Recognition of Human Emotions from Cerebral Blood Flow Changes in the Frontal Region: A Study with Event-Related Near-Infrared Spectroscopy

Abstract

The aim of this study is to develop a near-infrared spectroscopy (NIRS)-based system that recognizes pleasant and unpleasant human emotions based on cerebral blood flow (CBF) in order to understand the minds of patients whose brain function is severely impaired. The forehead region is easily accessible to NIRS measurements, whereas the role of the anterior prefrontal cortex (PFC) in the processing of emotion remains to be elucidated. Initially, using event-related NIRS we examined changes in oxygenated hemoglobin (oxy-Hb) as an indicator of regional CBF changes, which reflect brain activity directly related to emotions, but not to cognitive operations in the anterior frontal regions, during viewing affective pictures. The event-related potentials (ERPs), systemic blood pressure, and pulse rate were also measured simultaneously. The event-related analysis of changes in oxy-Hb for a 6 s-picture presentation period showed that very unpleasant emotion was accompanied by an increase in oxy-Hb in the bilateral ventrolateral PFCs, while very pleasant emotion was accompanied by a decrease in oxy-Hb in the left dorsolateral PFC. There were no significant differences in either ERPs or autonomic nervous system activities between the two emotional states. These findings suggest the possibility of recognizing patients' emotions from CBF changes.