Impaired Sensory Gating During Standing Balance in Parkinson's Disease

Abstract

While motor deficits in Parkinsons disease (PD) are well-studied, the role of somatosensory processing in postural instability remains unclear. It is unknown whether sensory gating, a mechanism for filtering irrelevant sensory input, is impaired during standing balance in individuals with PD. To address this, we investigated cortical sensory processing in individuals with PD, age-matched older adults (OA), and young adults (YA) as they performed four balance tasks of increasing difficulty. We measured postural sway using a force platform and recorded somatosensory-evoked potentials (SEPs) from the primary somatosensory cortex (S1) following tibial nerve stimulation. Our results showed a clear dissociation between behavior and neurophysiology. Although postural sway was comparable between the PD and OA groups, only the OA and YA groups showed intact sensory gating, with SEP amplitudes decreasing as the balance challenge increased. In contrast, participants with PD demonstrated consistently elevated SEP amplitudes across all conditions. This study provides the first direct evidence of impaired sensory gating during standing balance in PD. These findings indicate a fundamental deficit in the cortical processing of sensory information essential for postural control. Consequently, they underscore the critical need for therapeutic interventions that target sensory integration deficits, not just motor symptoms. Key pointsO_LIHealthy young and older adults demonstrate intact sensory gating during standing balance, with somatosensory-evoked potential (SEP) amplitudes decreasing as postural difficulty increases. C_LIO_LIIndividuals with Parkinsons disease (PD) show impaired sensory gating, with elevated SEP amplitudes that are not appropriately modulated by increasing postural demands. C_LIO_LIDespite comparable postural sway to healthy older adults, the PD group exhibited fundamentally different neurophysiological responses to balance challenges. C_LIO_LIThis dissociation between motor performance and neurophysiology indicates a primary deficit in cortical sensory processing in PD. C_LIO_LIImpaired sensory gating may reflect a key, independent contributor to postural instability in PD, highlighting the need to target sensory deficits in treatment. C_LI