Abstract
Touching is a fundamental human behavior used to evaluate objects in the external world. Many previous studies have used tactile stimulation to conduct psychological and psychophysiological experiments. However, most of these studies used solid material, not water stream, as an experimental stimulus. To investigate water perception, or to easily control the temperature of an experimental stimulus, it is important to be able to control the water stimulus. In this study, we investigated the usability of water as an experimental stimulus for electroencephalography (EEG) experiments and report the basic EEG response to water stimulus. We developed a tactile stimulation device using a water stream to study EEG responses, with the ability to control the stimulus onset timing. As stimuli, we selected two types of water stream, normal and soft, based on a psychological experiment to confirm a difference of subjective feeling induced by these water streams. We conducted a typical oddball task using the two different water streams and recorded EEG waveforms from 64 electrodes while participants touched the water streams. We calculated P300 at the Pz electrode, alpha asymmetry at the frontal electrodes, and alpha suppression at the parietal area. As a result, we observed typical P300 differentiation based on the stimulus proportion (target 20% and standard 80%). We observed a weaker alpha suppression when participants touched the soft water stream compared to the normal shower. These results demonstrate the usability of water stream in psychophysiological studies and suggested that alpha suppression could be a candidate to evaluate comfort of water stream.
Highlights
Recent technologies for modulation of tactile experiences demonstrated that, in the very near future, tactile perception might be freely created to induce a specific affective response, in the same way that is currently possible with visual and auditory perception
The time period in which the waveforms to target stimuli were greater than those to standard stimuli was from about 300–800 ms. This time period is typical for P300 to low-frequency target stimuli
We aimed to test two hypotheses: first, whether a water stream as a tactile stimulus could induce P300 and whether amplitudes were different between target and standard stimulation in the typical oddball task; second, whether tactile comfort induced by a water stream could be indexed by alpha oscillation
Summary
Recent technologies for modulation of tactile experiences demonstrated that, in the very near future, tactile perception might be freely created to induce a specific affective response, in the same way that is currently possible with visual and auditory perception. The softness experience could be modulated with vibrotactile stimuli (Hayward, 2008; Visell and Okamoto, 2014). These stimuli could be induced with typical solid materials but possibly with ultrasonic mid-air stimulation (Hoshi et al, 2009; Long et al, 2014). A water stream is an ethologically important stimulus for inducing tactile perception on the surface of the human body. Some uses of water include cleaning one’s body; in this regard, touching water can induce a comforting feeling. To elucidate the neural mechanisms underscoring the pleasure of touching, water may be a useful stimulation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
