Equivalent current dipole estimated from SSR potential distribution over the human hand. Sympathetic skin response

Area of Science:

• Neuroscience
• Physiology
• Biophysics

Background:

• The sympathetic skin response (SSR) is a physiological indicator of sympathetic nervous system activity.
• Understanding the precise source and distribution of SSR is crucial for accurate interpretation in clinical and research settings.

Purpose of the Study:

• To determine if the potential distribution of the sympathetic skin response (SSR) on the hand can be modeled using an equivalent current dipole (ECD).
• To investigate the localization of the SSR source on the palm or dorsum of the hand.

Main Methods:

• Simultaneous recording of SSR from palm and dorsum electrodes in 22 healthy subjects.
• Measurement of SSR potential distribution using 18 electrodes in 10 subjects.
• Estimation of ECD from measured potential distribution after auditory, vocal, and inspiratory stimulation.

Main Results:

• SSR potentials were negative on the palm and positive on the dorsum in most subjects.
• Maximum potentials were observed near the base of the middle finger on both palm and dorsum.
• Dorsal SSR amplitude was approximately one-third of the palmar amplitude.

Conclusions:

• The SSR source is likely located on the palm, potentially the sweat glands.
• Equivalent current dipole (ECD) modeling supports a source with a negative pole on the palm and a positive pole on the dorsum.
• The SSR may arise from a potential difference due to Na+ concentration gradients in sweat, influenced by reabsorption.