Objective: The aim of the study is to assess the association of freezing of gait (FoG) with disturbed time processing in Parkinson´s disease (PD) by combining a stepping-in-place paradigm with a time-estimation task.

Background: FoG is a debilitating and therapeutically challenging gait impairment in advanced PD. Previous kinematical observations demonstrate disturbed temporal gait parameters as increased gait asymmetry and variability promoting FoG (1). Neural mechanisms underlying FoG are poorly understood, though dysfunction of fronto-striatal projections in PD might impact sensorimotor processing possibly resulting in FoG (2). Those fronto-striatal circuits are supposed to be also involved in time estimation in PD (3). Synthesizing kinematic and theoretical hypothesis of fronto-striatal dysfunction we suggest a possible link between time perception deficits and FoG.

Method: We investigated ten PD patients (mean age 67.1 ± 8,27 y., 9 male) in MED ON with implanted subthalamic electrodes who frequently experience FoG episodes. The stepping-in-place task consisted of self-paced stepping movements determined by auditory start and stop signals. Step cycles and FoG episodes were recorded via accelerometers attached to foot ankles. To evaluate rhythmicity and gait asymmetry, the coefficient of variability (CV) of step time and a stepping frequency ratio between the more and less affected leg were calculated. In the time-estimation task, patients were asked to estimate a fixed 1.2 second time interval. After each response, patients got direct visual “accuracy” feedback. Accuracy as time interval deviation from 1.2 seconds and CV of the estimation times were calculated.

Results: Increased stepping rhythmicity deficits and stepping frequency asymmetry were correlated with higher numbers of FoG episodes (r = 0.97, p < 0.001; r = 0.75, p < 0.012). Increased stepping arrhytmicity was correlated with larger CV of time estimation (r = 0.80, p = 0.006), and worse timing accuracy (r = 0.83, p = 0.003). Increased variability in time estimation was associated with higher numbers of FoG episodes (r = 0.84, p = 0.002).

Conclusion: The findings of this study demonstrate a strong linkage between time estimation performance and temporal gait deficits resulting in increased incidence of FoG episodes. Time processing disturbances in PD might therefore play an important role in the pathophysiology of FoG.

References: (1) Nieuwboer, A. and Giladi, N., 2013. Characterizing freezing of gait in Parkinson’s disease: Models of an episodic phenomenon, Movement Disorders, 28, 11, 1509-1519 (2) Wu T, Hallett M, Chan P., 2015. Motor automaticity in Parkinson’s disease. Neurobiol, Dis., 82:226-234 (3) Buhusi, C.V., Meck, W.H., 2005. What makes us tick? Functional and neural mechanisms of interval timing. Nat. Rev. Neurosci. 6, 755–765

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MDS Abstracts - https://www.mdsabstracts.org/abstract/freezing-of-gait-as-a-reflection-of-disturbed-general-time-processing-in-parkinsons-disease-a-new-look-on-a-complex-phenomenon/