A general neuropsychological model of delusion

Bridging perspectives - A review and synthesis of 53 theoretical models of delusions

The degree to which numerous existing models of delusion formation disagree or propose common mechanisms remains unclear. To achieve a comprehensive understanding of delusion aetiology, we summarised 53 theoretical models of delusions extracted from a systematic literature search. We identified central aspects and unique or overarching features of five core perspectives: cognitive (n = 22), associative learning (n = 4), social (n = 6), neurobiological (n = 6), and Bayesian inference (n = 15). These perspectives differ in foci and mechanistic explanations. Whereas some postulate delusions to result from associative and operant learning, others assume a disbalance in the integration of prior beliefs and sensory input or emphasise the relevance of information processing biases. Postulated moderators range from maladaptive generalised beliefs over neurocognitive impairment to dopamine, stress, and affective dysregulation. The models also differ in whether they attempt to explain delusion formation in general or the delusional content (i.e., persecutory). Finally, some models postulate functional aspects of delusions, such as insight relief. Despite their differences, the perspectives converge on the idea that delusions form as an explanation for an experienced ambiguity. Building on this common ground, we propose an integrative framework incorporating essential mechanistic explanations from each perspective and discuss its implications for research and clinical practice.

Altered connectivity between the central executive network and the salience network in delusion-prone individuals: A resting state eLORETA report

Although the Triple Network (TN) model has been proposed as a valid neurophysiological framework for conceptualizing delusion-like experiences, the neurodynamics of TN in relation to delusion proneness have been relatively understudied in nonclinical samples so far. Therefore, the main aim of the current study was to investigate the functional connectivity of resting state electroencephalography (EEG) in subjects with high levels of delusion proneness. Twenty-one delusion-prone (DP) individuals and thirty-seven non-delusion prone (N-DP) individuals were included in the study. The exact Low-Resolution Electromagnetic Tomography (eLORETA) software was used for all EEG analyses. Compared to N-DP participants, DP individuals showed an increas of theta connectivity (T = 3.618; p = 0.045) between the Salience Network (i.e., the left anterior insula) and the Central Executive Network (i.e., the left posterior parietal cortex). Increased theta connectivity was also positively correlated with the frequency of delusional experiences (rho = 0.317; p = 0.015). Our results suggest that increased theta connectivity between the Salience Network and the Central Executive Network may underline brain correlates of altered resting state salience detection, information processing, and cognitive control processes typical of delusional thinking.

Spectrum of neuropsychiatric symptoms in chronic post-stroke aphasia

BACKGROUND

Neuropsychiatric symptoms (NPS) have been insufficiently examined in persons with aphasia (PWA) because most previous studies exclude participants with language and communication disorders.

AIM

To report a two-part study consisting of a literature review and an observational study on NPS in post-stroke aphasia.

METHODS

Study 1 reviewed articles obtained from PubMed, PsycINFO, Google Scholar and Cochrane databases after cross-referencing key words of post-stroke aphasia to NPS and disorders. Study 2 examined language deficits and activities of daily living in 20 PWA (median age: 58, range: 28-65 years; 13 men) with the Western Aphasia Battery-Revised and the Barthel Index, respectively. Informants of these 20 PWA were proxy-evaluated with the Neuropsychiatric Inventory and domain-specific scales, including the Stroke Aphasia Depression Questionnaire-10 item version and the Starkstein Apathy Scale. In addition, an adapted version of the Hospital Anxiety and Depression Scale was directly administered to the PWA themselves. This observational study is based on the baseline assessment of an intervention clinical trial (EudraCT: 2017-002858-36; ClinicalTrials.gov identifier: NCT04134416).

RESULTS

The literature review revealed a broad spectrum of NPS in PWA, including depression, anxiety, apathy, agitation/aggression, eating and sleep disorders, psychosis, and hypomania/mania. These findings alert to the need for improving assessment and treatment approaches of NPS taking into consideration their frequent occurrence in PWA. Study 2 showed that the 20 participants had mild- to-moderate aphasia severity and were functionally independent. A wide range of comorbid NPS was found in the post-stroke aphasic population (median number of NPS: 5, range: 1-8). The majority of PWA (75%) had depressive symptoms, followed by agitation/aggression (70%), irritability (70%), anxiety (65%) and appetite/eating symptoms (65%). Half of them also presented symptoms of apathy, whereas euphoria and psychotic symptoms were rare (5%). Domain-specific scales revealed that 45% of participants had apathy and 30% were diagnosed with depression and anxiety.

CONCLUSION

Concurrent NPS are frequent in the chronic period of post-stroke aphasia. Therefore, further research on reliable and valid assessment tools and treatment for this aphasic population is strongly warranted.

Opposed attentional hemi-bias on a visuoconstructive task in children with severe hyperactivity versus severe inattention

Twenty six empirical investigations have now established that children and adults with DSM-defined Attention deficit/Hyperactivity disorder (ADHD) of the Hyperactive type (ADHD-H) or, more commonly, Combined Hyperactive/Inattentive types (ADHD-C) manifest a small but significant visual attentional bias to the right side (left subclinical neglect), consistently suggesting the existence of a subtle right hemisphere dysfunction or hemispheric imbalance in hyperactive people. Only one research team has investigated and compared the DSM-defined Inattentive subtype (ADHD-I) to the Hyperactive subtype (ADHD-H), confirming that line bisection is biased to the right in ADHD-H and discovering that it is biased to the left in ADHD-I. We aimed to test whether a similar crossed double dissociation would extend to Rey's Complex Figure Copy Task (RCF-CT), a simple visuospatial-constructive task. Clinical files of 205 juvenile clients from 6 to 16 years of age from a neuropsychological private clinic specialized in ADHD were analysed. Extreme scores on the Connors-3 Hyperactivity vs Inattention Parent Rating scales associated, respectively, with significant rightward and significant leftward emplacement of the drawing on the page on the RCF-CT. These results replicate previous findings and extend the "energetics" model of hemispheric specialization.

Classical Koro and Koro-Like Symptoms: Illustration from Canada

Koro syndrome has been colorfully described as a pathological distortion of one’s body image of the genital organ. In Koro, body image dysphoria is characterized by severe anxiety related to the delusional idea that one’s genitals will shrink and retract into one’s abdomen, eventually leading to death. This syndrome was first reported in South East Asia, where endemics have been described, but it has also sporadically occurred globally. We present a systematic literature review on Koro syndrome and report 7 cases from Canada. A search review with PubMed and Google Scholar resulted in 504 entries. Sixty-seven manuscripts were eventually selected following a thorough elimination process. The resultant literature underscored the cultural diversity that underlay the reported cases. Various aspects of Koro have been examined (eg, etiological, clinical, diagnostic, and cultural aspects). It has stimulated substantial scholarly debate, discussions, correspondences, and arguments from anthropological, psychiatric, psychological, and biological perspectives. In our series, it seems that Koro could have been misattributed here. The primary concern was not with penile retraction of the cases. To our knowledge, this is the first time that a series of cases is documented from North America where the syndrome is often ignored. We highlight the potential differences between the classical Koro syndrome and a collection of beliefs related to the perception or delusion of penile retraction in other codable psychiatric disorders, Koro-like syndrome. Understanding Koro syndrome beyond geographic boundaries is in line with our collected case reports of Koro from outside Asia.

Failure of hypothesis evaluation as a factor in delusional belief

INTRODUCTION

In accounts of the two-factor theory of delusional belief, the second factor in this theory has been referred to only in the most general terms, as a failure in the processes of hypothesis evaluation, with no attempt to characterise those processes in any detail. Coltheart and Davies ([2021]. How unexpected observations lead to new beliefs: A Peircean pathway. Consciousness and Cognition, 87, 103037. https://doi.org/10.1016/j.concog.2020.103037) attempted such a characterisation, proposing a detailed eight-step model of how unexpected observations lead to new beliefs based on the concept of abductive inference as introduced by Charles Sanders Peirce.

METHODS

In this paper, we apply that model to the explanation of various forms of delusional belief.

RESULTS

We provide evidence that in cases of delusion there is a specific failure of the seventh step in our model: the step at which predictions from (delusional) hypotheses are considered in the light of relevant evidence.

CONCLUSIONS

In the two-factor theory of delusional belief, the second factor consists of a failure to reject hypotheses in the face of disconfirmatory evidence.

Looking into a Deluded Brain through a Neuroimaging Lens

Delusions are irrational, tenacious, and incorrigible false beliefs that are the most common symptom of a range of brain disorders including schizophrenia, Alzheimer's, and Parkinson's disease. In the case of schizophrenia and other primary delusional disorders, their appearance is often how the disorder is first detected and can be sufficient for diagnosis. At this time, not much is known about the brain dysfunctions leading to delusions, and hindering our understanding is that the complexity of the nature of delusions, and their very unique relevance to the human experience has hampered elucidation of their underlying neurobiology using either patients or animal models. Advances in neuroimaging along with improved psychiatric and cognitive modeling offers us a new opportunity to look with more investigative power into the deluded brain. In this article, based on data obtained from neuroimaging studies, we have attempted to draw a picture of the neural networks involved when delusion is present and evaluate whether different manifestations of delusions engage different regions of the brain.

Celiac Disease Diagnosed in an Older Adult Patient with a Complex Neuropsychiatric Involvement: A Case Report and Review of the Literature

We present a case of celiac disease (CD) diagnosis in a 75-year-old woman with a long-term history of chronic delusional jealousy and a complex neurological involvement. The case describes a very unusual clinical picture, provides some clinical clues, and highlights the importance of being aware of CD extraintestinal manifestations in order to get a timely diagnosis.

Psychosis of Alzheimer's disease: Neuropsychological and neuroimaging longitudinal study

OBJECTIVES

Psychosis of Alzheimer's disease (AD) may represent a distinct disease phenotype; however, neuropsychological profile and neural basis linked to this phenotype have not yet been clarified. In this study, we aimed at detecting whether impairment in specific cognitive domains predicts the onset of psychosis in AD patients and what grey matter alterations, their location, and the rate of atrophy are associated with psychosis of AD.

METHODS

Longitudinal neuropsychological data from AD patients with and without psychosis were analysed to determine whether the neuropsychological profile can predict the onset of psychosis. A voxel-based morphometry (VBM) on longitudinal T1-weighted images was used to explore differences in grey matter volume and in the rate of atrophy between groups.

RESULTS

Noncognitive domain predicted the psychosis onset. However, AD patients with psychosis exhibited greater atrophy in the right anterior-inferior temporal lobe, including the fusiform gyrus (cluster-p-family-wise error [pfwe] < 0.05; peak-p uncorrected [pUNC] < 0.001) as well as greater rate of atrophy in the right insula than nonpsychotic patients (cluster-pFWE = 0.075; peak-pUNC < 0.001). The anterior-inferior temporal lobe is part of the ventral visual stream, and the insula plays a key role in the salience network.

CONCLUSIONS

This finding suggests that damage in these areas underpins an impairment in the visual processing of the objects and an impairment in the attribution of salience to the misperceived stimuli, which in turn leads to the onset of psychosis. These findings tie in well with the neuropsychological model of psychosis, according to which the simultaneous presence of two factors, namely misperception and misattribution, underlies psychosis in dementia.

Uncommon psychopathological syndromes in psychiatry

Introduction: The development of biological sciences, as well as cultural and civilizational changes have led to the emergence of practice within the medicine of science, called psychiatry. Already at the turn of the 19th and the beginning of the 20th century, Karl Jaspers - a German scholar - father of psychopathology - in the work “Allgemeine Psychopathologie” crystallized his intuitions in the field of psychopathology, which classifies and describes states that are deviations from the physiological mental state of a human being.

Material and method: his paper reviews available literature to approximate the symptoms of the most interesting psychopathological syndromes in psychiatry such as: Clerambault syndrome, Otheller syndrome, Cotard syndrome, Ekboma syndrome and Folie à deux.

Results: A multitude of psychopathological syndromes results from the wealth of survival of psychiatric patients. They represent the delusions of different contents that develop in a primitive way or as a consequence of other types of disorders. Psychopathological teams have been inspiring the poets and directors for centuries. The relationship between psychiatry and culture, film and literature undoubtedly testifies to its interdisciplinary nature.

Discussion: Despite the passage of time, the descriptions of these syndromes with a rich historical description, symptomatology and criteria have not lost their relevance and are still a clinical reality.

Reduplicative paramnesia for places: A comprehensive review of the literature and a new case report

Reduplicative paramnesia for places (i.e., the delusional belief that a place has been duplicated or exists in two different locations) is a rare disorder observed in neurological patients. We review the existing literature on the topic, highlighting commonalities and differences among the 51 cases published since the first report in 1903. Our results highlight the combination of multiple factors in the pathogenesis of this monothematic spatial delusion. From a neurological perspective, a crucial role is played by damage to the right frontal and temporal lobe. Deficits of non-verbal memory and executive functions, along with topographical disorientation, appear to be the most common (but, not systematic) cognitive impairments. The clinical picture of the disorder is further complicated by often overlooked psychological and motivational factors. Consequently, the precise neuro-cognitive substrate of this disorder is yet to be described in detail. We stress the need for a more detailed and systematic approach exploiting neurological, neuroimaging, neuropsychological and psychopathological methods. To guide future investigations, we provide clinical- and research-oriented recommendations. Finally, we illustrate the interplay of all above-mentioned factors with a new case report.

Rethinking Social Cognition in Light of Psychosis: Reciprocal Implications for Cognition and Psychopathology

The positive symptoms of psychosis largely involve the experience of illusory social actors and yet our current measures of social cognition, at best, only weakly predict their presence. We review evidence to suggest that the range of current approaches in social cognition is not sufficient to explain the fundamentally social nature of these experiences. We argue that social agent representation is an important organising principle for understanding social cognition and that alterations in social agent representation may be a factor in the formation of delusions and hallucination in psychosis. We evaluate the feasibility of this approach in light of clinical and non-clinical studies, developmental research, cognitive anthropology and comparative psychology. We conclude with recommendations for empirical testing of specific hypotheses and how studies of social cognition could more fully capture the extent of social reasoning and experience in both psychosis and more prosaic mental states.

Hemispheric Differences in White Matter Microstructure between Two Profiles of Children with High Intelligence Quotient vs. Controls: A Tract-Based Spatial Statistics Study

Objectives: The main goal of this study was to investigate and compare the neural substrate of two children's profiles of high intelligence quotient (HIQ). Methods: Two groups of HIQ children were included with either a homogeneous (Hom-HIQ: n = 20) or a heterogeneous IQ profile (Het-HIQ: n = 24) as defined by a significant difference between verbal comprehension index and perceptual reasoning index. Diffusion tensor imaging was used to assess white matter (WM) microstructure while tract-based spatial statistics (TBSS) analysis was performed to detect and localize WM regional differences in fractional anisotropy (FA), mean diffusivity, axial (AD), and radial diffusivities. Quantitative measurements were performed on 48 regions and 21 fiber-bundles of WM. Results: Hom-HIQ children presented higher FA than Het-HIQ children in widespread WM regions including central structures, and associative intra-hemispheric WM fasciculi. AD was also greater in numerous WM regions of Total-HIQ, Hom-HIQ, and Het-HIQ groups when compared to the Control group. Hom-HIQ and Het-HIQ groups also differed by their hemispheric lateralization in AD differences compared to Controls. Het-HIQ and Hom-HIQ groups showed a lateralization ratio (left/right) of 1.38 and 0.78, respectively. Conclusions: These findings suggest that both inter- and intra-hemispheric WM integrity are enhanced in HIQ children and that neural substrate differs between Hom-HIQ and Het-HIQ. The left hemispheric lateralization of Het-HIQ children is concordant with their higher verbal index while the relative right hemispheric lateralization of Hom-HIQ children is concordant with their global brain processing and adaptation capacities as evidenced by their homogeneous IQ.

Psychosis associated behavioral and psychological signs and symptoms in mild cognitive impairment and Alzheimer's dementia

OBJECTIVES

The aim of this study is to determine the prevalence of psychosis in mild cognitive impairment (MCI, Petersen's criteria) and patients with Alzheimer's dementia, and to characterize the associated behavioral and psychological signs and symptoms of dementia (BPSD).

METHOD

A cross-sectional analysis of baseline data from an ongoing, prospective, longitudinal study on BPSD was performed, including 270 MCI and 402 AD patients. BPSD assessment was performed through Middelheim Frontality Score (MFS), Behave-AD, Cohen-Mansfield Agitation Inventory (CMAI) and Cornell Scale for Depression in Dementia (CSDD). Psychosis was considered to be clinically relevant when delusions and/or hallucinations occurred at least once in the last two weeks prior to the BPSD assessment.

RESULTS

The prevalence of psychosis in AD (40%) was higher than in MCI (14%; p < 0.001). AD patients with psychosis showed more severe frontal lobe, BPSD, agitation and depressive symptoms (MFS, Behave-AD, CMAI and CSDD total scores), whereas MCI patients with psychosis only showed more severe frontal lobe and physically non-aggressive agitated behavior. In addition, only in psychotic AD patients, all BPSD and types of agitation were more severe compared to non-psychotic AD patients. Comparing MCI and AD patients, MCI patients with psychosis did not show more severe frontal lobe, behavioral and psychological (Behave-AD), depressive symptoms or agitation than AD patients without psychosis.

CONCLUSION

AD patients clearly display psychosis associated BPSD, whereas MCI patients only display more severe frontal lobe symptoms and physically non-aggressive agitated behavior, but also less pronounced than in AD.

Hemispheric lateralization in reasoning

A growing body of evidence suggests that reasoning in humans relies on a number of related processes whose neural loci are largely lateralized to one hemisphere or the other. A recent review of this evidence concluded that the patterns of lateralization observed are organized according to two complementary tendencies. The left hemisphere attempts to reduce uncertainty by drawing inferences or creating explanations, even at the cost of ignoring conflicting evidence or generating implausible explanations. Conversely, the right hemisphere aims to reduce conflict by rejecting or refining explanations that are no longer tenable in the face of new evidence. In healthy adults, the hemispheres work together to achieve a balance between certainty and consistency, and a wealth of neuropsychological research supports the notion that upsetting this balance results in various failures in reasoning, including delusions. However, support for this model from the neuroimaging literature is mixed. Here, we examine the evidence for this framework from multiple research domains, including an activation likelihood estimation analysis of functional magnetic resonance imaging studies of reasoning. Our results suggest a need to either revise this model as it applies to healthy adults or to develop better tools for assessing lateralization in these individuals.

First rank symptoms of schizophrenia: their nature and origin

Kurt Schneider's insight nearly 80 years ago that schizophrenia could be demarcated from other psychoses by a small set of particular delusions and hallucinations powerfully influenced diagnostic practice. The theoretical status of such 'first rank symptoms' as a whole, however, has rarely been addressed. But if they are sensitive and specific to the condition, it is about time that their essential nature and potential origin be considered. This is the purpose of the present paper. I argue that these psychopathological phenomena are indeed relatively sensitive and specific to the condition, that their nature can be formulated within a Schelerian model of what constitutes a human being, and that their origin fits anthropological and neuropsychological notions of the make-up of contemporary human beings.

A cognitive account of belief: a tentative road map

Over the past decades, delusions have become the subject of growing and productive research spanning clinical and cognitive neurosciences. Despite this, the nature of belief, which underpins the construct of delusions, has received little formal investigation. No account of delusions, however, would be complete without a cognitive level analysis of belief per se. One reason for this neglect is the assumption that, unlike more established and accessible modular psychological process (e.g., vision, audition, face-recognition, language-processing, and motor-control systems), beliefs comprise more distributed and therefore less accessible central cognitive processes. In this paper, we suggest some defining characteristics and functions of beliefs. Working back from cognitive accounts of delusions, we consider potential candidate cognitive processes that may be involved in normal belief formation. Finally, we advance a multistage account of the belief process that could provide the basis for a more comprehensive model of belief.

Divergent hemispheric reasoning strategies: reducing uncertainty versus resolving inconsistency

Converging lines of evidence from diverse research domains suggest that the left and right hemispheres play distinct, yet complementary, roles in inferential reasoning. Here, we review research on split-brain patients, brain-damaged patients, delusional patients, and healthy individuals that suggests that the left hemisphere tends to create explanations, make inferences, and bridge gaps in information, while the right hemisphere tends to detect conflict, update beliefs, support mental set-shifts, and monitor and inhibit behavior. Based on this evidence, we propose that the left hemisphere specializes in creating hypotheses and representing causality, while the right hemisphere specializes in evaluating hypotheses, and rejecting those that are implausible or inconsistent with other evidence. In sum, we suggest that, in the domain of inferential reasoning, the left hemisphere strives to reduce uncertainty while the right hemisphere strives to resolve inconsistency. The hemispheres’ divergent inferential reasoning strategies may contribute to flexible, complex reasoning in the healthy brain, and disruption in these systems may explain reasoning deficits in the unhealthy brain.

Working memory dysfunction in delusional disorders: an fMRI investigation

BACKGROUND

Delusional disorder (DD) is a rare and understudied psychiatric disorder. There is limited number of studies concerning cognitive characteristics in DD. Using an established working memory paradigm with variable levels of memory load, we investigated alterations in functional magnetic resonance imaging (fMRI) of brain regions in patients with DD.

METHODS

This case control study included 9 patients with DD and 9 healthy control subjects matched for age, sex, and education level. Diagnosis of DD was confirmed using the Structured Clinical Interview for DSM-IV Axis I. The severity of the symptoms was evaluated using the Positive and Negative Syndrome Scale. All patients were asked to perform 0-back and 2-back tasks during fMRI experiments. Functional imaging was performed using the 3.0 T Philips whole-body scanner using an 8-channel head coil.

RESULTS

Participants with DD had less neural activation of the left dorsolateral prefrontal cortex in fMRI scans obtained during performance tasks. On the other hand, neural activation of the left and right superior temporal gyrus, left middle and inferior temporal gyrus, right and left posterior cingulate gyrus, right amygdala, left and right fusiform gyrus was more prominent in patients with DD in comparison with the control group.

DISCUSSION

Patients with DD had dysfunction in the prefrontal, temporal and limbic regions of the brain in particular, during performance tasks of working memory. Our findings were in line with the findings of the early reports on deficient functioning in temporal or limbic regions of the brain. Further, patients with DD displayed prefrontal dysfunction as seen in patients with schizophrenia.

Cerebral lateralization of pro- and anti-social tendencies

Mounting evidence suggest that the right-hemisphere (RH) has a relative advantage, over the left-hemisphere (LH), in mediating social intelligence - identifying social stimuli, understanding the intentions of other people, awareness of the dynamics in social relationships, and successful handling of social interactions. Furthermore, a review and synthesis of the literature suggest that pro-social attitudes and behaviors are associated with physiological activity in the RH, whereas unsocial and anti-social tendencies are mediated primarily by the LH. This hemispheric asymmetry is rooted in several neurobiological and functional differences between the two hemispheres. (I) Positive social interactions often require inhibiting one's immediate desires and considering the perspectives and needs of others. Given that self-control is mediated by the RH, pro-social emotions and behaviors are, therefore, inherently associated with the RH as it subserves the brain's self-restraint mechanisms. (II) The RH mediates experiences of vulnerability. It registers the relative clumsiness and motor weakness of the left limbs, and it is involved, more than the LH, in processing threats and mediating fear. Emotional states of vulnerability trigger the need for affiliation and sociality, therefore the RH has a greater role in mediating pro-social attitudes and behaviors. (III) The RH mediates a holistic mode of representing the world. Holistic perception emphasizes similarities rather than differences, takes a long-term perspective, is associated with divergent thinking and seeing other points-of-view, and it mediates a personal mode of relating to people. All these features of holistic perception facilitate a more empathetic attitude toward others and pro-social behaviors.

The development of delusion revisited: a transdiagnostic framework

This study proposes a transdiagnostic framework for delusion development, analysing psychiatric (schizophrenia, bipolar disorder, major depressive disorder) and neurological disorders (stroke, and neurodegenerative diseases) in which delusions are predominant. Our aim is to identify a transdiagnostic core of neural and cognitive alterations associated with delusions across distinct clinical disorders. Reviewed empirical evidence suggests delusions are associated: on the neural level with changes in the ventromedial prefrontal cortex (vmPFC) networks, and on the neuropsychological level with dysfunction in the processes (generation of affective value, the construction of internal models of the world, and the reflection about Self and/or Other's mental states) that these network mediate. The concurrent aberration of all these processes could be critical for the clinical transition to a psychotic delusional state. In particular, delusions could become clinically manifest when (1) stimuli are attributed an aberrant affective salience, that (2) is explained by the patient within distorted explanatory internal models that (3) are poorly inhibited by cognitive control systems. This framework extends the two-factor account of delusion model and suggests that common neural mechanisms for the delusions in psychiatric and in neurological disorders.

Dangerous passion: Othello syndrome and dementia

Jealousy is a complex emotion that most people have experienced at some time in life; pathological jealousy refers primarily to an irrational state. Othello syndrome is a psychotic disorder characterized by delusion of infidelity or jealousy; it often occurs in the context of medical, psychiatric or neurological disorders. At least 30% of cases in the literature show a neurological basis for their delusion of infidelity, although its biological basis is not fully understood. The purpose of this paper is to examine the phenomenon of pathological jealousy in people with dementia. We searched the electronic databases for original research and review articles on Othello syndrome in demented patients using the search terms 'Othello syndrome, morbid jealousy, pathological jealousy, delusional disorders, dementia'. Convictions about the partner's infidelities may form the content of psychopathological phenomena, such as delusions. Delusional jealousy is a frequent problem in dementia. Coexistent delusions and hallucinations are frequent. The violence in demented patients suffering from this syndrome is well documented and forensic aspects are highlighted. There are no systematic researches about the clinical characteristics of Othello syndrome in persons suffering from dementia, but only case reports and it is not possible to differentiate or compare differences of delusional jealousy across the various type of dementia or distinguish the syndrome in demented patients from the syndrome in other psychiatric disorders. Frontal lobe dysfunction may be called into question in delineating the cause of the delusional jealousy seen in Othello syndrome.

Neuroimaging of delusions in Alzheimer's disease

MEDLINE, Embase and PsycINFO were searched using the keywords "imaging", "neuroimaging", "CT", "MRI", "PET", "SPECT", "Alzheimer's", "dementia", "delusions" and "psychosis" to find studies specifically assessing or reporting on neuroimaging of delusions in Alzheimer's Dementia (AD), separate from hallucinations or psychosis in general in AD. Twenty-five studies were found meeting criteria and are included in this review which reports on structural, regional perfusion, metabolic and receptor binding imaging modalities assessing delusions as a whole, as well as persecutory and misidentification delusional subtypes. The majority of studies implicate right-sided pathology, primarily frontal lobe. Left-frontal predominance and release, secondary to right-sided pathology, may create a hyperinferential state resulting in the formation of delusions. This perturbation and imbalance of normal networks is associated with delusional phenomenology. Temporal lobe structures are also important in misidentification syndromes, which have a different natural history than paranoid delusions. Consistent with the neuropathological and genetic literature, neuroimaging has shown that paranoid versus misidentification delusions are associated with different phenomenology and different neural substrates. Delusional subtype is an important factor in understanding the neurobiological underpinnings of delusions in dementia. We also discuss methodological issues related to neuroimaging of delusions in AD.