Distinct Cortical Pathways for Music and Speech Revealed by Hypothesis-Free Voxel Decomposition

• Published in: Neuron (Cambridge, Mass.) Mass.), 2015-12, Vol.88 (6), p.1281-1296
• Main Authors: Norman-Haignere, Sam, Kanwisher, Nancy G., McDermott, Josh H.
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation - methods; Adult; Auditory Cortex - physiology; Auditory Pathways - physiology; Decomposition; Female; Humans; Hypotheses; Magnetic Resonance Imaging - methods; Male; Music; Random variables; Sound; Speech; Speech - physiology; Young Adult
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2015.11.035

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. •Voxel decomposition infers canonical components of responses to natural sounds•Decomposition reveals speech and music selectivity in distinct non-primary regions•Music selectivity is diluted in raw voxel responses due to component overlap•Organization of primary regions reflects tuning for frequency, modulation, and pitch Norman-Haignere et al. introduce voxel decomposition: a method that infers putative neural populations (“components”) from fMRI responses to natural stimuli. This method reveals distinct cortical pathways selective for music and speech, despite being unconstrained by prior functional hypotheses.