Signal in the Noise: Dispersion as a Marker of Post-Stroke Cognitive Impairment

Stroke often results in lasting cognitive impairments that severely reduce independence and quality of life. Traditional neuropsychological assessments rely on mean scores that provide an average estimate of overall cognitive function but neglect the fluctuations in performance. The variability in performance can be captured as inconsistency, i.e., fluctuations across multiple trials within a single task or as dispersion, i.e., fluctuations across multiple tasks. While inconsistency has been extensively studied, the impact of post-stroke cognitive impairment on cognitive dispersion is unknown. In this study, ninety-five stroke survivors (41 cognitively impaired and 54 cognitively normal) completed a neuropsychological battery that captured performance across five cognitive domains: executive function, attention, memory, language, and processing speed. We compared the stroke groups on across- and within-domain cognitive dispersion. Cognitively impaired stroke individuals showed elevated dispersion within executive function compared to cognitively normal individuals. The two groups did not differ on any other within-domain or across-domain cognitive dispersion. Post-stroke cognitive impairment increased variability within executive functioning. Incorporating cognitive dispersion into routine post-stroke assessment can advance clinical practice by identifying subtle cognitive instability, anticipate supportive needs, and tailor rehabilitation plans for improving stroke care.