Fronto-medial theta instability error signal correlates with postural sway in Parkinson's disease and progressive supranuclear palsy.

BACKGROUND

Postural instability is a common feature in progressive supranuclear palsy (PSP) and idiopathic Parkinson's disease (PD). Understanding the neural mechanisms behind the loss of postural stability may aid identification of patients at an increased risk of falls.

OBJECTIVES

To examine differences in postural sway between PSP and PD cohorts during dual-task assessment with electroencephalography (EEG) recording to identify neural mechanisms associated with postural control in Parkinsonism patients.

METHODS

We assessed static postural stability in healthy controls (HC; n = 15), people with PD (n = 18), and people with PSP (n = 9), during the following conditions: Eyes open, eyes closed and during cognitive tasks. EEG data were simultaneously recorded using a 24-channel electrode array. The groups were matched for age, sex and disease duration.

RESULTS

The PSP cohort demonstrated greater executive dysfunction during cognitive task (p ≤ 0.01). PD and PSP groups exhibited greater instability during different postural task conditions compared to the control group; however, no significant differences were found between PD and PSP groups. The PSP group exhibited a significant reduction in fronto-medial theta power compared to the PD group (p < 0.03). A negative correlation was observed between fronto-medial theta and measures of postural sway for Parkinsonism cohorts (p < 0.05 for all).

CONCLUSION

Increased fronto-medial theta activity, which has been shown to reflect anterior cingulate cortex generated 'error signals' when stability is challenged, is associated with postural stability in PD and PSP. The differences in this 'error signal' in PD and PSP possibly reflect differing abilities to compensate for challenges in stability.