Role of Superior Colliculus in Visual to Movement Spatial Transformations During Memory-Guided and Reactive Head-Unrestrained Gaze Shifts

The fundamental process in the brain which allows the generation of what is known as behavior, is the transformation of sensory or internally generated information to commands for movement. For example, shifting the line of gaze to look at and interact with our environment requires transformation of visual information into proper contraction of eye and neck muscles. In this thesis I studied the transformation of visual signals to movement commands in the primates superior colliculus, a key structure in sensory integration and gaze movement generation. In the first chapter the frames of reference and the spatial information encoded by the visual and motor activity of superior colliculus, in different neuron types, are investigated in a memory delay task, and the results provide support for visuomotor transformation process that occurs between and within neurons during the memory delay task. In the second chapter the focus of study is on reactive gaze shift task and we show that the spatial information occurs during the burst of activity of single neurons even in such a short interval and without a presence of a memory delay. In the last (third) chapter, I compared the visual and motor spatial coding and their transformation between the reactive and the memory delay tasks and found that although similarities exist, there are important differences in neural activity profiles and the spatial codes and the extent of visual to movement transformation. Together the findings in this dissertation suggest that the process of visual to movement transformation occurs between and within neurons in SC regardless of the duration of the gaze shift or the task, however task demands influence both the activity and spatial coding of neurons which are consequently translated in the differences in behavior in each task