Supplementary Figure 2: Biceps spinal reflex is tuned to hand displacement
From: Spinal stretch reflexes support efficient hand control
a, Mean rectified biceps EMG activity when the wrist flexor muscles were pre-excited prior to the mechanical perturbation (experiment 2; n = 20). Green and blue traces representwrist perturbations that flexed and extended the wrist, respectively, whereas the red trace represents trials in which no perturbation was applied to the wrist. Data are aligned to perturbation onset. Shading represents1 s.e.m. b,Mean rectified biceps EMG activity in the spinal stretch reflex epoch for the three wrist perturbations (F flexion; N, none; E, extension). Thin grey lines represent individual participants and the thick black lines represent the group mean. The biceps spinal stretch reflex was tuned to the hand’s displacement from the target, and not to the elbow extension, (F(2,38) = 44.47, p < 0.001, η2partial = 0.701; post-hoc trend analysis, linear F(1,19) = 47.21, p < 0.001, η2partial = 0.713; quadratic F(1,19) = 5.43, p = 0.03, η2partial = 0.22).
