Remote Subthreshold Stimulation Enhances Skin Sensitivity in the Lower Extremity.

Area of Science:

• Neuroscience
• Biomechanics
• Sensory Physiology

Background:

• The foot sole's glabrous skin is crucial for balance, but reduced sensitivity impairs this function.
• Stochastic resonance (SR) enhances tactile sensitivity by adding noise, particularly in glabrous skin.
• Hairy skin, found on residual limbs after amputation, has higher sensory thresholds, posing challenges for sensory restoration.

Purpose of the Study:

• To investigate if stochastic resonance (SR) improves tactile sensitivity in hairy skin.
• To determine if a specific noise intensity is most effective for SR in hairy skin.
• To explore potential variations in SR effects based on location, age, and noise modality.

Main Methods:

• Sixty healthy participants received vibrotactile stimuli on the lower extremity concurrently with proximal noisy stimuli.
• A remote SR effect was tested using electrotactile noise on the calf in a subset of participants.
• Detection ability was assessed using a forced-choice protocol with varying noise levels (0-100% of perceptual threshold).

Main Results:

• Evidence of SR was found across all tested groups, with 33-47% of individuals showing improved stimulus detection with added noise.
• No specific noise intensity consistently enhanced SR effects.
• No significant differences in SR effectiveness were observed across tested locations, ages, or modalities.
• Approximately 33% of participants exhibited fluctuating sensory thresholds during testing.

Conclusions:

• Stochastic resonance (SR) can enhance vibrotactile perception in hairy skin.
• The effectiveness and repeatability of SR in hairy skin may be contingent on stable sensory thresholds.
• Further research is needed to optimize SR application for individuals with sensory deficits, particularly those with hairy skin interfaces.