Functional organization of mouse auditory cortex in response to stimulus complexity and brain state

Abstract

The functional organization of sensory cortices is modulated by both extrinsic events and intrinsic states. The present study aimed to assess the mouse auditory cortex (AC) responses under varying conditions of stimulus complexity and brain state. Using wide-field calcium imaging, our results suggest a complete outline of topographic maps of frequency and FM rate as well as highly responsive regions to mouse ultrasonic vocalizations (USVs) in both awake and anesthetized states. Three new regions responsive to high-frequency tones and four new gradients responsive to frequency modulations (FMs) were identified. These maps are highly replicable across weeks and between animals. In awake versus anesthetized states, cortical responsiveness to pure tones was stronger, and regions that preferentially responded to slow rate FMs were smaller. In both states, fast FM regions showed the greatest contribution to the processing of USVs. Finally, our modeling of how best tone frequency or FM rate changes as a function of distance along a topographic gradient resulted in a sigmoid function. Together, our findings provide a better understanding of mouse AC functional organization and how this organization is modulated by changes in stimulus complexity and brain state. The function of newly identified regions in higher-order auditory/vocal processing and animal behavior should be considered in future research.