Alara Akcan^1,2 (), Ufuk Önen¹, Zahide Pamir^1,2; ¹Bilkent University, Ankara, Türkiye, ²Aysel Sabuncu Brain Research Center, Ankara, Türkiye

In this study, we tested whether the primary visual cortex (V1) shows retinotopy-like responses to auditory stimuli with rich spatial structure. If auditory input can evoke such spatial maps, it would imply that topographic organization in V1 is not uniquely visual, but instead reflects a metamodal architecture in which the fundamental organizational principles of early visual cortex extend to other sensory modalities. To address this, we first generated auditory stimuli using the Dolby Atmos system, which turns the sounds into 3D sound “objects” and thus enables them to be located at a specific spatial location, with their immersive, real-like sound qualities. Then, inspired by the principles of classical retinotopy paradigms, we created a novel auditory retinotopic mapping procedure with 2-second spatialized virtual sounds consisting of pure tones alternating between lower and higher frequencies to reflect the flickering checkerboard effect, and each sound was delivered sequentially from 19 distinct spatial positions, spaced 10 degrees apart across a 180-degree horizontal field in front of the participant. After a brief period of blindfolding and 10 minutes of training, three participants completed this auditory-adapted paradigm in fMRI. Our results showed that V1 boundaries defined using auditory stimuli were substantially consistent with the individually defined V1 boundaries by the classical retinotopy procedure. However, in control conditions where auditory stimuli did not contain any spatial information, drawing V1 boundaries using auditory stimuli was either not possible or the correlations were weaker for the patterns consistent with the visually defined boundaries. Previously, a retinotopic-like mapping using auditory stimuli was shown in blind echolocaters, only using the echolocation sounds, indicating the formation of these maps through extensive training. Our findings indicate that auditory stimuli carrying rich spatial information evoke retinotopy-like organization in V1 even in neurotypical individuals with minimal training and short-term and reversible deprivation.

Acknowledgements: This project is funded by the Scientific and Technological Research Council of Türkiye (TUBITAK) through the 3501 Program.