Corollary discharge (CD) signals are "copies" of motor signals sent to sensory areas to predict the impending input. Because they are used to distinguish actions generated by oneself versus external forces, altered CD has been hypothesized to result in the commonly-observed agency disturbances in schizophrenia patients (SZP). Behavioral evidence for altered CD in SZP has been observed in multiple sensorimotor domains, including the oculomotor system; however, its exact neural underpinning is unknown. One oculomotor CD pathway identified in primates projects from motor neurons in the superior colliculus (SC) to visual neurons in the frontal eye fields (FEF) via the mediodorsal thalamus (MDT). The current study aimed to examine the structural connectivity of MDT-FEF pathway in SZP and whether it relates to oculomotor CD abnormalities. Twenty-four SZP and 22 healthy controls (HC) underwent diffusion tensor imaging (DTI), and a large subset of those individuals also performed the blanking task, an eye movement task that measures the influence of CD on visual perception. Probabilistic tractography was used to identify white matter tracts connecting FEF and MDT. Microstructural integrity of these tracts was compared across groups and correlated with behavioral indices of oculomotor CD from the blanking task and symptom severity. We found that SZP had compromised microstructural integrity in MDT-FEF pathway. This hypoconnectivity was correlated with both impaired oculomotor CD signals and more severe positive symptoms in SZP. These data suggest that the MDT-FEF pathway may serve an important role in transmitting oculomotor CD signals, which in turn may relate to positive symptom manifestation in SZP.
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