Objective: The purpose of this study was to evaluate the temporal dynamics of cortical activity and postural control for the first levodopa dose of the day during a challenging static standing task in people with Parkinson’s Disease (PD).

Background: Our understanding of how balance control responds to levodopa over the course of a single day in people with PD is limited with the majority of studies focused on isolated comparisons of ON vs. OFF levodopa medication [1,2]. The understanding of how balance control responds to levodopa over the course may help to elucidate the role of levodopa on postural control in people with PD.

Method: We evaluated changes in postural control by monitoring cortical activity (frontal, motor, parietal and occipital cortical areas), body sway parameters (CoP parameters) and lower limb muscle activity (tibialis anterior and gastrocnemius medialis) in 15 individuals with PD during standing with the feet semi-tandem. Participants were assessed for two 60-s trials every 30 minutes (ON-30, ON-60, ON-90, ON-120, ON-150) for 3 hours after the first matinal dose (ON-180). Repeated MANOVAs were performed for CoP, muscle and cortical activities parameters – factor: medication status.

Results: Levodopa intake increased body sway, cortical activity and muscle activity during the semi-tandem standing task (Table 1). Ankle muscle co-contraction also increased after levodopa intake. Specifically, levodopa had a significant effect on cortical activity, body sway parameters and muscle activity after 60-minutes, with significant effects until 120-minutes after levodopa intake. None of the outcomes at ON-150 and ON-180 were not significantly different to OFF medication except for GM muscle activity.

Conclusion: We recommend measuring the effects of levodopa on postural control in people with PD from 60 to 120-minutes of first levodopa dose intake. Observations outside of this window may reflect altered responses due to suboptimal medication.

References: [1] Rocchi, L. et al. J. Neurol. Neurosurg. Psychiatry. 73: 267–274, 2002. [2] Bonnet, C.T. et al. Behav. Brain Res. 331: 67–75, 2017.

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