CEREBRAL GANGLIA ON THE UNOONDITIONED
RESPONSES OF EARTHWORMS

by Donald Gerald Stein

Ninety-six earthworms were divided into 6 surgical
treatment groups. Half of the animals in each group
received massed presentation of a strong photic stimulus
while the other half received spaced presentation of the
US. Frequency, direction, and latency of URs were recorded
for all groups. Results showed that normal worms made
fewer URs under massed trial conditions than under spaced
trials although the direction of URs did not change. Dur-
ation of ITI did not appear to affect the degree of adapta-
tion of the UR to light for the normal, intact worm.

No differences in latency, frequency or direction were
obtained for §g.with either sub- or suprapharyngeal ganglia
removed for comparisons made within the same III. These
g; were consistently positive to the US as compared to the
negative URs of the intact animal. No evidence of specificity
of function of the cerebral ganglia was obtained regarding the
worn's UR to light.

Operated worms did not differ from normal §g_under

massed trial conditions. However, extirpation of neural

Donald Gerald Stein
tissue and long III were found to decrease frequency and
increase latency of URs for the operated groups. Direction
of the URs was not affected by spacing of training. Adapta-
tion of the UR occurred under both massed and spaced trials
but appeared more pronounced under spaced trials.

Results cannot be interpreted in terms of existing
statements of neural function of invertebrates. At the
descriptive level, results suggest that operated worms become
response-bound while normal worms remain stimulus-bound

with regard to reactions to light.

5353::st

.l’) I7GL

TO DAREL

THE EFFECTS OF SPACING OF TRAINING AND EXTIRPATION
OF CEREBRAL GANGLIA ON THE UNCONDITIONED
RESPONSES OF EARTHWORMS

By

Donald Gerald Stein

A THESIS

submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF ARTS

Department of Psychology

1952

\i

ACKNOWLEDGMENTS

The author would like to express his gratitude to
Dr. Stanley 0. Ratner for his guidance and help which was
freely given whenever needed, and to Dr. Donald Montgomery
of the Physics Department whose loan of valuable equipment
made this research possible. The author would also like
to thank Dre. C. Henley and A. .Barch for their careful
review and criticism of the experimental design.

11

ACKNOWLEDGMENTS
INTRODUCTION .
METHOD . . . .
RESULTS . . . .
DISCUSSION . .
SUMMARY . . . .
APPENDIX . . .
REFERENCES . .

TABLE

OF CONTENTS

111

Page
ii

14
27
36
38
48

LIST OF FIGURES

Figure Page

A. Diagram of cerebral ganglia in the earthworm,
anbricus terrestris . . . . . . . . . . . . . 10

1. Median frequency of responses for 6 second
ITI groups . . . . . . . . . . . . . . . . . . 15

2. Median frequency of responses for 88 second
ITI groups 0 O O O O O O O O O O O O I O O O O 16

3. Median latency of responses for 6 second ITI
groups . . . . . . . . . . . . . . . . . . . . 22

4. median latency of responses for 88 second ,
ITIgroupaeeeeeeeeeeeeeeeeee 23

iv

LIST OF TABLES

Table Page

1. Statistical analysis employing the Mann-
Whitney Q,test to determine if spacing
of trials (ITI) affects the fzeguency
OfURBt°116hteeeeeeeeeeeeeeee39

2. Statistical analysis employing the Mann-
Whitney g,test to determine if "surgery"
affects freguency of URs to light under
massed trial conditions . . . . . . . . . . . . 4O

3. Statistical analysis employing the Mann-
Whitney Q_test to determine if "surgery"
affects freguency of URs to light under-
spaced trial conditions . . . . . . . . . . . . 41

4. Statistical analysis employing the Fisher
Exact Probability Test to determine if
duration of ITI affects the direction of
URB to light 0 O 0 O O O O O O O O O O O O O O 42

5. Statistical analysis employing the Fisher
Exact Probability Test to determine if
surgical treatment affects the gizggtigg
or me to light 0 O O O O O O O O O O O O 0 O O 43

6. Statistical analysis employing the Mann-
Whitney U test to determine if duration of
ITI affects the latency of URs . . . . . . . . 44

7. Statistical analysis employing the Mann-
Whitney Q_test to determine if surgery
affects the latency of URs under spaced
trial conditions . . . . . . . . . . . . . . . 45

8. Statistical analysis employing the Mann-
Whitney g_test to determine if surgery
affects the latency of URs under massed
trial conditions . . . . . . . . . . . . . . . #6

9. Statistical analysis employing the Binomial
Test to determine if there is a difference in
frequency of URs between the first block of
trials (1-10) and the last (51-60) . . . . . . 47

INTRODUCTION

Use of the Annelid, Lumbzicus tgyrestyis, as an experi-

mental subject is not a recent phenomenon. Darwin (1881),
attempted some research into the "habits and intelligence"

of the earthworm, but his studies were rather crude and poorly
controlled and.not much data could be gleaned from them.
Yerkes (1912), using one subject, demonstrated that an
earthworm can learn to make a discriminatory response in a
simple T-maze when differential reinforcement to each side

is given. For the most part, early research on annelid
behavior dealt with the attempt to modify rather than specify
the worm's responses to its environment. In addition, little
emphasis was placed on the study of the neural mechanisms
involved in the organism's behavioral responses.

The physiology and morphology of L. tegyestyis are well
understood due to the efforts of the comparative physiologists
and ecologists (Hess, Presser, Stevenson, gt_§1,). Research-
ers in these areas provided much information as to the classes
of stimuli to which the organism is sensitive. However, these
workers were not generally interested in the peculiar char-
acteristics of the earthworm's behavior and.the conditions
under which it could be made to vary.

One of the early attempts to specify the function of
the ”cerebral ganglia" in earthworms was made by Heck (as

1

2

reported in Presser, 1950). Following Yerkes (1912), he
found that earthworms are capable of learning a simple T-
maze, and that removal of the ”cephalic ganglia" does not
result in the loss of an "acquired habit" until the new
segments have been regenerated. Bees (1924) studied the
reactions of Lumbricus terrestris to light of varying intensity
under several surgical conditions. He found that removal of,
the cerebral ganglia caused earthworms to become ”definitely
positive in their reactions to lights of moderate intensity
and that this behavior also occurs when the suprapharyngeal
lobes are separated, although to a lesser degree” (p. 541).
He further determined that the cerebral ganglion ”is the
controlling factor in negative reactions to strong and
moderate stimuli." Presser (1950) in a review of his own
research states that the cerebral ganglia of the earthworm
control the animal's behavior and motor reactions to various
types of interoceptive and exteroceptive stimulation.

much of the research dealing with the functions of the
ganglia has been contradictory. For example, some workers
reported that extirpation of the cerebral ganglia caused
no differences in behavior (Buddenbrock, Friedlander, Steen-
Maxwell), while others have reported that removal of the sub-
and suprapharyngeal ganglia has modified behavior in several
ways (Hayner and Zellner, Ratner and Miller, Ratner). In
many of these studies, however, sample size was very small,

the responses being observed were not clearly specified, and,

3
in several cases, the procedures were difficult to under-
stand. It is possible that these factors would explain some
of the discrepant findings reported by these workers.

In more recent research, Wayner and Zellner (1958)
demonstrated that removal of the suprapharyngeal ganglia is
related to a decrease in the number of negative responses
at a choice point in the simple T-maze. They theorized
that such removal increases reactive inhibition, therefore
decreasing the number of alternations at the choice point.
Swartz (1929), using a T-mase with electric shock in one
arm of the maze, found that worms formed an ”association”
with the correct (shockless) direction of turning. The
"habit" was not lost after removal of the suprapharyngeal
ganglia, and worms from which the anterior segments had
been removed learned the habit (p. 33). Bharucha-Reid
(1961) attempted to demonstrate that directional behavior
can be influenced by differentially removing either the
right or left lobe of the suprapharyngeal ganglia. She
reported that when the worms were placed in a choice situa-
tion, they would turn to the side Opposite that from which
the lobe had been removed. However, study of her procedures
suggested that the ganglia of'her subjects had regenerated
so her conclusions are not firm.

Until 1959. all of the research.dealing with learning
in the earthworm and the functions of the ganglia in such
learning, had utilized the instrumental learning situation;

4
for example, the T-maze. Rather and Miller (1959a, b)
utilized classical conditioning procedures for the study of
annelid behavior. In the first study (1959s), it was
demonstrated that a withdrawal response to strong photic
stimulation could be conditioned to occur to a weak vibra-
tory stimulus. It was also found that the duration of the
intertrial interval influenced the percentage of conditioned
responses. That is, animals trained.under spaced trials
showed a higher percentage of 083 than animals trained under
massed trial conditions. The more recent studies (1959b,
1962) were designed to investigate the effect of both
removal of "cephalic ganglia” and spacing of trials on
conditioning of a withdrawal response. It was found.that
the non-operated (normal) spaced trials group had the highest
percentage of Gas while the operated spaced trial group did
not condition at all. The operated massed trials group had
about 60 per cent one which was significantly different
from the operated control groups and the operated spaced
trials groups whose responses were almost negligible.

I Ratner (1962) showed that decerebrate worms condition
when tested under massed trials even when given a long delay
in the apparatus. When conditions were reversed from massed
to spaced trials, the percentage of URs decreased for the
operated worms. Rather concluded that duration of inter-
trial interval and not confinement in the apparatus was
responsible for the decrease in the percentage of one for

decerebrate worms. Thus, "failure in conditioning of

5
decerebrate worms trained with spaced trials. . .is based
on some particular relationship between decerebratien and
spacing of training.’ It was further determined that
removal of the anterior five segments of the worm inhibited
not only the URs but suppressed the URs to the photic stimp
ulus as well. However, no specification of the role of the
sub- and suprapharyngeal ganglia in the unconditioned responses
of the earthworm has been undertaken. Defining the function
of each of the neural centers in the responses of ngbyicug
teygegtgis would be a contribution to the neurophysiology
of learning and the mechanisms involved in it.

Problem

The present experiment was designed to study the effect
of: (1) differential extirpation of the suprapharyngeal
and subpharyngeal ganglia, and (2) spacing of trials on the

unconditioned response to strong photic stimulation of the

earthworm, Lumbricug terrestris.

METHOD

Appgpatus
The part of the apparatus which.held the worm during

the experiment consisted of clear, round, non-toxic "Tigon"
plastic tubing with a 3/8-inch internal diameter. The
tubing was ventilated by small holes located at 1/2-inch
intervals on both the sides and the top of the tube. Both
ends of the tube were fastened together with a piece of
clear plastic of a larger internal diameter to form a com-
plete circle. The tube was then placed in a square plywood
box 10 inches on each side and 2.5 inches deep. To increase
reflectance from the photic source and.insure equal stimu-
lation on all sides of the tube, the floor and sides of the
box were covered with translucent plastic sheeting.

A standard #2 photoflood lamp in an aluminum reflector
was mounted 39.5 inches above the table top, the bulb it-
self being 24.5 inches directly above the tube. This
source provided the photic stimulation used as the uncon-
ditioned stimulus (US). At all times during the experiment,
an 8 watt dark red bulb was used to provide a low level of
illumination for the experimenter. Previous research
(Hess, 1929) showed that earthworms of this species are
insensitive to the red end of the spectrum.

6

7

Presentation of the US was automatically timed by Meylan
interval timers. One timer presented the US every 6 seconds
and the other every 88 seconds. In both cases presentation
consisted of two second durations. Latency ef the uncon-
ditioned response (UR) was timed by a Lafayette timer acti-
vated by a microswitch operated by the experimenter when the
onset of the UR.was observed to occur.

In order to prevent any extraneous vibration from influp
encing gig responses, all parts of the apparatus that could
have produced vibration or were sensitive to it were padded
with pieces of foam rubber. This included the base on which
the tube rested, the experimenter's writing surface, and the
Lafayette timer.

To reduce any increase in temperature produced by the
photic source, the floor of the box on which the tube rested
was sprayed with cool water before and between trials,
especially for the 88 second ITI groups which remained in
the tube and apparatus for one hour and forty minutes. An
attempt was made to keep room temperature below 65° F. during

the time the experiment was in progress.

Subjecps
Ninety-six earthworms, Lppppiggp'terpestpip, with an

average weight of 3.8 grams,were studied. The annelids were
obtained from the Tanner Bait Supply Company in New York
State. Upon receipt, the worms were taken from their ship-
ping cartons and placed in a large plastic container filled

8
with fresh sphagnum moss and humus which was kept in a refrig-
erator at a temperature of 40° P., 13°. Approximately 250

worms were kept in this container from which.the sub-sample

studied was drawn.

Surgicpl pppcedure
Immediately prior to the surgical treatment, a number

of worms were haphazardly selected from the large container
using a forceps to grasp them. Each animal was then placed
in a small non-toxic plastic freezer carton with a bed of
moist sphagnum moss and a ventilated lid. The animals chosen
were then weighed and randomly assigned to one of the follewb
ing surgical treatment groups:

normal, non-operated (Normal)

sham-operated dorsal side (SD)

sham-Operated ventral side.(SV)

anterior five segments removed (5-seg-R)

suprapharyngeal ganglia removed (Sup-R).
subpharyngeal ganglia removed (Sub-R)

H0906”

Each of'the surgical treatment groups contained 16
worms and each of these groups was subdivided after surgery
into a group which received massed trials and a group which
received spaced trials. This variable will be discussed
below. Excepting the 5-seg-R.group, §p_were placed on a
piece of non-toxic plastic sheeting and were anesthetized
with 2 ml. of .008 per cent solution of chlorotone (6.25
gms. chlorobutynol crystals per 125 cc. distilled water).
Anesthetized animals were allowed to remain in the solution

approximately 10 minutes, or until tactual stimulation with

9

a glass probe produced no response of contraction or move-
ment. When no response could be elicited, Slwas removed
from the anesthetic with a forceps and placed on a styre-
foam dissecting board covered with a clean and thoroughly
moistened cloth. The anterior portion of the animal was
held in place by a strip of white paper placed over §_and
pinned on either side to the board. The board with §,on it
was then placed on the stage of a binocular dissecting
microscope. This allowed E to observe the ganglia more
clearly and facilitated extirpation of the neural tissue.

In the SD and Sup-R groups, an incision was made on
the dorsal side of the animal from the first to the fifth
or sixth anterior segment. If §,were in the sham dorsal
group (SD), the incision was made and'§ was checked for
bleeding and damage to the suprapharyngeal ganglia. If
bleeding occurred or if the ganglia appeared to be dis-
turbed in any way, the animal was rejected and another
chosen. After the "operation" the worm was returned to
its individual container and placed in the refrigerator for
48 hours. Animals whose ganglia were removed were incised
in the same manner except that small hemostats were attached
to the musculature on either side of the incision to hold it
epen and expose the ganglia. The circumpharyngeal connectives
were severed, the sub- pp.suprapharyngeal ganglia removed,
the hemostats removed, and the animal returned to its con-
tainer and placed in the refrigerator for the 48-hour recov-

ery period.

1O

 

.udaaueaaoe .lldllllmse .333
.saosnpfio one 5 335m detaches no 5933114 enema

 

 

11

A similar procedure was carried out for the sham ventral
(SV) and Sub-R groups except that the incision was made on
the ventral surface from the second to the seventh or eighth
segments.

In the 5-seg-R group, no chlorotone was administered.
The animals were placed on a plastic sheet moistened with
tap water and the anterior five segments were removed with a
very sharp razor blade. The sectioned segments were then
examined to make certain that the ganglia had been completely
extirpated. The p was then returned to its individual con-
tainer, placed in the refrigerator and.given the 48-hour
recovery period as were all other Sp,used in the experiment.

The non-operated.normal animals (Normal) were simply
weighed, placed in their containers and returned to the
refrigerator for’the same amount of time allowed for the

recovery period of the operated groups.

Teptipg procedupg
After the 48-hour'recovery period, §,was removed from

its container and placed in the Tigon plastic tube which had
been moistened with .6 cc. of tap water immediately prior to
‘Qip entry. To help eliminate contamination from salts and
other substances on the D's hands, all‘gg‘were handled with
rubber gloves while being placed in the tube. The worm's
anterior portion was placed in the tube while gently stimu-
lating the posterior portion of the animal. When §,was
completely in the tube, the ends were fastened together so

12
as to form a complete circle for §_to transverse. The tube
with S inside was then placed on its base and a 10-minute
"dark adaptation period" was allowed for each.animal prior
to the onset of the trials.

The eight is assigned to the M m cpngtion
from each surgical group were given a total of 60 trials
with an intertrial interval of 6 seconds. The US was pre-
sented on each trial. Thus, for Sp,in these groups the US
was presented for two seconds followed by the 6 second ITI
period. Responses to the Us were observed during the 6
second period, after which another US presentation occurred.
The entire procedure including the habituation to the tube
and darkness required 18 minutes for each.animal. The‘gp
assigned to the spaced trial condition (88 second ITI) were
also given a total of 60 trials in which.the US was presented
on every trial. Thus, for S; in these groups the US was
presented for 2 seconds followed by the 88 second ITI period.
Responses to the US were observed during the first 6 seconds
of the 88 second period, after which another US presentation
occurred. The entire procedure for this group, including
the habituation period, took one hour and 38 minutes for
each animal. In both conditions, the US was presented for
a total of 2 seconds on each trial. No subjects were given

both massed and spaced trials.

Measurement

The UR.can be described as follows: (1) a withdrawal

13
and/or contraction extending approximately for 1/4 to 1
inch in length of the anterior segments of‘gig body.
(2) A rapid forward movement of approximately the same
length of the anterior portion of'SLg‘body. If the worm
happened to be moving at the time the US was presented the
response consisted of an abrupt stop followed by either
of the responses described above. A response occurring
before 6 seconds had lapsed from the onset of the US was
recorded as an unconditioned response. Prostomial movement
was‘ggt_cansidered to be a UR. In operated subjects a for-
ward movement was observed to occur more often than a with-
drawal response. Therefore, the direction of glglresponse
was recorded as either a forward (F) or withdrawal (I)
reaction. The time lapsed between the onset of the US and
the beginning of the animal's response was recorded for all
groups and.has been designated as latency of response.
Records were also taken of the number of times a worm
doubled back or turned around while in the tube. During
the 6 second ITI, an assistant recorded latency, frequency
and direction of URs, thus allowing E to observe the worn
for the entire 6 second ITI period.

In order to reduce Judgmental bias, the identity of
the group to which §,belonged was not known by E (except
5-seg-R) until after the last trial had been completed.
Animals studied on any given day were chosen by the date in
which they were placed in their individual containers.

RESULTS

Frequency of unconditioned responses

Three measures of SLgDURs were taken-for all groups:
frequency of response, direction of response, and latency of
response. Figures 1 and 2 present the median frequency of
'URs for the Nbrmal, SD, SV, 5-seg-R, Sup-R, and Sub-R groups
subjected to the 6 second and 88 second ITI.

To determine if spacing of trials affected the total
number of URs to light, the Hilcoxin test (Uilcoxin, 1949)
for groups of replicates was used. The median frequency of
URs was 33 URs for the massed trial groups and 24 URs for the
spaced trial groups. The sum of the ranks of frequency of
URs was found to be 369.0 for the massed trial group and
261.0 for the spaced trial group. The probability of ob-
taining a rank total of 369 as compared to a rank total of
261 is less than 0.01. Thus, it was concluded that the groups
given massed trials had a significantly greater total number
of URs to light than did §§,given spaced trials.

Observation of'Figures 1 and 2 suggests that an inter-
action exists between surgical treatment and intertrial
interval. That is, it appears that the effects of surgical
treatment on total frequency of URs vary according to the
temporal conditions under which g; are tested. This obser-
vation was tested by using a non-parametric test for Inter-
action as described in Wilcoxin (1949). A.highly significant

14

MEDIAN FREQUENCY OF URs

fl 15

Figure 1.--Median Frequency of Responses for 6 Second
ITI Groups

 

 

 

3."; Normal *-—--—*
SD . ....... .

1 3V c——————-—o
3 5-seg-R o— ----- —o
2 .__,: Sup-R x——-—~x
§ Sub-R ..__...._.

 

 

 

 

BLOCKS 0F TRIALS

MEDIAN FREQUENCY OF URs

F

 

16

 
  
  
  

Normal o———-——-0

SD e ~~~~~~ 0
SV o———-———o

 

 

 

 

1 1 l
l 2 3 4 5 6
BLOCKS OF TRIALS

Figure 2.--Median Frequency of Responses for 88 Second ITI

fl r

17
interaction (x2, = 21.12, p .001) was obtained.

To determine if spacing of trials affected total fre-
quency of URs between groups which received the same
surgical treatment, Mann-Whitney'g tests (hereafter referred
to as Q,tests) were made by comparing the total frequency
of URs in each group given the 6 second ITI with its equiva-
lent group given the 88 second ITI. Table 1 presents the
median total frequencies, Q_values, and the probabilities
associated with them for each comparison. It can be seen
that the Normal massed trial group differed significantly
from the Normal spaced trial group in the total number of
URs to light (9.: 8.5, p .007). Thus, for the Normal
animals, frequency of URs was greater under spaced trials
than under massed trials. Both the Sup-R and Sub-R massed
trials groups differed significantly from their spaced
trials counterparts (g,= 5.5, p .002; 2,: 7.0, p .003
respectively). In both cases the frequencies of URs was
significantly higher for‘gg tested with massed trials than
for §§,tested with spaced trials. No significant differ-
ences were obtained for the SD, SV, or 5-seg-R comparisons.

To determine if "surgery” had an effect on the total
frequency of URs, Q_tests were performed comparing some
massed trials groups with other massed trials groups and
some spaced trials groups with other spaced trials groups.
Table 2 in the Appendix shows the comparisons that were
carried out between groups tested with massed trials. Not

all comparisons were made because some groups obviously did

18
not differ. Thirteen Q,tests were performed.and no signi-
ficant differences were obtained for the massed trial
groups. The same statistical procedure was carried out for
those'gg tested with spaced trials. All possible comparisons
, were made and Table 3 in the Appendix presents the median
total frequencies, theig values, and associated.p,values.
Comparisons between the Normal group and each of the other
spaced trials groups, including groups SD, SV, 5-seg-R,
Sup-R, and Sub-R, shows that in all cases the glvalues were
highly significant. Total frequency of URs in the Normal
group were significantly greater than the total frequency
of URs for each of the surgically treated groups. In addition,
significant Q,values were obtained when the sham-operated‘gg
were compared with their ganglion extirpated counterparts
(e.g. SD--Sup-R, SVe-Sub—R). In both cases the total fre-
quency of URs was greater for the sham-operated animals. A
significant difference in total frequency of URs was found
comparing the sub-R and 5-seg-R groups. No significant
differences were found between sham-operated §§_nor were
there any significant differences between sham-operated
animals and those with their anterior five segments removed.
No significant differences were found between Sup-R and Sub-R
§3,although it appeared as if there were a "trend” towards
greater frequency of responding in the Sup-R group. When
5eseg-R‘gg were compared with Sup-R.and Sub-R.respectively,
it was found that no differences in total frequency of URs
existed between the 5-seg-R and Sup-R animals.

19
In summary, frequency of URs was greater in the surgi-
cally treated §§_given massed trials than for the equivalent
surgical groups given spaced trials. This relationship,
however, did.not hold for the NormalԤ3,whose total frequency

of URs was depressed by massed trials. See Figures 1 and 2.

Direction of response
To assess whether ITI affected the direction of S's

response, the Fisher exact probability test was used (Siegel,
1956). Anl§ was assigned to category F (forward) if greater
than 50 per cent of its total URs were forward. If greater
than 50 per cent of its URs were withdrawals, §_was assigned
to category W (withdrawal). Table 4 presents the comparisons
made and their significance levels. In comparing §§,receiv-
ing massed trials with their spaced trials counterparts, no
significant differences were obtained. It can be concluded
that in this sample spacing of trials (ITI) did not influence
the direction of URs.

To determine the effects of surgical treatment on the
direction of the response, the Fisher exact probability test
was again employed. Now, instead of comparing groups tested
under different ITIs, groups tested under the same ITI were
individually compared. The same criterion described above
was used to assign §§,to either the F (forward) or H (with-
drawal) category. Within the 6 second ITI significant differ-
ences in total frequency of forward response were obtained

between the Normal and ganglionic tissue removed groups,

20
i.e. Sub-R, Sup-R, and 5-seg-R animals. Although a highly
significant difference was obtained between the SD and Sup-R
groups (p .01), no significant difference was obtained
between the SV and Sub-R groups. No significant differences
were found between the Normal and sham-operated groups (SD,
SV). Similarly, comparisons between groups in which the
ganglia had been removed (5-seg-R, Sub-R, Sup-R) yielded
no significant differences. An interesting finding was
that the 5-seg-R group (with both sub- and suprapharyngeal
ganglia removed) did not differ significantly from either
the Sub-R.or Sup-R groups.

When the same comparisons were made between groups given
the spaced trials, the identical results were obtained. Table
5 in the Appendix presents the comparisons that were made
and the probabilities of obtaining the observed differences.
The fact that the results were identical for both the massed
trials and spaced trials groups is taken as evidence that
surgical removal of the "cerebral ganglia" and not spacing
of trials (ITI) affects the direction of,§L§,URs to light.

Latency of response
In order to determine if spacing of trials had an effect

on latency of URs, the Wilcoxin test for groups of replicates
was used (19#9). The median latency of URs was 3.31 seconds
for the massed trial groups and 6.00 seconds for the spaced
trial groups. The sum of ranks of median latency of URs was
found to be 241.5 for the massed trial groups and 388.5 for

21
the spaced trial groups. The probability of obtaining a
rank total of 388.5 as compared to a rank total of 241.5 is
less than 0.01. Thus, the overall latencies of the URs
were significantly shorter for the massed trial‘gg than for
§§,tested under spaced trials (see Figures 3 and 4). This
is consistent with the finding that‘gg tested under massed
trials have a significantly greater total frequency of URs
than §§ given spaced trials.

Q_tests were used to compare latencies of URs between
groups given massed trials or spaced trials. Both the Sup-R
and Sub-R massed trial groups were found to have significantly
shorter latencies than their spaced trial counterparts.
.Mbdian latencies of the Normal spaced trial group and Nbrmal
massed trial group were leagt_different of all the groups
compared (median latency spaced = 2.31, median latency
massed, 2.32). A finding consistent with the frequency data
was that no significant differences were obtained when 5-seg-R
massed Sg,were compared with their spaced trial counterparts.
In all the other comparisons no significant differences were
obtained. The "trend," however, is towards shorter overall
latencies for operated.§g tested under massed trials. Al-
though spacing of trials affects the latency of URs in the
Sup-R and Sub-R fig, it does not seem to affect the overall
latency of URs for g; with both supra- and subpharyngeal
ganglia removed (5-seg-R group). Table 6 in the Appendix

presents the g_values and other relevant information.

MEDIAN LATENCY OF URs

6

I

.7

Figure

 

1
J.

--Nedian Latency of Reaponses for 6 Second ITI
Groups

 

 

    

Normal
SD

SV
5-seg-R
Sup-R
Sub-R

 

 

BLOCKS OF

I
4
TRIALS

o____———e

o _____ c

x x

I————-——0
6

MEDIAN LATENCY'OF.UR8

 

23

Figure 4.-+Median Latency of Responses for 88 Second ITI
Group

 

 

 

 

M I I _ ‘fl—ngé: —_ 8 %
“”w J "" .._—.— “I.“
——9 "-

/ / I

/
. /
/ ’
/ /
/ / Normal *“-——"
/ 0/ / SD . ————— C
/ /
./ / / SV D«-—-——-——-——(:
,' f O ““““ /
5 // “‘0‘ ~~~~~ d’ 5-seg-R o —————— c
/ -
/ X /
/ f / Sub-R ‘———-~’
0 If /
1 /
‘ /
g! /
i /
.' /
f /
//
1/ .
I
/ \
o
‘\

‘\\\\\\\\’fl/wflf”’,,

 

T l I I [
1 2 3 4 5 6
BLOCKS OF TRIALS

24
To determine the effects of "surgery" on overall

latency of URs U_tests were made between the groups within

 

each ITI. Under spaced conditions, highly significant
differences were obtained between the Normal and all the
other remaining groups. Normal animals had significantly
shorter latencies than did the sham-Operated (SD, SV) and
ganglionic extirpation groups (Sup-R, Sub-R, 5-seg-R). The
§p_most similar to the Normal group were in the 5-seg-R
group. Other comparisons between sham-operated and ganglia
removed groups yielded non-significant findings. Table 7
presents the comparisons, and the probabilities associated
with them.

Latencies of response were similarly tested for those
§p,given massed trials. Within the 6 second ITI no signi-
ficant differences in overall latency were obtained between
any of the groups. However, observation of the data suggests
that there is a "trend" towards longer latencies in the groups
that were subjected to anesthesia and surgical treatment.

Table 8 shows the comparisons and other relevant information.

Adaptation
It can be seen in Figures 1 and 2 that median frequency

of URs diminishes over blocks of trials. A test was made
to determine whether there were significant differences in
frequency of URs and in latency of URs between the first
block of trials (1 - 10) and the last(51 - 60). In the
massed trials condition the number of Sp,making an equal

25
number more URs on trials 1 - 10 were compared with the
number of Sp,in the pppp,group making more URs on trials
51 - 60. The binomial test as described in Siegel (1956)
was used to analyze the data. On the basis of the results,
it can be concluded that adaptation to the USS occurs in
both massed and spaced trial conditions. Further, it appears
that adaptation, measured in terms of decrement of URs over
trials, is more pronounced under spaced than under massed
trials. Table 9 in the Appendix presents the prvalues
obtained.

As several previous studies have been carried out using
”decerebrate” worms (Ratner and Miller, Rather) _S__s_ in the
S-seg-R groups were compared to see if ITI affected frequency
of responding,over trials. The frequency of URs over trials
1 - 10 for the 88 second ITI group was compared with the
frequency of URs of Sp,tested under the 6 second ITI. No
significant differences were found between massed and spaced
pp,with the anterior five segments removed on trials 1 - 10
(2,: 30.5, p = .439). The same subjects were then compared
on the last block of trials (51 - 60) and a highly signifi-
cant difference in frequency of URs was obtained (2,: 7.5,

p .005). 5-seg-R Sp.given massed trials made significantly
pppp,URs during the last block of trials than did the equiva-
lent spaced trial animals. This was taken as evidence that
adaptation occurs at a greater rate under spaced trial con-
ditions than under massed for "decerebrate" worms (average

frequency of URs massed = 5.87, average frequency spaced =

26 .
1.25; sum of ranks massed = 92.5, sum of ranks spaced =
48.5).

Since the latency measure was not clearly defined and
was not independent of the frequency measure on any given
trial, it is felt that the latency measure could not provide
adequate information as to the effects of spacing of trials
on adaptation of the UR.to light. Therefore, no analysis
comparing latency of URs at onset of the experiment with
latency of URs on the last block of trials will be made at

this time.

DISCUSSION

Behavior of the normal animal

The variable of spacing of trials was found to have a
strong effect on the unconditioned responses of the normal
earthworm, Lumbricus terrestris. Norms tested for 60
trials with a 6 second intertrial interval made less URs
than those animals tested with an 88 second ITI. However,
the median latencies of the URs of these groups did not
differ. It is felt that the latency measure was less meaning-
ful than the frequency measure because the latency measure
is less well defined in terms of the time of onset of the
UR and includes reaction time of the experimenter. Thus,
it is concluded that the normal groups did differ in URs as
a function of the ITI. This finding is consistent with a
report by Clark (1960), on the unconditioned responses of
marine worms. He reports that these animals showed a greater
rate of adaptation under massed trials than under spaced
trials. That is, the total frequency of URs to light was
less for animals tested under massed trials than for animals

tested under spaced trial conditions.

The finding regarding the effect of spacing of trials
on URs is of interest because it can be used to explain the
effects of spacing of training on conditioning. That is,
spaced conditioning trials have been found to lead to better

27

28
conditioning than massed trials. Ratner and Miller (1960)
reported that normal, intact worms trained under spaced
trials showed a higher percentage of 03s than animals
trained under massed trial conditions. Calvin (1939)
reported that for the acquisition of a CR in rats, 3 trials
per minute were superior to 9 or 18 trials per minute. The
present results suggest that higher percentages of CRs ob-
tained under spaced trial conditions are due to the fact
that organisms make more URs under spaced trials than under
massed trials and therefore make more conditioned responses.
The frequencies of URs cannot be evaluated for the typical
conditioning study because they are usually not reported.

The normal worms were found to make almost all negative
responses to photic stimulation. That is, a rapid withdrawal
response occurred at the onset of the light (US). Hess
(1924), Nomura (1926, as reported in warden, g;,al., 1940),
and Prosser (1950) report similar findings that normal,
intact worms show a negative phototaxis to moderate and
strong photic stimulation.

Over the 60 test trials, neither group of normal worms
showed adaptation of the withdrawal response to the photic
stimulation. That is, frequency of URs did not change com-
paring the first block of trials with the last. Clark
(1960) reports marked adaptation to photic stimulation within
60 trials for normal marine worms under both massed and spaced

trial conditions. The difference between the present study

29
and Clark's may be due to differences between them in test
conditions, media in which the us was presented, and/or

species of annelid studied.

The differential funcpions of the suppa- and subppppypgep;
Séflfillé

The unconditioned responses (URs) of the group with
the suprapharyngeal ganglia removed did not differ from the
URs of the group with the subpharyngeal ganglia removed.
Specifically, the Sup-R groups did not differ from the
Sub-R groups in frequency, latency, direction, or rate of
adaptation comparing groups within the same ITI. Kovaleva
(1961) in a recent paper reports that worms with the supra-
pharyngeal ganglia removed show an increase in activity and
oxygen consumption while those with the subpharyngeal ganglia
removed consume less oxygen and show a decrease in activity
as a result of loss of muscle tension in the body wall. His
findings regarding activity would suggest that the Sup-R and
Sub-R groups in the present study should differ. Such
differences were not found and the reasons are not clear.

The present results regarding no differences in response
to light by Sup-R and Sub-R groups within the same ITI are
in disagreement with the theories of Hess (1924), Kovaleva
(1961), and Nomura (1926). These workers hold that the sub-
and suprapharyngeal ganglia serve differential functions.
Specifically, they hypothesize that the suprapharyngeal
ganglia serve an inhibitory function and thetnbpharyngeal

30
ganglia an excitatory function. However, the results of the

present study show no evidence for specificity of function

of the cerebral ganglia with regard to the earthworm's URs

to light.
The general functions pf the cepebrpl gapslia

The results of the present study clearly indicate that
removal of any neural tissue changes direction of the URs
to light regardless of ITI. This finding is supported by
the work of Hess (1924) and Nomura (1926) who also reported
that removal of the cerebral ganglia (specifically the supra-
pharyngeal ganglia) changes the direction of the UR from
negative to positive under moderate or intense photic stim-
ulation. Ratner and Miller (1959) and Ratner (1962) also
report similar findings for "decerebrate" worms (5-seg-R
group). Nomura's theory (as reported in Warden, pp_§;,)
that positive phototaxis is increased as a result of removing
the suprapharyngeal ganglia is not supported by the findings
of the present study since non-significant differences
regarding direction of response were obtained regarding
direction of response for comparisons between Sup-R, Sub-R,
and 5-seg-R groups. These findings, however, cannot be
attributed to surgical shock, handling, or anesthesia
since the sham-Operated groups behaved like normals with
regard to direction of response.

The effect of removal of any neural tissue on URs has

been found to depend on the ITI under which the earthworm

31
is tested. Operated worms tested with massed trials (ITI =
6 seconds) do not differ in frequency or in latency of URs
as compared with normal and sham-operated animals. This
finding is consistent with the work of Ratner and Miller
(1959). who reported that operated animals tested under
massed trials did not differ significantly in percentages
of URs and CRs from normal, intact worms given massed trials.
The sham-Operated groups (SV and SD) also did.not differ
from the normal and Operated massed trial groups on frequency
or latency of URs. This suggests that the findings of no
differences among the experimental groups is reliable regard-
ing these measures. The sham dorsal and Sub-R groups were
found to show significant adaptation although no other massed
trials groups showed adaptation of the UR. These results
cannot be interpreted at the present time.

Extirpation of neural tissue and long ITI (88 seconds)
were found to significantly affect the URs of the earthworm.
That is, under spaced trial conditions total frequency of
URs decreased and overall latencies increased for animals
with the cerebral ganglia removed as compared with normal,
intact worms given spaced trials. In addition, sham-
operated worms had higher latencies, lower frequencies, and
showed more adaptation than normal animals. Although the
sham-operated worms differed from the normal animals, they
were still significantly more responsive than those worms
with either the sub-or suprapharyngeal ganglia removed.
However, the hypothesis that the anesthetic might have

32

accounted for the differences between normal and sham-operated
groups does not appear to be tenable due to the fact that
under massed trial conditions, non-significant differences
were obtained on comparisons among all of the massed trial
groups.

A.finding which is difficult to interpret in the light
of present theory of neural function is that worms with
both sets of ganglia removed did not differ in total fre-
quency or latency of URs from the sham -operated animals
given spaced trials. The 5-seg-R animals also differed in
total frequency of URs from the Sub-R group but not the Sup-
R group. Kovaleva's report (1961) that worms with the supra»
pharyngeal ganglia removed are more responsive while those
with the subpharyngeal ganglia removed are less responsive
is not consistent with the findings of the present study
of non-significant differences between groups tested under
massed trials. Thus, the reasons for differences between
5-seg-R and Sub-R animals given spaced trials are not clear.

A recent study by Ratner (1962) showed that changes in
the URs of worms given spaced training could not be due to
length of time the animals remained in the apparatus. He
was able to demonstrate that conditioning of decerebrate
worms could occur even after a long delay in the apparatus.
Subjects in Ratner's study were given either massed or spaced
trials after a long delay in the tube (40 minutes) with spac-
ing conditions being reversed after 60 trials. Decrease in

frequency of URs was shown to be the result of long ITI

33
rather than amount of time spent in the tube. Thus, it
would appear that in the present study, lack of responding
over trials in the ganglia removed groups given spaced
training could.not be attributable to length of time the
animal remained in the apparatus.

The findings of the present study again demonstrate
that the impaired worm under spaced trials is less respon-
sive than either the normal worm under spaced trials or the
impaired worm under massed trials. Ratner (1962) reported
similar findings using S-seg-R worms. The interpretation
of the interaction between surgery and ITI on URs to light
does not follow from existing statements about neural
function in invertebrates. At the descriptive level, it
appears that the impaired organism becomes MORE EOERQDEO‘
ggugg_as compared to the normal, intact organism Which is
more stimulus-bound. That is, the impaired worm tends to
continue what it had been previously doing prior to the
onset of the following US. Thus, under massed trial con-
ditions the Operated animal which responds to the US con-
tinues to do so as a result of the rapid, repeated presen-
tation of the US which occurs every 6 seconds. Under spaced
trial conditions, the US is presented less frequently (every
88 seconds) and therefore the worm is inactive for a greater
amount of time than it is active. Under these conditions
the operated animal will continue to remain inactive when the

photic stimulus is presented.

34

Adaptation to the US

Analysis of the results indicates that adaptation of
the UR to photic stimulation occurs for surgically treated
animals in both massed and spaced trial conditions.
Specifically, some of the groups showed a decrease in fre-
quency of URs comparing the first block of trials with the
last. However, this relationship was not consistent for
all the groups tested. Normal, intact worms showed no
decrease in frequency or increase in latency under either
massed or spaced trial conditions. This finding is not
consistent with the work of Clark (1960) who reported that
adaptation of a UR to light occurs to a greater extent under
massed trial conditions. In general, operated animals showed
less adaptation under massed trials than under spaced trial
conditions. However, some of the specific findings are not
clear. That is, under massed trial conditions the Bub-R
group and SD group showed adaptation while the Sup-R group
did.not. However, under spaced trial conditions the Sup-R
group did not show evidence of adaptation of the UR to light.
It would be expected that adaptation to the photic source
would occur more rapidly in the massed trial groups since
these animals were subjected to more rapid intense stimu-
lation (every 6 seconds) over a shorter period of time (8
minutes) than their spaced trials counterparts (90 minutes).
The results regarding adaptation cannot be interpreted at
this time.

35

Since Ratner (1962) used decerebrate worms in an earlier
study, the S-seg-R massed trial and 5-seg-R spaced trial
animals were compared in order to determine if adaptation
occurred to a greater extent under massed or spaced training
for decerebrate worms. Frequency of URs for the first and
last block of trials were compared for these two groups.
No significant differences were obtained on trials 1 - 10
comparing massed and spaced decerebrate worms, while highly
significant differences were obtained comparing the two
groups on the last block of trials. These results are con-
sistent with those of Ratner who reported that percentage
of URs decreases over trials especially for those‘gg given
spaced training. As reported earlier, these results cannot
be attributed to the length of time the animal remained in

the apparatus.

SUMMARY

The present experiment was designed to study the
effects of spacing of trials and differential extirpation
of the cerebral ganglia on the unconditioned responses of
the earthworm, Lumbricus terrestris. Ninety-six worms were
randomly divided into 6 surgical treatment groups. Each of
the surgical treatment groups contained 16 worms, and each
of these groups was subdivided after surgery into a group
which received massed trials and a group which received
spaced trials. Each animal received a total of 60 trials
in which the US was presented either every 6 seconds or
every 88 seconds. The frequency, direction, and latency of
the UR were recorded for each g,

The results showed that normal worms make fewer URs
under massed trials than under spaced trials. The UR to
strong photic stimulation in the normal worms was consis-
tently negative. These animals also showed no adaptation
of the UR to light under either massed trial or spaced trial
conditions.

worms with either the sub- or suprapharyngeal ganglia
removed showed no differences in frequency, latency, direc-
tion, or adaptation of the UR when comparisons were made
within the same ITI. The results of the present study offer
no evidence for specificity of function of the cerebral gang-
lia with regard to the worm's URs to photic stimulation.

36

37

Results indicate that removal of any neural tissue
changes the direction of the UR regardless of the ITI. The
effect of removal of neural tissue on frequency of URs was
found to be dependent on the intertrial interval under which
the animals were tested. Operated worms given massed train-
ing did not differ from normals and sham-operated worms in
frequency or latency of URs. Extirpation of neural tissues
and long ITI were found to significantly affect URs. Latency
is increased, total frequency of URs decreased, and adapta-
tion of the UR to light is more frequent among groups and
is more pronounced. Operated animals, including the sham-
operated groups,were much less responsive under spaced
training than under massed training.

Adaptation to the photic stimulus for operated fig
occurred under both massed and spaced trials but appeared
to be greater under spaced trial conditions.

The results cannot be interpreted in terms of the
existing statements about neural function of invertebrates.
At the descriptive level, the results suggest that Operated
worms become response bound as compared to the normal,
intact organism which remains stimulus bound with regard
to its reactions to photic stimulation.

LPPEN D IX

39

Table 1.--Statistical analysis employin the Mann-Whitney g
test to determine if spacing of trials (ITI) affects the
frequency of URs to light.

 

 

 

Groups Totlfidihagqggncy LYalue“ Sigfiigicgce
333 3883222) 233% 8'5 P °°°7
23 Semi) 32:2 18-5 P ~09?
23 (3882233) 32:3 5'0 P '253
33:33:: (gasggl) 3;:3 ‘9°5 P '1‘7
2313222383322) $222 5-5 P W
332$ E2822!) 3:? 7-0 P W

 

*The n's used to evaluate the U values for each

ison were 8 and 8.

compar-

Table 2.--Statistical "analysis employing the Mann-Hhitney U
test to determine if" surgery" affects frequency of‘URs to-
light under massed trial conditions.

 

 

 

Median of . Level of

Groups Total Frequency U,Value* Significance
Normal 35.0
SD 37.5 .3‘°° P '48°
Roma-1 350°
sv 25.5 21.5 p .164
Normal 35.0
5-geg-R 31.0 30.5 P .480
Normal 3530
Sup-R 28,5 29.0 P .399
Normal 35.0
13an 3505
SD 37.5 .
8v 25.5 15.5 P .052
SD 37.5
Sup-R 28 . 5 28 e O p e 360
SV 2 .
SUD-R 3%.; 1900 P e097
5-seg-R 31.0 ‘
Sup-R 28.5 31.5 P .520
5-seg-R 31.0 .
Sub-R 35,5 29.0 p 399
S‘Ip-R 28s 5
Sub-R 35.5 27-0 p .323

*The n's used to evaluate the U values for each compari-

son were 8 and 8.

41

Table 3.--Statistical analysis employing the Mann-Whitney U
test to determine if" surgery" affects frequency of URs to
light under spaced trial conditions.

 

 

 

Groups Togfiigfiégency 31 Value* Sigxgicgce
Egrmal 32:; 6.5 ‘ p .003
§%‘m‘1 33:3 0.0 p .0001
§3§Zéin 2:2; 4.0 p .001
gfigffié $2 2 0.0 p .0001
$3331 ‘8: 2 0.0 p .0001
33 33, g 31.5 p .520
geseg-R 3;: g 31.0 p .480
3313-3 fig: g 111.0 P .032
33b.a $3 2 7.5 p .005
gfees-R g; g 32~0 p .520
33,-3 $2 g 13.5 p .032
Sgt-R $2 2 4.0 p .001
333237“ f; g 13.0 p .025
33322?“ §§Z§ 17.5 p .080
33%;? 13:; 26.0 p .287
*The n' s used to evaluate the U values for each compar-

ison were 8 and 8.

42

Table 4.--Statistical analysis employing the Fisher Exact
Probability Test to determine if duration of ITI affects the
direction of URs to light.

 

 

Freq. of §§_making Significance

Group 50% WithdrawalfiRs_ Level

Normal 6 sec) 8 NS

Normal 88 sec) 8

SD (6 sec) 7

SD (88 sec) 8 NS
' SV (6 sec) 6 NS

SV (88 sec) 6

S-seg-R 6 sec) 0 NS

5-seg-R 88 sec) 0

Sup-R 6 sec) 1

Sup-R (88 sec) 3 NS

Sub-R 6 sec) 3

Sub-R 88 sec) 3 NS

 

43

Table 5.--Statistical analysis employing the Fisher Exact
Probability Test to determine if surgical treatment affects
the direction of URs to light.

 

 

 

 

W
Freq. o 1§§ eq. of 3

ing 50% Level of Making 50% Level of
groups ithdrawal Rs Significance Withdrawal Rs Significance
33 2 us 2 1 us
33pm '17 p .01 g ’ p .025
ga-R g I ”5 3 NS
331;; ; NS 2, us
3,3334 g I NS 2 NS
3.1123?” 3 N8 3 NS
gm“ :3, NS 3 us
£3“ 2 us 2 us
53333: 3 P '°°5 1 3 1" '°°5
EEEEE} ? I p .005 g p .025
gfififfi} __f g p .025 g p _:01

 

 

 

 

 

Table 6.--Statistical analysis employing the Mhnn-Whitney
test to determine if duration

 

Groups

of ITI affects the

H
of

a 6110

_ .v31 0f—
Overall Latency g Value* Significance

 

Normal (6 sec)
Normal (88 sec)

SD (6 sec)
SD (88 sec)

SV (6 sec)
SV (88 sec)

S-seg-R (6 sec)
5-seg-R (88 sec)

Sup-R.§6 sec)
Sup-R 88 sec)

Sub-R $6 sec)
Sub-R. 88 sec)

*The n's used to evaluate the §_values for each compar-

ison were 8 and 8.

2.32
2.31

.39
.00

O
O
O

.00

0
U!

.00

O
O
.4

.00

ow: OM13- OSU O\O\ O‘Ul
O
U!
CD

0
O

31.0

14.0

26.0

22.0

6.5

9.0

P

P

.480

.032

.287

.164

.003

.007

45

Table 7.--Statistical analysis employing the Mann-Whitney U
test to determine if surgery affects the latency of URs

under spaced trial conditions.

~W~-——---.- ~ _ _._..__

Grand Median of

   
 
      

 

Level of-

 

 

Groups __ Overall Latency _fl2 Ealue* Significance
ggrmal 2:33 8.5 p .007
ggrmal §233 4.0 p .001
gififigfa 2:33. 18.5 .041 p .052
£3333} 2.30 0.0 p .00001
gfififg? €233 0-0 p .00001
SD 6.00

sv 6.00 27.5 p .323
33p-n $288 20.0 p .117
glib-R 2:88 20.0 p .117
3333* 2:33 19.0 p .097
Eafiffi'R 2.83 18.0 p .080
33%;: 2283 31.5 p .520

 

‘_———_

*The n's used to evaluate the g,values for each compar-
ison were 8 and 8.

Table 8.--Statistical analysis employing the Mann-Whitney Q

test to determine if surgery affects the lategcz of URs

under massed trial conditions.

 

 

 

Grand Median of Level of
Groulg 0:erall_Latency 2 Value“ Significance
1gng 3;; 29.0 p .399
gyrmal Efgé 19.0 p .097
§3§§§§a §:g§ 26.0 p .287
$33331 i133 25.0 p .253
1:33:11 33% 27-0 p .323
3% 2:33 20.0 p .117
33p-a 2:33 34.5 p .520
gZh-R 3:28 23.0 p .323
33333-11 2.8?! 31 . 5 p . 52o
3111:3341 3:23 31 . o p . 480
335:? ’3‘2‘5’21’ 27.0 p .323

 

*The n's used to evaluate the I; value for each compar-

ison were 8 and 8.

47

Table 9.--Statistical analysis employing the Binomial Test
to determine if there is a difference in frequency of URs
between the first block of trials (1-10) and the last (51-

 

60).
M
6 Second ITI
Normal 5 3 .145 8
SD 6 2 .045 8
SV 4 4 .363 8
S-seg-R 4 4 .363 8
Sup-R 5 3 .1h5 8
Sub-R 6 2 .045 8
88 Second ITI
Normal 5 3 .145 8
SD 5 2 .045 8
SV 6 2 .O#5 8
S-seg-R 8 0 .002 8
Sup-R 5 3 .145 8
Sub-R 8 0 .002 8

 

*Number of g; making more URs on trials 1-10 than on

**Number of‘gg making the same number or more URs on
trials 51-60 than on trials 1-10.

1e

2.

3.

10.

11.

12.

13.

REFERENCES

Bharucha-Reid, R. P. Neuroanatomical correllates of
directional behavior in the earthworm. J, 9gp.

phygiol, ngchol., 1961, fig, p. 337.

Calvin, J. S. The effects of regularity of stimulation
in conditioned-response learning. Psychoi, buil.,
1939: 2Q: P0 596.

Clark, R. B. Habituation of the Polychaete Neyeig to
sugden stimuli (1). Animgi Behav., 8, Nos. 1 and 2,
19 0.

Darwin, C. The fermation of vegetable mould tgzough the
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New ork: Appleton an ompany, 1 1.

Heck, L. (as reported in warden, Jenkins, and Warner.
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Hess, W. N. Reactions to light in the earthworm L,
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Kovaleva, N. E. The effects of extirpation of parts
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and.physiological functions in the earthworm.

Sechenov Physiol, J, 0; U.S,S,R., 1961, £1, p. 78.

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Prosser, C. L. Comparative Animai Physioiogy. Phila-
delphia: W. B. Saunders ompany, 1950.

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