Fig. 1: Aβ-fiber blockade inhibits innocuous pressure sensation in the hand.

a A cartoon depicting the administration of a pressure block during quantitative sensory evaluation. A blood pressure cuff was placed on the upper arm of five healthy adult volunteers and inflated to ~100 mmHg above the participant’s systolic blood pressure. Repeated tests of vibration (1), heat threshold (2), and deep pressure (3) perception were conducted both before and after the placement of the cuff. A barrier blocked visual perception of the test stimuli and noise-isolating headphones played white noise to mask auditory cues. b Vibration sensation (left graph), which is known to be mediated by Aβ afferents, was observed to be substantively eliminated during the course of the nerve block before the heat detection threshold (right graph) noticeably changed. Participants were asked to report when the vibrating probe turned on/off; correct scores indicated preserved sensation. At baseline all participants performed at 100%; a large drop in performance of 50–100% was observed in all participants before pressure testing was conducted (one-sided paired permutation test *p = 0.03). Heat thresholds (right graph) were determined using a thermode placed on the ventral forearm. Increased temperature threshold indicates decreased sensitivity. Heat thresholds were unaltered at the time of pressure testing (one-sided paired permutation test p = 0.47). N = 5 healthy participants. c Pressure sensing with the hand massage device. Pressure ratings between the left and right arms did not differ at baseline (one-sided paired permutation test p = 0.16). At the time of pressure testing, after loss of vibration, intensity ratings were lower on the blocked arm than on the control arm (one-sided paired permutation test *p = 0.03). Ratings dropped significantly more for the blocked arm than the control arm (one-sided paired permutation test *p = 0.03). N = 5 healthy participants.