Hemodynamic responses (fNIRS) and EEG modulation of prefrontal cortex during emotion processing

The investigation of neural networks underlying emotion perception and recognition has received considerable attention during the past few years within the affective neuroscience domain. Neuroimaging studies revealed that the prefrontal cortex (PFC) is involved during emotional stimuli comprehension and evaluation, based on stimulus valence and arousal. Nevertheless, the way in which these emotional parameters affect hemodynamic variations has to be clarified. The present study investigated the changes in prefrontal hemodynamic activation by means of an event-related near-infrared spectroscopy (fNIRS) paradigm during the presentation of emotional patterns taken from the International Affective Picture System (IAPS). During the task, 20 subjects (12 females and 8 males) passively viewed neutral, positive and negative emotional images, which could also be low or high arousing (20 stimuli for each category). Stimuli were presented for 6 s in a randomized order, with 12s inter- stimulus interval. Hemodynamic and electrocortical (EEG) activities were simultaneously recorded from 6 NIRS and 16 EEG channels, in the same session. Changes in oxygenated (oxyHb) and deoxygenated (deoxyHb) hemoglobin were measured with respect to the different experimental conditions. Results showed that the emotional valence of the picture modulates the activation of the PFC, with increased activity for negative patterns and decreased activity for positive ones, if compared to neutral condition. Moreover, preliminary analyses revealed a consonance between EEG (frequency band oscillations) and hemodynamic responses. In conclusion, the present study revealed that prefrontal blood oxygenation and brain oscillations are differently modulated by the emotional content mainly related to the stimulus valence, and demonstrated that the PFC is involved in emotional processing.