Attending to External Cues and Movement Strategies in Parkinson Disease

External cues and cognitive movement strategies are common compensatory modes that people with Parkinson's disease can use to overcome typical gait disturbances. It is suggested that these modes utilize alternative neural pathways, bypassing the impaired basal ganglia motor circuits in the brain. In addition, both compensatory modes, in particular the movement cognitive strategies, are suggested to rely on attentional mechanisms. Cognitive deficits are common in PwP and include among others, impairment of attention, particularly in tasks requiring internal control of attention. Considering that gait compensatory modes may rely on cognitive function, in particular the cognitive movement strategies, it is not clear whether People with Parkinson's disease can engaged with these strategies for a prolonged time or distance as in many cases required in daily living. Therefore, the objectives of this study are 1) to test the effect of compensatory modes- external cueing and cognitive movement strategy on gait in prolonged walking. 2) to test whether people with Parkinson's disease can stay engaged and focus their attention to these compensatory modes for prolonged time. 3) to test whether subject's cognitive function is related to the ability to stay engaged with these compensatory modes. Subjects are recruited from a community physical- therapy groups for people with Parkinson's disease. Healthy older adults will be recruited from the community and will serve as a control group. Participants are invited for two separate evaluation sessions that includes: 1. Assessment of background characteristic: demographic details, severity of disease ( assessed by the Unified Parkinson's Disease Rating Scale-UPDRS), Levodopa Equivalent Dose (LED), freezing of gait questionnaire (FOG-Q) and Montreal cognitive assessment (MoCA). 2\. Evaluation of gait while attending to external cues and cognitive movement strategy. 3\. Evaluation of brain engagement during gait 4. Computerized cognitive assessment