Intraindividual Variability in Reaction Time and Gait with Increasing Cognitive Impairment in Lewy Body Disease and Associated Nucleus Basalis and Thalamic Atrophy

Student Researcher:
Kerry Howell

Supervisor / Principle Investigator:
Richard Camicioli

Additional Authors:
Stuart MacDonald
Natalie Ravid
Myrlene Gee
Sandra Bradford
Nancy Fisher

MD Class of 2021


Factors that predict a decline in cognitive functioning are useful in clinical evaluations of aging adults, specifically in patients with neurodegenerative disorders, such as Parkinson’s Disease (PD), where cognitive decline is often part of the prognosis. Attentional fluctuations are commonly seen in these cognitively impaired patients and can affect gait and cognition. These cognitive changes are reflected in neurodegeneration in specific brain structures, most recently believed to be the cholinergic system, specifically the nucleus basalis. We predicted that individuals with more cognitive impairment would have increased attentional fluctuations, and corresponding neurodegeneration in the nucleus basalis. Individuals diagnosed with PD with varying degrees of cognitive impairment completed a gait analysis and reaction time testing. Participants included PD patients without impairment (n=10; mean age=65.9), PD with mild cognitive impairment (n=7; mean age=71.9), and PD with dementia (n=4; mean age=72.6). Intraindividual variability in gait and reaction time was assessed as an indicator of attentional fluctuations. A region-of-interest volume analysis for the nucleus basalis was completed using MRI imaging. Our results demonstrated that individuals with more cognitive impairment had greater intraindividual variability in gait (including step time, stride length, and swing time) and reaction time, demonstrating the relationship between cognitive abilities and attentional fluctuations. Although not statistically significant, there was a trend of decreased volume in the nucleus basalis and thalamus in individuals with more cognitive impairment and attentional fluctuations. This study adds to the literature on neurocognitive markers of cognitive decline in PD, potentially contributing to earlier diagnoses and better patient outcomes.