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Background Individuals with Parkinson’s disease (PD), Alzheimer’s disease (AD), multiple sclerosis (MS), and stroke experience various cognitive and motor impairments, which can negatively affect their ability to complete daily activities such as walking and talking. Walking and talking or dual-task walking often leads to a decline in performance in one or both tasks, which is called dual-task cost. This dual-task cost seems to be more pronounced in individuals with neurological conditions compared to age-matched healthy individuals, possibly due to disease-associated impairments. While the results of neuroimaging studies are inconsistent, several studies have found structural or functional brain changes that might contribute to a decrease in dual-task walking performance in people with neurological disorders. Research question/objective The objective of this study was to systematically review peer-reviewed articles that examined the neural correlates of cognitive-motor dual-task interference in people with neurological conditions. The primary aim was to identify brain areas or measures that might underlie dual-task walking performance of people with MS, stroke, AD, and PD. The secondary aim was to compare their dual-task performance with other groups such as healthy individuals. Methods A systematic review of the literature was conducted, following PRISMA guidelines, on Medline, Embase, and Scopus databases. Studies were included if they examined dual-task walking performance and associated structural or functional brain changes in adults with stroke, MS, PD, and AD. Studies were first screened using a title and abstract and then full-text review was performed. The quality of each study was assessed using the Joanna Briggs Institute (JBI) critical appraisal checklist and then the data regarding cognitive and motor performance during dual- versus single task conditions and brain imaging were extracted. The findings were grouped according to neurological condition and then by imaging technique. Results After screening, 23 studies were selected to be included in this review. The majority (90%) showed a decline in dual-task walking performance compared to single-walking in people with neurological conditions and this decline was greater than healthy individuals. Most structural imaging studies (75%) reported a significant positive correlation between lower brain structural integrity and poorer dual-task walking performance. Specifically, the striatum regions including pedunculopontine nucleus and hippocampus in PD demonstrated this positive correlation. In MS, the supplementary motor area showed a positive correlation. In terms of functional brain changes, 60% observed an increase in prefrontal cortex activity during dual tasking in people with PD and stroke, which was associated with decreased performance in most cases (n = 3) while some found an association with maintained performance (n = 2). Further, people with MS and stroke both showed a significant relationship between a higher supplementary motor area activity and poor dual-task walking performance. Conclusions This systematic review identified several structural and functional neural correlates of dual-task walking in people with PD, MS, and stroke and has facilitated a better understanding of neural basis of dual-task interference in people with neurological conditions. However, the relationship between the brain and behavioural outcomes is complicated and various factors may influence neural correlates, such as individuals’ characteristics (e.g., neural reserve, age), the nature of cognitive task used, and presentation modality (e.g., visual). |
