Effects of Forearm Bathing on Prefrontal Cortex Activity

Abstract

　The purpose of this study was to investigate how forearm bathing affects cerebral hemodynamics while controlling for components of skin hemodynamics that may impact the results. Previous research has indicated that peripheral thermal stimulation can increase prefrontal blood flow, as measured by near-infrared spectroscopy. However, these studies may have included both cutaneous and cerebral blood flow, making it unclear whether forearm bathing actually activated the brain. Therefore, this study focused on activation of the prefrontal cortex by isolating the components of brain functioning.
　This study enrolled 25 healthy adults who underwent a forearm bathing session in water at a temperature of 42.0±0.1℃. The evaluation indices were forebrain oxygenated hemoglobin concentration (as a component of brain function) , which was separated from the cutaneous hemoglobin component of the total hemoglobin component, and subjective mood. The results showed that changes in forebrain oxygenated hemoglobin concentration were significantly greater during forearm bathing than during a control condition. Furthermore, changes in subjective sensations of warmth and relaxation were significantly higher during forearm bathing than during the control condition. These findings suggest that forearm bathing can activate bilateral prefrontal cortices.