System Level Assessment of Motor Control through Patterned Microstimulation in the Superior Colliculus

We are immersed in an environment full of sensory information, and without much thought or effort we can produce orienting responses to appropriately react to different stimuli. This seemingly simple and reflexive behavior is accomplished by a very complicated set of neural operations, in which motor systems in the brain must control behavior based on populations of sensory information. The oculomotor or saccadic system is particularly well studied in this regard. Within a visual environment consisting of many potential stimuli, we control our gaze with rapid eye movements, or saccades, in order to foveate visual targets of interest. A key sub-cortical structure involved in this process is the superior colliculus (SC). The SC is a structure in the midbrain which receives visual input and in turn projects to lower-level areas in the brainstem that produce saccades. Interestingly, microstimulation of the SC produces eye movements that match the metrics and kinematics of naturally-evoked saccades. As a result, we explore the role of the SC in saccadic motor control by manually introducing distributions of activity through neural stimulation.\ud \ud Systematic manipulation of microstimulation patterns were used to characterize how ensemble activity in the SC is decoded to generate eye movements. Specifically, we focused on three different facets of saccadic motor control. In the first study, we examine the effective influence of microstimulation parameters on behavior to reveal characteristics of the neural mechanisms underlying saccade generation. In the second study, we experimentally verify the predictions of computational algorithms that are used to describe neural mechanisms for saccade generation. And in the third study, we assess where neural mechanisms for decoding occur within the oculomotor network in order to establish the order of operations necessary for saccade generation. The experiments assess different aspects of saccadic motor control, which collectively, reveal properties and mechanisms that contribute to the comprehensive understanding of signal processing in the oculomotor system