The relation between human hair follicle density and touch perception

Area of Science:

• Neuroscience
• Human Physiology
• Sensory Perception

Background:

• Unmyelinated C-tactile fibers are crucial for processing pleasant touch sensations.
• These fibers optimally respond to slow skin stroking (1-10 cm/s).
• Low threshold mechanoreceptors near hair follicles in rodents suggest a potential link between hair follicle density (HFD) and human tactile perception.

Purpose of the Study:

• To investigate the relationship between human hair follicle density (HFD) and the perception of pleasantness during tactile stroking.
• To determine if HFD influences affective touch perception, similar to findings in rodent models.

Main Methods:

• Two studies involving 138 healthy volunteers assessed pleasantness and intensity of tactile stimulation on the forearm.
• A robotic tactile stimulator delivered stroking at C-tactile optimal and non-optimal velocities.
• Hair follicle density (HFD) was measured using the Cyanoacrylate Skin Stripping Method (CSSM); discriminative touch was assessed in study 2.

Main Results:

• Women exhibited higher HFD than men, attributable to differences in body size and weight.
• Women rated affective touch stimuli as more pleasant and demonstrated higher tactile acuity.
• Depilation did not alter touch perception.
• A weak correlation was observed between C-tactile specific aspects of affective touch and HFD, offering limited support for the hypothesis.

Conclusions:

• The study found a weak relationship between hair follicle density (HFD) and the pleasantness of stroking touch in humans.
• While women have higher HFD and perceive touch more pleasantly, HFD is not a strong predictor of affective touch pleasantness.
• Further research is needed to fully elucidate the mechanisms underlying pleasant touch perception.