DOUG CRAWFORD, York University
Title: Cellular Basis of Visual Working Memory during Simple Gaze Behaviours
Ebbinghaus Empire Series 2015-2016
Abstract: An important question in neuroscience is: how is spatial information retained in working memory, and how is this information updated when the body moves relative to external space? We approach these questions by looking at neural activity during gaze behaviors, which are controlled by a well-described network that is closely associated with both visual working memory and attention. I will begin by describing our new method for extracting spatial codes from single neurons and neuron populations in the frontal cortex and midbrain superior colliculus. This method suggests visual responses encode target direction relative to the eye, whereas motor responses for rapid saccade eye movements encode future gaze direction. I will then describe what happens during a short memory delay between these sensory and motor events, showing that frontal cortex memory activity follows a progressive transition from coding visual direction to intended action. Finally, we will look at memory activity in the superior colliculus when a slow pursuit eye movement changes the spatial relationship between a future gaze target and current eye position. It turns out that in this situation, the future target direction is continuously updated relative to current gaze direction through the movement of a 'hill' of activation across a retinotopic map of visual space in the superior colliculus. This fundamental research is important for understanding brain function, but it also has practical applications for understanding how we deal with normal spatial tasks, and what goes wrong with this behavior in pathologies that affect working memory.
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