The influence of feature salience over microsaccades in normal and blindsight humans and monkeys: an experimental and theoretical investigation

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Microsaccades are tiny saccadic eye movements that take place during periods of gaze fixation. Even though the detailed mechanisms for microsaccade generation, as well as their functional role in vision, are not fully understood, recent research has revealed that these eye movements can act as an important proxy for larger saccades in understanding several aspects of perception and cognition. One such aspect concerns the relationship between selective visual attention and eye movements, in which it was shown that microsaccades, in contrast to their classic description as random and spontaneous, are related to attention. The neural mechanisms for such a relationship are not fully understood, and its characteristics in pathological states of vision are completely unexplored. The purpose of the proposed research is to understand how feature salience that is commonly included in models of selective visual attention can influence microsaccades. We will approach this problem by using a combination of behavioral, neurophysiological, lesion, and computational modeling techniques. We will conduct model-driven experiments designed to titrate the effects of feature salience, as predicted computationally, on microsaccades. These experiments will then ultimately culminate in a comprehensive neural network model of microsaccade generation that takes into account the important roles of visual salience and attention in influencing these tiny eye movements. We will specifically compare the possible distinct roles of primary visual cortex (V1) and superior colliculus (SC) in mediating vision in the normal state, as well as during V1 lesions. By selectively probing two distinct pathways for vision (one through V1 and one bypassing it), not only will we understand the influence of feature salience on the smallest possible saccades, but we will also identify the opportunities and challenges faced by blindsight patients (who lose V1 function), and ultimately provide guidelines on how these patients may optimize their quality of life despite their loss of conscious vision