Auditory cortex conveys non-topographic sound localization signals to visual cortex.

Perception requires binding spatiotemporally congruent multimodal sensory stimuli. The auditory cortex (AC) sends projections to the primary visual cortex (V1), which could provide signals for binding spatially corresponding audio-visual stimuli. However, it is unknown whether AC inputs in V1 encode sound location. We used dual-color two-photon axonal calcium imaging and an array of speakers to measure the auditory spatial information that AC transmits to V1. We found that AC relays information about the location of ipsilateral and contralateral sound sources to V1. Sound location could be accurately decoded by sampling AC axons in V1, providing a substrate for making location-specific audiovisual associations. However, AC inputs were not retinotopically arranged in V1, and audio-visual modulations of V1 neurons did not depend on the spatial congruency of the sound and light stimuli. The distributed, non-topographic sound localization signals provided by AC might allow the association of specific audiovisual spatial patterns in V1 neurons.