Friday, March 21, 2025
3/21/2025
Social communication depends on the integration of sensory, emotional and cognitive information by a large network of brain regions. While many brain regions integrate auditory and visual information, the inferior frontal lobes (IFG) receive a wealth of sensory afferents from multiple modalities, has influence over many brain regions involved in motor and cognitive processes, and plays a major role in our speech and language processes. Previous investigations in primate ventrolateral prefrontal cortex (VLPFC), a proposed homologue of human IFG, revealed that neurons are selectively responsive to species-specific faces and to vocalizations and perform complex integration of these communication stimuli. Furthermore, VLPFC is essential during crossmodal working memory. These varied functions of VLPFC occur over several cytoarchitectonic regions, each of which receives different anatomical afferents and demonstrates diverse sensory and cognitive responses. Inability to integrate face and vocal information impairs speech processing, language learning, recognition and semantic processing, all essential elements of social communication that VLPFC participates in. Hence, identifying the integrative and cellular functions of VLPFC subdivisions will clarify the organization of the primate frontal lobe and its role in disorders of communication. In this proposal, we will determine what components of face and vocal information are integrated within VLPFC subregions and what neural mechanism underlie integration in these subregions. In Aim 1, we will investigate which features of face and vocal information are integrated and whether subregions of VLPFC process and integrate these stimuli differently (i.e. What is integrated Where). We hypothesize that modality specific subregions of VLFPC will show differential responses to manipulations of spectrotemporal features of face and vocal stimuli. In Aim 2, we will interrogate how face and vocal stimuli are integrated by single neurons and across simultaneously recorded ensembles during the presentation of dynamic naturalistic audiovisual stimuli. In particular we will determine if VLPFC neurons perform time division multiplexing, where the neural response to face-vocalization movie shows evidence of “switching” back and forth between neural representations of the face or the vocal stimulus during integration. Furthermore we will degrade the face and vocal stimuli in an audiovisual pair in order to selectively diminish the contribution of the face or the vocal stimuli during integration and to determine how this affects our temporal model of these responses. Merging ensemble recordings of responses to naturalistic stimuli in the prefrontal cortex of Old World Primates with novel computational methods, will provide new and valuable data on how we combine social communication information. This is of particular relevance to understanding changes in sensory integration in intellectual disabilities such as autism spectrum disorders.
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