Pareidolias: complex visual illusions in dementia with Lewy bodies

Visual hallucinations in neurological and ophthalmological disease: pathophysiology and management

Visual hallucinations are common in older people and are especially associated with ophthalmological and neurological disorders, including dementia and Parkinson's disease. Uncertainties remain whether there is a single underlying mechanism for visual hallucinations or they have different disease-dependent causes. However, irrespective of mechanism, visual hallucinations are difficult to treat. The National Institute for Health Research (NIHR) funded a research programme to investigate visual hallucinations in the key and high burden areas of eye disease, dementia and Parkinson's disease, culminating in a workshop to develop a unified framework for their clinical management. Here we summarise the evidence base, current practice and consensus guidelines that emerged from the workshop.Irrespective of clinical condition, case ascertainment strategies are required to overcome reporting stigma. Once hallucinations are identified, physical, cognitive and ophthalmological health should be reviewed, with education and self-help techniques provided. Not all hallucinations require intervention but for those that are clinically significant, current evidence supports pharmacological modification of cholinergic, GABAergic, serotonergic or dopaminergic systems, or reduction of cortical excitability. A broad treatment perspective is needed, including carer support. Despite their frequency and clinical significance, there is a paucity of randomised, placebo-controlled clinical trial evidence where the primary outcome is an improvement in visual hallucinations. Key areas for future research include the development of valid and reliable assessment tools for use in mechanistic studies and clinical trials, transdiagnostic studies of shared and distinct mechanisms and when and how to treat visual hallucinations.

Towards the interpretation of complex visual hallucinations in terms of self-reorganization of neural networks

Patients suffering from dementia with Lewy body (DLB) often see complex visual hallucinations (CVH). Despite many pathological, clinical, and neuroimaging studies, the mechanism of CVH remains unknown. One possible scenario is that top-down information is being used to compensate for the lack of bottom-up information. To investigate this possibility and understand the underlying mathematical structure of the CVH mechanism, we propose a simple computational model of synaptic plasticity with particular focus on the effect of selective damage to the bottom-up network on self-reorganization. We show neurons that undergo a change in activity from a bottom-up to a top-down network framework during the reorganization process, which can be understood in terms of state transitions. Assuming that the pre-reorganization representation of this neuron remains after reorganization, it is possible to interpret neural response induced by top-down information as the sensation of bottom-up information. This situation might correspond to a hallucinatory situation in DLB patients. Our results agree with existing experimental evidence and provide new insights into data that have hitherto not been experimentally validated on patients with DLB.

Pareidolia-proneness, reality discrimination errors, and visual hallucination-like experiences in a non-clinical sample

Introduction: It has been proposed that hallucinations occur because of problems with reality discrimination (when internal, self-generated cognitions are misattributed to an external, non-self source) and because of elevated levels of top-down processing. In this study, we examined whether visual reality discrimination abilities and elevated top-down processing (assessed via face pareidolia-proneness) were associated with how often non-clinical participants report visual hallucination-like experiences.Methods: Participants (N = 82, mean age = 23.12 years) completed a visual reality discrimination task and a face pareidolia task, as well as self-report measures of schizotypy and of the frequency of visual hallucination-like experiences.Results: Regression analysis demonstrated that the number of false alarms made on the visual reality discrimination task and the number of hits made on the face pareidolia task were independent predictors of the frequency of visual hallucination-like experiences. Correlations between performance on the tasks and levels of schizotypy were not statistically significant.Conclusions: These findings suggest that weaker visual reality discrimination abilities and elevated levels of top-down processing are associated with visual hallucination-proneness and are discussed in terms of the idea that clinical visual hallucinations and non-clinical visual hallucination-like experiences share similar cognitive mechanisms.

Clinical and Cerebral Metabolic Changes in Parkinson's Disease With Basal Forebrain Atrophy

BACKGROUND

Cholinergic dysfunction plays a key role in cognitive dysfunction in Parkinson's disease (PD). Recent studies revealed that atrophy in the nucleus basalis of Meynert (NBM), the largest cholinergic nucleus in the basal forebrain, heralds cognitive decline in PD. Despite clinical importance of NBM atrophy in PD, clinical and radiological correlates of NBM atrophy remains to be elucidated.

OBJECTIVE

We investigated the longitudinal changes in clinical and cerebral glucose metabolic characteristics in PD with atrophy in the NBM.

METHODS

We analyzed the 3-year longitudinal data of 56 PD patients who underwent motor, nonmotor, and imaging evaluations at baseline. The patients were classified into PD with and without NBM atrophy based on the results of magnetic resonance imaging volumetry. We compared clinical characteristics and cerebral glucose metabolic changes between PD with and without NBM atrophy.

RESULTS

At baseline, 20 patients and 36 patients were classified into PD with and without NBM atrophy groups, respectively. At follow-up, the data of the 14 PD patients in the NBM atrophy group and the 18 patients in the group without NBM atrophy completed full assessments and were available for the analysis. The PD with NBM atrophy group showed severe cognitive dysfunction and psychiatric symptoms both at baseline and follow-up. The NBM volume significantly correlated with motor and nonmotor functions. The PD with NBM atrophy showed significantly reduced metabolism in the parietal and occipital cortices both at baseline and follow-up.

CONCLUSIONS

Basal forebrain atrophy is a simple and sensible marker of faster disease progression and cortical hypometabolism in PD. © 2020 International Parkinson and Movement Disorder Society.

The Pharmacology of Visual Hallucinations in Synucleinopathies

Visual hallucinations (VH) are commonly found in the course of synucleinopathies like Parkinson's disease and dementia with Lewy bodies. The incidence of VH in these conditions is so high that the absence of VH in the course of the disease should raise questions about the diagnosis. VH may take the form of early and simple phenomena or appear with late and complex presentations that include hallucinatory production and delusions. VH are an unmet treatment need. The review analyzes the past and recent hypotheses that are related to the underlying mechanisms of VH and then discusses their pharmacological modulation. Recent models for VH have been centered on the role played by the decoupling of the default mode network (DMN) when is released from the control of the fronto-parietal and salience networks. According to the proposed model, the process results in the perception of priors that are stored in the unconscious memory and the uncontrolled emergence of intrinsic narrative produced by the DMN. This DMN activity is triggered by the altered functioning of the thalamus and involves the dysregulated activity of the brain neurotransmitters. Historically, dopamine has been indicated as a major driver for the production of VH in synucleinopathies. In that context, nigrostriatal dysfunctions have been associated with the VH onset. The efficacy of antipsychotic compounds in VH treatment has further supported the notion of major involvement of dopamine in the production of the hallucinatory phenomena. However, more recent studies and growing evidence are also pointing toward an important role played by serotonergic and cholinergic dysfunctions. In that respect, in vivo and post-mortem studies have now proved that serotonergic impairment is often an early event in synucleinopathies. The prominent cholinergic impairment in DLB is also well established. Finally, glutamatergic and gamma aminobutyric acid (GABA)ergic modulations and changes in the overall balance between excitatory and inhibitory signaling are also contributing factors. The review provides an extensive overview of the pharmacology of VH and offers an up to date analysis of treatment options.

Neuropsychiatric Symptoms in Dementia: Considerations for Pharmacotherapy in the USA

Dementia affects all domains of cognition. The relentless progression of the disease after diagnosis is associated with a 98% incidence of neuropsychiatric symptoms (NPS) at some point in the disease, including depression, psychosis, agitation, aggression, apathy, sleep disturbances, and disinhibition. These symptoms can be severe and lead to excess morbidity and mortality. The purpose of this article was to describe current literature on the medication management of NPS of dementia and highlight approaches to and concerns about the pharmacological treatment of NPS in the USA. Guidelines and expert opinion favor nonpharmacologic management of NPS as first-line management. Unfortunately, lack of adequate caregiver training and a high failure rate eventually result in the use of psychotropic agents in patients with dementia. Various psychotropic medications have been studied, although how they should be used in the management of NPS remains unclear. A systematic approach to evaluation, treatment, and monitoring, along with careful documentation and evidenced-based agent and dose selection, is likely to reduce risk and improve patient outcomes. Considerations should be given to the NPS presentation, including type, frequency, and severity, when weighing the risks and benefits of initiating, continuing, or discontinuing psychotropic management. Use of antidepressants, sedative/hypnotics, antipsychotics, and antiepileptic agents should include a clear and documented analysis of risk and benefit in a given patient with dementia.

Impaired face-like object recognition in premanifest Huntington's disease

Progressive striatal atrophy has long been considered the pathological hallmark of Huntington's disease (HD), but is it now recognized that malfunction and degeneration of posterior-cortical territories are also prominent characteristics of the disease. The limited knowledge about the functional impact of these posterior-cortical changes could be partially attributed to the lack of sensitive measures to capture them. We hypothesized that early malfunction of specific territories of the ventral visual pathway in premanifest HD would lead to difficulties in the recognition of complex stimuli and to differences in their neurophysiological correlates. To test this idea, we used an object, face and face-like object recognition task to be conducted during an electroencephalographic recording. Compared to healthy-matched controls, premanifest participants showed a significantly increased number of recognition errors in the face-like object condition. Moreover, premanifest participants showed a dramatic decrease in the N170 component elicited for the face-like objects. This N170 decrease was significantly associated with the number of recognition errors and with severity of apathy and global cognitive performance. The lack of differences in other clinical and cognitive measures supports a selective deficit in recognition of face-like objects and their neurophysiological correlates in premanifest HD. These deficits occurred in participants up to 15 years before the estimated time to disease onset and correlated strongly with cognitive and behavioral measures known to be sensitive to HD progression. This finding highlights the existence of selective visuoperceptive deficits years before motor-based onset of HD and emphasizes the need to develop sensitive measures to capture early visual system changes in this population. Assessing the integrity of the visual cortex and its related functions in HD could help to identify early markers of disease progression.

Minor hallucinations in Parkinson disease: A subtle symptom with major clinical implications

OBJECTIVE

Psychosis is one of the most debilitating complications of Parkinson disease (PD). Although research on PD psychosis has been focused on the study of well-structured visual hallucinations (VH), currently accepted National Institute of Neurological Disorders and Stroke-National Institute of Mental Health diagnostic criteria emphasize minor hallucinations (MH) as the most common psychotic phenomena in PD. The objective of this review is to comprehensively describe the clinical and research advances on the understanding of MH and to provide future directions for obtaining further insights into their potential major implications for PD management and prognosis.

METHODS

A PubMed search was done in November 2018 to identify articles on minor psychotic phenomena in PD.

RESULTS

MH often precede the onset of well-structured VH and are associated with other nonmotor symptoms such as REM sleep behavior disorder and depression. The pattern of functional brain connectivity changes associated with MH involve visual-processing areas and attention control networks, which overlap with abnormalities described in patients with well-structured VH. The dysfunction of cortical networks in patients with MH may be an early indicator of a more widespread form of the disease.

CONCLUSION

Although called "minor," MH may have major clinical and prognostic implications. Further research is needed to establish whether MH are associated with a higher risk of disabling psychotic complications, cognitive deterioration, or a more accelerated disease progression. Understanding the early neurobiological underpinnings of MH may provide the background for future studies to identify the progressive dysfunction of neural circuits leading to more severe forms of psychosis in PD.

Amisulpride for very late-onset schizophrenia-like psychosis: the ATLAS three-arm RCT

BACKGROUND

Very late-onset (aged ≥ 60 years) schizophrenia-like psychosis (VLOSLP) occurs frequently but no placebo-controlled, randomised trials have assessed the efficacy or risks of antipsychotic treatment. Most patients are not prescribed treatment.

OBJECTIVES

The study investigated whether or not low-dose amisulpride is superior to placebo in reducing psychosis symptoms over 12 weeks and if any benefit is maintained by continuing treatment thereafter. Treatment safety and cost-effectiveness were also investigated.

DESIGN

Three-arm, parallel-group, placebo-controlled, double-blind, randomised controlled trial. Participants who received at least one dose of study treatment were included in the intention-to-treat analyses.

SETTING

Secondary care specialist old age psychiatry services in 25 NHS mental health trusts in England and Scotland.

PARTICIPANTS

Patients meeting diagnostic criteria for VLOSLP and scoring > 30 points on the Brief Psychiatric Rating Scale (BPRS).

INTERVENTION

Participants were randomly assigned to three arms in a two-stage trial: (1) 100 mg of amisulpride in both stages, (2) amisulpride then placebo and (3) placebo then amisulpride. Treatment duration was 12 weeks in stage 1 and 24 weeks (later reduced to 12) in stage 2. Participants, investigators and outcome assessors were blind to treatment allocation.

MAIN OUTCOME MEASURES

Primary outcomes were psychosis symptoms assessed by the BPRS and trial treatment discontinuation for non-efficacy. Secondary outcomes were extrapyramidal symptoms measured with the Simpson-Angus Scale, quality of life measured with the World Health Organization's quality-of-life scale, and cost-effectiveness measured with NHS, social care and carer work loss costs and EuroQol-5 Dimensions.

RESULTS

A total of 101 participants were randomised. Ninety-two (91%) participants took the trial medication, 59 (64%) completed stage 1 and 33 (56%) completed stage 2 treatment. Despite suboptimal compliance, improvements in BPRS scores at 12 weeks were 7.7 points (95% CI 3.8 to 11.5 points) greater with amisulpride than with placebo (11.9 vs. 4.2 points; p = 0.0002). In stage 2, BPRS scores improved by 1.1 point in those who continued with amisulpride but deteriorated by 5.2 points in those who switched from amisulpride to placebo, a difference of 6.3 points (95% CI 0.9 to 11.7 points; p = 0.024). Fewer participants allocated to the amisulpride group stopped treatment because of non-efficacy in stages 1 (p = 0.01) and 2 (p = 0.031). The number of patients stopping because of extrapyramidal symptoms and other side effects did not differ significantly between groups. Amisulpride treatment in the base-case analyses was associated with non-significant reductions in combined NHS, social care and unpaid carer costs and non-significant reductions in quality-adjusted life-years (QALYs) in both stages. Including patients who were intensive users of inpatient services in sensitivity analyses did not change the QALY result but resulted in placebo dominance in stage 1 and significant reductions in NHS/social care (95% CI -£8923 to -£122) and societal costs (95% CI -£8985 to -£153) for those continuing with amisulpride.

LIMITATIONS

The original recruitment target of 300 participants was not achieved and compliance with trial medication was highly variable.

CONCLUSIONS

Low-dose amisulpride is effective and well tolerated as a treatment for VLOSLP, with benefits maintained by prolonging treatment. Potential adverse events include clinically significant extrapyramidal symptoms and falls.

FUTURE WORK

Trials should examine the longer-term effectiveness and safety of antipsychotic treatment in this patient group, and assess interventions to improve their appreciation of potential benefits of antipsychotic treatment and compliance with prescribed medication.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN45593573 and EudraCT2010-022184-35.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 67. See the NIHR Journals Library website for further project information.

A comparison of visual hallucinations across disorders

Research into hallucinations typically regards them as single sensory or unimodal experiences leading to a comparative neglect of co-occurring multi-sensory hallucinations (MSH). People with psychosis who have visual hallucinations (VH) report high rates of hallucinations in other senses (auditory, olfactory, tactile). However, it is not known if this is similar to other groups who report VH. Consequently, this study explored MSH in four different patient groups who all had current VH. Archival data from standardised assessments of visual hallucinations in people with psychosis (n = 22), eye disease (ED) (n = 82), Lewy body Dementia (LBD) (n = 41), and Parkinson's disease (PD) (n = 41) determined the presence of MSH. People with psychosis and visual hallucinations reported significantly higher rates of MSH (auditory, 73%; tactile, 82%; olfactory/gustatory hallucinations, 27%) than the LBD group (auditory, 21%; tactile, 28%; olfactory/gustatory, 6%), ED (auditory, 1%; tactile, 11%; olfactory/gustatory, 0%) and PD patients (auditory, 3%; tactile, 8%; olfactory/gustatory, 3%). Regardless of diagnostic grouping, participants with MSH reported greater conviction that the VH were real, and reported greater distress. People with psychosis with VH report high rates of MSH unlike groups of older adults with VH. These between group differences in MSH prevalence have implications for clinical practice and theory.

Neural mechanisms underlying visual pareidolia processing: An fMRI study

Objectives

Pareidolia is the interpretation of previously unseen and unrelated objects as familiar due to previous learning. The present study aimed to determine the specific brain areas that exhibited activation during real-face and face-pareidolia processing.

Methods

Functional Magnetic Resonance Imaging (fMRI) scans were performed on 20 healthy subjects under real-face and face-pareidolia conditions in National Magnetic Resonance Research Center (UMRAM), Ankara, Turkey from April 2016 to January 2017. FSL software was used to conduct a FEAT higher level (group) analysis to identify the brain areas activated during real-face and face-pareidolia processing.

Results

Under both the real-face and face-pareidolia conditions, activation was observed in the Prefrontal Cortex (PFCX), occipital cortex V1, occipital cortex V2, and inferior temporal regions. Also under both conditions, the same degree of activation was observed in the right Fusiform Face Area (FFA) and the right PFCX. On the other hand, PFCX activation was not evident under the real-face versus face scrambled or face-pareidolia versus pareidolia scrambled conditions.

Conclusions

The present findings suggest that, as in real-face perception, face-pareidolia requires interaction between top-down and bottom-up brain regions including the FFA and frontal and occipitotemporal areas. Additionally, whole-brain analyses revealed that the right PFCX played an important role in processing real faces and in face pareidolia (illusory face perception), as did the FFA.

Characteristics of facial expression recognition ability in patients with Lewy body disease

Background

The facial expression of medical staff has been known to greatly affect the psychological state of patients, making them feel uneasy or conversely, cheering them up. By clarifying the characteristics of facial expression recognition ability in patients with Lewy body disease, the aim of this study is to examine points to facilitate smooth communication between caregivers and patients with the disease whose cognitive function has deteriorated.

Methods

During the period from March 2016 to July 2017, we examined the characteristics of recognition of the six facial expressions of “happiness,” “sadness,” “fear,” “anger,” “surprise,” and “disgust” for 107 people aged 60 years or more, both outpatient and inpatient, who hospital specialists had diagnosed with Lewy body diseases of Parkinson’s disease, Parkinson’s disease with dementia, and dementia with Lewy bodies. Based on facial expression recognition test results, we classified them by cluster analysis and clarified features of each type.

Results

In patients with Lewy body disease, happiness was kept unaffected by aging, age of onset, duration of the disease, cognitive function, and apathy; however, recognizing the facial expression of fear was difficult. In addition, due to aging, cognitive decline, and apathy, the facial expression recognition ability for sadness and anger decreased. In particular, cognitive decline reduced recognition of all of the facial expressions except for happiness. The test accuracy rates were classified into three types using the cluster analysis: “stable type,” “mixed type,” and “reduced type”. In the “reduced type”, the overall facial recognition ability declined except happiness, and in the mixed type, recognition ability of anger particularly declined.

Conclusion

There were several facial expressions that the Lewy body disease patients were unable to accurately identify. Caregivers are recommended to make an effort to compensate for such situations with language or body contact, etc., as a way to convey correct feeling to the patients of each type.

Visual Hallucinations and Paranoid Delusions

Visual well-formed hallucinations, fluctuations in the level of cognition, and alertness and extrapyramidal signs are core features of dementia with Lewy bodies. Some patients realize that what they are seeing or hearing are just hallucinations and learn to accept them. Others, however experience these hallucinations as quite real and cannot be dissuaded from the firm belief that they are. In fact, efforts to dissuade them often serve only to confirm the often associated paranoid delusions and this may lead to a catastrophic ending. Hence, it is best not to contradict the patient. Instead, attempts should be made to distract the patient and change the focus of her or his attention. In this case scenario, we present a 68-year-old man who has been diagnosed with dementia with Lewy bodies. He lives with his daughter. He has visual hallucinations and paranoid delusions that worsen at night: He thinks there are people outside the house plotting to kill him. We discuss what went wrong in the patient/caregiver interaction and how the catastrophic ending could have been avoided or averted.

Characteristics of dementia patients who described or did not describe the relationship between two people on the COGNISTAT speech sample

Speech sample of Cognitive Status Examination (COGNISTAT) is a task in which examinees freely talk about what is happening in a presented picture. We investigated whether there are differences in the characteristics between patients who described or did not describe the relationship between two people in the speech sample based on age, gender, cognitive dysfunction, and type of dementia (Alzheimer's disease and dementia with Lewy bodies). The participants were 60-year-old or older patients diagnosed with Alzheimer's disease or dementia with Lewy bodies who undertook the Mini-Mental State Examination (MMSE) and COGNISTAT at a general hospital specialized in care for the elderly. MMSE and COGNISTAT were performed by a female clinical psychologist in all patients. In a stepwise logistic regression analysis using the two groups (description and no description groups) as a response variable, and the age, gender, diagnosis, MMSE score, and score of each COGNISTAT subtest as explanatory variables, the MMSE score (OR = 1.09; 95% CI [1.03, 1.15]) and gender (OR = 1.79; 95% CI [1.09, 2.93]) factors were extracted. These results indicated that patients with severer overall cognitive dysfunction and male patients were unlikely to describe the relationship between two people in a speech sample.

Changes in pupil diameter are correlated with the occurrence of pareidolias in patients with dementia with Lewy bodies

Pareidolias are visual illusions of meaningful objects, such as faces and animals, that arise from ambiguous forms embedded in visual scenes. Pareidolias and visual hallucinations have been suggested to have a common underlying neural mechanism in patients with dementia with Lewy bodies (DLB). The aim of the present study was to find an externally observable physiological indicator of pareidolias. Using a pareidolia test developed by Uchiyama and colleagues, we evoked pareidolias in patients with DLB and recorded the resultant changes in the diameters of their pupil. The time frequencies of changes in pupil diameters preceding pareidolic utterances and correct utterances by the patients, as well as correct utterances by healthy control participants, were analyzed by a fast Fourier transform program. The power at time frequencies of 0–0.46 Hz was found to be greatest preceding pareidolic utterances in patients with DLB, followed by that preceding correct utterances in control participants, followed by that preceding correct utterances in patients with DLB. When the changes in power preceding the utterance were greater than the median value of correct utterances by the control group, the frequency of pareidolic utterances was significantly greater than that of correct utterances and when the changes were the same as or lower than the median value, the frequency of correct utterances was significantly greater than that of pareidolic utterances. Greater changes in power preceding the utterance at time frequencies of 0–0.46 Hz may thus be an externally observable physiological indicator of the occurrence of pareidolias.

Differences in responses to the Rorschach test between patients with dementia with Lewy bodies and Alzheimer's disease -from the perspective of visuoperceptual impairment

Patients with Dementia with Lewy bodies (DLB) tend to perform worse in tasks on visuoperception than patients with Alzheimer's disease (AD). The Rorschach inkblot test has its utility for assessing perceptual and visuospatial abilities. In this study, we examined the differences in responses to the Rorschach test between patients with DLB and those with AD in terms of visuoperception, and investigated the utility of the test for assessing visuoperceptual impairment in DLB. Using the comprehensive system of Rorschach test, six variables were significantly higher, and three variables were significantly lower in DLB patients compared to AD patients. Among those variables, PTI showed high sensitivity and specificity for differentiating DLB from AD. Furthermore, when the PTI score was combined with the Dd score and a number of times a patient saw an eye in a shading part of an inkblot, the sensitivity and specificity reached 90.6% and 73.1%, respectively. These results indicate that the patients with DLB perceive objects in the inkblot differently from patients with AD, and suggest that some variables of the Rorschach test could assist with neuropsychological examinations when differentiating DLB from AD.

Deconstructing psychosis and misperception symptoms in Parkinson's disease

OBJECTIVE

Patients with Lewy body disease develop a variety of psychotic and misperception symptoms, including visual hallucinations and delusions, as well as 'minor hallucinations', that is, a sense of presence, passage hallucinations and visual illusions. Although these symptoms have been suggested to have common underlying mechanisms, the commonalities and differences among them have not been systematically investigated at the neural level.

METHODS

Sixty-seven patients with Parkinson's disease underwent neuropsychological and behavioural assessments, volumetric MRI and 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET). A factor analysis was performed to discover correlations among psychotic and misperception symptoms, other behavioural symptoms and neuropsychological performances. Partial least-squares correlation analysis was used to investigate the relationship between these symptoms and the joint features of MRI and FDG-PET.

RESULTS

A sense of presence, passage hallucinations and visual illusions constituted a single behavioural factor (minor hallucinations/illusions). Visual hallucinations formed another behavioural factor along with delusions, depression and fluctuating cognition (psychosis/dysphoria). Three distinct brain-behaviour correlation patterns were identified: (1) posterior cortical atrophy/hypometabolism associated with minor hallucinations/illusions and visuospatial impairment; (2) upper brainstem and thalamic atrophy/hypometabolism associated with psychosis/dysphoria and (3) frontal cortical atrophy/hypometabolism associated with non-visual cognition. No significant differences in neuroimaging findings were identified between patients who had minor hallucinations/illusions alone and patients who also had visual hallucinations.

CONCLUSIONS

Our findings suggest that combined damage to the upper brainstem/thalamus and the posterior neocortex underlies both minor hallucinations/illusions and visual hallucinations and that the former pathology is more associated with visual hallucinations/frank psychosis and the latter is more associated with minor hallucinations/illusions.

Psychosis in Parkinson Disease: A Review of Etiology, Phenomenology, and Management

Parkinson disease psychosis (PDP) is a common phenomenon in Parkinson disease (PD) patients treated with dopaminergic drugs, and is associated with high morbidity and mortality. It also correlates with depression and dementia, and can contribute to considerable caregiver stress and burnout. While symptoms can be relieved by decreasing doses or number of anti-PD medications, this may lead to an unacceptable worsening of motor function. When general medical or psychiatric conditions have been ruled out, and decreasing dopaminergic agents is not effective in treating psychosis, therapies include atypical antipsychotics, primarily clozapine and quetiapine. Of these, clozapine is effective but is associated with a poor side-effect profile and the necessity for frequent blood draws. Clinicians prefer quetiapine for its theoretically better safety profile, although there is no evidence for efficacy in treating psychosis. All atypical antipsychotics are associated with increased mortality in this patient population. Cholinesterase inhibitors can ameliorate psychosis symptoms. The serotonin 5-HT_2A receptor inverse agonist pimavanserin was recently approved by the US FDA for the treatment of PDP and may prove to be a more targeted therapy without the downsides of atypical antipsychotics.

Compensatory shifts in visual perception are associated with hallucinations in Lewy body disorders

Visual hallucinations are a common, distressing, and disabling symptom of Lewy body and other diseases. Current models suggest that interactions in internal cognitive processes generate hallucinations. However, these neglect external factors. Pareidolic illusions are an experimental analogue of hallucinations. They are easily induced in Lewy body disease, have similar content to spontaneous hallucinations, and respond to cholinesterase inhibitors in the same way. We used a primed pareidolia task with hallucinating participants with Lewy body disorders (n = 16), non-hallucinating participants with Lewy body disorders (n = 19), and healthy controls (n = 20). Participants were presented with visual “noise” that sometimes contained degraded visual objects and were required to indicate what they saw. Some perceptions were cued in advance by a visual prime. Results showed that hallucinating participants were impaired in discerning visual signals from noise, with a relaxed criterion threshold for perception compared to both other groups. After the presentation of a visual prime, the criterion was comparable to the other groups. The results suggest that participants with hallucinations compensate for perceptual deficits by relaxing perceptual criteria, at a cost of seeing things that are not there, and that visual cues regularize perception. This latter finding may provide a mechanism for understanding the interaction between environments and hallucinations.

Divergent functional connectivity during attentional processing in Lewy body dementia and Alzheimer's disease

Attention and executive dysfunction are features of Lewy body dementia (LBD) but their neuroanatomical basis is poorly understood. To investigate underlying dysfunctional attention-executive network (EXEC) interactions, we examined functional connectivity (FC) in 30 patients with LBD, 20 patients with Alzheimer's disease (AD), and 21 healthy controls during an event-related functional magnetic resonance imaging (fMRI) experiment. Participants performed a modified Attention Network Test (ANT), where they were instructed to press a button in response to the majority direction of arrows, which were either all pointing in the same direction or with one pointing in the opposite direction. Network activations during both target conditions and a baseline condition (no target) were derived by (ICA) Independent Component Analysis, and interactions between these networks were examined using the beta series correlations approach. Our study revealed that FC of ventral and dorsal attention networks DAN was reduced in LBD during all conditions, although most prominently during incongruent trials. These alterations in connectivity might be driven by a failure of engagement of ventral attention networks, and consequent over-reliance on the DAN. In contrast, when comparing AD patients with the other groups, we found hyperconnectivity between the posterior part of the default mode network (DMN) and the DAN in all conditions, particularly during incongruent trials. This might be attributable to either a compensatory effect to overcome DMN dysfunction, or be arising as a result of a disturbed transition of the DMN from rest to task. Our results demonstrate that dementia syndromes can be characterized both by hyper- and hypoconnectivity of distinct brain networks, depending on the interplay between task demand and available cognitive resources. However these are dependent upon the underlying pathology, which needs to be taken into account when developing specific cognitive therapies for LBD as compared to Alzheimer's.

Predictions penetrate perception: Converging insights from brain, behaviour and disorder

It is argued that during ongoing visual perception, the brain is generating top-down predictions to facilitate, guide and constrain the processing of incoming sensory input. Here we demonstrate that these predictions are drawn from a diverse range of cognitive processes, in order to generate the richest and most informative prediction signals. This is consistent with a central role for cognitive penetrability in visual perception. We review behavioural and mechanistic evidence that indicate a wide spectrum of domains-including object recognition, contextual associations, cognitive biases and affective state-that can directly influence visual perception. We combine these insights from the healthy brain with novel observations from neuropsychiatric disorders involving visual hallucinations, which highlight the consequences of imbalance between top-down signals and incoming sensory information. Together, these lines of evidence converge to indicate that predictive penetration, be it cognitive, social or emotional, should be considered a fundamental framework that supports visual perception.

Detection of Low-Signal Pulvinar Areas Using Diffusion-Weighted Imaging in Patients with Dementia Experiencing Visual Hallucinations

BACKGROUND

Little research has been conducted regarding the role of pulvinar nuclei in the pathogenesis of visual hallucinations due to the difficulty of assessing abnormalities in this region using conventional magnetic resonance imaging (MRI). The present study aimed to retrospectively investigate the relative abilities of diffusion-weighted imaging (DWI), fluid-attenuated inversion recovery (FLAIR), and susceptibility-weighted imaging (SWI) to visualize the pulvinar and to ascertain the relationship between pulvinar visualization and visual hallucinations.

METHODS

A retrospective analysis of 3T MRIs from 73 patients (31 males, 42 females; mean age 73.5 ± 12.7 years) of the Memory Clinic of Mie University Hospital was conducted. Correlations between pulvinar visualization and the following were analyzed: age, sex, education, hypertension, hyperlipidemia, diabetes mellitus, Mini-Mental State Examination score, Evans index, and visual hallucinations.

RESULTS

DWI detected low-signal pulvinar areas in approximately half of the patients (52.1%). Participants with pulvinar visualization were significantly older, and the pulvinar was more frequently visualized in patients who had experienced visual hallucinations compared to those who had not. No significant association was observed between whole brain atrophy and pulvinar visualization.

CONCLUSIONS

The results of the present study indicate that diffusion-weighted 3T MRI is the most suitable method for the detection of pulvinar nuclei in patients with dementia experiencing visual hallucinations.

The Pareidolia Test: A Simple Neuropsychological Test Measuring Visual Hallucination-Like Illusions

Background

Visual hallucinations are a core clinical feature of dementia with Lewy bodies (DLB), and this symptom is important in the differential diagnosis and prediction of treatment response. The pareidolia test is a tool that evokes visual hallucination-like illusions, and these illusions may be a surrogate marker of visual hallucinations in DLB. We created a simplified version of the pareidolia test and examined its validity and reliability to establish the clinical utility of this test.

Methods

The pareidolia test was administered to 52 patients with DLB, 52 patients with Alzheimer’s disease (AD) and 20 healthy controls (HCs). We assessed the test-retest/inter-rater reliability using the intra-class correlation coefficient (ICC) and the concurrent validity using the Neuropsychiatric Inventory (NPI) hallucinations score as a reference. A receiver operating characteristic (ROC) analysis was used to evaluate the sensitivity and specificity of the pareidolia test to differentiate DLB from AD and HCs.

Results

The pareidolia test required approximately 15 minutes to administer, exhibited good test-retest/inter-rater reliability (ICC of 0.82), and moderately correlated with the NPI hallucinations score (r_s = 0.42). Using an optimal cut-off score set according to the ROC analysis, and the pareidolia test differentiated DLB from AD with a sensitivity of 81% and a specificity of 92%.

Conclusions

Our study suggests that the simplified version of the pareidolia test is a valid and reliable surrogate marker of visual hallucinations in DLB.

Visual Hallucinations in Eye Disease and Lewy Body Disease

OBJECTIVES

Visual hallucinations (VH) most commonly occur in eye disease (ED), Parkinson disease (PD), and Lewy body dementia (LBD). The phenomenology of VH is likely to carry important information about the brain areas within the visual system generating them.

METHODS

Data from five controlled cross-sectional VH studies (164 controls, 135 ED, 156 PD, 79 [PDD 48 + DLB 31] LBD) were combined and analyzed. The prevalence, phenomenology, frequency, duration, and contents of VH were compared across diseases and sex.

RESULTS

Simple VH were most common in ED patients (ED 65% versus LBD 22% versus PD 9%, χ(2) = 31.43, df = 2, p < 0.001), whereas complex VH were more common in LBD (LBD 76% versus ED 38%, versus PD 28%, χ(2) = 96.80, df = 2, p < 0.001). The phenomenology of complex VH was different across diseases and sex. ED patients reported more "flowers" (ED 21% versus LBD 6% versus PD 0%, χ(2) = 10.04, df = 2, p = 0.005) and "body parts" (ED 40% versus LBD 17% versus PD 13%, χ(2) = 11.14, df = 2, p = 0.004); in contrast, LBD patients reported "people" (LBD 85% versus ED 67% versus PD 63%, χ(2) = 6.20, df = 2, p = 0.045) and "animals/insects" (LBD 50% versus PD 42% versus ED 21%, χ(2) = 9.76, df = 2, p = 0.008). Men reported more "machines" (13% versus 2%, χ(2) = 6.94, df = 1, p = 0.008), whereas women reported more "family members/children" (48% versus 29%, χ(2) = 5.10, df = 1, p = 0.024).

CONCLUSIONS

The phenomenology of VH is likely related to disease-specific dysfunctions within the visual system and to past, personal experiences.

Altered functional connectivity in lesional peduncular hallucinosis with REM sleep behavior disorder

Brainstem lesions causing peduncular hallucinosis (PH) produce vivid visual hallucinations occasionally accompanied by sleep disorders. Overlapping brainstem regions modulate visual pathways and REM sleep functions via gating of thalamocortical networks. A 66-year-old man with paroxysmal atrial fibrillation developed abrupt-onset complex visual hallucinations with preserved insight and violent dream enactment behavior. Brain MRI showed restricted diffusion in the left rostrodorsal pons suggestive of an acute ischemic stroke. REM sleep behavior disorder (RBD) was diagnosed on polysomnography. We investigated the integrity of ponto-geniculate-occipital circuits with seed-based resting-state functional connectivity MRI (rs-fcMRI) in this patient compared to 46 controls. Rs-fcMRI revealed significantly reduced functional connectivity between the lesion and lateral geniculate nuclei (LGN), and between LGN and visual association cortex compared to controls. Conversely, functional connectivity between brainstem and visual association cortex, and between visual association cortex and prefrontal cortex (PFC) was significantly increased in the patient. Focal damage to the rostrodorsal pons is sufficient to cause RBD and PH in humans, suggesting an overlapping mechanism in both syndromes. This lesion produced a pattern of altered functional connectivity consistent with disrupted visual cortex connectivity via de-afferentation of thalamocortical pathways.

Imagine that: elevated sensory strength of mental imagery in individuals with Parkinson's disease and visual hallucinations

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.

Divergent brain functional network alterations in dementia with Lewy bodies and Alzheimer's disease

The clinical phenotype of dementia with Lewy bodies (DLB) is different from Alzheimer's disease (AD), suggesting a divergence between these diseases in terms of brain network organization. To fully understand this, we studied functional networks from resting-state functional magnetic resonance imaging in cognitively matched DLB and AD patients. The DLB group demonstrated a generalized lower synchronization compared with the AD and healthy controls, and this was more severe for edges connecting distant brain regions. Global network measures were significantly different between DLB and AD. For instance, AD showed lower small-worldness than healthy controls, while DLB showed higher small-worldness (AD < controls < DLB), and this was also the case for global efficiency (DLB > controls > AD) and clustering coefficient (DLB < controls < AD). Differences were also found for nodal measures at brain regions associated with each disease. Finally, we found significant associations between network performance measures and global cognitive impairment and severity of cognitive fluctuations in DLB. These results show network divergences between DLB and AD which appear to reflect their neuropathological differences.

Comprehensive treatment of dementia with Lewy bodies

Dementia with Lewy bodies is an under-recognized disease; it is responsible for up to 20 % of all dementia cases. Accurate diagnosis is essential because the management of dementia with Lewy bodies is more complex than many neurodegenerative diseases. This is because alpha-synuclein, the pathological protein responsible for dementia with Lewy bodies (and Parkinson's disease), produces symptoms in multiple domains. By dividing the symptoms into cognitive, neuropsychiatric, movement, autonomic, and sleep categories, a comprehensive treatment strategy can be achieved. Management decisions are complex, since the treatment of one set of symptoms can cause complications in other symptom domains. Nevertheless, a comprehensive treatment program can greatly improve the patient's quality of life, but does not alter the progression of disease. Cholinesterase inhibitors are effective for cognitive and neuropsychiatric symptoms; rivastigmine has the widest evidence base. Special care needs to be taken to avoid potentially fatal idiopathic reactions to neuroleptic medications; these should be used for short periods only when absolutely necessary and when alternative treatments have failed. Pimavanserin, a selective serotonin 5-HT2A inverse agonist, holds promise as an alternative therapy for synuclein-associated psychosis. Levodopa/carbidopa treatment of parkinsonism is often limited by dopa-induced exacerbations of neuropsychiatric and cognitive symptoms. Autonomic symptoms are under-recognized complications of synucleinopathy. Constipation, urinary symptoms and postural hypotension respond to standard medications. Rapid eye movement sleep behavior disorder is highly specific (98 %) to the synucleinopathies. Nonpharmacological treatments, melatonin and clonazepam are all effective.

Abnormal connectivity between the default mode and the visual system underlies the manifestation of visual hallucinations in Parkinson's disease: a task-based fMRI study

BACKGROUND

The neural substrates of visual hallucinations remain an enigma, due primarily to the difficulties associated with directly interrogating the brain during hallucinatory episodes.

AIMS

To delineate the functional patterns of brain network activity and connectivity underlying visual hallucinations in Parkinson's disease.

METHODS

In this study, we combined functional magnetic resonance imaging (MRI) with a behavioral task capable of eliciting visual misperceptions, a confirmed surrogate for visual hallucinations, in 35 patients with idiopathic Parkinson's disease. We then applied an independent component analysis to extract time series information for large-scale neuronal networks that have been previously implicated in the pathophysiology of visual hallucinations. These data were subjected to a task-based functional connectivity analysis, thus providing the first objective description of the neural activity and connectivity during visual hallucinations in patients with Parkinson's disease.

RESULTS

Correct performance of the task was associated with increased activity in primary visual regions; however, during visual misperceptions, this same visual network became actively coupled with the default mode network (DMN). Further, the frequency of misperception errors on the task was positively correlated with the strength of connectivity between these two systems, as well as with decreased activity in the dorsal attention network (DAN), and with impaired connectivity between the DAN and the DMNs, and ventral attention networks. Finally, each of the network abnormalities identified in our analysis were significantly correlated with two independent clinical measures of hallucination severity.

CONCLUSIONS

Together, these results provide evidence that visual hallucinations are due to increased engagement of the DMN with the primary visual system, and emphasize the role of dysfunctional engagement of attentional networks in the pathophysiology of hallucinations.

Pareidolia in Parkinson's disease without dementia: A positron emission tomography study

BACKGROUND

Pareidolia, which is a particular type of complex visual illusion, has been reported to be a phenomenon analogous to visual hallucinations in patients with dementia with Lewy bodies. However, whether pareidolia is observed in Parkinson's disease (PD) or whether there are common underlying mechanisms of these two types of visual misperceptions remains to be elucidated.

METHODS

A test to evoke pareidolia, the Pareidolia test, was administered to 53 patients with PD without dementia and 24 healthy controls. The regional cerebral metabolic rate of glucose was measured using 18F-fluorodeoxyglucose positron emission tomography in the PD patients.

RESULTS

PD patients without dementia produced a greater number of pareidolic illusions compared with the controls. Pareidolia was observed in all of the patients having visual hallucinations as well as a subset of those without visual hallucinations. The number of pareidolic illusions was correlated with hypometabolism in the bilateral temporal, parietal and occipital cortices. The index of visual hallucinations was correlated with hypometabolism in the left parietal cortex. A region associated with both pareidolia and visual hallucinations was found in the left parietal lobe.

CONCLUSIONS

Our study suggests that PD patients without dementia experience pareidolia more frequently than healthy controls and that posterior cortical dysfunction could be a common neural mechanism of pareidolia and visual hallucinations. Pareidolia could represent subclinical hallucinations or a predisposition to visual hallucinations in Lewy body disease.

On visual hallucinations and cortical networks: a trans-diagnostic review

Our current clinical approach to visual hallucinations is largely derived from work carried out by Georges de Morsier in the 1930s. Now, almost a century after his influential papers, we have the research tools to further explore the ideas he put forward. In this review, we address de Morsier's proposal that visual hallucinations in all clinical conditions have a similar neurological mechanism by comparing structural imaging studies of susceptibility to visual hallucinations in Parkinson's disease, Alzheimer's disease, Dementia with Lewy bodies and schizophrenia. Systematic review of the literature was undertaken using PubMed searches. A total of 18 studies across conditions were identified reporting grey matter differences between patients with and without visual hallucinations. Grey matter changes were categorised into brain regions relevant to current theories of visual hallucinations. The distribution of cortical atrophy supports de Morsier's premise that visual hallucinations are invariably linked to aberrant activity within visual thalamo-cortical networks. Further work is required to determine by what mechanism these networks become predisposed to spontaneous activation, and whether the frontal lobe and hippocampal changes identified are present in all conditions. The findings have implications for the development of effective treatments for visual hallucinations.

Hallucinators find meaning in noises: pareidolic illusions in dementia with Lewy bodies

By definition, visual illusions and hallucinations differ in whether the perceived objects exist in reality. A recent study challenged this dichotomy, in which pareidolias, a type of complex visual illusion involving ambiguous forms being perceived as meaningful objects, are very common and phenomenologically similar to visual hallucinations in dementia with Lewy bodies (DLB). We hypothesise that a common psychological mechanism exists between pareidolias and visual hallucinations in DLB that confers meaning upon meaningless visual information. Furthermore, we believe that these two types of visual misperceptions have a common underlying neural mechanism, namely, cholinergic insufficiency. The current study investigated pareidolic illusions using meaningless visual noise stimuli (the noise pareidolia test) in 34 patients with DLB, 34 patients with Alzheimer׳s disease and 28 healthy controls. Fifteen patients with DLB were administered the noise pareidolia test twice, before and after donepezil treatment. Three major findings were discovered: (1) DLB patients saw meaningful illusory images (pareidolias) in meaningless visual stimuli, (2) the number of pareidolic responses correlated with the severity of visual hallucinations, and (3) cholinergic enhancement reduced both the number of pareidolias and the severity of visual hallucinations in patients with DLB. These findings suggest that a common underlying psychological and neural mechanism exists between pareidolias and visual hallucinations in DLB.

[Neuropsychology of dementia]

As cognitive dysfunction is the core symptom of dementia, the assessment of it is essential for the clinical practice. The role of "neuropsychology" is none other than analysis and interpretation of the central symptoms of brain damaged including dementing illnesses. "Neuropsychology" in this sense does not refer only to the neuropsychological tests that psychologists employ, but certainly implies mental status examination as a part of the neurological examination, which enables us to make focal diagnosis and differential diagnosis, to evaluate the disability, to predict the problems in living, and to measure disease severity, rate of progression, and response to treatment are essential. This paper, citing aphasia due to degenerative diseases, behavioral neurological signs, and the relationship between visuoperceptive impairments and visual hallucinations as examples, discussed the clinical roles and scientific potentials of neuropsychology in dementia.

Gaze cueing by pareidolia faces

Visual images that are not faces are sometimes perceived as faces (the pareidolia phenomenon). While the pareidolia phenomenon provides people with a strong impression that a face is present, it is unclear how deeply pareidolia faces are processed as faces. In the present study, we examined whether a shift in spatial attention would be produced by gaze cueing of face-like objects. A robust cueing effect was observed when the face-like objects were perceived as faces. The magnitude of the cueing effect was comparable between the face-like objects and a cartoon face. However, the cueing effect was eliminated when the observer did not perceive the objects as faces. These results demonstrated that pareidolia faces do more than give the impression of the presence of faces; indeed, they trigger an additional face-specific attentional process.

The role of dysfunctional attentional control networks in visual misperceptions in Parkinson's disease

Visual misperceptions and hallucinations represent a problematic symptom of Parkinson's disease. The pathophysiological mechanisms underlying these symptoms remain poorly understood, however, a recent hypothesis has suggested that visual misperceptions and hallucinations may arise from disrupted processing across attentional networks. To test the specific predictions of this hypothesis, 22 patients with Parkinson's disease underwent 3T fMRI while performing the Bistable Percept Paradigm, a task that has previously been shown to identify patients with hallucinations. Subjects are required to study a battery of randomly assigned "monostable" and "bistable" monochromatic images for the presence or absence of a bistable percept. Those patients who scored a high percentage of misperceptions and missed images on the task were less able to activate frontal and parietal hubs of the putative Dorsal Attention Network. Furthermore, poor performance on the task was significantly correlated with the degree of decreased activation in a number of these hubs. At the group level, the difference between processing a bistable versus a monostable cue was associated with increased recruitment of the anterior insula. In addition, those patients with impaired performance on the paradigm displayed decreased resting state functional connectivity between hubs of the Ventral and Dorsal Attention Networks. These same patients had significantly decreased gray matter in the insula bilaterally. In addition, a combined analysis of the separate neuroimaging approaches revealed significant relationships across the impaired networks. These findings are consistent with specific predictions from a recently proposed hypothesis that implicates dysfunction within attentional networks in Parkinsonian hallucinations.

'Distorteidolias' - fantastic perceptive distortion. A new, pure dorsomedial thalamic syndrome

The role of the thalamus in the pathogenesis of the visual and auditory hallucinations has been reported under the name of peduncular hallucinosis, usually with coexisting midbrain involvement. These hallucinations typically take the form of dreamy de novo productions (phanteidolias), less often that of transformations of perceptions into new items (such as seeing faces in clouds) called pareidolias. However, hallucinations taking the form of a complex distortion of perception is a different phenomenon, which to our knowledge has not been reported. We studied 2 patients with complex, 'fantastic', perceptive distortion involving the visual and auditory systems after thalamic stroke limited to the region of the dorsomedial nucleus, sparing the intralaminar nuclei and the midbrain (explaining the lack of disorders of consciousness and confusional state). Our patients reported the modification of usual stimuli (face, body, voices) into unreal, fantastically distorted perceptions (monstrous change of shapes or sounds without appearance of new items). While the exact mechanism leading to such perceptive distortions remains unknown, a release phenomenon due to damage to the dorsomedial thalamus (probably affecting cholinergic system) responsible for a disinhibition of cortical function involved in familiarity of perception seems likely. We suggest that these hallucinations should be called 'distorteidolias'.

Can we clinically diagnose dementia with Lewy bodies yet?

Dementia with Lewy Bodies (DLB) was initially identified and confirmed primarily by pathology, but is soon to be incorporated into the Diagnostic and Statistical Manual criteria as a clinical disease entity. Despite these advances over more than 20 years, current data suggest that the sensitivity of accurate clinical diagnosis of DLB is still very low, although there is mounting evidence that supportive features may increase diagnostic accuracy. Although DLB remains easy to identify pathologically with different cellular pathologies differentiating it from other dementia syndromes, pathological identification using only Lewy body pathology has been shown to be inaccurate due to overlap with patients without dementia symptoms. A number of studies now suggest that a combination of cellular pathologies, which include α-synuclein and β-amyloid deposition as well as dopamine denervation, assist with differentiating this dementia syndrome from others. The clinical and pathological overlap with the tauopathy of Alzheimer's disease still remains to be clarified. To determine more robust and independent clinicopathological correlates from Alzheimer's disease, longitudinal prospective studies, using specific clinical batteries on dementia patients reaching the proposed criteria for DLB, with post-mortem assessment of the multiple pathologies associated with dementia, are required. Identifying genetic causes for DLB is another approach to investigate the pathogenesis of DLB. However this approach has been hindered to date by difficulties with identifying DLB clinically. The use of novel techniques is likely to advance knowledge on the pathogenesis of DLB and assist with redefining clinical and pathologic diagnostic criteria. To achieve the goal of more accurate clinical diagnosis of DLB, breakthroughs are necessary on the pathogenesis of DLB.