Objective: This study investigated the relationship between prefrontal cortex (PFC) activity and turning characteristics with and without a dual-task in in people with Parkinson’s disease (PD) and elderly control subjects.

Background: Difficulty turning while walking is common among in PD and may lead to significant disability, freezing of gait (FoG), falls and reduced mobility. Turning may be less automatic than straight walking as it requires control of dynamic balance and sequential, whole-body coordination. Turning deficits (e.g. FoG) have been related to executive-attentional mechanisms through dual-task paradigms, with PFC activity implicated. However, the role of the PFC during turning under single or dual-task and association with FoG is not clear.

Methods: Twenty-four subjects with PD (13 freezers, FoG+, and 11 nonfreezers, FoG-) in the “off” state and 7 healthy control subjects were tested. Subjects wore 3 inertial sensors (1x each shin and 1x waist) and a functional near infra-red spectroscopy (fNIRS) system while turning in place for 2 minutes (alternating 360 degrees to the right with 360 degrees to the left) under single and dual-task (modified AX-CPT) conditions.

Results: No significant differences in FoG Ratio were found in dual-task compared to single-task conditions (p>0.05). However, average turn peak velocity was significantly reduced under dual-task compared to single-task in both FoG+ (p=0.01) and FoG- (p=0.04). Unlike the PD group, healthy controls showed significantly higher PFC activation with dual-task compared to single-task turns (p=0.03). Within PD, both FoG+ and FoG- showed a tendency for higher PFC activity with single-task turns compared to healthy controls, but no significant changes between single- and dual-task (p=0.10). A significant association between the FoG Ratio and PFC activity was found only in FoG+ (r=0.68, p=0.02).

Conclusions: Higher PFC activation with single-task turning in PD compared to healthy controls suggests that the PFC may play an important role in turning control in PD. Association between higher PFC activity and greater FoG severity suggests increased cortical compensation is required with greater loss of movement automaticity. Interestingly, dual-task performance slowed turning without increasing FoG severity, which may indicate that slowing turns is a compensatory mechanism to reduce FoG, likely underpinned by the PFC activation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cortical-correlates-of-dual-task-turning-with-and-without-freezing-of-gait/