Flavie Waters

Auditory Hallucinations in Schizophrenia and Nonschizophrenia Populations: A Review and Integrated Model of Cognitive Mechanisms

While the majority of cognitive studies on auditory hallucinations (AHs) have been conducted in schizophrenia (SZ), an increasing number of researchers are turning their attention to different clinical and nonclinical populations, often using SZ findings as a model for research. Recent advances derived from SZ studies can therefore be utilized to make substantial progress on AH research in other groups. The objectives of this article were to (1) present an up-to-date review regarding the cognitive mechanisms of AHs in SZ, (2) review findings from cognitive research conducted in other clinical and nonclinical groups, and (3) integrate these recent findings into a cohesive framework. First, SZ studies show that the cognitive underpinnings of AHs include self-source-monitoring deficits and executive and inhibitory control dysfunctions as well as distortions in top-down mechanisms, perceptual and linguistic processes, and emotional factors. Second, consistent with SZ studies, findings in other population groups point to the role of top-down processing, abnormalities in executive inhibition, and negative emotions. Finally, we put forward an integrated model of AHs that incorporates the above findings. We suggest that AHs arise from an interaction between abnormal neural activation patterns that produce salient auditory signals and top-down mechanisms that include signal detection errors, executive and inhibition deficits, a tapestry of expectations and memories, and state characteristics that influence how these experiences are interpreted. Emotional factors play a particular prominent role at all levels of this hierarchy. Our model is distinctively powerful in explaining a range of phenomenological characteristics of AH across a spectrum of disorders.

Auditory hallucinations in schizophrenia: Intrusive thoughts and forgotten memories

Introduction. This paper presents a new cognitive model of auditory hallucinations in schizophrenia. We suggest that auditory hallucinations are auditory representations derived from the unintentional activation of memories and other irrelevant current mental associations. Our model proposes that a combination of deficits in intentional inhibition and contextual memory is critical to the experience of auditory hallucinations. The failure in intentional inhibition produces unwanted and uncontrollable mental events which are not recognised because they have lost the contextual cues that would normally facilitate recognition. Methods. This article amalgamates recently published data and presents a reanalysis of the findings on 43 patients with a diagnosis of schizophrenia (Badcock, Waters, Maybery, & Michie, 2005; Waters, Badcock, Maybery, & Michie, 2003a; Waters, Maybery, Badcock, & Michie, 2004a). Relative risk was also estimated to determine whether the combination of deficits increases the risk of having auditory hallucinations. Results. Almost 90% of patients currently experiencing auditory hallucinations showed the predicted combination of deficits on both inhibition and context memory, compared to only a third of patients without hallucinations. In addition, the results showed that those patients with the specified cognitive deficits were at an especially increased risk of having auditory hallucinations relative to patients without the deficits. Conclusions. The results of our investigations strongly support the role of intentional inhibition and context memory in auditory hallucinations. Critical consideration of the findings also suggests that additional cognitive processes might be important for the expression of this symptom.

The characteristic features of auditory verbal hallucinations in clinical and nonclinical groups: state-of-the-art overview and future directions.

Despite a growing interest in auditory verbal hallucinations (AVHs) in different clinical and nonclinical groups, the phenomenological characteristics of such experiences have not yet been reviewed and contrasted, limiting our understanding of these phenomena on multiple empirical, theoretical, and clinical levels. We look at some of the most prominent descriptive features of AVHs in schizophrenia (SZ). These are then examined in clinical conditions including substance abuse, Parkinsons disease, epilepsy, dementia, late-onset SZ, mood disorders, borderline personality disorder, hearing impairment, and dissociative disorders. The phenomenological changes linked to AVHs in prepsychotic stages are also outlined, together with a review of AVHs in healthy persons. A discussion of key issues and future research directions concludes the review.

SELF-RECOGNITION DEFICITS IN SCHIZOPHRENIA PATIENTS WITH AUDITORY HALLUCINATIONS: A META-ANALYSIS OF THE LITERATURE

Theories about auditory hallucinations in schizophrenia suggest that these experiences occur because patients fail to recognize thoughts and mental events as self-generated. Different theoretical models have been proposed about the cognitive mechanisms underlying auditory hallucinations. Regardless of the cognitive model being tested, however, experimental designs are almost identical in that they require a judgment regarding whether an action was self-originated or not. The aim of the current study was to integrate all available literature for a meta-analysis on this topic and reach conclusions about self-recognition performance in (1) patients with schizophrenia compared with healthy controls and (2) patients with auditory hallucinations compared with patients without these symptoms. A comprehensive literature review identified 23 studies that contrasted the performance of schizophrenia patients with healthy controls (1370 participants) and 9 studies that directly compared patients with and without auditory hallucinations (315 participants). We found significantly reduced self-recognition performance in schizophrenia patients, which was more pronounced in patients with auditory hallucinations compared with patients without. In patients with hallucinations, this pattern of performance was specific to self-recognition processes and not to the recognition of new external information. A striking finding was the homogeneity in results across studies regardless of the action modality, timing delay, and design used to measure self-recognition. In summary, this review of studies from the last 30 years substantiates the view that self-recognition is impaired in patients with schizophrenia and particularly those with auditory hallucinations. This suggests an association, perhaps a causal one, between such deficit and hallucinatory experiences in schizophrenia.

Context memory and binding in schizophrenia

The current study aimed to provide evidence for the context-memory hypothesis, which proposes that schizophrenia is linked to a deficit in retrieving contextual information and in binding the different components of a memory together. A new task was developed in which memory for the content of events could be assessed in conjunction with memory for both source and temporal information. Forty-three patients with schizophrenia and 24 normal controls took part in the study. Patients were found to be less accurate in identifying the source and temporal context of events. Furthermore, whereas controls tended to identify correctly both source and temporal context of events, patients tended to have a more fractionated recollection of those events. The study provides support for the context-memory hypothesis by demonstrating that patients with schizophrenia show a fundamental deficit in binding contextual cues together to form a coherent representation of an event in memory.

Inhibition in schizophrenia: association with auditory hallucinations

The study investigated whether auditory hallucinations (AH) in schizophrenia are linked to a deficit in inhibition. Two tasks assessing the intentional suppression of cognitive events-the Hayling Sentence Completion Test (HSCT) [Neuropsychologia 34 (1996) 263] and the Inhibition of Currently Irrelevant Memories Task (ICIM) [Nature Neuroscience 2 (1999) 677]-were administered to 42 patients with schizophrenia and 24 normal controls. Presence and severity of symptoms in the patient group were examined using the Positive and Negative Syndrome Scale (PANSS). Patients performed significantly worse on the measures of inhibition compared to controls. More importantly, among patients, significant positive correlations were obtained between an index of AH severity (defined as an increase in frequency of AH on PANSS) and the number of type A errors on the HSCT and errors in the last three runs of the ICIM. An increase in AH severity was, therefore, associated with increasingly impaired control of intentional inhibition. Furthermore, no significant correlations were found between these indices of inhibition and either negative, general or positive symptoms (excluding AH scores).

Validation of self-reported sleep against actigraphy

Background Self-report remains the most practical and cost-effective method for epidemiologic sleep studies involving large population-based samples. Several validated questionnaires have been developed to assess sleep, but these tools are lengthy to administer and may be impractical for epidemiologic studies. We examined whether a 3-item sleep questionnaire, similar to those typically used in epidemiologic studies, closely corresponded with objective measures of sleep as assessed using actigraphy monitoring. Methods Eligible participants were Western Australian women aged 18 to 80 years. Participants completed a sleep questionnaire, wore a wrist actigraph for 7 nights, and completed a brief daily sleep log. Objective actigraphy measurements for 56 participants were summarized by mean and mode and compared with the subjective reports, using weighted kappa and delta. Results Data collected from the questionnaire showed poor agreement with objectively measured sleep, with kappas ranging from −0.19 to 0.14. Conclusions Our results indicate that sleep questions typically used in epidemiologic studies do not closely correspond with objective measures of sleep as assessed using actigraphy. The findings have implications for studies that have used such sleep questions. A means of appropriately measuring sleep as a risk factor in epidemiologic studies remains to be determined.

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.

First-Rank Symptoms in Schizophrenia: Reexamining Mechanisms of Self-recognition

Disturbances of self are a common feature of schizophrenic psychopathology, with patients reporting that their thoughts and actions are controlled by external forces, as shown in first-rank symptoms (FRS). One widely accepted explanatory model of FRS suggests a deficiency in the internal forward model system. Recent studies in the field of cognitive sciences, however, have generated new insights into how complex sensory and motor systems contribute to the sense of self-recognition, and it is becoming clear that the forward model conceptualization does not have unique access to representations about the self. We briefly evaluate the forward model explanation of FRS, reassess the distinction made between the sense of agency and body ownership, and outline recent developments in 4 domains of sensory-motor control that have supplemented our understanding of the processes underlying the sense of self-recognition. The application of these findings to FRS will open up new research directions into the processes underlying these symptoms.

Auditory hallucinations: failure to inhibit irrelevant memories

Introduction. The frequency of auditory hallucinations (AH) is associated with efficiency in inhibiting irrelevant memories, suggesting that the presence of AH may be related to the intrusion of strongly activated representations in memory. Therefore, we hypothesised that the inability to suppress irrelevant memories would be found only in patients currently experiencing AH. Method. Performance on a repeated, continuous recognition task was examined in 23 schizophrenia patients with AH present, 20 schizophrenia patients with AH absent, and 24 healthy controls. Results. Patients with current AH made significantly more inappropriate responses (false alarms) to distractors seen on previous runs of the task than nonhallucinating patients. The ability to detect targets (hits) was significantly better in healthy controls than schizophrenia patients, however, there was no significant difference between the two patient subgroups. Conclusions. The findings confirm that the presence of AH involves a failure to suppress memories that are not relevant to ongoing reality. We propose that a combination of deficits in inhibition and (episodic) memory provides a useful model of AH, which can accommodate many of the characteristic features of the symptom and fits well with the neuroanatomical circuitry that is believed to underlie the occurrence of AH.