No abstract

Parkinson’s disease (PD) is characterized by disorders of visuospatial function that can impact everyday functioning. Visuospatial difficulties are more prominent in those whose motor symptoms begin on the left body side (LPD) than the right body side (RPD) and have mainly been attributed to parietal dysfunction. The source of visuospatial dysfunction is unclear, as in addition to subcortical–cortical changes, there are irregularities of visual scanning and potentially of retinal-level vision in PD. To assess these potential contributors, performance on a visuospatial task—line bisection—was examined together with retinal structure (nerve fiber layer thickness, measured by optical coherence tomography [OCT]), retinal function (contrast sensitivity, measured by frequency-doubling technology [FDT]), and visual scanning patterns. Participants included 20 nondemented patients (10 LPD, 10 RPD) and 11 normal control (NC) adults. Relative to the other groups, LPD were expected to show rightward bias on horizontal line bisection, especially within the left visual hemispace, and downward bias on vertical bisection. LPD relative rightward bias was confirmed, though not mainly within the left hemispace and not correlated with retinal structure or function. Retinal thinning was seen in LPD relative to RPD. Qualitative visualization of eye movements suggested greater LPD exploration of the right than left side of the line during horizontal bisection, and some overall compression of scanning range in RPD (both orientations) and LPD (primarily vertical). Results indicated that rightward visuospatial bias in our LPD sample arose not from abnormalities at the retinal level but potentially from attentional biases, reflected in eye movement patterns.

External support may improve task performance regardless of an individual’s ability to compensate for cognitive deficits through internally-generated mechanisms. We investigated if performance of a complex, familiar visual search task (the game of bingo) could be enhanced in groups with suboptimal vision by providing external support through manipulation of task stimuli. Participants were 19 younger adults, 14 individuals with probable Alzheimer’s disease (AD), 13 AD-matched healthy adults, 17 non-demented individuals with Parkinson’s disease (PD), and 20 PD-matched healthy adults. We varied stimulus contrast, size, and visual complexity during game play. The externally-supported performance interventions of increased stimulus size and decreased complexity resulted in improvements in performance by all groups. Performance improvement through increased stimulus size and decreased complexity was demonstrated by all groups. AD also obtained benefit from increasing contrast, presumably by compensating for their contrast sensitivity deficit. The general finding of improved performance across healthy and afflicted groups suggests the value of visual support as an easy-to-apply intervention to enhance cognitive performance.

Background: Previous studies have demonstrated an association between white matter hyperintensities (WMH) and cognitive performance primarily in Caucasian samples, limiting generalizability to other ethnic and racial groups. This study investigated the association of WMH and cognition in an ethnic and racial minority cohort (Omni) of the Framingham Heart Study and compared these results to the Caucasian (Offspring) cohort. Methods: Quantitative brain MRI and neuropsychological evaluations were performed on stroke- and dementia-free participants. Cognitive assessment included verbal memory, visuospatial memory and organization, language, and executive functioning. Linear regression models were conducted to assess the association between WMH and cognitive function. Results: The Omni group presented with demographic factors that significantly differed from those of the Offspring group: they were younger, but had more stroke risk factors such as hypertension. In the Offspring group, WMH volume was significantly associated with poorer performance on tests of executive function and visual organization. No significant associations between WMH and cognitive measures were found in the Omni group, but no differences (significant interaction terms) were seen between the regression coefficients. Conclusions: The Omni cohort had greater variability in factors that may mediate the association of WMH and cognition. More research is needed to investigate how stroke risk factors impact on the occurrence of WMH and its association with cognition in more diverse cohorts.

Contrast sensitivity is strongly associated with daily functioning among older adults, but the genetic and environmental contributions to this ability are unknown. Using the classical twin method, we addressed this issue by examining contrast sensitivity at five spatial frequencies (1.5-18 cycles per degree) in 718 middle-aged male twins from the Vietnam Era Twin Study of Aging (VETSA). Heritability estimates were modest (14-38%), whereas individual-specific environmental influences accounted for 62-86% of the variance. Identifying the types of individual-specific events that impact contrast sensitivity may suggest interventions to modulate this ability and thereby improve overall quality of life as adults age.