Vicarious processing of affective touch: an electroencephalography (EEG) study

Affective touch is a somatosensory modality involved in forming and consolidating positive social interactions. It is transduced in our skin presumably through C-Tactile mechanoreceptors, which are preferentially activated when touch is performed at speeds around 3cm/s (or CT-optimal speed). This increased activation, in turn, is related to greater pleasantness feelings. Given its social relevance, the observation of the affective touch can cause high empathic resonance in the observer. However, little is known whether the observation of CT-optimal touch is processed differently in our brain than at other CT-suboptimal speeds. In the present study, we evaluated the pleasantness ratings and the electroencephalogram of 30 healthy participants while they watched videos of affective touch at 3 speeds: static, slow (CT-optimal), and fast touch. We found that CT-optimal touch received higher evaluations of pleasantness and was related to a higher amplitude of the P3 component and desynchronization of beta activity compared to static or fast touch. Other frequency bands, such as theta and alpha, showed increased modulation to slow and fast touch compared to static touch, but did not allow us to distinguish between slow and fast conditions. Our results suggest that vicarious processing of affective touch at the optimal speed for CT receptors involves more processing resources and higher activation of somatosensory areas, evidencing that this modality of touch is a prioritized type of information.