The integration of auditory and visual stimuli is crucial for recognizing objects by sight and sound, communicating effectively, and navigating through our complex world. While it is not clear where in the brain information from these two modalities are combined and processed to govern specific behaviors, the frontal lobes have been identified as a region associated with memory and language, which depend on cross- sensory integration. Moreover, recent analysis of the inferior convexity (IFC) of the prefrontal cortex in the macaque monkey has revealed juxtaposed and overlapping areas of visual and auditory processing, indicating a possible role in multimodal sensory integration. Previous research on the prefrontal cortex has focused on its role in visual memory processing. The goal of this project is to obtain a fundamental understanding of how the frontal lobes process complex auditory, visual and combined stimuli which serve meaningful communication and object recognition. Our experiments will focus on the neurophysiological and anatomical analysis of the IFC in the macaque monkey. Specifically, experiments will characterize the selectivity, specificity and organization of auditory and visual responses within the IFC. In addition, we will ascertain whether auditory or visual responsive neurons within the IFC are, in fact, multimodal (i.e. respond to combined visual and auditory stimuli). Moreover we will compare the modulation of unit responsiveness to multimodal stimuli presented passively or in an associative memory task. Finally, we will elucidate the neuronal circuitry underlying auditory, visual and multimodal responses in the frontal lobes by determining the anatomical connections of physiologically characterized regions of the IFC. Findings from the present study will help to reveal the circuitry and cellular mechanisms underlying communication processes relevant to speech perception. Our findings will also have implications for understanding neurological disorders which affect communication and language, including schizophrenia and autism in which dysfunction has been implicated in the frontal lobes.
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