Early specialization for voice and emotion processing in the infant brain
Blasi, A., Mercure, E., Lloyd-Fox, S., Thomson, A., Brammer, M., Sauter, D., Deeley, Q., Barker, G. J., Renvall, V., Deoni, S., Gasston, D., Williams, S. C., Johnson, M. H., Simmons, A., & Murphy, D. G.
Early specialization for voice and emotion processing in the infant brain. Current Biology, 21
, 1220-1224. doi:10.1016/j.cub.2011.06.009.
Human voices play a fundamental role in social communication, and areas of the adult ‘social brain’ show specialization for processing voices and its emotional content (superior temporal sulcus - STS, inferior prefrontal cortex, premotor cortical regions, amygdala and insula [1-8]. However, it is unclear when this specialization develops. Functional magnetic resonance (fMRI) studies suggest the infant temporal cortex does not differentiate speech from music or backward speech [10, 11], but a prior study with functional near infrared spectroscopy revealed preferential activation for human voices in 7-month-olds, in a more posterior location of the temporal cortex than in adults . Yet, the brain networks involved in processing non-speech human vocalizations in early development are still unknown. For this purpose, in the present fMRI study, 3 to 7 month olds were presented with adult non-speech vocalizations (emotionally neutral, emotionally positive and emotionally negative), and non-vocal environmental sounds. Infants displayed significant activation in the anterior portion of the temporal cortex, similarly to adults . Moreover, sad vocalizations modulated the activity of brain regions known to be involved in processing affective stimuli such as the orbitofrontal cortex  and insula [7, 8]. These results suggest remarkably early functional specialization for processing human voice and negative emotions.