Distinct functional levels of human voice processing in the auditory cortex

Voice signaling is integral to human communication, and a cortical voice area seemed to support the discrimination of voices from other auditory objects. This large cortical voice area in the auditory cortex (AC) was suggested to process voices selectively, but its functional differentiation remained elusive. We used neuroimaging while humans processed voices and nonvoice sounds, and artificial sounds that mimicked certain voice sound features. First and surprisingly, specific auditory cortical voice processing beyond basic acoustic sound analyses is only supported by a very small portion of the originally described voice area in higher-order AC located centrally in superior Te3. Second, besides this core voice processing area, large parts of the remaining voice area in low- and higher-order AC only accessorily process voices and might primarily pick up nonspecific psychoacoustic differences between voices and nonvoices. Third, a specific subfield of low-order AC seems to specifically decode acoustic sound features that are relevant but not exclusive for voice detection. Taken together, the previously defined voice area might have been overestimated since cortical support for human voice processing seems rather restricted. Cortical voice processing also seems to be functionally more diverse and embedded in broader functional principles of the human auditory system.

Automated summary

Voice signaling is an integral part of human communication, and the voice area in the auditory cortex plays a crucial role in discriminating voices from other auditory objects. However, the functional differentiation of this voice area remains unclear and might have been overestimated. Neuroimaging studies revealed that only a small portion of the originally described voice area in the higher-order auditory cortex is specifically involved in voice processing. The remaining parts of the voice area in both low- and higher-order auditory cortex mainly process non-specific psychoacoustic differences between voices and nonvoices. Additionally, a specific subfield in the low-order auditory cortex appears to decode relevant acoustic sound features for voice detection but not exclusively.