Visual memory errors in Parkinson's disease patient with visual hallucinations

Contribution of cognitive and bodily navigation cues to egocentric and allocentric spatial memory in hallucinations due to Parkinson's disease: A case report

Parkinson's disease (PD) manifestations can include visual hallucinations and illusions. Recent findings suggest that the coherent integration of bodily information within an egocentric representation could play a crucial role in these phenomena. Egocentric processing is a key aspect of spatial navigation and is supported by the striatum. Due to the deterioration of the striatal and motor systems, PD mainly impairs the egocentric rather than the allocentric spatial frame of reference. However, it is still unclear the interplay between spatial cognition and PD hallucinations and how different navigation mechanisms can influence such spatial frames of reference. We report the case of A.A., a patient that suffers from PD with frequent episodes of visual hallucinations and illusions. We used a virtual reality (VR) navigation task to assess egocentric and allocentric spatial memory under five navigation conditions (passive, immersive, map, path decision, and attentive cues) in A.A. and a PD control group without psychosis. In general, A.A. exhibited a statistically significant classical dissociation between the egocentric and allocentric performance with a greater deficit for the former. In particular, the dissociation was statistically significant in the "passive" and "attentive cues" conditions. Interestingly in the "immersive" condition, the dissociation was not significant and, in contrast to the other conditions, trends showed better performance for egocentric than allocentric memory. Within the theories of embodiment, we suggest that body-based information, as assessed with VR navigation tasks, could play an important role in PD hallucinations. In addition, the possible neural underpinnings and the usefulness of VR are discussed.

Cognitive and visual processing performance in Parkinson's disease patients with vs without visual hallucinations: A meta-analysis

IMPORTANCE

Cognitive and visual impairments in Parkinson's Disease Psychosis (PDP) raise the question of whether a specific profile of impaired cognition and visual function is linked to vulnerability to visual hallucinations (VHs). Previous studies have limited sample sizes and only included a sub-sample of tests. This is the first meta-analysis quantifying visuo-cognitive impairments in PDP patients across a spectrum of tests and taking into account potential confounding factors such as levodopa medication, illness duration and general cognitive ability.

OBJECTIVE

Compare visual processing and cognitive performance between PD patients with and without VHs (PDVH and PDnoVH).

METHODS

Four databases (PubMed, PsychINFO, Scopus, WebOfScience) were searched for studies on visual and/or cognitive performance of PDnoVH and PDVH published up to 02/2020. For each task, means and SDs were extracted and standardized-mean-differences (SMDs) between-groups calculated. Effect-sizes (Hedges' g) were calculated for all comparisons and synthesized in random-effects meta-analyses with robust-variance-estimation (accounting for multiple correlated measures within each study per cognitive/visual domain). Publication bias was assessed with funnel plots and Egger intercept.

RESULTS

N = 99 studies including 2508 PDVH patients (mean age 68.4 years) and 5318 PDnoVH (mean age 66.4 years) were included in the seven meta-analyses. PDVH patients performed worse than PDnoVH across all measures of cognition and visual processing, with the greatest between-group effect-sizes in executive functions, attention, episodic memory and visual processing. Study characteristics were not significantly associated with between-group differences in the domains investigated. Age-differences were significantly associated with performance differences in general cognition, working memory and executive functions.

CONCLUSION

Models of PDVH need to incorporate a wider range of cognitive and processing domains than currently included. There is a need for studies disentangling the temporal relationship between cognitive/visual deficits and VHs as early identification of risk before the onset of VHs could mitigate later outcomes such as progression to dementia.

Neuroanatomical and cognitive correlates of visual hallucinations in Parkinson's disease and dementia with Lewy bodies: Voxel-based morphometry and neuropsychological meta-analysis

Visual hallucinations (VH) are common in Parkinson's disease and dementia with Lewy bodies, two forms of Lewy body disease (LBD), but the neural substrates and mechanisms involved are still unclear. We conducted meta-analyses of voxel-based morphometry (VBM) and neuropsychological studies investigating the neuroanatomical and cognitive correlates of VH in LBD. For VBM (12 studies), we used Seed-based d Mapping with Permutation of Subject Images (SDM-PSI), including statistical parametric maps for 50% of the studies. For neuropsychology (35 studies), we used MetaNSUE to consider non-statistically significant unreported effects. VH were associated with smaller grey matter volume in occipital, frontal, occipitotemporal, and parietal areas (peak Hedges' g -0.34 to -0.49). In patients with Parkinson's disease without dementia, VH were associated with lower verbal immediate memory performance (Hedges' g -0.52). Both results survived correction for multiple comparisons. Abnormalities in these brain regions might reflect dysfunctions in brain networks sustaining visuoperceptive, attention, and executive abilities, with the latter also being at the basis of poor immediate memory performance.

Cognitive correlates and baseline predictors of future development of visual hallucinations in dementia with Lewy bodies

Visual hallucinations (VH) are common in dementia with Lewy bodies (DLB), and are among the core symptoms for its clinical diagnosis. VH have been associated with cognitive alterations, although research findings in this area are still limited. The present study aimed at investigating the cognitive correlates of VH in DLB, and the baseline neuropsychological features predicting the future development of VH. A cross sectional study compared the cognitive profile of 18 DLB patients with VH with that of 32 DLB without VH. A longitudinal study involved 34 DLB patients with no VH at baseline, among whom 17 developed VH and 17 remained without VH at follow-up. Logistic regression analyses were carried out to investigate what baseline cognitive variables independently predicted the development of VH at follow-up. DLB patients with VH had worse performance on the copy of the Rey complex figure, assessing visual construction/perception, than those without VH in the cross-sectional study (p = .001). Significant impairments in attention and visual memory delayed recall were also present. Baseline performance on the immediate prose memory was the only significant predictor of VH development in the longitudinal study (p = .03). DLB patients are more at risk of developing VH if presenting more severe immediate verbal memory impairment, and this might be related to a combination of (a) DMN-related dysfunctions, (b) impairment in medial temporal lobe-related functions, and (c) frontal abilities including long-term encoding of information and working memory. Differences between hallucinating and non-hallucinating patients in visual construction/perception, typical of DLB symptomatology, may be essential for VH to emerge in individuals with an at risk cognitive profile.

The psychosis spectrum in Parkinson disease

In 2007, the clinical and research profile of illusions, hallucinations, delusions and related symptoms in Parkinson disease (PD) was raised with the publication of a consensus definition of PD psychosis. Symptoms that were previously deemed benign and clinically insignificant were incorporated into a continuum of severity, leading to the rapid expansion of literature focusing on clinical aspects, mechanisms and treatment. Here, we review this literature and the evolving view of PD psychosis. Key topics include the prospective risk of dementia in individuals with PD psychosis, and the causal and modifying effects of PD medication. We discuss recent developments, including recognition of an increase in the prevalence of psychosis with disease duration, addition of new visual symptoms to the psychosis continuum, and identification of frontal executive, visual perceptual and memory dysfunction at different disease stages. In addition, we highlight novel risk factors - for example, autonomic dysfunction - that have emerged from prospective studies, structural MRI evidence of frontal, parietal, occipital and hippocampal involvement, and approval of pimavanserin for the treatment of PD psychosis. The accumulating evidence raises novel questions and directions for future research to explore the clinical management and biomarker potential of PD psychosis.

Multimodal MRI of the hippocampus in Parkinson's disease with visual hallucinations

Visual hallucinations carry poor prognosis in Parkinson's disease. Here we tested the hypothesis that the hippocampus and visuospatial memory impairment play a central role in the pathology of PD with visual hallucinations. Multimodal magnetic resonance imaging of the brain was carried out in 12 people with PD and visual hallucinations; 15 PD individuals without hallucinations; and 14 healthy controls. Age, gender, cognitive ability, and education level were matched across the three groups. PD patients were taking dopaminergic medication. Hippocampal volume, shape, mean diffusivity (MD), and functional connectivity within the whole brain were examined. Visuospatial memory was compared between groups, and correlations with hippocampal MD, functional connectivity, and the severity of hallucinations were explored. There were no macrostructural differences across groups, but individuals with hallucinations had higher diffusivity in posterior hippocampus than the other two groups. Visuospatial memory was poorer in both PD groups compared to controls, and was correlated with hallucinations. Finally, hippocampal functional connectivity in the visual cortices was lower in those with hallucinations than other groups, and this correlated with visuospatial memory impairment. In contrast, functional connectivity between the hippocampus and default mode network regions and frontal regions was greater in the PD hallucinators compared to other groups. We suggest that hippocampal pathology, which disrupts visuospatial memory, makes a key contribution to visual hallucinations in PD. These findings may pave the way for future studies of imaging biomarkers to measure treatment response in those with PD who are most at risk of poor outcomes.

A comparison of montreal cognitive assessment between patients with visual hallucinations and without visual hallucinations in Parkinson's disease

BACKGROUND

Visual hallucination (VH) is closely associated with cognitive impairment in Parkinson's disease (PD). The aim of this study is to analyze the domain of cognitive impairment related to the VH by analyzing cognition in PD.

METHOD

Twenty-six of 58 patients had VH (PD-VH), whereas 32 patients had no hallucinations (PD-NH); patients assigned to the PD-VH on the basis of having at least one VH per week for one month before participation in the study. All of the patients were administered the Montreal Cognitive Assessment-Korean test (MoCA-K). We analyzed the differences in cognition between PD-VH and PD-NH.

RESULTS

The Hoehn-Yahr (HY) stage and the Beck Depression Inventory version I (BDI) scores in PD-VH were significantly different from those in PD-NH. After adjusting for the HY stage and BDI, the language domain of the MoCA-K cognitive domains presents a significant difference between PD-VH and PD-NH.

CONCLUSION

Sentence processing and naming as the composition of the language domain in the MoCA-K have been associated in common with posterior cortical dysfunction. Although our result shows that the language domain of MoCA-K is sensitive to cognitive deficit in PD-VH patients, it needs further neuroimaging analysis for certifying the relationship between language impairment and posterior cortical deficit as the pathophysiology of PD-VH.