Neural Processing During Sequential Saccades - Project Summary/Abstract Visually scanning the environment requires a series of rapid eye movements, known as saccades, interspersed with brief fixations, highlighting the remarkable speed of the brain’s oculomotor system. This raises fundamental questions about whether the brain plans each saccade sequentially or plans future movements before completing the current one. If the latter is true, this suggests that the brain must compute the amplitude and direction of the future movement while accounting for the first saccade before it is even initiated. This proposed research investigates the neural processing of the superior colliculus (SC) and frontal eye fields (FEF) – crucial nodes in the oculomotor circuit – during the generation of sequential saccades. The FEF, associated with cognitive processes like memory, and the SC, responsible for producing corollary discharge signals, communicate bidirectionally to compute saccade metrics. Using laminar multicontact probes, I will simultaneously record neural activity from the FEF and SC as rhesus macaques perform tasks designed in a 2x2 framework, involving single or two sequential saccades, in visually- or memory-guided domains. Advanced computational analyses will quantify the timing, directionality, and representation of neural communication between these regions, specifically testing the hypothesis that communication between the FEF and SC is enhanced during periods of increased cognitive processing (Aim 1). Furthermore, suprathreshold stimulation of the SC after prolonged fixation evokes a site-specific saccade, but stimulation immediately after a saccade does not produce this movement. The oculomotor system requires ~250 ms to reset after a saccade, aligning with typical intersaccadic intervals during visual scanning. I will apply electrical stimulation to the SC and FEF to test this phenomenon in tasks requiring sequential saccades. Specifically, this work will test the hypothesis that if sequential saccades are treated as a unified action, the resetting of the saccadic system should start with the second saccade (Aim 2). This proposed research will uncover the neural signatures associated with executing sequences of movements, providing fundamental insights into the neural mechanisms of sensorimotor integration. These findings may also inform treatments for conditions that disrupt eye movement control, such as neurodegenerative diseases and traumatic brain injury.
