Spectroscopy Study Reveals Hemodynamic Responses for Infant's Facial Expressions

A Japanese research group, led by Professor Ryusuke Kakigi and Dr. Emi Nakato (National Institute for Physiological Sciences) and Professor Masami K. Yamaguchi (Chuo University) have released a study that finds hemispheric differences in the temporal area overlying superior temporal sulcus (STS) when processing positive and negative facial expressions in infants using near-infrared spectroscopy (NIRS).

NIRS, an optimal imaging technique that measures changes in the concentrations of oxyhemoglobin, deoxyhemoglobin and total hemoglobin as an index of neural activation, has recently been used to reveal the brain activity in infants that are awake.

The study, which examined whether the STS is in fact responsible for the perception of facial expressions in infants, showed that the hemodynamic responses elicited by the perception of positive imagery continued to increase even after the happy face stimuli had disappeared, whereas the neural response to negative imagery tended to decrease at a more rapid rate with the presentation of angry face stimuli was halted.

According to the research group, "the different hemodynamic responses between the perception of positive and negative expressions in infants is related to the different biological meanings of positive and negative facial expressions; a positive facial expression can convey a pleasant meaning, while a negative facial expression can be unpleasant or convey danger. The hemispheric lateralization of neural responses to facial expressions develops by the age of 6 months."