Multichannel NIRS analysis of brain activity during semantic differential rating of drawing stimuli containing different affective polarities.

We used 24-channel near-infrared spectroscopy (NIRS) to measure activity in the temporal, parietal, and frontal regions of the brain in eight Japanese women while the participants rated line drawings using semantic differential scales. Participants rated the seven line drawings on 15 bipolar semantic scales, each of which belonged to one of three semantic classes: Evaluation, Activity, or Potency. Suzuki et al. [M. Suzuki, J. Gyoba, Y. Sakuta, Multichannel near-infrared spectroscopy analysis of brain activities during semantic differential rating of drawings, Tohoku Psychologica Folia 62 (2003) 86-98.] had reported previously that the right superior temporal gyrus and the right inferior parietal lobule are associated with Activity rating, while the brain regions around the central fissure were related to Potency rating. Based on these suggestions, we investigated the brain activity in these regions during rating of stimuli containing different affective polarities. When drawings were reported as 'static' or 'calm', oxyhemoglobin concentration was higher around the right superior temporal gyrus as compared to when they were considered 'noisy' or 'excitable'. Oxyhemoglobin concentrations around the central fissure were also higher when drawings were rated as 'soft', 'smooth', or 'blunt' compared to 'hard', 'rough', or 'sharp'. Any characteristic oxyhemoglobin changes were not found during the ratings on the evaluation scales. Our results suggest that activation patterns of the temporal and parietal regions are significantly modified by semantic polarities of Activity and Potency.