Dreaming and hallucinations – Continuity or discontinuity? Perspectives from dementia with Lewy bodies

From Dreams to Hallucinations: Jean Lhermitte's Contribution to the Study of Peduncular Hallucinosis and the Dissociation of States

Jean Lhermitte (1877-1959) was one of the pioneers of behavioral neurology, including the field of hallucinations. This article focuses on his work concerning the relationship between hallucinations, sleep, and dreams. From 1910, Lhermitte became interested in sleep and its disorders, particularly narcolepsy and its accompanying symptoms. He also reported on sleep disorders and hallucinations occurring in people with lesions of the diencephalic region ("infundibular syndrome"), and later encephalitis lethargica. In 1922, he described a syndrome of complex, predominantly visual hallucinations in patients with vascular damage to the midbrain, known as peduncular hallucinosis. Twelve historical cases of peduncular hallucinosis, including 10 from Lhermitte, are reviewed. He gave a precise phenomenological description of peduncular hallucinosis, and put forward the hypothesis that the lesion disrupted the anatomy and connections of a center regulating wakefulness and sleep, thus enabling a dissociation of the mechanisms of dream and waking states. Although the pathophysiology of peduncular hallucinosis remains to this day partly obscure, the model of a limited subcortical lesion acting through complex mechanisms and ultimately involving the cortex remains valid. Lhermitte was also a pioneer in characterizing what contemporary sleep specialists call dissociation of states.

Differentiating Oneiric Stupor in Agrypnia Excitata From Dreaming Disorders

Oneiric Stupor (OS) in Agrypnia Excitata represents a peculiar condition characterized by the recurrence of stereotyped gestures such as mimicking daily-life activities associated with the reporting of a dream mentation consisting in a single oneiric scene. It arises in the context of a completely disorganized sleep structure lacking any physiological cyclic organization, thus, going beyond the concept of abnormal dream. However, a proper differential diagnosis of OS, in the complex world of the “disorders of dreaming” can become quite challenging. The aim of this review is to provide useful clinical and videopolygraphic data on OS to differentiate it from other dreaming disorders. Each entity will be clinically evaluated among the areas of dream mentation and abnormal sleep behaviors and its polygraphic features will be analyzed and distinguished from OS.

Insight and Dissociation in Lucid Dreaming and Psychosis

Dreams and psychosis share several important features regarding symptoms and underlying neurobiology, which is helpful in constructing a testable model of, for example, schizophrenia and delirium. The purpose of the present communication is to discuss two major concepts in dreaming and psychosis that have received much attention in the recent literature: insight and dissociation. Both phenomena are considered functions of higher order consciousness because they involve metacognition in the form of reflective thought and attempted control of negative emotional impact. Insight in dreams is a core criterion for lucid dreams. Lucid dreams are usually accompanied by attempts to control the dream plot and dissociative elements akin to depersonalization and derealization. These concepts are also relevant in psychotic illness. Whereas insightfulness can be considered innocuous in lucid dreaming and even advantageous in psychosis, the concept of dissociation is still unresolved. The present review compares correlates and functions of insight and dissociation in lucid dreaming and psychosis. This is helpful in understanding the two concepts with regard to psychological function as well as neurophysiology.

Informant- and Self-Appraisals on the Psychosis and Hallucinations Questionnaire (PsycH-Q) Enhances Detection of Visual Hallucinations in Parkinson's Disease

Background

Clinicians vary in their ability to elicit and interpret hallucinatory symptoms in patients with Parkinson's disease (PD). There is limited evidence for informant-report measures of PD hallucinations as adjuncts to clinician-rated scales.

Objectives

To determine the utility of an informant version of the validated Psychosis and Hallucinations Questionnaire (PsycH-Q) for assessing the presence and severity of hallucinations in PD; and, to evaluate accuracy of clinician judgements by comparison with informant report and self-report.

Methods

One hundred sixty-three PD patient-informant dyads completed self- and informant-report versions of PsycH-Q and three common questionnaire measures: Neuropsychiatric Inventory Questionnaire; Parkinson's Psychosis Questionnaire; and Scales for Outcomes in Parkinson's disease-Psychiatric Complications. We compared self-ratings and informant ratings across analogous subscales for the presence of hallucinations with clinician interview ratings on MDS-UPDRS as a diagnostic standard.

Results

There was a low level of agreement between dyads (average κ = 0.39; κ range = 0.32-0.47; P < 0.001), and patients indicated the highest prevalence of hallucinations compared to informant or clinician estimates. Clinician interview missed 32% of PsycH-Q hallucinators identified by dyads. Relative to the sample, 22 patients with exclusively clinician-appraised hallucinations had poorer overall quality of life measured by the Parkinson's Disease Questionnaire.

Conclusions

The sole use of clinician-rated scales may underestimate prevalence of PD hallucinations, and there is room for introducing self- and informant-report tools. Nonetheless, clinician appraisals are critical in cases when informant and patient insight might be affected by the impact of illness on quality of life.

What Is the Link Between Hallucinations, Dreams, and Hypnagogic-Hypnopompic Experiences?

By definition, hallucinations occur only in the full waking state. Yet similarities to sleep-related experiences such as hypnagogic and hypnopompic hallucinations, dreams and parasomnias, have been noted since antiquity. These observations have prompted researchers to suggest a common aetiology for these phenomena based on the neurobiology of rapid eye movement (REM) sleep. With our recent understanding of hallucinations in different population groups and at the neurobiological, cognitive and interpersonal levels, it is now possible to draw comparisons between the 2 sets of experiences as never before. In the current article, we make detailed comparisons between sleep-related experiences and hallucinations in Parkinson's disease, schizophrenia and eye disease, at the levels of phenomenology (content, sensory modalities involved, perceptual attributes) and of brain function (brain activations, resting-state networks, neurotransmitter action). Findings show that sleep-related experiences share considerable overlap with hallucinations at the level of subjective descriptions and underlying brain mechanisms. Key differences remain however: (1) Sleep-related perceptions are immersive and largely cut off from reality, whereas hallucinations are discrete and overlaid on veridical perceptions; and (2) Sleep-related perceptions involve only a subset of neural networks implicated in hallucinations, reflecting perceptual signals processed in a functionally and cognitively closed-loop circuit. In summary, both phenomena are non-veridical perceptions that share some phenomenological and neural similarities, but insufficient evidence exists to fully support the notion that the majority of hallucinations depend on REM processes or REM intrusions into waking consciousness.

Validation of the Psychosis and Hallucinations Questionnaire in Non-demented Patients with Parkinson's Disease

People diagnosed with Parkinson's disease (PD) frequently experience visual and non-visual hallucinations often with comorbid psychosis, however, there is currently no gold standard tool for accurately assessing these symptoms. To address this problem, we designed a novel questionnaire to evaluate the presence of hallucinatory and psychotic symptoms in PD, as well as related symptoms, such as attentional dysfunction and sleep disturbance. We administered the 20-item Psychosis and Hallucinations Questionnaire (PsycH-Q) and three common questionnaire measures in a large cohort of 197 patients with idiopathic PD via a postal survey. We established concurrent validity, convergent validity, and internal consistency of the questionnaire and then assessed test-retest reliability in a subcohort of 44 patients. PsycH-Q was found to be a valid instrument when analogous items were compared across three other existing tools (Spearman's rho range: 0.34-0.64; P < 0.01). PsycH-Q demonstrated a strong relationship between self-reported hallucinations and psychosis and symptoms of the broader hallucinatory phenotype (Kendall's tau = 0.41; P < 0.01; positive predictive value = 0.97). PsycH-Q also displayed a high level of internal consistency (Cronbach's alpha = 0.900; range, 0.696-0.923) and reproducibility (intraclass correlation coefficient = 0.928). PsycH-Q is a simple, valid, self-completed instrument that reliably identifies hallucinations and psychosis in PD and has the ability to characterize related patterns of attentional and sleep impairments. As such, PsycH-Q is a highly valuable tool for use in both clinical and research settings.

Visual hallucinations in Parkinson's disease: theoretical models

One of the most challenging tasks in neuroscience is to be able to meaningfully connect information across the different levels of investigation, from molecular or structural biology to the resulting behavior and cognition. Visual hallucinations are a frequent occurrence in Parkinson's disease and significantly contribute to the burden of the disease. Because of the widespread pathological processes implicated in visual hallucinations in Parkinson's disease, a final common mechanism that explains their manifestation will require an integrative approach, in which consideration is taken across all complementary levels of analysis. This review considers the leading hypothetical frameworks for visual hallucinations in Parkinson's disease, summarizing the key aspects of each in an attempt to highlight the aspects of the condition that such a unifying hypothesis must explain. These competing hypotheses include implications of dream imagery intrusion, deficits in reality monitoring, and impairments in visual perception and attention.

A phenomenology of meditation-induced light experiences: traditional buddhist and neurobiological perspectives

The scientific study of Buddhist meditation has proceeded without much attention to Buddhist literature that details the range of psychological and physiological changes thought to occur during meditation. This paper presents reports of various meditation-induced light experiences derived from American Buddhist practitioners. The reports of light experiences are classified into two main types: discrete lightforms and patterned or diffuse lights. Similar phenomena are well documented in traditional Buddhist texts but are virtually undocumented in scientific literature on meditation. Within Buddhist traditions, these phenomena are attributed a range of interpretations. However, because it is insufficient and problematic to rely solely upon the textual sources as a means of investigating the cause or significance of these phenomena, these qualitative reports are also considered in relation to scientific research on light-related experiences in the context of sensory deprivation, perceptual isolation, and clinical disorders of the visual system. The typologies derived from these studies also rely upon reports of experiences and closely match typologies derived from the qualitative study of contemporary practitioners and typologies found in Buddhist literary traditions. Taken together, these studies also provide evidence in support of the hypothesis that certain meditative practices – especially those that deliberately decrease social, kinesthetic, and sensory stimulation and emphasize focused attention – have perceptual and cognitive outcomes similar to sensory deprivation. Given that sensory deprivation increases neuroplasticity, meditation may also have an enhanced neuroplastic potential beyond ordinary experience-dependent changes. By providing and contextualizing these reports of meditation-induced light experiences, scientists, clinicians, and meditators gain a more informed view of the range of experiences that can be elicited by contemplative practices.

Psychotherapy and brain plasticity

In this paper, I will review why psychotherapy is relevant to the question of how consciousness relates to brain plasticity. A great deal of the research and theorizing on consciousness and the brain, including my own on hallucinations for example (Collerton and Perry, 2011) has focused upon specific changes in conscious content which can be related to temporal changes in restricted brain systems. I will argue that psychotherapy, in contrast, allows only a focus on holistic aspects of consciousness; an emphasis which may usefully complement what can be learnt from more specific methodologies.