Alice Cronin-Golomb

Visual and spatial symptoms in Parkinson’s disease

The interaction of visual/visuospatial and motor symptoms in Parkinsons disease (PD) was investigated by means of a 31-item self-report questionnaire. The majority of 81 non-demented patients reported problems on non-motor tasks that depended on visual or visuospatial abilities. Over a third reported visual hallucinations, double vision and difficulty estimating spatial relations. Freezing of gait was associated with visual hallucinations, double vision and contrast sensitivity deficits. Visual strategies frequently were employed to overcome freezing. The results underscore the importance of investigating visual and visuospatial impairments in PD and their relation to motor symptoms, in order to help patients develop successful compensatory strategies.

GENDER DIFFERENCES IN PARKINSON'S DISEASE: CLINICAL CHARACTERISTICS AND COGNITION

More men than women are diagnosed with Parkinsons disease (PD), and a number of gender differences have been documented in this disorder. Examples of clinical characteristics that appear in men more often than women include rigidity and rapid eye movement behavior disorder, whereas more women than men exhibit dyskinesias and depression. Differences between men and women in cognition have not been extensively examined, though there are reports of deficits in men in aspects of cognition that contribute to activities of daily living, in verbal fluency, and in the recognition of facial emotion, and deficits in women in visuospatial cognition. Side of disease onset may interact with gender to affect cognitive abilities. One possible source of male‐female differences in the clinical and cognitive characteristics of PD is the effect of estrogen on dopaminergic neurons and pathways in the brain. This effect is not yet understood, as insight into how the fluctuation of estrogen over the lifetime affects the brain is currently limited. Further attention to this area of research will be important for accurate assessment and better management of PD. Attention should also be directed to multiple covariates that may affect clinical characteristics and cognition. Knowledge about differences in the presentation of PD symptoms in men and women and about the pathophysiology underlying those differences may enhance the accuracy and effectiveness of clinical assessment and treatment of the disease.

Patterns of visual scanning as predictors of emotion identification in normal aging

Emotion identification appears to decline with age, and deficient visual scanning may contribute to this effect. Eye movements of 20 older adults (OAs) and 20 younger adults (YAs) with normal saccades were recorded while viewing facial expressions. OAs made fewer fixations overall, and they made a higher proportion of fixations to the lower halves of faces. Topographical distribution of fixations predicted better OA accuracy for identifying disgust than other negative emotions. Impaired OA accuracy for fear and anger was specific to vision, with normal identification of these emotions in the auditory domain. Age-related frontal-lobe atrophy may affect the integrity of the frontal eye fields, with consequent scanning abnormalities that contribute to difficulties in identifying certain emotions.

Visual Dysfunction Predicts Cognitive Deficits in Alzheimer's Disease

Deficits in basic visual capacities are prevalent in Alzheimers disease (AD), raising the question of their impact on cognitive function. We examined the relation between vision and cognition in 72 patients with AD. Vision tests assessed color discrimination, stereoacuity, contrast sensitivity, and backward pattern masking. For cognitive tests of object recognition, at least 25% (up to 50%) of score variance was predicted by performance on a vision test. For tests of spatial localization, only 2 to 11% of the variance was predicted by performance on a vision test. The results indicated that: (1) visual dysfunction was a significant predictor of cognitive dysfunction in AD, and (2) visual deficits in AD may have a strong functional impact on performance in specific cognitive domains.

Specific impairments in the recognition of emotional facial expressions in Parkinson's disease.

Studies investigating the ability to recognize emotional facial expressions in non-demented individuals with Parkinsons disease (PD) have yielded equivocal findings. A possible reason for this variability may lie in the confounding of emotion recognition with cognitive task requirements, a confound arising from the lack of a control condition using non-emotional stimuli. The present study examined emotional facial expression recognition abilities in 20 non-demented patients with PD and 23 control participants relative to their performance on a non-emotional landscape categorization test with comparable task requirements. We found that PD participants were normal on the control task but exhibited selective impairments in the recognition of facial emotion, specifically for anger (driven by those with right hemisphere pathology) and surprise (driven by those with left hemisphere pathology), even when controlling for depression level. Male but not female PD participants further displayed specific deficits in the recognition of fearful expressions. We suggest that the neural substrates that may subserve these impairments include the ventral striatum, amygdala, and prefrontal cortices. Finally, we observed that in PD participants, deficiencies in facial emotion recognition correlated with higher levels of interpersonal distress, which calls attention to the significant psychosocial impact that facial emotion recognition impairments may have on individuals with PD.

Prevalence of visual deficits in Alzheimer's disease

This study addressed the issue of prevalence and pattern of visual deficits in 77 subjects with Alzheimers disease (AD) and 111 healthy control subjects. We defined cutoff scores that would be expected from only 1 control subject of 100 (p = 0.01). The percentage of AD subjects who performed at or worse than this level varied across the 16 visual tests from a high of 58% to a low of 0%. The distribution of impairment across tests suggests a high vulnerability in AD of pattern vision, moderate vulnerability of spatial vision, and low vulnerability of motion and flicker perception. We found evidence for heterogeneity in the AD subject group: a subgroup (N = 14) emerged that was characterized by poor performance on the Backward Pattern Masking test, relatively young age, and relatively short duration of AD. Overall, the results indicate that visual dysfunction, especially on Backward Masking, is a common sign of AD.

Frontostriatal circuits are necessary for visuomotor transformation : Mental rotation in Parkinson's disease

The mental rotation of objects requires visuospatial functions mediated by the parietal lobes, whereas the mental rotation of hands also engages frontal motor-system processes. Nondemented patients with Parkinsons disease (PD), a frontostriatal disorder, were predicted to be impaired on mentally rotating hands. Side of PD motor symptom onset was investigated because the left motor cortices likely have a causal role in hand mental rotation. The prediction was that patients with right-side onset (RPD, greater left-hemisphere dysfunction) would commit more errors rotating hands than patients with left-side onset (LPD). Fifteen LPD, 12 RPD, and 13 normal control adults (NC) made same/different judgments about pairs of rotated objects or hands. There were no group differences with objects. When rotating hands, RPD, but not LPD, made more errors than the NC group. A control experiment evaluated whether visual field of presentation explained differences between PD subgroups. In the first experiment (1A), the hand to be mentally rotated was presented in the right visual field, but here (1B) it was presented in the left visual field. Only the LPD group made more errors than the NC group. The evidence suggests a double dissociation for the RPD and LPD groups between tasks differing in visual-field presentation. The findings indicate that hemifield location of a to-be-rotated hand stimulus can cause the hemispheric frontoparietal networks to be differentially engaged. Moreover, frontostriatal motor systems and the parietal lobes play a necessary role during the mental rotation of hands, which requires integrating visuospatial cognition with motor imagery.

Incomplete achromatopsia in Alzheimer's disease.

We report that patients with Alzheimers disease (AD) have a selective deficit in blue hue discrimination, as assessed with three clinical measures of color vision. The Farnsworth D-15 Test, the Lanthony New Color Test, and the City University Color Vision Test were administered to 32 patients with AD (ranging in dementia severity from mild to severe) and 32 age-matched normal control subjects (NCS). Of the AD patients, 11 who were representative of the larger group for age, education level, and dementia severity received a complete neuro-ophthalmological examination that ruled out obvious disorders of the anterior visual structures. AD patients made significantly more tritan (blue) errors than NCS on all three color vision tests but did not make more protan (red) or deutan (green) errors on two of the three tests. The results support the conclusion that there is a deficit in color discrimination in AD that is specific to blue hues, and oppose the hypothesis that AD does not deleteriously affect the color-opponent visual channel. In the absence of obvious damage to anterior visual structures, the likely substrates for the observed deficit are peristriate and inferotemporal visual cortices, which are subject to significant neuropathology in AD.

Visuospatial dysfunction and problem solving in Parkinson's disease.

Individuals with Parkinsons disease (PD) perform deficiently on Ravens Coloured Progressive Matrices (RCPM), in contrast to their relatively good performance on many other problem-solving tasks. The question is raised as to whether a visuospatial deficit may account for poor RCPM performance in PD. The authors analyzed RCPM results in 50 nondemented participants with PD and 39 age-matched healthy control participants. The PD group made significantly more errors than the control group on all RCPM subtests, including the subtest that mainly assessed visuospatial function (RCPM-A). For the PD group, the composite score of other visuospatial tests, but not the composite scores of tests of executive function or verbal memory, significantly predicted performance on the RCPM-A. Visuospatial impairment in PD may arise from dysfunction of the basal ganglia-thalamocortical circuit that also includes the dorsolateral prefrontal cortex and, importantly, the posterior parietal lobes.

Enhanced stimulus strength improves visual cognition in aging and Alzheimer's disease.

Deficits in visual cognition in Alzheimers disease (AD) arise from neuropathological changes in higher-order association areas of the cortex and from defective input from lower-level visual processing areas. We investigated whether enhanced signal strength may lead to improvement of visual cognition in AD. We tested 35 individuals with probable AD, 35 age-matched elderly control (EC) and 58 young control (YC) adults on letter identification, word reading, picture naming, discrimination of unfamiliar faces, and pattern completion. The contrast sensitivity step-difference across an independent sample of AD and EC groups was used in calculating an image filter, from which we produced stimulus-strength conditions of low-degraded, medium-normal, and high-enhanced. Using this filter we created a hypothetical proximal-strength equivalence between AD at medium strength and EC at low strength, and between AD at high strength and EC at medium strength. For letter identification, word reading, picture naming, and face discrimination, medium strength elicited AD accuracy levels and reaction times that were similar to those of EC at low strength. On picture naming, increased strength reduced perceptual-type errors for EC and AD and random errors for AD. For word reading, high strength elicited AD accuracy levels and reaction times that were equivalent to those of EC at medium strength. We saw no effect of signal-strength manipulation on performance of pattern completion, possibly owing to the complex cognitive demands of that task or to the inadequacy of the filter for its images. The results indicate that putative AD-EC differences in cognition directly reflect contrast sensitivity differences between the groups. Enhancement of stimulus strength can ameliorate vision-based deficits and lead to improvement in some aspects of cognitive performance. These results suggest new non-pharmacological avenues to explore in the attempt to improve cognition in elderly adults and especially in individuals with AD.