Neurophysiological Responses to Vicarious Affective Touch: An Electroencephalography (EEG) Study

Area of Science:

• Neuroscience
• Somatosensory processing
• Social cognition

Background:

• Affective touch, mediated by C-tactile afferents (CTs), is crucial for social bonding.
• CTs respond best to caressing touch at ~3 cm/s (CT-optimal speed).
• Vicarious observation of touch can evoke empathy, but processing of CT-optimal vs. suboptimal touch is unclear.

Purpose of the Study:

• To investigate how the brain processes vicariously observed affective touch at CT-optimal speeds.
• To compare subjective pleasantness and EEG responses to static, CT-optimal, and fast touch videos.

Main Methods:

• Participants watched touch videos at static, slow (CT-optimal), and fast speeds.
• Subjective ratings of pleasantness and willingness to receive touch were collected.
• Electroencephalogram (EEG) data were recorded to analyze brain activity.

Main Results:

• CT-optimal touch was rated significantly more pleasant and elicited greater willingness to engage than static or fast touch.
• CT-optimal touch resulted in lower beta power (EEG desynchronization) compared to other speeds.
• Alpha and theta bands showed modulation for slow and fast touch versus static, but not between slow and fast touch.

Conclusions:

• Vicarious processing of CT-optimal affective touch engages more neural resources and activates somatosensory areas more intensely.
• The speed of observed touch significantly influences its affective and neural processing.
• This highlights the importance of specific tactile parameters in social sensory processing.