Neural Mechanisms of Light Driven Analgesia

Summary

The goal of this study will be to understand the biological mechanisms that are responsible to light-driven analgesia. Light presented to the retina has been shown to have pain relieving properties in pre-clinical and clinical studies. In this study the investigators will evaluate the functional connectivity between subcortical visual areas and non-image forming brain areas that are involved in pain sensation. The investigators will also evaluate how three colored light stimuli presented to the retina results in changes in whole brain evoked activation patterns in participants with chronic musculoskeletal pain and in healthy controls. The investigators will also assess while brain evoked activation patterns in response to a pressure pain stimulus in the presence of three light stimuli in individuals with chronic musculoskeletal pain and healthy controls.

Conditions

• Musculoskeletal Pain
• Fibromyalgia
• Healthy Controls Group - Age and Sex-matched

Interventions

OTHER

S-cone modulating visual stimulus

The investigators will deliver a uniform wide-field, S-cone modulating stimulus via a fiberoptic, MRI-safe visual stimulator. This stimulus approximates the appearance of white but modulates the S-cone, driving the S-ON and S-OFF pathways by alternating two lights at 19 Hz using a mixture of light emitting diodes (LEDs), including those embedded in our stimulus with spectral peaks of 405, 565, and 660 nm. This stimulus will differentially activate the S-cones where, between the two phases the ratio of S-cone activity is 100. The frequency alternating between the two lights, 19 Hz, was chosen because retinal ganglion cells in the retina still respond robustly but above the cortical perceptual flicker detection threshold.

OTHER

Equal Energy White Visual Stimulus

The investigators will deliver a uniform wide-field, equal-energy light stimulus via a fiberoptic, MRI-safe visual stimulator. This will serve as a reference condition in which chromatic opponency has been eliminated. This stimulus ensures that the quantal catch of each cone photoreceptor (S-, M- and L-) is held constant using a mixture of LEDs, including those embedded in our stimulus with spectral peaks of 405, 565, and 660 nm. The stimulus will modulate to nearly approximate the appearance of the S-cone modulating light.

OTHER

Green light visual stimulus (S-OFF)

The investigators will deliver a uniform wide-field, green light modulating stimulus via a fiberoptic, MRI-safe visual stimulator. Static Green (565 nm) Light presented via MRI compatible light guides.

OTHER

Evoked Pressure Pain Stimulus

The pressure in which a rapid inflation cuff positioned over the left gastrocnemius achieves a pain severity of 40 where 0 is "no pain" and 100 is the "worst pain imaginable will be determined pre-scan and applied during the entire functional imaging acquisition to evoke a deep pressure pain.

Sponsors & Collaborators

• National Institute of Neurological Disorders and Stroke (NINDS)

  collaborator NIH

• University of North Carolina, Chapel Hill

  lead OTHER

Principal Investigators

• Matthew Mauck, MD, PhD · University of North Carolina, Chapel Hill

Study Design

Allocation

NA

Purpose

OTHER

Masking

NONE

Model

SINGLE_GROUP

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2026-02-24

Primary Completion

2030-01-31

Completion

2030-01-31

Countries

• United States

Study Locations