Near-InfraRed Spectroscopy of Auricular Stimulation

Neural Responses to Tactile Auricular Stimulation Measured by Functional Near-infrared Spectroscopy in Pain-free Volunteers

This is a single-visit non-invasive study of healthy volunteer subjects. Brain activity will be measured with infra-red light sensors attached to a cap worn on the head, while both ears are gently stimulated with plastic filaments.

The aim of this study is to localize and quantify brain activations from experimental stimulation of auricular points in pain-free volunteers. Investigators will stimulate auricular points for the shoulder, thumb, and lumbar spine with von Frey filaments and measure functional near-infrared spectroscopy (fNIRS) responses in the primary somatosensory (S1) and prefrontal cortex (PFC). This will test the hypothesis that stimulation across different points in the auricular cartography maps to distinct brain responses, an assumption underpinning AT theory. Stimulation of different ear points is anticipated to induce similar PFC responses, but activate distinct areas within the S1 homunculus, validating the concept of auricular cartography.

Inclusion Criteria:

Age of at least 18 years

Exclusion Criteria:

1. frequent or chronic pain requiring the use of pain-relieving medications more than twice per week, on average, in the last 3 months,
2. history or symptoms of neuropathy,
3. active lesions or skin disruptions to either ear,
4. recent (< 3 mo) illicit drug use,
5. history of substance misuse/abuse,
6. current or recent (<1 month) opioid or marijuana use, and
7. current regular use of psychoactive prescription medications