The power of tactile imagery: parallels between imagined and physical CT-optimal touch in pleasantness and velocity

Interpersonal, caress-like touch evokes pleasant sensations and can reduce stress, anxiety and pain. These effects likely stem from stimulation of C-Tactile (CT) fibers, activating brain regions involved in affective processing. Imagined touch, tactile imagery, elicits similar brain activation and pleasant sensations. However, a direct comparison of CT-optimal touch perception during imagery and stimulation is lacking. Moreover, it is unclear whether individuals can imagine touch at CT-optimal velocities. Here we compared perceived pleasantness of CT-optimal and CT-non-optimal touch during imagery and stimulation in 48 healthy adults. We additionally recorded imagery durations, to investigate whether individuals can differentially imagine slower, CT-optimal (3 cm/s), and faster, CT-non-optimal (18 cm/s) stroking. Participants first performed tactile imagery of slow or fast stroking with a brush or stick, followed by equivalent stimulation by an assessor. Overall, pleasantness scores were slightly, albeit significantly, lower for imagery than stimulation. Importantly, in both imagery and stimulation, slow stroking and brush stroking (CT-optimal) were perceived as significantly more pleasant. Moreover, relative pleasantness scores for imagery and stimulation showed significant positive correlations. Importantly, participants took significantly longer to imagine slow stroking, suggesting that individuals can accurately imagine CT-optimal touch velocities. Our findings illustrate parallels between imagery and stimulation in terms of temporal congruency and affective appreciation of touch. This suggests that similar top-down processes are likely involved, and confirms tactile imagery's potential for future clinical applications.