Population coding for visual and auditory quantity in human numerotopic maps

Neural populations that are able to extract quantitative information from multiple sensory domains are essential for the survival of numerous species. How quantity is encoded across different senses is far from understood. Here, we identified an overarching coding scheme for visual and auditory numerosity using high-field functional magnetic resonance imaging at 7 Tesla in humans. Based on a neurobiologically plausible model informed by electrophysiological data, we discovered hemodynamic responses revealing logarithmic Gaussian tuning to numerosity in both domains. Responses were organized topographically, forming numerotopic maps. We found several visual maps scattered over the association cortices and anatomically distinct auditory maps in superior temporal and premotor cortices. The present data shed light on the multisensory foundations of numerical information processing in the human brain. These insights open avenues for future research exploring how different species detect quantity in different sensory modalities.