Dissecting the neural basis of visual continuity using blinks

About This Grant

Project Summary: For millions of years, sensory systems have compensated for sensory generated through body movements. This is epitomized in the primate visual system which must account for rapid shifts in eye position three times a second and massive blink-related disruptions to retinal illumination every few seconds. Amazingly, primate visual experience is stable across these frequent and extensive disruptions. Little is known about the neural mechanisms underlying this visual continuity. Visual continuity, at minimum, requires two neuronal processes. First, a process by which ongoing perception is maintained during the retinal disruption; second, a process by which retinal disruptions are prevented from reaching perceptual thresholds. Behavioral work in the 1980s found that sensitivity to luminance changes, independent of eyelid closure, dramatically decreased if the change co- occurred with a blink. This phenomenon was coined blink suppression. Although little physiological evidence has been found for either mechanism of visual continuity, each offers a unique approach to interrogate the neuronal mechanism of perception: blink suppression as a means to preclude input from perception, and cortico-thalamic loops as a means of maintaining perception independent of visual input. In the first aim of this proposal, I will establish a blink suppression paradigm for use in animal models. This paradigm will be valid if behavioral performance is worse when an eyelid independent luminance change is paired with a blink compared to when unpaired. I will then record at multiple levels of the visual hierarchy while animals perform the task. I hypothesize that a copy of the blink motor command – a corollary discharge – alters early visual cortical activity in a such a way that it aligns blink-induced activity with aspects of visual activity that do not contribute to perception. In the second aim of this proposal, I will determine the contribution of cortico-thalamic loops to visual continuity. I will record from pulvinar neurons with known projections to V1 and V4 by using optogenetic tagging. I predict that pulvinar and V4 will more strongly modulate one another during blinks and that this activity underlies visual continuity. In the final aim of this proposal, I will causally test the necessity and sufficiency of blink corollary discharge to produce visual continuity. I will use optogenetics to inhibit and excite the lateral premotor cortex (LPMC), the likley origin of blink corollary discharge. I will inhibit LPMC on trials where a blink occludes an external stimulus or stimulate LPMC when an external stimulus changes in luminance. I predict that trials with an inhibition of LPMC will result in monkeys reporting their own blinks as a luminance change, and trials with a stimulation of LPMC paired with an external luminance change will result in monkeys failing to detect the luminance change. By leveraging a novel blink suppression paradigm and powerful analytical methods to extract activity patterns related to perception, I will delineate the neuronal mechanisms of perception and visual continuity.