Neural correlates of balance in people with Parkinson's disease, older and younger adults: an fNIRS study

Background:
Postural instability is one of the most debilitating symptoms of Parkinson’s disease (PD). Moreover, older adults (OA) often show issues with postural control leading to increased fall-risk. However, the current understanding of the neural underpinnings of standing postural control remains limited. This study aims to investigate cortical control of postural control in OA, younger adults (YA), and people with PD (PwPD), using functional near-infrared spectroscopy (fNIRS).
Methods:
A total of four 2-minute standing conditions were performed. Postural control and cortical activity were recorded in 80 PwPD, 33 OA, and 38 YA. A wireless fNIRS system recorded changes in relative oxygenated haemoglobin (∆HbO2) across cortical regions including the prefrontal cortex (PFC), supplementary motor area (SMA), primary motor cortex (M1), primary somatosensory cortex (S1), and primary visual cortex (V1). Six wearable sensors provided sway outcome measures (area, jerkiness velocity, root mean square, and frequency).
Results:
Sway outcomes were greater across several conditions in PwPD. Significant group effects were found with increased ∆HbO2 in the PFC in PD compared to OA. Moreover, YA had increased ∆HbO2 in the S1 compared to OA and PD.
Conclusions:
PwPD showed greater PFC recruitment, indicating reliance on executive-attentional resources for balance. In contrast, YA engaged somatosensory regions more strongly, suggesting that ageing may affect the integration of sensory information for postural control. Findings support interventions that (a) reduce executive load during balance in PD and (b) bolster somatosensory integration in ageing.