Hallucinations and conscious access to visual inputs in Parkinson's disease.
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ABSTRACT:
SUBMITTER: Lefebvre S
PROVIDER: S-EPMC5107911 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The aim of this work was to report on 7 patients presenting a distinctive form of multimodal (tactile and visual) hallucinations for which the term "string hallucinations" is proposed. Having observed a patient interacting with imaginary strips of skin in his hands at our movement disorders unit, we prospectively studied PD patients and caregivers over a 6-month period using a semistructured interview addressed to this particular phenomenon. Demographic characteristics as well as cognitive and motor function were assessed. A total of 7 of 164 PD patients (4.3%) observed during the study period had string hallucinations. One patient was cognitively intact and the other 6 had some degree of cognitive impairment. Common to the phenomenology of the hallucinations was the unpleasant feeling and vision of threads emerging from the subjects' hands. Patients interacted with these "threads," trying to remove them from their hands. Our study identifies a previously undescribed type of hallucinations in PD, characterized by a complex pattern of multimodal tactile and visual hallucinations.
| S-EPMC6353331 | biostudies-literature
Project description:BackgroundNon-visual hallucinations in Parkinson's disease (PD) can be prevalent and distressing. Most existing research has however, focused on visual hallucinations as well as related risk factors. The current study thus conducted a systematic review to collate existing evidence on non-visual hallucinations in PD, focusing on their prevalence, phenomenology, and clinical-cognitive correlates.MethodsNinety-one relevant studies were included from a systematic search across PsycINFO APA, PubMed, and Web of Science, for peer-reviewed publications in the English language, from 1970 to the present. These comprised a mix of case (30 studies; n = 56) and group design (62 studies; n = 7346) studies, divided into three somewhat overlapping collections to address our three research foci.ResultsPrevalence estimates for hallucinations were: auditory 1.5-72.0%, olfactory 1.6-21.0%, somatic-tactile 0.4-22.5%, gustatory 1.0-15.0%, and sensed presence 0.9-73.3%. Phenomenological inquiries revealed descriptions of vivid, consuming events replete with elaborate detail, adversely affecting PD patients in different ways. Overt experiences of multisensory hallucinations were also highly variable (0.4-80%) but exceedingly common, reported by almost half of the 45 included prevalence studies. There was some evidence for modality-specific hallucination predictors, but this was largely tentative, pending robust replication.ConclusionsMarked prevalence figures coupled with phenomenological descriptions implicating distress denote that non-visual and multisensory hallucinations in PD are of clinical significance. More direct research and clinical attention need to be devoted to the study and management of such hallucinatory experiences.
| S-EPMC10188425 | biostudies-literature
Project description:BackgroundDeficits in basic vision are associated with visual hallucinations in Parkinson's disease. Of particular interest is contrast sensitivity loss in this disorder and its effect on object identification.ObjectivesEvaluate whether increased contrast improves object perception in persons with Parkinson's disease and visual hallucinations, without dementia.MethodsWe assessed 26 individuals with mild to moderate idiopathic Parkinson's disease, half of whom reported one or more episodes of hallucinations/unusual perceptual experiences in the past month, with a letter-identification task that determined the contrast level required to achieve 80% accuracy. Contrast sensitivity was further assessed with a chart that presented stimuli at multiple spatial frequencies. The groups were closely matched for demographic and clinical characteristics except for experience of hallucinations.ResultsRelative to participants without visual hallucinations, those with hallucinations had poorer spatial frequency contrast sensitivity and required significantly greater contrast to correctly identify the letters on the identification task. Specifically, participants with hallucinations required a mean contrast of 52.8%, whereas participants without hallucinations required 35.0%. When given sufficient contrast, the groups with and without hallucinations were equally accurate in letter identification.ConclusionsCompared to those without hallucinations, individuals with Parkinson's disease and hallucinations without dementia showed poorer contrast sensitivity. Once contrast was individually enhanced, the groups were equally accurate at object identification. These findings suggest the potential of visual perception tests to predict, and perception-based interventions to reduce, hallucinations in Parkinson's disease.
| S-EPMC7780942 | biostudies-literature
Project description: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.
| S-EPMC4720723 | biostudies-literature
Project description:Objective: To determine whether Parkinson disease (PD) patients with (VH) have different clinical characteristics and gray-matter volume than those with visual misperceptions (VM) or other visual symptoms (OvS). Background: The spectrum of visual complaints in PD is broad and complex. Methods: We conducted a retrospective chart review of 525 PD patients to identify the frequency of visual symptoms and the association with clinical and radiological features. Brain volumetric MRI data was analyzed using multivariate logistic regression to differentiate cases with and without visual symptoms. Results: Among 525 PD cases, visual complaints were documented in 177 (33.7%). Among these, 83 (46.9%) had VH, 31 (17.5%) had VM, and 63 (35.6%) had OvS (diplopia, blurry vision, photophobia, dry eyes, and eye pain or soreness). When compared to OvS, patients with VH had significantly higher age, duration of disease, rate of REM sleep behavior disorder, and cognitive impairment. Visual hallucinations patients had decreased age-adjusted volumetric averages in 28/30 gray-matter regions when compared to PD without visual symptoms and 30/30 gray-matter regions when compared to VM patients. Conclusions: Visual symptoms in PD may represent a spectrum from OvS to VM to VH, with progression of the latter associated with older age, duration of disease, presence of REM sleep behavior disorder, cognitive impairment, and decreased gray-matter volume.
| S-EPMC6277574 | biostudies-literature
Project description:BackgroundClinicians vary in their ability to elicit and interpret hallucinatory symptoms in patients with Parkinson's disease (PD). There is limited evidence for informant-report measures of PD hallucinations as adjuncts to clinician-rated scales.ObjectivesTo determine the utility of an informant version of the validated Psychosis and Hallucinations Questionnaire (PsycH-Q) for assessing the presence and severity of hallucinations in PD; and, to evaluate accuracy of clinician judgements by comparison with informant report and self-report.MethodsOne hundred sixty-three PD patient-informant dyads completed self- and informant-report versions of PsycH-Q and three common questionnaire measures: Neuropsychiatric Inventory Questionnaire; Parkinson's Psychosis Questionnaire; and Scales for Outcomes in Parkinson's disease-Psychiatric Complications. We compared self-ratings and informant ratings across analogous subscales for the presence of hallucinations with clinician interview ratings on MDS-UPDRS as a diagnostic standard.ResultsThere was a low level of agreement between dyads (average ??=?0.39; ? range?=?0.32-0.47; P?<?0.001), and patients indicated the highest prevalence of hallucinations compared to informant or clinician estimates. Clinician interview missed 32% of PsycH-Q hallucinators identified by dyads. Relative to the sample, 22 patients with exclusively clinician-appraised hallucinations had poorer overall quality of life measured by the Parkinson's Disease Questionnaire.ConclusionsThe sole use of clinician-rated scales may underestimate prevalence of PD hallucinations, and there is room for introducing self- and informant-report tools. Nonetheless, clinician appraisals are critical in cases when informant and patient insight might be affected by the impact of illness on quality of life.
| S-EPMC6277359 | biostudies-literature
Project description:Hallucinations are a core feature of psychosis and common in Parkinson's. Their transient, unexpected nature suggests a change in dynamic brain states, but underlying causes are unknown. Here, we examine temporal dynamics and underlying structural connectivity in Parkinson's-hallucinations using a combination of functional and structural MRI, network control theory, neurotransmitter density and genetic analyses. We show that Parkinson's-hallucinators spent more time in a predominantly Segregated functional state with fewer between-state transitions. The transition from integrated-to-segregated state had lower energy cost in Parkinson's-hallucinators; and was therefore potentially preferable. The regional energy needed for this transition was correlated with regional neurotransmitter density and gene expression for serotoninergic, GABAergic, noradrenergic and cholinergic, but not dopaminergic, receptors. We show how the combination of neurochemistry and brain structure jointly shape functional brain dynamics leading to hallucinations and highlight potential therapeutic targets by linking these changes to neurotransmitter systems involved in early sensory and complex visual processing.
| S-EPMC9458713 | biostudies-literature
Project description:Visual hallucinations occur when our conscious experience does not accurately reflect external reality. However, these dissociations also regularly occur when we imagine the world around us in the absence of visual stimulation. We used two novel behavioural paradigms to objectively measure visual hallucinations and voluntary mental imagery in 19 individuals with Parkinson's disease (ten with visual hallucinations; nine without) and ten healthy, age-matched controls. We then used this behavioural overlap to interrogate the connectivity both within and between the major attentional control networks using resting-state functional magnetic resonance imaging. Patients with visual hallucinations had elevated mental imagery strength compared with patients without hallucinations and controls. Specifically, the sensory strength of imagery predicted the frequency of visual hallucinations. Together, hallucinations and mental imagery predicted multiple abnormalities in functional connectivity both within and between the attentional control networks, as measured with resting-state functional magnetic resonance imaging. However, the two phenomena were also dissociable at the neural level, with both mental imagery and visual misperceptions associated with specific abnormalities in attentional network connectivity. Our results provide the first evidence of both the shared and unique neural correlates of these two similar, yet distinct phenomena.
| S-EPMC4262172 | biostudies-other
Project description:Visual hallucinations are common in Parkinson's disease and are associated with a poorer quality of life and a higher risk of dementia. An important and influential model that is widely accepted as an explanation for the mechanism of visual hallucinations in Parkinson's disease and other Lewy body diseases is that these arise due to aberrant hierarchical processing, with impaired bottom-up integration of sensory information and overweighting of top-down perceptual priors within the visual system. This hypothesis has been driven by behavioural data and supported indirectly by observations derived from regional activation and correlational measures using neuroimaging. However, until now, there was no evidence from neuroimaging for differences in causal influences between brain regions measured in patients with Parkinson's hallucinations. This is in part because previous resting-state studies focused on functional connectivity, which is inherently undirected in nature and cannot test hypotheses about the directionality of connectivity. Spectral dynamic causal modelling is a Bayesian framework that allows the inference of effective connectivity-defined as the directed (causal) influence that one region exerts on another region-from resting-state functional MRI data. In the current study, we utilize spectral dynamic causal modelling to estimate effective connectivity within the resting-state visual network in our cohort of 15 Parkinson's disease visual hallucinators and 75 Parkinson's disease non-visual hallucinators. We find that visual hallucinators display decreased bottom-up effective connectivity from the lateral geniculate nucleus to primary visual cortex and increased top-down effective connectivity from the left prefrontal cortex to primary visual cortex and the medial thalamus, as compared with non-visual hallucinators. Importantly, we find that the pattern of effective connectivity is predictive of the presence of visual hallucinations and associated with their severity within the hallucinating group. This is the first study to provide evidence, using resting-state effective connectivity, to support a model of aberrant hierarchical predictive processing as the mechanism for visual hallucinations in Parkinson's disease.
| S-EPMC9798302 | biostudies-literature
Project description:BackgroundThere is growing evidence that the serotonergic system, in particular serotonin 2A receptors, is involved in neuropsychiatric symptoms in Parkinson's disease (PD), including cognitive processing and visual hallucinations. However, the relationship between serotonin 2A receptor availability, visual hallucinations, and cognitive profile is unknown. The objective of this study was to investigate the level of serotonin 2A receptor availability in brain regions affected by visual hallucinations and to test the association with cognitive/behavioral changes in patients who have PD with visual hallucinations.MethodsNondemented patients who had PD with (n = 11) and without (n = 8) visual hallucinations and age-matched controls (n = 10) were recruited. All participants completed neuropsychological testing, which consisted of visuoperceptual, executive, memory, language, and frontal-behavioral function. Positron emission tomography scans using [18F]setoperone, a serotonin 2A antagonist radioligand, were acquired in patients with PD, and a parametric binding potential map of [18F]setoperone was calculated with the simplified reference tissue model using the cerebellum as a reference.ResultsPatients who had PD with visual hallucinations exhibited significantly lower scores on measures of executive and visuoperceptual functions compared with age-matched controls. These changes were paralleled by decreased [18F]setoperone binding in the right insula, bilateral dorsolateral prefrontal cortex, right orbitofrontal cortex, right middle temporal gyrus, and right fusiform gyrus. The psychometric correlation analysis revealed significant relationships among tests associated with visuoperceptual function, memory and learning, and serotonin 2A binding in different prefrontal and ventral visual stream regions. There was also reduced serotonin 2A receptor binding in patients who had PD with depression.ConclusionsThese findings support a complex interaction between serotonin 2A receptor function and cognitive processing in patients who have PD with visual hallucinations.
| S-EPMC6174444 | biostudies-literature