Abstract
As we interact with our environment, the features of objects in the visual scene are not consistently present on the retina and sensory cues used to guide visual behavior are not always available. Thus, active observers are faced with a ubiquitous task of comparing sensory stimuli across time and space. When monkeys compare the direction of motion of two foveally presented stimuli, S1 and S2, separated by a delay, neurons in the dorsolateral prefrontal cortex (DLPFC) show direction selective (DS) responses suggestive of their origins in area MT (Zaksas & Pasternak, 2006). Furthermore, responses to S2 are often modulated by the preceding direction, reflecting the process of sensory comparison (Hussar & Pasternak, 2012). However, DLPFC neurons respond to motion not only at the fovea but also across the entire visual field, receiving direct bottom-up inputs from ipsilateral MT representing contralateral stimuli and indirectly from the opposite MT representing ipsilateral stimuli. Since MT is highly retinotopic, we examined whether DS in DLPFC retains the spatial specificity of its inputs by presenting stimuli in the contralateral and ipsilateral hemifields during the direction comparison task. We found that DLPFC responses often showed large differences in DS for stimuli presented at different visual field locations and these differences were preserved on trials with S1 and S2 appearing in opposite hemifields. This demonstrates that these responses may reflect the convergence of MT inputs representing different spatial locations. We also found that the comparison effects during S2 appeared only when both S1 and S2 were placed in the contralateral hemifield, suggesting that the direct input from ipsilateral MT may be necessary for producing comparison effects in DLPFC. These results demonstrate that the topography of sensory representation in DLPFC is governed by its connectivity with MT.
Meeting abstract presented at VSS 2013