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Abstract

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 [12]. 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 [1]. Moreover, sad vocalizations modulated the activity of brain regions known to be involved in processing affective stimuli such as the orbitofrontal cortex [13] and insula [7, 8]. These results suggest remarkably early functional specialization for processing human voice and negative emotions.