Schizophrenic auditory hallucinations are associated with increased regional cerebral blood flow during verbal memory activation in a study using single photon emission computed tomography

The Etiology of Auditory Hallucinations in Schizophrenia: From Multidimensional Levels

Enormous efforts have been made to unveil the etiology of auditory hallucinations (AHs), and multiple genetic and neural factors have already been shown to have their own roles. Previous studies have shown that AHs in schizophrenia vary from those in other disorders, suggesting that they have unique features and possibly distinguishable mechanisms worthy of further investigation. In this review, we intend to offer a comprehensive summary of current findings related to AHs in schizophrenia from aspects of genetics and transcriptome, neurophysiology (neurometabolic and electroencephalogram studies), and neuroimaging (structural and functional magnetic resonance imaging studies and transcriptome–neuroimaging association study). Main findings include gene polymorphisms, glutamate level change, electroencephalographic alterations, and abnormalities of white matter fasciculi, cortical structure, and cerebral activities, especially in multiple regions, including auditory and language networks. More solid and comparable research is needed to replicate and integrate ongoing findings from multidimensional levels.

Neural Signature for Auditory Hallucinations in Schizophrenia: A High-Resolution Positron Emission Tomography Study with Fludeoxyglucose (18F)

Objective

Auditory hallucinations (AHs) are a core symptom of schizophrenia. We investigated the neural signature of AHs by comparing hallucinating patients with schizophrenia with non-hallucinating patients with schizophrenia.

Methods

We recruited hallucinating patients with schizophrenia meeting the criteria for persistent, prominent, and predominant AHs (n=10) and non-hallucinating patients with schizophrenia (n=12). Various clinical assessments were performed incluing Psychotic Symptom Rating Scale for Auditory Hallucinations. Using fludeoxyglucose (¹⁸F) positron emission tomography, regional differences in neural activity between the groups were analyzed.

Results

The regions of interest analysis showed significantly lower standardized uptake value ratio (SUVR) in the superior, middle, and inferior frontal gyri, and higher SUVR in the putamen in patients with AHs versus patients without AHs. These findings were confirmed in the voxel-wise analysis.

Conclusion

Our findings indicate that hypoactivity in the frontal and cingulate gyri, coupled with hyperactivity in the temporal gyrus and putamen, may contribute to the pathophysiology of AHs.

Specific and unspecific auditory hallucinations in patients with schizophrenia: a magnetoencephalographic study

BACKGROUND/AIMS

Different neuroimaging techniques have indicated that auditory association and language cortices are active in patients with schizophrenia and auditory hallucinations. Auditory verbal hallucinations are thought to arise from a disorder of inner speech, but little is known about their origin.

METHODS

Spontaneous magnetoencephalographic (MEG) measurements were recorded with a 74-channel two-sensor system (BIOMAGNES II) in 16 patients with schizophrenia and 8 healthy subjects in frequency ranges from 2 to 6 and 12.5 to 30 Hz. Eight patients had auditory hallucinations during the MEG recordings.

RESULTS

The total group of patients with schizophrenia showed a statistically significant elevation of the number of dipoles and dipole density maxima in slow frequency ranges compared to healthy subjects (p <0.001). Significant dipole activities in the fast frequency range were only found during auditory hallucinations (p <0.001). Dipole localization was concentrated in frontal and temporal regions depending on different qualities of hallucinations. In patients with external imperative voices we found a parallel activation of the dorsolateral frontal and temporal cortex.

CONCLUSION

We conclude that various auditory hallucinations in schizophrenia are induced by different neuronal activities and may be represented by different cortical regions.

Transcranial magnetic stimulation for auditory hallucinations in schizophrenia

It has been suggested that low frequency transcranial magnetic stimulation (TMS) over left temporo-parietal cortex may reduce the frequency and intensity of auditory hallucinations in schizophrenia. Sixteen patients with hallucinations, treatment-resistant for at least 2 months, were randomised into a placebo-controlled crossover study of TMS at 1 Hz and 80% of motor threshold over left temporo-parietal cortex. Treatment periods lasted for 4 days, with daily duration escalating from 4 to 8, 12 and 16 min on subsequent days. Each minute of stimulation was followed by 15 s of rest to check coil position and allow the patient to move, if necessary. Both patients and symptom raters were unaware of the treatment condition. Patients' hallucination scores improved from baseline with both real and sham TMS, and there was no significant difference between real and sham treatments. There was a trend for second treatments, whether sham or real, to be more effective than first treatments. Other psychopathology scales (apart from positive symptoms) and verbal memory were not affected by real or sham TMS. Previous positive studies could not be replicated with these parameters. TMS is safe if applied within the protocol used.

The cognitive neuropsychiatry of auditory verbal hallucinations: an overview

INTRODUCTION

The cognitive neuropsychiatric approach to auditory verbal hallucinations (AVHs) attempts to explain the phenomena in cognitive or information-processing terms and ultimately their brain bases.

METHODS

A narrative review of the literature and an overview of this special issue of Cognitive Neuropsychiatry.

RESULTS

First, an operational definition of AVHs is offered. Next, clues to etiology are derived from a detailed consideration of the clinical phenomenology of "voices", their form and content. Functional and structural neuroimaging studies suggest the importance of left-side language areas in the generation/perception of AVHs.

CONCLUSIONS

Existing cognitive neuropsychiatric models provide a useful framework for the understanding of AVHs. However, data need to be applied more specifically to these models so that they may be refined.

Verbal declarative memory dysfunction in schizophrenia: from clinical assessment to genetics and brain mechanisms

The recent literature on the neuropsychology of schizophrenia has emphasized memory deficits as a key area of impairment. Abnormalities in the medial temporal lobe, a brain region crucial for long-term memory formation, have also consistently been reported. We conducted a comprehensive review of verbal declarative memory (VDM) in schizophrenia with the aim of systematically addressing the nature of this impairment. We conclude that verbal declarative memory is significantly impaired in schizophrenia and is largely accounted for by deficits in the encoding stage. Subtle impairments in increased rates of forgetting are present, but are mild compared with those in amnestic disorders. Impairment in other cognitive domains studied thus far (e.g., attention), medication effects, or fluctuations in symptoms do not completely account for the deficit. VDM is among the most impaired neurocognitive domains in schizophrenia (along with attention and executive functions). Milder encoding deficits are present in high-risk subjects and non-psychotic relatives of individuals with schizophrenia suggesting that components of the deficit are associated with a genetic vulnerability to the illness, and are independent of the frank psychotic illness. Furthermore, VDM is observed in individuals experiencing their first-psychotic episode and it remains fairly consistent over time. Preliminary imaging studies and other work suggest abnormalities in prefrontal-hippocampal processing networks. Future work should emphasize delineating specific information processing components contributing to the deficit. This would allow imaging studies to determine which brain regions contribute to specific information processing deficits in schizophrenia.

Cortical activation associated with the experience of auditory hallucinations and perception of human speech in schizophrenia: a PET correlation study

A [H(2)(15)O] PET correlation analysis technique was employed to correlate brain activations associated with self-reports of auditory hallucinations in hallucinating patients (n=8) and perception of transient, random human speech in non-hallucinating (n=7) patients and normal control subjects (n=8). Perception of externally generated human speech amongst the non-hallucinating and normal control participants was associated with a consistent pattern of extensive bilateral auditory cortex activation (Brodmann areas 40/41/42/22). Hallucinating participants demonstrated a network of cortical activations including bilateral auditory cortex, left limbic regions, right medial frontal and right prefrontal regions. The observed pattern of activation is consistent with models of auditory hallucinations as mis-remembered episodic memories of speech.

Functional abnormalities of medial temporal cortex during novel picture learning among patients with chronic schizophrenia

BACKGROUND

Learning deficits are prominent among patients with chronic schizophrenia and are associated with poor everyday functioning. Little is known, however, about the brain physiology underlying these difficulties with encoding new information.

PURPOSE

The purpose of the current study was to compare the brain response during novel picture encoding between patients with chronic schizophrenia and healthy individuals using functional magnetic resonance imaging (fMRI).

METHODS

Nine middle-aged patients with DSM-III-R or DSM-IV schizophrenia and 10 age- and education-comparable healthy individuals were studied. Using fMRI, the blood oxygenation level dependent (BOLD) signal was measured during novel picture encoding (experimental condition) and during presentation of a repeated picture (control condition). Encoding-related brain response was examined in both groups and compared between the patient and comparison groups in each voxel within four bilateral search regions (fusiform gyrus, parahippocampal gyrus, hippocampus, and inferior frontal gyrus).

RESULTS

Despite comparable subsequent ability to recognize the presented pictures, patients with schizophrenia showed abnormal encoding-related brain response in regions of the hippocampus and parahippocampal and fusiform gyrii compared to healthy individuals. In medial temporal regions, patients showed greater BOLD response during the control condition (repeated picture) than during the experimental condition (novel pictures).

CONCLUSION

Abnormalities of the medial temporal brain systems examined in this study may underlie learning deficits in schizophrenia. Further research is needed to illuminate the role of these brain dysfunctions in poor everyday functioning and their amenability to treatment.

Auditory hallucinations: phenomenology, neuropsychology and neuroimaging update

Auditory verbal hallucinations (AVHs) are a cardinal feature of psychosis. Recent research is reviewed which has attempted to advance our knowledge of the mechanisms underlying this symptom. Phenomenological surveys have confirmed the importance of the content of such hallucinations and their meaning to the voice-hearer. Psychological and neuroimaging studies of inner speech and source monitoring have provided a neuropsychological framework for AVHs as well as some novel therapeutic strategies. There have also been successful attempts to 'capture' neural activity coincident with the experience of hallucinations using PET, SPECT and functional magnetic resonance imaging (MRI). This body of knowledge in combination with work on in-vivo receptor binding (dopamine and GABA) provides the beginnings of a cognitive and neurophysiological understanding of this complex and intriguing phenomenon.

Hallucinations

Hallucinations, sensory perceptions without environmental stimuli, occur as simple experiences of auditory, gustatory, olfactory, tactile, or visual phenomena as well as mixed- or complex experiences of more than one simple phenomenon. The nature of the hallucination assists localization, differential diagnosis, and treatment planning. In particular, the presence of persistent visual hallucinations of persons with Parkinson's disease predicts dementia, rapid deterioration, permanent nursing home placement, and death. Hallucinations in persons with Alzheimer's disease are often associated with serious behavioral problems and predict a rapid cognitive decline. Theories of the etiology of hallucinations include (1) stimulation, e.g., neurochemical, electrical, seizure, and ephaptic, and (2) inhibition, e.g., destruction of normally inhibitory functions, resulting in disinhibition as in the Charles Bonnet and phantom limb syndromes. Functional neuroimaging procedures suggest anatomical associations for hallucinations. While hallucinations may be a symptom of medical, neurologic, and psychiatric disorders, they may also occur in a wide range of human experiences.

Schizophrenia, psychosis, and the basal ganglia

Schizophrenia is one of the most common and perhaps the most disabling of mental disorders, for which effective forms of treatment have not yet been established definitively. The findings reviewed in this article strongly suggest that basal ganglia abnormalities are involved in the pathophysiology of psychotic syndromes in general, and schizophrenia in particular.

Deficits in Source Monitoring in Subjects with Auditory Hallucinations May be Due to Differences in Verbal Intelligence and Verbal Memory

Previous research has proposed that the experience of auditory hallucinations in schizophrenia represents a failure to monitor self-generated verbal mental imagery. However, recent neuropsychological investigations into this matter have provided inconclusive and even contradictory findings with respect to the proposed relationship. This study compared the performance of three groups of adult males, schizophrenic inpatients (hallucinators and nonhallucinators), and normal controls, matched for age, education, and medication, on a source monitoring task. Initial analysis indicated that performance on a Verbal IQ and Verbal Memory test were significantly related to performance on the source monitoring task. Comparisons between groups were made on the basis of state and trait group characteristics with respect to hallucinations. After controlling for the influence of Verbal IQ and Verbal Memory on task performance, no between-group differences were found for overall accuracy in attribution of self-generated items or in the number of self to experimenter misattribution errors. This finding suggests that the inconsistent findings previously noted in this field may be due to a failure to identify and control for these important covariates. The implications of these findings for theoretical models of hallucination are discussed.