Intra-epidermal Stimulation (IES) of Small Nerve Fibers (A-delta Fibers)

The epidermis is the outermost layer of the skin that includes skin cells and small nerve
fibers called A-delta fibers. A-delta fibers send signals to the brain about pin-prick type
of pain and temperature. The investigators want to study whether the investigators can
stimulate A-delta fibers and document this by recording electrical potentials from the nerves
in subjects' limbs.

Study Procedures:

A small piece of plastic will be applied to your foot and your hand. A tiny sharp tip
protrudes from this piece of plastic. You will be barely able to feel this sharp tip when
touching the piece of plastic. This is the electrode for intra-epidermal stimulation.

With stimulation, you will feel a pin-prick type of sensation. The stimulus will be adjusted
so that you barely feel the pin-prick type of sensation. The investigators will record
responses of stimulation from nerves in your skin.

Inclusion Criteria:

- Individuals aged 21 through 60 years with no history or clinical signs of neuropathy.

Exclusion Criteria:

1. History of peripheral nerve disease or disease of somatosensory pathways.

2. Abnormalities on neurologic examination.

3. Prior or current exposure to known neurotoxins, such as excessive alcohol use or
chemotherapy.

4. Neurologic or psychiatric conditions that would prevent the subject from being able to
cooperate with testing.