81 J. Cosmet. Sci., 74, 81–91 (March/April 2023) *Address all correspondence to Takayuki Kodama, kodama-t@tachibana-u.ac.jp Effects of Tactile Stimulation by Foams of Different Viscosities on Electroencephalogram Signals From Brain Regions Involved in Emotional Processing AKIO GODA, KAZUYA INOKO, MAYUMI KAGAMI, TAKAYUKI KUMEI, TOMOHIRO UEDA, KANO HIKINO AND TAKAYUKI KODAMA Department of Physical Therapy, Faculty of Health Sciences, Kyoto Tachibana University, Kyoto, Japan (A.G., T.U., K.H., T.K.) FANCL Research Institute, FANCL Corporation, Yokohama, Japan (K.I., M.K.) Accepted for publication July 01, 2023. Synopsis Objective evaluation of the influence of foam-induced tactile stimulation on participants’ emotions is important. This study aimed to quantify neurophysiological indices of the emotional effect of tactile stimulation by foam of different viscosities. Twelve healthy adult females were asked to wash their faces with three types of facial cleansing foams of low, medium, or high viscosity while electroencephalograms of their brain activities were recorded. Salivary cortisol levels were measured before and after face-washing. Foam-mediated tactile stimulation during face-washing increased activity in the orbitofrontal and anterior cingulate cortex. However, the increase in both regions was significantly smaller with the use of high viscosity foam than that with other foam types. With low viscosity foam, the neural activity was significantly higher when the foam was placed on participants’ faces compared to on their hands. Furthermore, the neural activity hemisphericity and the extent of changes in salivary cortisol levels during face-washing indicated that the high viscosity foam elicited more negative emotions than the low viscosity foams. The results suggest that tactile stimulation with foam causes emotional changes in participants according to foam viscosity, with low and medium viscosity foams causing pleasing sensations and high viscosity foams causing distinctly stressful emotions. INTRODUCTION During somatosensation, signals are generated on the dermal surface by touch stimuli. These signals are then transmitted to the central nervous system via peripheral nerves and are processed by neural networks.1 Through a wide range of tactile receptors located on the surface of our bodies, we constantly receive and process information from the external world. Tactile information can cause a myriad of emotional stimulations.2 For example, touching smooth or soft objects often elicits a sense of comfort.3 Studies suggest that the role of tactile information in creating pleasant emotions may be important in designing and developing appropriate stimuli to elicit emotional responses.4