Sensory reweighting for balance in people living with Parkinson's Disease: Postural adaptation, muscle co-contraction, and perceptual delays.

Background: Postural instability is common in people with Parkinson's Disease (PwPD), increasing their risk of injurious falls. Evidence suggests a sensory reweighting deficit in PwPD, along with compensatory muscle co-contraction in response to postural challenges. During balance tasks requiring sensory reweighting, older adults exhibit elevated postural sway and muscle co-contraction, as well as longer perceptual delays, compared to young adults. Such responses may be exacerbated in PwPD, with implications for fall risk.

Research Question: The aim of this study was to assess postural sway, muscle co-contraction, and perceptual delays in PwPD and healthy age-matched controls during a sensory reweighting balance task.

Methods: Eleven PwPD and 16 control participants completed a sensory reweighting protocol: standing without vision on a fixed platform (2-min), which then undergoes a period of body sway-referencing (3-min) before returning to its fixed position (2.5-min). Anteroposterior (AP) path length, co-contraction index (CCI), and perceptual delay were analysed across task phases.

Results: PwPD showed a longer delay in perceiving when the body sway-referenced platform returned to a fixed position. This perceptual delay in PwPD (43.40-s) was over double that observed in control participants (21.25-s). AP path length and co-contraction aftereffects were longer in control participants than PwPD.

Significance: Where conditions require it, PwPD can effectively adjust their reliance on proprioceptive information for postural control. However, the significant delay shown by PwPD in perceiving changes to sensory conditions could be detrimental during everyday sensory transitions, potentially increasing fall risk.