Understanding visual hallucinations: a new synthesis.

Despite decades of research, we do not definitively know how people sometimes see things that are not there. Eight models of complex visual hallucinations have been published since 2000, including Deafferentation, Reality Monitoring, Perception and Attention Deficit, Activation, Input, and Modulation, Hodological, Attentional Networks, Active inference, and Thalamocortical Dysrhythmia Default Mode Network Decoupling. Each was derived from different understandings of brain organisation. To reduce this variability, representatives from each research group agreed an integrated Visual Hallucination Framework that is consistent with current theories of veridical and hallucinatory vision. The Framework delineates cognitive systems relevant to hallucinations. It allows a systematic, consistent, investigation of relationships between the phenomenology of visual hallucinations and changes in underpinning cognitive structures. The episodic nature of hallucinations highlights separate factors associated with the onset, persistence, and end of specific hallucinations suggesting a complex relationship between state and trait markers of hallucination risk. In addition to a harmonised interpretation of existing evidence, the Framework highlights new avenues of research, and potentially, new approaches to treating distressing hallucinations

About psychotic-like experiences and auditory verbal hallucinations : Transdiagnostic investigations of neurobiological, cognitive, and emotional aspects of a continuous phenomenon

Hallucinations and delusions are known to be key symptoms of psychotic disorders, such as schizophrenia, and have been studied extensively. However, these experiences also occur in other mental disorders, which suggests a transdiagnostic perspective with shared underlying cognitive mechanisms across various psychological illnesses. In addition, hallucinations and delusions are continuous phenomena that occur not only in patients with mental disorders, but also in healthy individuals in the general population, spanning from childhood to adulthood. To understand the development and maintenance of such psychotic-like experiences (PLEs) in general, and auditory verbal hallucinations (AVHs) specifically, neurobiological, cognitive, and emotional factors need to be taken into consideration. The aim of this thesis is to examine these factors by investigating underlying brain mechanisms of inner speech processes, the impact of emotions, and core schemas about the self and others in different groups of individuals along the continuum from healthy individuals to voice hearers with different underlying disorders. In paper 1, we investigated PLEs in Norway in a sample from the general population, using the screening questions of the Questionnaire for Psychotic Experiences (QPE), an interview that captures the presence and phenomenology of various psychotic experiences separately. Participants with mental disorders reported more frequent lifetime and current hallucinatory experiences than participants without mental disorders, with childhood experiences being rather low. We further replicated findings that young age, illegal drug use, lower level of education, and having parents with a mental disorder are associated with higher endorsement rates of PLEs. Finally, we revealed that the mere presence of PLEs does not discriminate between individuals with and without a mental disorder. Taken together, the findings of paper 1 support existing models that both hallucinations and delusions exist on a structural and phenomenological continuum. In paper 2, we investigated neurobiological factors of cognitive inner speech processes by using a neurostimulation method called transcranial direct current stimulation (tDCS) to modulate source monitoring abilities in healthy individuals. We modulated reality monitoring (distinguishing between external and internal sources) and internal source monitoring abilities (distinguishing between two or more internal sources). We found that internal source monitoring abilities were significantly enhanced during active online tDCS, while reality monitoring abilities were unaffected by stimulation. Our findings suggest that there are different brain areas involved in reality and internal source monitoring: Internal source monitoring seems to involve Broca’s area. Reality monitoring, however, seems to rely more on the superior temporal gyrus (STG) and the dorsolateral prefrontal cortex (DLPFC) as shown in other studies. In paper 3, we focused on cognitive and emotional aspects of AVHs, namely the impact of emotions and affect on AVH phenomenology in non-clinical and different clinical populations. Depending on the underlying psychopathology, these phenomena show different phenomenological aspects. Our aim was to determine the mediating roles of anxiety and depression in the relationship between positive and negative core schemas about the self and others, and emotional aspects of AVHs for three groups: non clinical voice hearers, affective voice hearers, and non-affective voice hearers. Results showed full mediating effects of anxiety in affective voice hearers in the relationship between negative core schemas and all phenomenological aspects, but not in non-affective voice hearers. Depression was not a mediator in any of the groups. These findings suggest different emotional mechanisms for different groups of voice hearers, depending on the underlying psychopathology of individuals with AVHs. Overall, we conclude that the findings support a continuous and transdiagnostic perspective of PLEs in general, and AVHs specifically. However, more integrative transdiagnostic investigations in different groups of individuals along the continuum are needed as studying AVHs in only one modality or one clinical population is unlikely to bring us closer to understanding how these phenomena develop in the first place.Doktorgradsavhandlin

Visual hallucinations in the psychosis spectrum and comparative information from neurodegenerative disorders and eye disease

Much of the research on visual hallucinations (VHs) has been conducted in the context of eye disease and neurodegenerative conditions, but little is known about these phenomena in psychiatric and nonclinical populations. The purpose of this article is to bring together current knowledge regarding VHs in the psychosis phenotype and contrast this data with the literature drawn from neurodegenerative disorders and eye disease. The evidence challenges the traditional views that VHs are atypical or uncommon in psychosis. The weighted mean for VHs is 27% in schizophrenia, 15% in affective psychosis, and 7.3% in the general community. VHs are linked to a more severe psychopathological profile and less favorable outcome in psychosis and neurodegenerative conditions. VHs typically co-occur with auditory hallucinations, suggesting a common etiological cause. VHs in psychosis are also remarkably complex, negative in content, and are interpreted to have personal relevance. The cognitive mechanisms of VHs in psychosis have rarely been investigated, but existing studies point to source-monitoring deficits and distortions in top-down mechanisms, although evidence for visual processing deficits, which feature strongly in the organic literature, is lacking. Brain imaging studies point to the activation of visual cortex during hallucinations on a background of structural and connectivity changes within wider brain networks. The relationship between VHs in psychosis, eye disease, and neurodegeneration remains unclear, although the pattern of similarities and differences described in this review suggests that comparative studies may have potentially important clinical and theoretical implications. © 2014 The Author

Evidence That Environmental and Genetic Risks for Psychotic Disorder May Operate by Impacting on Connections Between Core Symptoms of Perceptual Alteration and Delusional Ideation

Background: Relational models of psychopathology propose that symptoms are dynamically connected and hypothesize that genetic and environmental influences moderate the strength of these symptom connections. Previous findings suggest that the interplay between hallucinations and delusions may play a crucial role in the development of psychotic disorder. The current study examined whether the connection between hallucinations and delusions is impacted by proxy genetic and environmental risk factors. Methods: Hallucinations and delusions at baseline and at 3-year follow-up were assessed in a sample of 1054 healthy siblings and 918 parents of 1109 patients with psychosis, and in 589 healthy controls (no familial psychosis risk). Environmental factors assessed were cannabis use, childhood trauma, and urbanicity during childhood. Logistic regression analyses tested whether familial psychosis risk predicted increased risk of delusions, given presence of hallucinations. Moderating effects of environmental factors on the hallucination-delusion association were tested in a similar fashion, restricted to the control and sibling groups. Results: The risk of delusions, given hallucinations, was associated with proxy genetic risk: 53% in parents, 47% in siblings, and 36% in controls. The hallucination-delusion association was stronger in those reporting cannabis use (risk difference: 32%) and childhood trauma (risk difference: 15%) although not all associations were statistically conclusive (respectively: p = .037; p = .054). A directionally similar but nonsignificant effect was found for urb anicity during childhood (risk difference: 14%, p = .357). Conclusion: The strength of the connection between delusions and hallucinations is associated with familial and environmental risks for psychotic disorder, suggesting that specific symptom connections in the early psychosis psychopathology network are informative of underlying mechanisms

Using Neural Networks to Simulate the Alzheimer's Disease

Making use of biologically plausible artificial neural networks that implement Grossberg’s presynaptic learning rule, we simulate the possible effects of calcium dysregulation in the neuron’s activation function, to represent the most accepted model of Alzheimer's Disease: the calcium dysregulation hypothesis. According to Cudmore and Turrigiano calcium dysregulation alters the shifting dynamic of the neuron’s activation function (intrinsic plasticity). We propose that this alteration might affect the stability of synaptic weights in which memories are stored. The results of the simulation supported the theoretical hypothesis, implying that the emergence of Alzheimer's disease's symptoms such as memory loss and learning problems might be correlated to intrinsic neuronal plasticity impairment due to calcium dysregulation

A first step toward cognitive remediation of voices: a case study.

Several studies have shown that source-monitoring errors are related to verbal hallucinations in schizophrenia. An exploratory pilot study has been carried out to investigate the possibility of training patients in how to avoid errors in source-monitoring. One patient with paranoid schizophrenia and persistent thought insertions was trained for 6 hours to use mnemonic techniques to compensate specific deficits in source-monitoring. Results show that the patient was able to improve his performance and maintain the acquired progress at a 1-month follow-up assessment. These preliminary results are interesting for developing a larger controlled study of cognitive remediation of source-monitoring deficits