Sound design for auditory biofeedback and motor performance in participants with stroke: a pilot study

Background: Although auditory biofeedback (ABF) has proved to be effective in stroke rehabilitation, there are a variety of means by which to present information through sound. Objectives: To examine if ABF sound design influences the motor performance of patients with stroke. Methods: A total of four people with chronic stroke participated . They were asked to track target signals by their paretic ankle dorsiflexion. Half of the participants were assigned to one of the two groups. Those in the Error ABF group heard ABF that alerted them to the error between the target and the joint angle. Those in the Full ABF group heard ABF that presented both the target and the angle separately by modulating the frequencies of two sounds. Therefore, when there was no error, no sound or two sounds with the identical frequency were heard in the Error and Full ABF sessions, respectively. The same visual BF (VBF) was always present regardless of the group. The accuracy of the task was quantified via an accuracy index (AI, ranging from -100 to 100). All participants were trained by repeating tracking, and the pre- and post-training AIs were obtained. Results: The AIs of all participants increased after training, but the increase was greater for the Error ABF group (mean increase = 8.9 and 14.9 for the Full and Error groups, respectively). Conclusions: The Full ABF was less effective than the Error ABF, probably because the VBF was present, and the information provided by the Full ABF was therefore redundant.