Cortical substrates of perceptual confusion between pitch and timbre
Pitch and timbre, two fundamental perceptual attributes of sound, are commonly regarded as distinct features, but can be confused when varied simultaneously. Here we combine human behavior and fMRI to demonstrate a neural substrate to explain the well-known perceptual confusion effects. We identify orderly mappings of both pitch and timbral brightness within auditory cortex and reveal two independent lines of evidence for cortical confusion between them. First, voxels' preferred pitch decreases systematically as brightness increases, and vice versa, consistent with predictions based on perceptual confusion. Second, pitch and brightness mapping share a common high-low-high gradient across auditory cortex, implying a shared trajectory of cortical activation for changes in each dimension. The results provide a cortical substrate at both local and global scales for an established auditory perceptual phenomenon that is thought to reflect efficient coding of ubiquitous features in natural sound statistics.