Egea Weiss, Alexander; (2025) Functional organisation of auditory inputs to visual cortex. Doctoral thesis (Ph.D), UCL (University College London).

Text Egea Weiss_Thesis.pdf - Accepted Version Access restricted to UCL open access staff until 1 May 2026. Download (7MB)

Abstract

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. Here, I characterised the functional response properties of auditory cortex axonal projections to the mouse visual cortex using two-photon calcium imaging. I found that while all visual cortical areas 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 elevation information was distributed to match the visual elevation tuning of the target area. Moreover, HVAs received auditory inputs that strongly differed in their sound azimuth representation. In contrast, auditory inputs to higher visual areas did not differ in their frequency tuning, or in their encoding of motor variables. However, auditory projections exhibited a tonotopic gradient within V1, matching the retinotopic elevation gradient found in this area. Lastly, signal correlation analysis revealed that auditory projections segregate into two processing streams, that match the functional and anatomical organisation of the visual cortex. Together, these results suggest that segregated auditory input to the visual cortex might lead to distinct multisensory representations across cortical areas and across visual processing streams.

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