Sensory Afferents for Deep Pressure Sensation

Objective: The sensory basis of non-painful deep pressure sensation is not known. We recently found that innocuous pressure sensation is eliminated in rare sensory neuronopathy patients with a specific loss of A-beta fibers, strongly suggesting that A-beta fibers underlie the ability to sense deep pressure. In addition, we and others have shown that deep pressure touch (observed in hugs and massage) frequently conveys a sense of pleasantness. The current study aims to examine the role of A-beta fibers in the perception of deep pressure touch including both its intensity and the pleasant affect it often elicits. This study constitutes the second study of the K99 phase of a K99/R00 grant application awarded to Dr. Laura Case by National Center for Complementary and Integrative Health (NCCIH). Study Population: Up to 24 healthy participants will be enrolled in the study with a goal of 12 completers. Participants will be invited based on previous screening and participation in our studies. Design: Participants will undergo an ischemic-compression block. Sensory stimuli will be administered at frequent intervals to capture the loss of sensation related to A fibers as the block progresses. Before and after A-beta-associated sensations have been lost, the perception of deep pressure will be tested. Participants will rate the intensity and pleasantness of the pressure. Ratings of pain and discomfort will be collected throughout the study session. Outcome measures: Primary outcome; Rating of intensity of deep pressure on the blocked arm before versus after loss of A-beta sensation, compared to ratings on the unblocked arm. Secondary outcomes: 1) Rating of pleasantness of deep pressure on the blocked arm after loss of A-beta sensation, compared to ratings on the unblocked arm; 2) Ratings of intensity and pleasantness of gentle brushing on the blocked arm after loss of A-beta sensation, compared to ratings on the unblocked arm.