A study on the emotional responses on hearing laughter from brain activity measurements using near-infrared spectroscopy

Abstract Background: Studies have recognized the beneficial effects of hearing laughter. However, its mechanism has not been sufficiently investigated. Therefore, we examined how laughter influenced affect and emotions and evaluated brain activity upon hearing laughter via near-infrared spectroscopy (NIRS). Methods: An experiment was conducted with seven healthy university students and used a block design with laughter and relaxing music as interventions. A portable brain activity measurement device (HOT-2000; NeU Corporation) was used to capture neural activity in the lateral prefrontal cortex, based on the degree of changes in total hemoglobin (Hb). Results: Comparison of the blood flow volume between the right and left prefrontal lateral cortices after each intervention revealed a significant difference in total Hb; however, this was only at rest. No differences were observed during either the laughter or music intervention. Furthermore, comparison of the cerebral blood flow volume between the three experimental conditions (rest period, laughter, music) revealed a significant difference (p = 0.016) between rest period and laughter. However, no significant difference was observed between the other factors. Discussion: The results did not provide substantial insights into the affect and emotions during laughter interventions based on the degree of change in total Hb between the right and left lateral prefrontal cortices. However, hearing laughter brought about changes in mental states, such as feelings of pleasure and calm, which suggested that hearing laughter relaxed brain activity.