Functional specificity of auditory inputs to the visual cortex

The brain continuously receives a wealth of sensory information, and uses this information to guide behaviour. However, the process by which different sensory streams are integrated to form a unified percept remains poorly understood. Cortical regions dedicated to a specific sensory modality nonetheless receive input related to other modalities. The mouse auditory cortex sends numerous projections to the primary visual cortex and surrounding higher visual areas. These inputs may be crucial to the integration and binding of auditory and visual signals. Yet the exact nature of the auditory information carried by these inputs, and how they are organised within the visual cortices remains undetermined. We characterised the functional response properties of auditory cortex axonal projections to the mouse visual cortex using two-photon calcium imaging. We found that while all visual cortical areas studied receive axons tuned to a wide range of sound frequencies and sound source locations, the encoding of these features is not uniformly distributed across target regions. In particular, sound frequency varies along the anterior-posterior axes of the visual cortex. Furthermore, while information about lateral sound locations is conveyed widely across the visual cortex, information about sounds originating from the centre of the visual field is most prominently conveyed to the rostrolateral visual cortex. Together, these results suggest that segregated auditory input to the visual cortex might lead to distinct multisensory representations across cortical areas.