Impaired visual reweighting and adaptive postural control in Parkinson's disease: insights from rambling-trembling...

Postural instability is a hallmark of advanced Parkinson's disease (PD) and substantially increases fall risk, injury incidence, and loss of functional independence. However, the mechanisms underlying impaired postural control, particularly sensory reweighting and adaptive regulation, remain incompletely understood.

To characterize postural control in PD using rambling-trembling decomposition and stabilogram diffusion analysis (SDA), and to examine the effects of visual and cognitive demands as well as their clinical relevance.

Sixty-four participants (42 PD; 62.81 ± 10.98 years; 22 age-matched healthy controls, 61.27 ± 12.29 years) performed quiet standing under four conditions combining vision (eyes open/closed) and cognitive load (single/dual task). Center of pressure signals were analyzed using linear metrics, rambling-trembling decomposition, and SDA parameters. Functional mobility and cognitive status were assessed.

PD participants exhibited greater sway, increased rambling displacement, elevated trembling velocity, and prolonged critical time, indicating impairments across central, peripheral, and stochastic domains. Visual reweighting was disrupted, as patients failed to adapt postural dynamics under visual and cognitive constraints, while controls showed context-dependent modulation. Postural parameters were significantly associated with functional mobility in PD but not in controls, whereas associations with global cognition were limited.

Postural instability in PD reflects a loss of adaptive control across multiple mechanisms linked to impaired visual reweighting. Multiscale postural analysis may provide clinically relevant markers and support the use of sensory and cognitive challenges in assessment and rehabilitation.