Side of motor symptom onset predicts sustained attention deficits and motor improvements after attention training in Parkinson's disease.

OBJECTIVE: Parkinson's disease (PD) side of motor symptom onset has been associated with distinct cognitive deficits; individuals with left-side onset (LPD) show more visuospatial impairments, whereas those with right-side onset (RPD) show more verbal impairments. Non-spatial attention is a critical cognitive ability associated with motor functioning that is right hemisphere lateralized but has not been characterized with regard to PD side of onset. We compared individuals with LPD and RPD on non-spatial attention tasks and examined differential responses to a 4-week sustained attention training program. METHOD: Participants included 9 with LPD and 12 with RPD, who performed both brief and extended go/no-go continuous performance tasks and an attentional blink task. Participants also engaged in an at-home sustained attention training program, Tonic and Phasic Alertness Training (TAPAT), 5 days/week for 4 weeks. We assessed cognitive and motor symptoms before and after training, and after a 4-week no-contact period. RESULTS: At baseline, participants with LPD exhibited worse performance than those with RPD on the extended continuous performance task, indicating specific deficits in sustaining attention. Poorer attention was associated with worse clinical motor scores. Notably, side of onset had a significant effect on clinical motor changes after sustained attention training, with only LPD participants improving after training, and 4/9 showing clinically meaningful improvements. CONCLUSIONS: Compared to RPD, participants with LPD had poorer sustained attention pre-training and were more likely to improve on clinical motor functioning after sustained attention training. These findings support mechanistic differences between LPD and RPD and suggest potential differential treatment approaches.

The functional relevance of visuospatial processing speed across the lifespan.

Visuospatial processing speed underlies several cognitive functions critical for successful completion of everyday tasks, including driving and walking. While it is widely accepted that visuospatial processing speed peaks in early adulthood, performance across the lifespan remains incompletely characterized. Additionally, there remains a lack of paradigms available to assess visuospatial processing speed in unsupervised web-based testing environments. To address these gaps, we developed a novel visuospatial processing speed (VIPS) task adapted from two tests sensitive to visuospatial processing speed declines in older adults, the Useful Field of View paradigm and the PERformance CEntered Portable Test. The VIPS task requires participants to make a central orientation discrimination and complete a simultaneous peripheral visual search task. Data were collected from 86 in-lab volunteers (18-30 years) to compare performance to traditional neuropsychological measures. Consistent with previous literature, performance on the novel VIPS task significantly correlated with measures of selective attention, executive functioning, visual speed, and working memory. An additional 4395 volunteers (12-62 years) were recruited on TestMyBrain.org to establish lifespan trajectories of visuospatial processing speed and associations with functional disability. VIPS task performance peaked in the early 20's, and steadily decreased such that thresholds doubled in 60-year-olds relative to 20-year-olds (817 ms vs. 412 ms). VIPS task performance significantly correlated with self-reported cognitive functioning deficits broadly across the lifespan but was specifically related to mobility issues in middle-age. These findings have important implications for early detection of cognitive decline and provide insights into potential early intervention targets for younger and middle-aged adults.

Evidence for a Specific Association Between Sustained Attention and Gait Speed in Middle-to-Older-Aged Adults.

Although cognitive decline has previously been associated with mobility limitations and frailty, the relationship between sustained attention and gait speed is incompletely characterized. To better quantify the specificity of the sustained attention and gait speed association, we examined the extent to which this relationship is unique rather than accounted for by executive functioning and physical health characteristics. 58 middle-to-older-aged community-dwelling adults without overt evidence of cognitive impairment (45-90 years old; 21 females) participated in the study. Each participant completed a 4-meter gait speed assessment and validated neuropsychological tests to examine various domains of executive functioning including working memory (i.e., Digit Span), inhibitory control (i.e., D-KEFS Color-Word Interference), and task switching (i.e., D-KEFS Number/Letter Switching). Multiple physical and vascular risk factors were also evaluated. Sustained attention was assessed using the gradual onset continuous performance task (gradCPT), a well-validated go/no-go sustained attention task. A series of linear regression models were used to examine how different aspects of cognition, including sustained attention and traditional measures of executive functioning, related to gait speed while controlling for a variety of physical and vascular risk factors. Among all predictors, gradCPT accuracy explained the most variance in gait speed (R 2 = 0.19, p < 0.001) and was the only significant predictor (ß = 0.35, p = 0.01) when accounting for executive functioning and other physical and vascular risk factors. The present results indicate that sustained attention may be uniquely sensitive and mechanistically linked to mobility limitations in middle-to-older adults.