An Approach to Understanding the Neural Circuitry of Saccade Control in the Cerebral Cortex Using Antidromic Identification in the Awake Behaving Maca

Saccadic eye movements are rapid conjugate movements of the eyes made to align the visual axis with objects of interest. Such movements are some of the most precise and well-controlled motor responses of which the nervous system is capable, and they display an enormous range of flexibility. Because saccades are controlled by a distributed network of brain areas including the cerebral cortex, basal ganglia, cerebellum, and brainstem, investigation of deficits in saccade control in movement disorders such as Huntington’s and Parkinson’s disease provide a potential window into their underlying neuropathology. A full understanding of pathological changes requires detailed investigations of the neural mechanisms of saccade control in the cerebral cortex. This requires invasive methods, which necessitate the use of an animal model. Here, we describe the rationale and use of the awake-behaving rhesus macaque model for the investigation of cortical control of eye movements. We focus on the technique of single neuron recording, particularly the use of antidromic identification of cortical projection neurons. Investigations of the circuit properties of the oculomotor system using this technique promise to provide unique insights into the neuropathology of movement disorders.