Project Summary/Abstract The prefrontal cortex (PFC) is widely reported to play a role in visual attention, employed through modulation of neuronal activity in visual processing regions, such as V4 and MT. Sub-regions within the PFC of monkeys, such as the frontal eye fields (FEF) and the ventral prearcuate region (VPA), are reported to govern spatial and feature-based attentional modulation of visual responses, respectively. However, the cellular-level circuitry and neurocomputational mechanisms involved in the modulatory control of visual processing remain unclear. Previous work suggests that interactions between diverse sub-populations in both FEF and VPA may facilitate modulation of visual processing signals as well as shifts of attention, but this remains untested. The purpose of my project is to determine the neuronal dynamics within sub-regions in PFC that govern top- down modulation of visual processing. It is possible, that FEF may integrate signals representing object identity which arise in VPA and transforms them to signals representing spatial locations of a target stimulus. We plan on addressing this hypothesis by: (1) characterizing the spatial- and feature-tuning properties of FEF in the context of visual search to understand how integration and transformation of attentional signals may be implemented; (2) establishing the temporal dynamics between FEF and VPA to reveal the nature of neuronal communication between both regions during visual search; and (3) determine the causal role of VPA towards feature-based attentional modulation of visual processing via reversible pharmacologic inactivation. Monkeys are trained on a visual search task designed to conditionally engage attentional processes that are dependent on feature or spatial information. Using neurophysiology and population analyses, we will determine the neuronal correlates of PFC which govern the computational processes needed to accomplish these tasks. These findings will provide a description of the circuit-level mechanisms involved in top-down attention which often times is affected in neuropsychological disorders and neurodegenerative diseases. Thus, this project aims to contribute knowledge concerning the neuronal correlates of visual processing that are involved in related underlying symptoms. Additionally, learning about how higher-level brain regions modulate visual processing may provide more information about how perception is conjured in the brain. My environment at UR fosters the opportunity to broaden my research skillset which ultimately facilitates my endeavor towards my career goal as a scientific leader pushing to improve our approach of intervening with mental illnesses. The social environment at UR provides great opportunity for outreach, allowing me to fulfill my aspirations as a community leader looking to pave a way for underrepresented individuals which get overlooked given their backgrounds.