Abstract
ObjectivesA common behavioural symptom of Parkinson׳s disease (PD) is reduced step length (SL). Whilst sensory cueing strategies can be effective in increasing SL and reducing gait variability, current cueing strategies conveying spatial or temporal information are generally confined to the use of either visual or auditory cue modalities, respectively. We describe a novel cueing strategy using ecologically-valid ‘action-related’ sounds (footsteps on gravel) that convey both spatial and temporal parameters of a specific action within a single cue. MethodsThe current study used a real-time imitation task to examine whether PD affects the ability to re-enact changes in spatial characteristics of stepping actions, based solely on auditory information. In a second experimental session, these procedures were repeated using synthesized sounds derived from recordings of the kinetic interactions between the foot and walking surface. A third experimental session examined whether adaptations observed when participants walked to action-sounds were preserved when participants imagined either real recorded or synthesized sounds. ResultsWhilst healthy control participants were able to re-enact significant changes in SL in all cue conditions, these adaptations, in conjunction with reduced variability of SL were only observed in the PD group when walking to, or imagining the recorded sounds. ConclusionsThe findings show that while recordings of stepping sounds convey action information to allow PD patients to re-enact and imagine spatial characteristics of gait, synthesis of sounds purely from gait kinetics is insufficient to evoke similar changes in behaviour, perhaps indicating that PD patients have a higher threshold to cue sensorimotor resonant responses.
Highlights
Many researchers have suggested that sensory cueing is effective in people with Parkinson's disease (PD) because of the neural pathways through which the sensory information is processed; namely pathways that bypass the basal ganglia, such as cortical and pre-motor areas (Rochester et al, 2007; Cunnington, Iansek, Bradshaw, & Phillips, 1995; Debaere, Wenderoth, Sunaert, Van Hecke, & Swinnen, 2003)
The within subject adaptations in step length (SL) were very similar between groups (Fig. 2), indicating that the basal ganglia are unlikely to play a major role in real-time action-imitation
Based on the observation that young healthy adults can perform adaptations in their SL with comparable success when re-enacting both recorded footsteps and their synthesised counterparts (Young et al, 2013), we suggest that, sounds that are synthesised to represent the kinetic dynamics of foot stepping actions on gravel will provide PD patients with sufficient information to enable effective gait cueing
Summary
The results from the previous two sessions have shown that continuous acoustic guides can be effective in inducing significant adaptations in SL, and remarkable reductions in both spatial and temporal variability of PD patients’ gait Such adaptations in mean SL are only realised when the sound stimuli are recorded footstep actions rather than synthesised from footstep kinetics (see Fig. 4). When imagining themselves walking uphill, downhill, or at different speeds, the relevant adaptations to gait are reflected in the actual walking of young adults, such that participants would walk slower when imagining walking uphill (Courtine, Papaxanthis, Gentili, & Pozzo, 2004) These suggestions are supported by studies showing bilateral activity in the supplementary motor area and primary sensori-motor cortex when healthy adults perform actual or simulated walking (Malouin, Richards, Jackson, Duman, & Doyon, 2003; Bakker, de Lange, Helmich, Scheeringa, & Bloem, 2008; Iseki, Hanakawa, Shinozaki, Nankaku, & Fukuyama, 2008). The neural systems associated with motor imagery may provide a means of retaining a perception of the relevant stepping action that participants can imitate in a similar fashion to that shown in the previous two sessions
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