Auditory feedback regulation of perturbed stance in stroke patients.

The effect of auditory input on impaired postural control perturbations was evaluated in two groups of stroke patients participating in a rehabilitation programme after a recent (< 12 months) and single episode of stroke, or less recent (> 12 months), and multiple episodes of stroke. Auditory input took the form of feedback signals generated by the forces actuated by the feet on a force platform in response to the patient's postural movements. Vibratory stimuli applied to the calf muscles induced sudden perturbations which the patients had to counteract to maintain an upright stance. The effect of auditory feedback in facilitating the maintenance of stance was measured in terms of sagittal torque variance (body sway) recorded on a force platform. In the presence of auditory feedback, body torque variance in response to perturbed posture was significantly reduced in the recent stroke group, whereas in the less recent stroke group the auditory feedback did not prove effective. Moreover, learning seems essential to utilize the auditory feedback.