Wednesday, February 17, 2016

Finally...a brain area specialized for music has been found.

Norman-Haignere, Kanwisher, and McDermott have devised a new method to computationally dissect scans from functional magnetic resonance imaging of the brain to reveal an area within the major crevice, or sulcus, of the auditory cortex in the temporal lobe just above the ears that responds to music (any kind of music, drumming, whistling, pop songs, rap, anything melodic or rhythmic) independent of general properties of sound like pitch, spectrotemporal modulation, and frequency. They also found an area for speech not explainable by standard acoustic features.

It is possible that music sensitivity is more ancient and fundamental to the human brain than speech perception, with speech having evolved from music.
The organization of human auditory cortex remains unresolved, due in part to the small stimulus sets common to fMRI studies and the overlap of neural populations within voxels. To address these challenges, we measured fMRI responses to 165 natural sounds and inferred canonical response profiles (“components”) whose weighted combinations explained voxel responses throughout auditory cortex. This analysis revealed six components, each with interpretable response characteristics despite being unconstrained by prior functional hypotheses. Four components embodied selectivity for particular acoustic features (frequency, spectrotemporal modulation, pitch). Two others exhibited pronounced selectivity for music and speech, respectively, and were not explainable by standard acoustic features. Anatomically, music and speech selectivity concentrated in distinct regions of non-primary auditory cortex. However, music selectivity was weak in raw voxel responses, and its detection required a decomposition method. Voxel decomposition identifies primary dimensions of response variation across natural sounds, revealing distinct cortical pathways for music and speech.

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