Characteristics of EEG Event-Related Potentials on Perception of Fast and Slow Stroking: Distinguishing Responses of the Discriminative and Affective Systems of Mechanoreception

Studies over the last 25 years have convincingly demonstrated that humans have several independent cutaneous mechanoreception systems. Best studied is the discriminative touch system, which combines cutaneous mechanoreceptors innervated by fast myelinated afferent type Aβ fibers and provides detailed information on the site of contact and nature of the stimulus. The affective C-tactile system was discovered relatively recently and provides unconditioned positive emotions in response to slow, gentle touching. The dynamics of the electrical response of the cortex to afferents from the C-tactile system have received almost no study, while existing data are insufficient to distinguish the components of the brain response associated with the activity of the Aβ- and C-tactile systems. This pilot study analyzed EEG event-related potentials in response to fast (30 cm/sec) and slow (5 cm/sec) stroking, applied using a robot device. A total of 13 adult subjects took part in the study. The first ERP components in the response to stroking were seen during the time interval 400–1800 msec in the lateral frontal and central leads; their amplitude was greater for fast stroking, indicating their association with activity in the Aβ system. A P2100–N2300 complex was seen only for slow stroking and was probably linked with the reaction of the Aβ system to termination of stimulation; it was accompanied by an ultra-late positive potential presumptively associated with the response of the C-tactile system. The results confirm the existent of the ultra-late positive potential identified in previous studies for slow stroking and allow this potential to be differentiated from other late components of the response. © 2022, Springer Nature Switzerland AG.