Activity in human auditory cortex represents spatial separation between concurrent sounds

Auditory spatial information can enhance stream segregation in an auditory scene, but little is known about how auditory space is represented in the human cortex. If spatial cues are used for scene analysis, then it is the distance between sounds rather than their absolute positions that is essential, and thus, we hypothesized that auditory cortical neurons encode separation between sounds rather than absolute location. To test this hypothesis, we measured human brain activity in response to spatially-separated concurrent sounds with magnetic resonance imaging at 7 Tesla. Stimuli were spatialized amplitude-modulated broadband noises, recorded for each participant via in-ear microphones prior to scanning. Using a linear support vector machine classifier, we investigated if sound location and/or spatial separation between sounds could be decoded from the activity in Heschl's gyrus and the planum temporale. The classifier was successful only when comparing patterns associated with the conditions that had the...