The integration of facial gestures and vocal signals is an essential process in communication and relies on an interconnected circuit of brain regions. The neural basis of face and vocal integration is a topic of great importance since sensory integration is essential to speech perception and object recognition and is impaired in autism spectrum disorders (ASD) and other intellectual disabilities. Neuroimaging studies have highlighted the ventral frontal lobe and the cortex surrounding the superior temporal sulcus region (STS) as locations where face and vocal information are brought together, and anatomical studies have described their robust connections. Thus a network where temporal lobe regions send unisensory and multisensory information to the ventral prefrontal cortex (VLPFC) for integration and maintenance in working memory likely underlies social communication. In this proposal we will identify the regions of the STS where neurons integrate face and vocal stimuli (Aim 1a). We will also determine whether STS neurons demonstrate selectivity in their integrative responses to social (face and vocal stimuli) vs. non-social (object) pairs of stimuli. Moreover we will establish whether STS neurons contribute to social cognition by demonstrating their activity during an audiovisual memory paradigm (Aim 1b). Finally, we will demonstrate STS-VLPFC connectivity in audiovisual working memory by revealing changes in STS neuronal responses while VLPFC is inactivated during the performance of audiovisual working memory (Aim 2). We have previously shown that inactivation of VLPFC disrupts audiovisual memory (Plakke et al., 2015) and we will extend these studies to quantify how STS neurons are affected by VLPFC inactivation. These studies will investigate which regions of the STS are affected by VLPFC inactivation and are necessary in the evaluation of audiovisual stimuli. We hypothesize that VLPFC inactivation will not affect STS neuronal responses during the sample period of the audiovisual memory task but will affect STS activity during the decision phase of the task when STS-VLPFC interaction is needed to compare the stimulus at hand (STS perception from bottom up afferents) with the sample stimulus held in memory (VLPFC top down influence). The identification of connected STS-VLPFC regions will help us to better understand audiovisual processing, integration and memory, in both health and disease.
The superior temporal sulcus (STS) is part of brain network involved in social communication. The STS processes and integrates face and vocal information and transfers this information to the prefrontal cortex where it is further combined with relevant information, and used in cognitive functions. Understanding the STS- prefrontal network at a cellular level will help us to understand the neural mechanisms that may be altered in autism spectrum disorders and other developmental disabilities.
