Monaural Auditory Cue Affects the Process of Choosing the Initial Swing Leg in Gait Initiation

Abstract

The authors investigated the effect of an auditory cue on the choice of the initial swing leg in gait initiation. Healthy humans initiated a gait in response to a monaural or binaural auditory cue. When the auditory cue was given in the ear ipsilateral to the preferred leg side, the participants consistently initiated their gait with the preferred leg. In the session in which the side of the monaural auditory cue was altered trial by trial randomly, the probability of initiating the gait with the nonpreferred leg increased when the auditory cue was given in the ear contralateral to the preferred leg side. The probability of choosing the nonpreferred leg did not increase significantly when the auditory cue was given in the ear contralateral to the preferred leg side in the session in which the auditory cue was constantly given in the ear contralateral to the preferred leg side. The reaction time of anticipatory postural adjustment was shortened, but the probability of choosing the nonpreferred leg was not significantly increased when the gait was initiated in response to a binaural auditory cue. An auditory cue in the ear contralateral to the preferred leg side weakens the preference for choosing the preferred leg as the initial swing leg in gait initiation when the side of the auditory cue is unpredictable.

The Left Posterior Parietal Cortex Contributes to the Selection Process for the Initial Swing Leg in Gait Initiation

“…A monaural auditory start cue to the ear ipsilateral to the non-preferred initial swing leg changed the probability of the initial swing leg when the cue side was not predictable [3]. The change in the selection process of the initial swing leg must have been processed within the reaction time in this previous study because the monaural auditory cue was given as the start cue.…”

“…Based on this view, the motor process of gait initiation, including the APA and step movement, occurs within the reaction time of the APA, and the APA latency reflects the time taken to execute the motor process of gait initiation. The direction of the COP displacement in the medial-lateral axis is contrary between gait initiation with the left leg and that with the right leg [2,3,29]. Thus, the APA latency of gait initiation with the left leg represents the time taken for execution of the motor process of gait initiation with the left leg, and vice versa.…”

“…For example, the probability of hand selection is affected by asymmetrical auditory input [31]. In addition, an asymmetrical auditory start cue has been found to influence the selection process of the initial swing leg of gait initiation [3]. Thus, one may speculate that the change in the probability of the initial swing leg of gait initiation induced by TMS over P3 could be explained by the asymmetrical auditory input caused by the coil click over the left scalp.…”

“…Healthy humans tend to consistently initiate gait with the same leg [1][2][3]. In contrast, in patients with Parkinson's disease (PD) with the symptom freezing of gait (FOG), there is an inter-trial variability of the initial swing leg of gait initiation [1].…”

“…To investigate this issue, one methodological concern needed to be resolved. In healthy humans, the initial swing leg of gait initiation is consistent [1][2][3]. Thus, the opportunity to increase the use of the preferred initial swing leg by some intervention is much lower than that of the non-preferred initial swing leg.…”