Perturbation-evoked electrodermal activity responds to instability, not just motor or sensory drives.

OBJECTIVE: To determine whether electrodermal responses (EDRs) evoked by postural perturbations were sensitive to the context of compensatory balance control, or simply reflected sensory or motor components of the reaction.

METHODS: Thirteen participants were perturbed backwards in an upright chair and (1) performed compensatory reach-to-grasp movements to a handhold to recover balance (COMP); (2) received the perturbation only and the chair stopped via mechanical support (SENS); and (3) performed rapid self-initiated reach-to-grasp movements without perturbation (MOT).

RESULTS: EDRs were most frequent and largest in the COMP task, observed in 100% of trials (1.42+/-0.16 microS), compared to 39% of SENS trials (0.31+/-0.12 microS, p<0.0001) and 85% of MOT trials (0.98+/-0.25 microS, p=0.073). EDRs in the MOT task followed two patterns across individuals, leading to post-hoc division of subjects into groups (smaller EDRs than COMP task, n=7, versus equivalent EDRs to COMP task, n=6). Motor patterns were equivalent in both groups, indicating that EDRs did not co vary with efferent drive.

CONCLUSIONS: Perturbation-evoked EDRs are not a direct reflection of sensory input or motor drive.

SIGNIFICANCE: These findings suggest that evoked autonomic activity may play a functional role in compensatory postural control.