The Early Social Brain – fMRI of Auditory Emotional Processing in Infants

Background: Social communication relies on the ability to interpret non-verbal social signals, but little is known about the early development of the neurocognitive systems underlying this ability. Studies in adults have found that nonverbal emotional stimuli - including observation of emotional facial expressions and passive listening to emotional nonverbal vocalisations - engage premotor regions of cerebral cortex (Carr et al. 2003; Warren et al. 2006), suggesting a link between perception and production of social signals. It has been proposed that this link may be a key component of the empathic response (Agnew et al. 2007). However, it is not known whether such an emotional “mirror” system exists in early infancy.

Objectives: This study aimed to investigate the early development of neural systems involved in the processing of non-verbal human emotional vocal signals, such as laughter and sighing, using functional magnetic resonance imaging.

Methods: Typically developing infants aged between 2 and 5 months were scanned using a fMRI passive listening task. They were played positive and negative nonverbal vocalisations, as well as neutral vocalisations and control sounds. Following pre-processing, fMRI volumes were mapped to an infant brain template.

Results: Preliminary group analyses suggest that frontal premotor, superior temporal and anterior cingulate areas are active in response to positively valenced vocalisations. Negatively valenced vocalisations activate cortical areas including posterior cingulate and superior temporal gyrus.

Conclusions: These results demonstrate that infant brain function is modulated by emotional sound, and in similar brain regions to adults.  These include limbic structures, cortical 'motor preparatory' areas, and regions including mirror neurons. We plan further investigations into how infants who are at risk of neurodevelopmental disorders differ from neurotypical controls.