Hearing scenes: A neuromagnetic signature of perceived auditory spatial extent

Perceiving the geometry of surrounding space is a multisensory process, crucial to contextualizing object perception and guiding navigation behavior. Auditory cues are informative about the shape and extent of large-scale environments: humans can make judgments about surrounding spaces from reverberation cues. However, how the scale of auditory space is represented neurally is unknown. Here, by orthogonally varying the spatial extent and sound source content of auditory scenes during magnetoencephalography (MEG) recording, we report a neural signature of auditory space size perception, starting ~145 ms after stimulus onset. Importantly, this neuromagnetic response is readily dissociable in form and time into representations of the source and its reverberant enclosing space: while the source exhibits an early and transient response, the neural signature of space is sustained and independent of the original source that produced it. Further, the space size response is robust to variations in sound source, and vice versa. The MEG decoding signal was distributed primarily across bilateral temporal sensor locations, significantly correlated with behavioral responses in a separate experiment. Together, our results provide the first neuromagnetic evidence for a robust auditory space size representation in the human brain, sensitive to reverberant decay, and reveal the temporal dynamics of how such a code emerges over time from the transformation of complex naturalistic auditory signals.