Auditory hallucinations and perception of external speech

Altered brain responses to emotional auditory stimuli in AVH subjects: an fMRI study

Purpose: Auditory verbal hallucinations (AVH) are a frequently occurring phenomenon in which subjects hear verbal sounds in the absence of any external stimuli. The prevalence of auditory hallucinations in schizophrenia has been revealed in many studies. Healthy subjects may also experience auditory hallucinations without accompanying psychological or neurological disorders, and in rare cases they seek clinical assistance for this emotionally disturbing condition. The aim of this study was to investigate the neural basis of emotional disturbance in auditory hallucinating subjects who do not suffer from any psychological or neurological disorder. Materials and Methods: Fourteen subjects suffering from auditory hallucinations and 15 age- and sex-matched healthy controls were recruited in this study. All participants underwent fMRI in two experimental sessions. In the first experimental session, all participants from both groups listened to pleasant auditory stimuli. In the second session, both groups listened to unpleasant auditory stimuli. The auditory stimuli were obtained from the International Affective Digitized Sounds (IADS). Results: Compared with the healthy control group, AVH subjects exhibited significantly increased activation in limbic, auditory, and frontal regions. Conclusion: Current results suggest that AVH may induce functional reorganization in emotion-related brain regions.

Alpha transcranial alternating current stimulation reduces depressive symptoms in people with schizophrenia and auditory hallucinations: a double-blind, randomized pilot clinical trial

People with schizophrenia exhibit reduced alpha oscillations and frontotemporal coordination of brain activity. Alpha oscillations are associated with top-down inhibition. Reduced alpha oscillations may fail to censor spurious endogenous activity, leading to auditory hallucinations. Transcranial alternating current stimulation (tACS) at the alpha frequency was shown to enhance alpha oscillations in people with schizophrenia and may thus be a network-based treatment for auditory hallucinations. We conducted a double-blind, randomized, placebo-controlled pilot clinical trial to examine the efficacy of 10-Hz tACS in treating auditory hallucinations in people with schizophrenia. 10-Hz tACS was administered in phase at the dorsolateral prefrontal cortex and the temporoparietal junction with a return current at Cz. Patients were randomized to receive tACS or sham for five consecutive days during the treatment week (40 min/day), followed by a maintenance period, during which participants received weekly tACS (40 min/visit) or sham. tACS treatment reduced general psychopathology (p < 0.05, Cohen's d = -0.690), especially depression (p < 0.005, Cohen's d = -0.806), but not auditory hallucinations. tACS treatment increased alpha power in the target region (p < 0.05), increased the frequency of peak global functional connectivity towards 10 Hz (p < 0.05), and reduced left-right frontal functional connectivity (p < 0.005). Importantly, changes in brain functional connectivity significantly correlated with symptom improvement (p < 0.05). Daily 10 Hz-tACS increased alpha power and altered alpha-band functional connectivity. Successful target engagement reduced depression and other general psychopathology symptoms, but not auditory hallucinations. Considering existing research of 10Hz tACS as a treatment for major depressive disorder, our study demonstrates its transdiagnostic potential for treating depression.

Do patients with hallucinations imagine speech right?

A direct relationship between auditory verbal hallucinations (AVHs) and decreased left-hemispheric lateralization in speech perception has been often described, although it has not been conclusively proven. The specific lateralization of AVHs has been poorly explored. However, patients with verbal hallucinations show a weak Right Ear Advantage (REA) in verbal perception compared to non AVHs listeners suggesting that left-hemispheric language area are involved in AVHs. In the present study, 29 schizophrenia patients with AVHs, 31 patients with psychotic bipolar disorder who experienced frequent AVHs, 27 patients with schizophrenia who had never experienced AVHs and 57 healthy controls were required to imagine hearing a voice in one ear alone. In line with previous evidence healthy controls confirmed the expected REA for auditory imagery, and the same REA was also found in non-hallucinator patients. However, in line with our hypothesis, patients with schizophrenia and psychotic bipolar disorder with AVHs showed no lateral bias. Results extend the relationship between abnormal asymmetry for verbal stimuli and AVHs to verbal imagery, suggesting that atypical verbal imagery may reflect a disruption of inter-hemispheric connectivity between areas implicated in the generation and monitoring of verbal imagery and may be predictive of a predisposition for AVHs. Results also indicate that the relationship between AVHs and hemispheric lateralization for auditory verbal imagery is not specific to schizophrenia but may extend to other disorders as well.

Visual hallucinations, thalamocortical physiology and Lewy body disease: A review

One of the core diagnostic criteria for Dementia with Lewy Bodies (DLB) is the presence of visual hallucinations. The presence of hallucinations, along with fluctuations in the level of arousal and sleep disturbance, point to potential pathological mechanisms at the level of the thalamus. However, the potential role of thalamic dysfunction in DLB, particularly as it relates to the presence of formed visual hallucinations is not known. Here, we review the literature on the pathophysiology of DLB with respect to modern theories of thalamocortical function and attempt to derive an understanding of how such hallucinations arise. Based on the available literature, we propose that combined thalamic-thalamic reticular nucleus and thalamocortical pathology may explain the phenomenology of visual hallucinations in DLB. In particular, diminished α7 cholinergic activity in the thalamic reticular nucleus may critically disinhibit thalamocortical activity. Further, concentrated pathological changes within the posterior regions of the thalamus may explain the predilection for the hallucinations to be visual in nature.

Auditory verbal hallucinations are related to cortical thinning in the left middle temporal gyrus of patients with schizophrenia

BACKGROUND

Auditory verbal hallucinations (AVHs) are one of the most common and severe symptoms of schizophrenia, but the neuroanatomical abnormalities underlying AVHs are not well understood. The present study aims to investigate whether AVHs are associated with cortical thinning.

METHODS

Participants were schizophrenia patients from four centers across China, 115 with AVHs and 93 without AVHs, as well as 261 healthy controls. All received 3 T T1-weighted brain scans, and whole brain vertex-wise cortical thickness was compared across groups. Correlations between AVH severity and cortical thickness were also determined.

RESULTS

The left middle part of the middle temporal gyrus (MTG) was significantly thinner in schizophrenia patients with AVHs than in patients without AVHs and healthy controls. Inferences were made using a false discovery rate approach with a threshold at p < 0.05. Left MTG thickness did not differ between patients without AVHs and controls. These results were replicated by a meta-analysis showing them to be consistent across the four centers. Cortical thickness of the left MTG was also found to be inversely correlated with hallucination severity across all schizophrenia patients.

CONCLUSION

The results of this multi-center study suggest that an abnormally thin left MTG could be involved in the pathogenesis of AVHs in schizophrenia.

Baseline connectome modular abnormalities in the childhood phase of a longitudinal study on individuals with chromosome 22q11.2 deletion syndrome

Occurring in at least 1 in 3,000 live births, chromosome 22q11.2 deletion syndrome (22q11DS) produces a complex phenotype that includes a constellation of medical complications such as congenital cardiac defects, immune deficiency, velopharyngeal dysfunction, and characteristic facial dysmorphic features. There is also an increased incidence of psychiatric diagnosis, especially intellectual disability and ADHD in childhood, lifelong anxiety, and a strikingly high rate of schizophrenia spectrum disorders, which occur in around 30% of adults with 22q11DS. Using innovative computational connectomics, we studied how 22q11DS affects high-level network signatures of hierarchical modularity and its intrinsic geometry in 55 children with confirmed 22q11DS and 27 Typically Developing (TD) children. Results identified 3 subgroups within our 22q11DS sample using a K-means clustering approach based on several midline structural measures-of-interests. Each subgroup exhibited distinct patterns of connectome abnormalities. Subtype 1, containing individuals with generally healthy-looking brains, exhibited no significant differences in either modularity or intrinsic geometry when compared with TD. By contrast, the more anomalous 22q11DS Subtypes 2 and 3 brains revealed significant modular differences in the right hemisphere, while Subtype 3 (the most anomalous anatomy) further exhibited significantly abnormal connectome intrinsic geometry in the form of left-right temporal disintegration. Taken together, our findings supported an overall picture of (a) anterior-posteriorly differential interlobar frontotemporal/frontoparietal dysconnectivity in Subtypes 2 and 3 and (b) differential intralobar dysconnectivity in Subtype 3. Our ongoing studies are focusing on whether these subtypes and their connnectome signatures might be valid biomarkers for predicting the degree of psychosis-proneness risk found in 22q11DS. Hum Brain Mapp 39:232-248, 2018. © 2017 Wiley Periodicals, Inc.

Interaction of language, auditory and memory brain networks in auditory verbal hallucinations

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The language, auditory and memory/limbic networks are of particular relevance for auditory verbal hallucinations.

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An increased interaction among the auditory-language and striatal brain regions occurs while patients hallucinate.

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Fronto-temporal connections are often altered in AVH individuals, but there is no consensus regarding increase or decrease.

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Connections of the interhemispheric auditory pathway are stronger for first episode patients, but they are weaker in chronic patients.

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The majority of studies support hybrid AVH hypotheses in which all three networks and the striatal network are involved.

Auditory verbal hallucinations (AVH) occur in psychotic disorders, but also as a symptom of other conditions and even in healthy people. Several current theories on the origin of AVH converge, with neuroimaging studies suggesting that the language, auditory and memory/limbic networks are of particular relevance. However, reconciliation of these theories with experimental evidence is missing. We review 50 studies investigating functional (EEG and fMRI) and anatomic (diffusion tensor imaging) connectivity in these networks, and explore the evidence supporting abnormal connectivity in these networks associated with AVH. We distinguish between functional connectivity during an actual hallucination experience (symptom capture) and functional connectivity during either the resting state or a task comparing individuals who hallucinate with those who do not (symptom association studies). Symptom capture studies clearly reveal a pattern of increased coupling among the auditory, language and striatal regions. Anatomical and symptom association functional studies suggest that the interhemispheric connectivity between posterior auditory regions may depend on the phase of illness, with increases in non-psychotic individuals and first episode patients and decreases in chronic patients. Leading hypotheses involving concepts as unstable memories, source monitoring, top-down attention, and hybrid models of hallucinations are supported in part by the published connectivity data, although several caveats and inconsistencies remain. Specifically, possible changes in fronto-temporal connectivity are still under debate. Precise hypotheses concerning the directionality of connections deduced from current theoretical approaches should be tested using experimental approaches that allow for discrimination of competing hypotheses.

A linguistic comparison between auditory verbal hallucinations in patients with a psychotic disorder and in nonpsychotic individuals: Not just what the voices say, but how they say it

BACKGROUND

Auditory verbal hallucinations (AVH) in psychotic patients are associated with activation of right hemisphere language areas, although this hemisphere is non-dominant in most people. Language generated in the right hemisphere can be observed in aphasia patients with left hemisphere damage. It is called "automatic speech", characterized by low syntactic complexity and negative emotional valence. AVH in nonpsychotic individuals, by contrast, predominantly have a neutral or positive emotional content and may be less dependent on right hemisphere activity. We hypothesize that right hemisphere language characteristics can be observed in the language of AVH, differentiating psychotic from nonpsychotic individuals.

METHOD

17 patients with a psychotic disorder and 19 nonpsychotic individuals were instructed to repeat their AVH verbatim directly upon hearing them. Responses were recorded, transcribed and analyzed for total words, mean length of utterance, proportion of grammatical utterances, proportion of negations, literal and thematic perseverations, abuses, type-token ratio, embeddings, verb complexity, noun-verb ratio, and open-closed class ratio.

RESULTS

Linguistic features of AVH overall differed between groups F(13,24)=3.920, p=0.002; Pillai's Trace 0.680. AVH of psychotic patients compared with AVH of nonpsychotic individuals had a shorter mean length of utterance, lower verb complexity, and more verbal abuses and perseverations (all p<0.05). Other features were similar between groups.

CONCLUSION

AVH of psychotic patients showed lower syntactic complexity and higher levels of repetition and abuses than AVH of nonpsychotic individuals. These differences are in line with a stronger involvement of the right hemisphere in the origination of AVH in patients than in nonpsychotic voice hearers.

Cortical processes of speech illusions in the general population

BACKGROUND

There is evidence that experimentally elicited auditory illusions in the general population index risk for psychotic symptoms. As little is known about underlying cortical mechanisms of auditory illusions, an experiment was conducted to analyze processing of auditory illusions in a general population sample. In a follow-up design with two measurement moments (baseline and 6 months), participants (n = 83) underwent the White Noise task under simultaneous recording with a 14-lead EEG. An auditory illusion was defined as hearing any speech in a sound fragment containing white noise.

RESULTS

A total number of 256 speech illusions (SI) were observed over the two measurements, with a high degree of stability of SI over time. There were 7 main effects of speech illusion on the EEG alpha band-the most significant indicating a decrease in activity at T3 (t = -4.05). Other EEG frequency bands (slow beta, fast beta, gamma, delta, theta) showed no significant associations with SI.

CONCLUSION

SIs are characterized by reduced alpha activity in non-clinical populations. Given the association of SIs with psychosis, follow-up research is required to examine the possibility of reduced alpha activity mediating SIs in high risk and symptomatic populations.

Using concurrent EEG and fMRI to probe the state of the brain in schizophrenia

Perceptional abnormalities in schizophrenia are associated with hallucinations and delusions, but also with negative symptoms and poor functional outcome. Perception can be studied using EEG-derived event related potentials (ERPs). Because of their excellent temporal resolution, ERPs have been used to ask when perception is affected by schizophrenia. Because of its excellent spatial resolution, functional magnetic resonance imaging (fMRI) has been used to ask where in the brain these effects are seen. We acquired EEG and fMRI data simultaneously to explore when and where auditory perception is affected by schizophrenia. Thirty schizophrenia (SZ) patients and 23 healthy comparison subjects (HC) listened to 1000 Hz tones occurring about every second. We used joint independent components analysis (jICA) to combine EEG-based event-related potential (ERP) and fMRI responses to tones. Five ERP-fMRI joint independent components (JIC) were extracted. The "N100" JIC had temporal weights during N100 (peaking at 100 ms post-tone onset) and fMRI spatial weights in superior and middle temporal gyri (STG/MTG); however, it did not differ between groups. The "P200" JIC had temporal weights during P200 and positive fMRI spatial weights in STG/MTG and frontal areas, and negative spatial weights in the nodes of the default mode network (DMN) and visual cortex. Groups differed on the "P200" JIC: SZ had smaller "P200" JIC, especially those with more severe avolition/apathy. This is consistent with negative symptoms being related to perceptual deficits, and suggests patients with avolition/apathy may allocate too few resources to processing external auditory events and too many to processing internal events.

Auditory verbal hallucinations of epileptic origin

Complex auditory hallucinations are often characterized by hearing voices and are then called auditory verbal hallucinations (AVHs). While AVHs have been extensively investigated in psychiatric patients suffering from schizophrenia, reports from neurological patients are rare and, in most cases, incomplete. Here, we characterize AVHs in 9 patients suffering from pharmacoresistant epilepsy by analyzing the phenomenology of AVHs and patients' neuropsychological and lesion profiles. From a cohort of 352 consecutively examined patients with epilepsy, 9 patients suffering AVHs were identified and studied by means of a semistructured interview, neuropsychological tests, and multimodal imaging, relying on a combination of functional and structural neuroimaging data and surface and intracranial EEG. We found that AVHs in patients with epilepsy were associated with prevalent language deficits and damage to posterior language areas and basal language areas in the left temporal cortex. Auditory verbal hallucinations, most of the times, consisted in hearing a single voice of the same gender and language as the patient and had specific spatial features, being, most of the times, perceived in the external space, contralateral to the lesion. We argue that the consistent location of AVHs in the contralesional external space, the prominence of associated language deficits, and the prevalence of lesions to the posterior temporal language areas characterize AVHs of neurological origin, distinguishing them from those of psychiatric origin.

Tinnitus and musical hallucinosis: the same but more

While tinnitus can be interpreted as a simple or elementary form of auditory phantom perception, musical hallucinosis is a more complex auditory phantom phenomenon not only limited to sound perception, but also containing semantic and musical content. It most often occurs in association with hearing loss. To elucidate the relation between simple and complex auditory phantom percepts a source localized electroencephalography (EEG) study is performed. The analyses showed in both simple and complex auditory phantoms an increase in theta-gamma activity and coupling within the auditory cortex that could be associated with the thalamocortical dysrhythmia model. Furthermore increased beta activity within the dorsal anterior cingulate cortex and anterior insula is demonstrated, that might be related to auditory awareness, salience and its attribution to an external sound source. The difference between simple and complex auditory phantoms relies on differential alpha band activity within the auditory cortex and on beta activity in the dorsal anterior cingulate cortex and (para)hippocampal area. This could be related to memory based load dependency, while suppression within the primary visual cortex might be due the presence of a continuous auditory cortex activation inducing an inhibitory signal to the visual system. Complex auditory phantoms further activate the right inferior frontal area (right sided Broca homolog) and right superior temporal pole that might be associated with the musical content. In summary, this study showed for the first time that simple and complex auditory phantoms might share a common neural substrate but differ as complex auditory phantoms are associated with activation in brain areas related to music and language processing.

Analysis of the VAV3 as candidate gene for schizophrenia: evidences from voxel-based morphometry and mutation screening

In recently completed Japanese genome-wide association studies (GWAS) of schizophrenia (JPN_GWAS) one of the top association signals was detected in the region of VAV3, a gene that maps to the chromosome 1p13.3. In order to complement JPN_GWAS findings, we tested the association of rs1410403 with brain structure in healthy individuals and schizophrenic patients and performed exon resequencing of VAV3. We performed voxel-based morphometry (VBM) and mutation screening of VAV3. Four independent samples were used in the present study: (1) for VBM analysis, we used case-control sample comprising 100 patients with schizophrenia and 264 healthy controls, (2) mutation analysis was performed on a total of 321 patients suffering from schizophrenia, and 2 case-control samples (3) 729 unrelated patients with schizophrenia and 564 healthy comparison subjects, and (4) sample comprising 1511 cases and 1517 healthy comparison subjects and were used for genetic association analysis of novel coding variants with schizophrenia. The VBM analysis suggests that rs1410403 might affect the volume of the left superior and middle temporal gyri (P=.011 and P=.013, respectively), which were reduced in patients with schizophrenia compared with healthy subjects. Moreover, 4 rare novel missense variants were detected. The mutations were followed-up in large independent sample, and one of the novel variants (Glu741Gly) was associated with schizophrenia (P=.02). These findings demonstrate that VAV3 can be seen as novel candidate gene for schizophrenia in which both rare and common variants may be related to increased genetic risk for schizophrenia in Japanese population.

Mechanisms Underlying Auditory Hallucinations-Understanding Perception without Stimulus

Auditory verbal hallucinations (AVH) are a common phenomenon, occurring in the “healthy” population as well as in several mental illnesses, most notably schizophrenia. Current thinking supports a spectrum conceptualisation of AVH: several neurocognitive hypotheses of AVH have been proposed, including the “feed-forward” model of failure to provide appropriate information to somatosensory cortices so that stimuli appear unbidden, and an “aberrant memory model” implicating deficient memory processes. Neuroimaging and connectivity studies are in broad agreement with these with a general dysconnectivity between frontotemporal regions involved in language, memory and salience properties. Disappointingly many AVH remain resistant to standard treatments and persist for many years. There is a need to develop novel therapies to augment existing pharmacological and psychological therapies: transcranial magnetic stimulation has emerged as a potential treatment, though more recent clinical data has been less encouraging. Our understanding of AVH remains incomplete though much progress has been made in recent years. We herein provide a broad overview and review of this.

Quantitative meta-analysis on state and trait aspects of auditory verbal hallucinations in schizophrenia

Auditory verbal hallucinations (AVHs) have a high prevalence in schizophrenic patients. An array of studies have explored the neural correlates of AVHs by means of functional neuroimaging and have associated AVHs with diverse brain regions, some of which have been shown to be involved in speech generation, speech perception, and auditory stimulus processing. We divided these studies into "state" studies comparing periods of presence and absence of AVHs within-subject and "trait" studies comparing patients experiencing AVHs with patients without AVHs or healthy controls during tasks with verbal material. We set out to test the internal consistency and possible dissociations of the neural correlates of AVHs. We used activation likelihood estimation to perform quantitative meta-analyses on brain regions reported in state and trait studies on AVHs to assess significant concordance across studies. State studies were associated with activation in bilateral inferior frontal gyrus, bilateral postcentral gyrus, and left parietal operculum. Trait studies on the other hand showed convergence of decreases in hallucinating subjects in left superior temporal gyrus, left middle temporal gyrus, anterior cingulate cortex, and left premotor cortex activity. Based on the clear dissociation of brain regions that show convergence across state in comparison to trait studies, we conclude that the state of experiencing AVHs is primarily related brain regions that have been implicated in speech production ie, Broca's area, whereas the general trait that makes humans prone to AVHs seems to be related to brain areas involved in auditory stimuli processing and speech perception, ie, auditory cortex.

Auditory hallucinations: expectation-perception model

In this paper, we aimed to present a hypothesis that would explain the mechanism of auditory hallucinations, one of the main symptoms of schizophrenia. We propose that auditory hallucinations arise from abnormalities in the predictive coding which underlies normal perception, specifically, from the absence or attenuation of prediction error. The suggested deficiencies in processing prediction error could arise from (1) abnormal modulation of thalamus by prefrontal cortex, (2) absence or impaired transmission of external input, (3) dysfunction of the auditory and association cortex, (4) neurotransmitter dysfunction and abnormal connectivity, and (5) hyperactivity activity in auditory cortex and broad prior probability. If there is no prediction error, the initially vague prior probability develops into an explicit percept in the absence of external input, as a result of a recursive pathological exchange between auditory and prefrontal cortex. Unlike existing explanations of auditory hallucinations, we propose concrete mechanisms which underlie the imbalance between perceptual expectation and external input. Impaired processing of prediction error is reflected in reduced mismatch negativity and increased tendency to report non-existing meaningful language stimuli in white noise, shown by those suffering from auditory hallucinations. We believe that the expectation-perception model of auditory hallucinations offers a comprehensive explanation of the underpinnings of auditory hallucinations in both patients and those not diagnosed with mental illness. Therefore, our hypothesis has the potential to fill the gaps in the existing knowledge about this distressing phenomenon and contribute to improved effectiveness of treatments, targeting specific mechanisms.

The future of functional MRI in clinical medicine

In the last 20 years or so, functional MRI has matured very rapidly from being an experimental imaging method in the hands of a few labs to being a very widely available and widely used workhorse of cognitive neuroscience and clinical neuroscience research internationally. FMRI studies have had a considerable impact on our understanding of brain system phenotypes of neurological and psychiatric disorders; and some impact already on development of new therapeutics. However, the direct benefit of fMRI to individual patients with brain disorders has so far been minimal. Here I provide a personal perspective on what has already been achieved, and imagine how the further development of fMRI over the medium term might lead to even greater engagement with clinical medicine.

A pilot double-blind sham-controlled trial of repetitive transcranial magnetic stimulation for patients with refractory schizophrenia treated with clozapine

Schizophrenia is a complex and heterogeneous psychiatric disorder. Auditory verbal hallucinations occur in 50-70% of patients with schizophrenia and are associated with significant distress, decreased quality of life and impaired social functioning. This study aimed to investigate the effects of active compared with sham 1-Hz repetitive transcranial magnetic stimulation (rTMS) applied to the left temporal-parietal cortex in patients with schizophrenia treated with clozapine. Symptom dimensions that were evaluated included general psychopathology, severity of auditory hallucinations, quality of life and functionality. Seventeen right-handed patients with refractory schizophrenia experiencing auditory verbal hallucinations and treated with clozapine were randomly allocated to receive either active rTMS or sham stimulation. A total of 384 min of rTMS was administered over 20 days using a double-masked, sham-controlled, parallel design. There was a significant reduction in Brief Psychiatric Rating Scale (BPRS) scores in the active group compared with the sham group. There was no significant difference between active and sham rTMS on Quality of Life Scale (QLS), Auditory Hallucinations Rating Scale (AHRS), Clinical Global Impressions (CGI) and functional assessment staging (FAST) scores. Compared with sham stimulation, active rTMS of the left temporoparietal cortex in clozapine-treated patients showed a positive effect on general psychopathology. However, there was no effect on refractory auditory hallucinations. Further studies with larger sample sizes are needed to confirm these findings.

Time course of regional brain activity accompanying auditory verbal hallucinations in schizophrenia

BACKGROUND

The pathophysiology of auditory verbal hallucinations remains poorly understood.

AIMS

To characterise the time course of regional brain activity leading to auditory verbal hallucinations.

METHOD

During functional magnetic resonance imaging, 11 patients with schizophrenia or schizoaffective disorder signalled auditory verbal hallucination events by pressing a button. To control for effects of motor behaviour, regional activity associated with hallucination events was scaled against corresponding activity arising from random button-presses produced by 10 patients who did not experience hallucinations.

RESULTS

Immediately prior to the hallucinations, motor-adjusted activity in the left inferior frontal gyrus was significantly greater than corresponding activity in the right inferior frontal gyrus. In contrast, motor-adjusted activity in a right posterior temporal region overshadowed corresponding activity in the left homologous temporal region. Robustly elevated motor-adjusted activity in the left temporal region associated with auditory verbal hallucinations was also detected, but only subsequent to hallucination events. At the earliest time shift studied, the correlation between left inferior frontal gyrus and right temporal activity was significantly higher for the hallucination group compared with non-hallucinating patients.

CONCLUSIONS

Findings suggest that heightened functional coupling between the left inferior frontal gyrus and right temporal regions leads to coactivation in these speech processing regions that is hallucinogenic. Delayed left temporal activation may reflect impaired corollary discharge contributing to source misattribution of resulting verbal images.

Formal thought disorder in non-clinical individuals with auditory verbal hallucinations

BACKGROUND

Auditory verbal hallucinations (AVH) and formal thought disorder (FTD) may originate from the same aberration in the language system. The hypothesis of a shared neurobiological basis would be strengthened by the presence of FTD in individuals who frequently experience AVH, but do not meet DSM-IV criteria for a psychotic disorder.

METHODS

In this study, FTD was quantified in 40 non-clinical subjects with AVH, in 50 healthy subjects without AVH and in 40 schizophrenia patients with AVH. Recorded speech samples were analysed by one rater who was blind to the presence/absence of AVH and to diagnosis, using the Thought and Language Index.

RESULTS

Negative FTD was barely present in non-clinical subjects with AVH and in healthy controls without AVH. Positive FTD, however, was significantly higher in both groups experiencing AVH than in controls without AVH. Severity of positive FTD did not differ significantly between non-clinical subjects with AVH and schizophrenia patients with AVH.

CONCLUSION

Negative FTD (alogia) appears not to be associated with AVH. However, the fact that positive FTD (disorganised speech) in schizophrenia patients with AVH is equally high in non-clinical subjects with AVH indicates that these two symptoms tend to co-occur, which may be suggestive of a shared neurobiological substrate.

Psychotic symptoms as a continuum between normality and pathology

This paper reviews the presence of psychotic features in the nonclinical population. The results of a literature review suggest that delusional and hallucinatory experiences are more common in the general population than we may think, and that there could well be a symptomatic continuum between people who have and people who have not been diagnosed with indisputable psychotic disorders. In the nonclinical population, voices are mainly positive and nonthreatening. Conversely, in the psychiatric population, they tend to be frequent, intrusive, and distressing. We address the question of voices considered as various human experiences and describe the emergence of the nonclinical group of people who hear voices. We also review the pathophysiology of auditory hallucinations as an illustration of a neurophysiological anomaly, which is useful to understand psychosis or schizophrenia. The main obstacle in the category-specific thought is that it remains impossible to unmistakably demarcate the border around schizophrenia. It is evident that the creation of a boundary is always possible by using arbitrary criteria that improve interrater reliability but exclude a considerable number of people who share multiple common features with diagnosed people.

Auditory verbal hallucinations predominantly activate the right inferior frontal area

The pathophysiology of auditory verbal hallucinations (AVH) is largely unknown. Several functional imaging studies have measured cerebral activation during these hallucinations, but sample sizes were relatively small (one to eight subjects) and findings inconsistent. In this study cerebral activation was measured using fMRI in 24 psychotic patients while they experienced AVH in the scanner and, in another session, while they silently generated words. All patients were right handed and diagnosed with schizophrenia, schizo-affective disorder or psychotic disorder not otherwise specified. Group analysis for AVH revealed activation in the right homologue of Broca's area, bilateral insula, bilateral supramarginal gyri and right superior temporal gyrus. Broca's area and left superior temporal gyrus were not activated. Group analysis for word generation in these patients yielded activation in Broca's and Wernicke's areas and to a lesser degree their right-sided homologues, bilateral insula and anterior cingulate gyri. Lateralization of activity during AVH was not correlated with language lateralization, but rather with the degree to which the content of the hallucinations had a negative emotional valence. The main difference between cerebral activity during AVH and activity during normal inner speech appears to be the lateralization. The predominant engagement of the right inferior frontal area during AVH may be related to the typical low semantic complexity and negative emotional content.

Left hemisphere lateralisation of auditory hallucinations in schizophrenia: a dichotic listening study

INTRODUCTION

We propose that auditory hallucinations are internally generated speech misrepresentations that are lateralised to the left temporal lobe. If hallucinations are misrepresentations involving the speech perception area of the left temporal lobe, then hallucinating patients should have problems identifying a simultaneously presented external speech sound, especially when the sound is lateralised to the left hemisphere. Lateralisation of speech perception can be experimentally studied with the dichotic listening task with consonant-vowel syllables. We predicted a negative relation between frequency of auditory hallucinations and performance on the dichotic listening task.

METHOD

We studied 87 right-handed patients with schizophrenia. Hallucination scores were taken from the BPRS symptom scale. Right and left ear scores in the dichotic listening task were recorded. A right ear advantage is expected in healthy individuals, indicating left temporal lobe processing superiority. The patients were compared with 36 right-handed healthy reference subjects.

RESULTS

A gradual decrease in the ability to process and report the right ear stimulus with increasing frequency of hallucinations was seen in the schizophrenia patients. No such relationship was found for processing and reporting of the left ear stimulus. There were no significant correlations with negative symptoms. Thus, the results were not the consequence of illness severity. There was however a significant correlation with unusual thought content symptom, pointing to a relationship also between delusions and auditory hallucinations.

CONCLUSION

The results support that auditory hallucinations may be internally generated speech misrepresentations, originating in the left temporal lobe.

The hallucinating brain: A review of structural and functional neuroimaging studies of hallucinations

Hallucinations remains one of the most intriguing phenomena in psychopathology. In the past two decades the advent of neuroimaging techniques have allowed researchers to investigate what is happening in the brain of those who experience hallucinations. In this article we review both structural and functional neuroimaging studies of patients with auditory and visual hallucinations as well as a small number of studies that have assessed cognitive processes associated with hallucinations in healthy volunteers. The current literature suggests that in addition to secondary (and occasionally primary) sensory cortices, dysfunction in prefrontal premotor, cingulate, subcortical and cerebellar regions also seem to contribute to hallucinatory experiences. Based on the findings of these studies we tentatively propose a neurocognitive model in which both bottom-up and top-down processes interact to produce these erroneous percepts. Finally, directions for future work are discussed.

Probing the pathophysiology of auditory/verbal hallucinations by combining functional magnetic resonance imaging and transcranial magnetic stimulation

Functional magnetic resonance imaging and repetitive transcranial magnetic stimulation (rTMS) were used to explore the pathophysiology of auditory/verbal hallucinations (AVHs). Sixteen patients with schizophrenia-spectrum disorder were studied with continuous or near continuous AVHs. For patients with intermittent hallucinations (N = 8), blood oxygenation level-dependent (BOLD) activation maps comparing hallucination and nonhallucination periods were generated. For patients with continuous hallucinations (N = 8) correlations between BOLD signal time course in Wernicke's area, and other regions were used to map functional coupling to the former. These maps were used to identify 3-6 cortical sites per patient that were probed with 1-Hz rTMS and sham stimulation. Delivering rTMS to left temporoparietal sites in Wernicke's area and the adjacent supramarginal gyrus was accompanied by a greater rate of AVH improvement compared with sham stimulation and rTMS delivered to anterior temporal sites. For intermittent hallucinators, lower levels of hallucination-related activation in Broca's area strongly predicted greater rate of response to left temporoparietal rTMS. For continuous hallucinators, reduced coupling between Wernicke's and a right homologue of Broca's area strongly predicted greater left temporoparietal rTMS rate of response. These findings suggest that dominant hemisphere temporoparietal areas are involved in expressing AVHs, with higher levels of coactivation and/or coupling involving inferior frontal regions reinforcing underlying pathophysiology.

Cortical folding abnormalities in schizophrenia patients with resistant auditory hallucinations

Gray matter volume and functional abnormalities have been reported in language-related cortex in schizophrenia patients with auditory hallucinations. Such abnormalities might denote abnormal cortical folding development, which can now be investigated using gyrification measures. Anatomic magnetic resonance images (MRIs) were obtained from 30 schizophrenia patients screened for resistant auditory hallucinations and 28 control subjects. We searched for overall gyrification abnormalities in the whole cortex as well as localized abnormalities in language-related cortex, assuming that gyrification is associated with brain sulcation. A fully automated method was applied to MRIs to extract, label and measure the sulcus area in the whole cortex. Gyrification was assessed using both global and local sulcal indices, respectively the ratio between total sulcal area, or area of each labeled sulcus, and outer cortex area. For both hemispheres, the patients had a lower global sulcal index. The local sulcal index decrease was not homogeneous across the whole cortex. It was more significant in the superior temporal sulcus bilaterally, in the left middle frontal sulcus and in the diagonal branch of left sylvian fissure (Broca's area). Findings suggest abnormalities in cortical gyrification in these patients. Sulcal abnormalities in language-related cortex might underlie these patients' particular vulnerability to hallucinations.

Emotional words induce enhanced brain activity in schizophrenic patients with auditory hallucinations

Neuroimaging studies of emotional response in schizophrenia have mainly used visual (faces) paradigms and shown globally reduced brain activity. None of these studies have used an auditory paradigm. Our principal aim is to evaluate the emotional response of patients with schizophrenia to neutral and emotional words. An auditory emotional paradigm based on the most frequent words heard by psychotic patients with auditory hallucinations was designed. This paradigm was applied to evaluate cerebral activation with functional magnetic resonance imaging (fMRI) in 11 patients with schizophrenia with persistent hallucinations and 10 healthy subjects. We found a clear enhanced activity of the frontal lobe, temporal cortex, insula, cingulate, and amygdala (mainly right side) in patients when hearing emotional words in comparison with controls. Our findings are consistent with other studies suggesting a relevant role for emotional response in the pathogenesis and treatment of auditory hallucinations.

Thalamic hyperperfusion in verbal hallucination of Parkinsonian patients

OBJECTIVE

We compared brain perfusion image using 3D-SSP analysis of (123)I-IMP SPECT between Parkinson's disease patients with auditory verbal hallucination and those without auditory hallucination.

METHODS

Eighty-three cases with Parkinson's disease were studied. In 6 of these patients, auditory hallucination was noted. Among them, four cases had verbal hallucination and two other cases had elementary hallucination. Auditory hallucination was not found in the other 77 cases.

RESULTS

Right thalamic perfusion was significantly increased in the verbal hallucination group compared to the group that lacked auditory hallucination.

CONCLUSION

In Parkinson's disease, the right thalamic hyperactive state may be related to verbal hallucination.

Imaging auditory hallucinations in schizophrenia

It is increasingly recognized that there are a heterogeneous range of symptoms within the syndrome of schizophrenia and that some of these also occur frequently within other psychiatric conditions. An approach similar to that in neuropsychology, where cases are grouped based on a discrete deficit, or in this case a discrete symptom, rather than a cause or diagnosis, may be useful in exploring the neural correlates of psychotic symptomatology. Functional neuroimaging provides an excellent tool for investigating the in vivo cortical function of patients with schizophrenia. Auditory verbal hallucinations are one of the most commonly occurring psychotic symptoms in schizophrenia; and this paper examines the progress that has been made in utilizing neuroimaging techniques to investigate auditory hallucinations in schizophrenia and review potential implications for treatment and future directions for research.

Correlations between rCBF and symptoms in two independent cohorts of drug-free patients with schizophrenia

We report on the correlations between whole brain rCBF and the positive and negative symptoms of schizophrenia in two cohorts of patients who were scanned while free of antipsychotic medication. We hypothesized that positive symptoms would correlate with rCBF in limbic and paralimbic regions, and that negative symptoms would correlate with rCBF in frontal and parietal regions. Both cohorts of patients with schizophrenia (Cohort 1: n=32; Cohort 2: n=23) were scanned using PET with H(2)(15)O while free of antipsychotic medication for an average of 21 and 15 days, respectively. Both groups were scanned during a resting state. Using SPM99, we conducted pixel by pixel linear regression analyses between BPRS scores and whole brain rCBF. As hypothesized, positive symptoms correlated with rCBF in the anterior cingulate cortex (ACC) in a positive direction and with the hippocampus/parahippocampus in a negative direction in both patient groups. When the positive symptoms were further divided into disorganization and hallucination/delusion scores, similar positive correlations with ACC and negative correlations with hippocampus rCBF were found. In both cohorts, the disorganization scores correlated positively with rCBF in Broca's area. As expected, negative symptoms correlated inversely with rCBF in frontal and parietal regions. This study provides evidence that limbic dysfunction may underlie the production of positive symptoms. It suggests that abnormal function of Broca's area may add a specific language-related dimension to positive symptoms. This study also provides further support for an independent neurobiological substrate of negative symptoms distinct from positive symptoms. The involvement of both frontal and parietal regions is implicated in the pathophysiology of negative symptoms.

Hypoperfusion of the auditory and prefrontal cortices in Parkinsonian patients with verbal hallucinations

We examined patients with and without auditory hallucinations, using n-isopropyl-p-[123I]iodoamphetamine single photon emission computed tomographic imaging. We assessed verbal hallucinations in the present study: patients with nonverbal auditory hallucinations were excluded. A total of 11 patients with verbal and visual hallucinations and 17 patients with visual hallucinations only were enrolled. Patients with both verbal and visual hallucinations revealed significant hypoperfusion in the bilateral prefrontal cortex and right superior temporal gyrus compared to patients with visual hallucinations only. There were no significant hyperperfusion in patients with verbal plus visual hallucinations. These results may support the release hallucination theory in verbal hallucinations of Parkinson's disease, although another explanations may be more appropriate and further studies are required.

Neural activity in speech-sensitive auditory cortex during silence

That auditory hallucinations are voices heard in the absence of external stimuli implies the existence of endogenous neural activity within the auditory cortex responsible for their perception. Further, auditory hallucinations occur across a range of healthy and disease states that include reduced arousal, hypnosis, drug intoxication, delirium, and psychosis. This suggests that, even in health, the auditory cortex has a propensity to spontaneously "activate" during silence. Here we report the findings of a functional MRI study, designed to examine baseline activity in speech-sensitive auditory regions. During silence, we show that functionally defined speech-sensitive auditory cortex is characterized by intermittent episodes of significantly increased activity in a large proportion (in some cases >30%) of its volume. Bilateral increases in activity are associated with foci of spontaneous activation in the left primary and association auditory cortices and anterior cingulate cortex. We suggest that, within auditory regions, endogenous activity is modulated by anterior cingulate cortex, resulting in spontaneous activation during silence. Hence, an aspect of the brain's "default mode" resembles a (preprepared) substrate for the development of auditory hallucinations. These observations may help explain why such hallucinations are ubiquitous.

[One decade of functional imaging in schizophrenia research. From visualisation of basic information processing steps to molecular-genetic oriented imaging]

Modern neuroimaging techniques such as magnetic resonance imaging (MRI) and positron emission tomography (PET) have contributed tremendously to our current understanding of psychiatric disorders in the context of functional, biochemical and microstructural alterations of the brain. Since the mid-nineties, functional MRI has provided major insights into the neurobiological correlates of signs and symptoms in schizophrenia. The current paper reviews important fMRI studies of the past decade in the domains of motor, visual, auditory, attentional and working memory function. Special emphasis is given to new methodological approaches, such as the visualisation of medication effects and the functional characterisation of risk genes.

Male and female voices activate distinct regions in the male brain

In schizophrenia, auditory verbal hallucinations (AVHs) are likely to be perceived as gender-specific. Given that functional neuro-imaging correlates of AVHs involve multiple brain regions principally including auditory cortex, it is likely that those brain regions responsible for attribution of gender to speech are invoked during AVHs. We used functional magnetic resonance imaging (fMRI) and a paradigm utilising 'gender-apparent' (unaltered) and 'gender-ambiguous' (pitch-scaled) male and female voice stimuli to test the hypothesis that male and female voices activate distinct brain areas during gender attribution. The perception of female voices, when compared with male voices, affected greater activation of the right anterior superior temporal gyrus, near the superior temporal sulcus. Similarly, male voice perception activated the mesio-parietal precuneus area. These different gender associations could not be explained by either simple pitch perception or behavioural response because the activations that we observed were conjointly activated by both 'gender-apparent' and 'gender-ambiguous' voices. The results of this study demonstrate that, in the male brain, the perception of male and female voices activates distinct brain regions.

Temporoparietal transcranial magnetic stimulation for auditory hallucinations: safety, efficacy and moderators in a fifty patient sample

BACKGROUND

Auditory hallucinations are often resistant to treatment and can produce significant distress and behavioral difficulties. A preliminary report based on 24 patients with schizophrenia or schizoaffective disorder indicated greater improvement in auditory hallucinations following 1-hertz left temporoparietal repetitive transcranial magnetic stimulation (rTMS) compared to sham stimulation. Data from the full 50-subject sample incorporating 26 new patients are now presented to more comprehensively assess safety/tolerability, efficacy and moderators of this intervention.

METHODS

Right-handed patients experiencing auditory hallucinations at least 5 times per day were randomly allocated to receive either rTMS or sham stimulation. A total of 132 minutes of rTMS was administered over 9 days at 90% motor threshold using a double-masked, sham-controlled, parallel design.

RESULTS

Hallucination Change Score was more improved for rTMS relative to sham stimulation (p = .008) as was the Clinical Global Impressions Scale (p = .0004). Hallucination frequency was significantly decreased during rTMS relative to sham stimulation (p = .0014) and was a moderator of rTMS effects (p = .008). There was no evidence of neurocognitive impairment associated with rTMS.

CONCLUSIONS

Left temporoparietal 1-hertz rTMS warrants further study as an intervention for auditory hallucinations. Data suggest that this intervention selectively alters neurobiological factors determining frequency of these hallucinations.

Middle and inferior temporal gyrus gray matter volume abnormalities in chronic schizophrenia: an MRI study

OBJECTIVE

The middle temporal gyrus and inferior temporal gyrus subserve language and semantic memory processing, visual perception, and multimodal sensory integration. Functional deficits in these cognitive processes have been well documented in patients with schizophrenia. However, there have been few in vivo structural magnetic resonance imaging (MRI) studies of the middle temporal gyrus and inferior temporal gyrus in schizophrenia.

METHOD

Middle temporal gyrus and inferior temporal gyrus gray matter volumes were measured in 23 male patients diagnosed with chronic schizophrenia and 28 healthy male subjects by using high-spatial-resolution MRI. For comparison, superior temporal gyrus and fusiform gyrus gray matter volumes were also measured. Correlations between these four regions and clinical symptoms were also investigated.

RESULTS

Relative to healthy subjects, the patients with chronic schizophrenia showed gray matter volume reductions in the left middle temporal gyrus (13% difference) and bilateral inferior temporal gyrus (10% difference in both hemispheres). In addition, the patients showed gray matter volume reductions in the left superior temporal gyrus (13% difference) and bilateral fusiform gyrus (10% difference in both hemispheres). More severe hallucinations were significantly correlated with smaller left hemisphere volumes in the superior temporal gyrus and middle temporal gyrus.

CONCLUSIONS

These results suggest that patients with schizophrenia evince reduced gray matter volume in the left middle temporal gyrus and bilateral reductions in the inferior temporal gyrus. In conjunction with findings of left superior temporal gyrus reduction and bilateral fusiform gyrus reductions, these data suggest that schizophrenia may be characterized by left hemisphere-selective dorsal pathophysiology and bilateral ventral pathophysiology in temporal lobe gray matter.

A neural basis for the perception of voices in external auditory space

We used functional imaging of normal subjects to identify the neural substrate for the perception of voices in external auditory space. This fundamental process can be abnormal in psychosis, when voices that are not true external auditory objects (auditory verbal hallucinations) may appear to originate in external space. The perception of voices as objects in external space depends on filtering by the outer ear. Psychoses that distort this process involve the cerebral cortex. Functional magnetic resonance imaging was carried out on 12 normal subjects using an inside-the-scanner simulation of 'inside head' and 'outside head' voices in the form of typical auditory verbal hallucinations. Comparison between the brain activity associated with the two conditions allowed us to test the hypothesis that the perception of voices in external space ('outside head') is subserved by a temperoparietal network comprising association auditory cortex posterior to Heschl's gyrus [planum temporale (PT)] and inferior parietal lobule. Group analyses of response to 'outside head' versus 'inside head' voices showed significant activation solely in the left PT. This was demonstrated in three experiments in which the predominant lateralization of the stimulus was to the right, to the left or balanced. These findings suggest a critical involvement of the left PT in the perception of voices in external space that is not dependent on precise spatial location. Based on this, we suggest a model for the false perception of externally located auditory verbal hallucinations.

Left ear (right temporal hemisphere) advantage and left temporal hemispheric dysfunction in schizophrenia

In this study, to investigate the right or left ear advantages in psychiatric patients. the durations of hearing for right and left ears were assessed in 61 psychiatric patients, 26 with schizophrenia, 17 with depressive disorder, 13 with bipolar affective disorder, and 5 with brief psychotic disorder, plus 24 controls. Diagnoses were made on the basis of information provided from clinical interviews and the Structured Clinical Interview for DSM-IV (SCID). Schizophrenia was associated with a left ear advantage, and both depressive disorder and brief psychotic disorder were associated with right ear advantage as well as controls. These results suggest that their schizophrenia may be associated with a left temporal lobe dysfunction.

Are auditory hallucinations the consequence of abnormal cerebral lateralization? A morphometric MRI study of the sylvian fissure and planum temporale

BACKGROUND

Auditory verbal hallucinations (AVHs) are a characteristic feature of schizophrenia. Patients with schizophrenia have been found to have reduced volumes of a variety of brain structures as well as a reduction in right-left asymmetries, using postmortem and magnetic resonance imaging (MRI) measures. There is also evidence that patients with AVHs differ in these structural asymmetries, relative to those patients who do not hallucinate. The aim of this study was to examine whether patients with and without a prominent history of AVHs differ, both from each other and in comparison with normal subjects, in the asymmetry of the sylvian fissure (SF) and planum temporale (PT).

METHODS

We recruited 74 DSM-IV male patients with schizophrenia (on the basis of their AVH history) and 32 matched normal control subjects. Thirty patients had no history of AVHs and 44 had a strong definitive history of AVHs. The SF length and PT area and volume were measured on a three-dimensional MRI spoiled GRASS volume sequence. Absolute measures and laterality coefficients were calculated.

RESULTS

: All groups had the normal leftward asymmetry in both the SF and PT. Planum temporale volume and surface area and SF length were all larger in the left hemisphere. There were no significant differences in any measures between the two patient groups or between schizophrenic patients and control subjects. Greater leftward asymmetry of the SF correlated with hallucinations and thought disorder within the prominent hallucinator group. An association was found between handedness and brain size, but this did not interact with diagnosis.

CONCLUSIONS

The results of this study do not confirm reports, based on smaller samples, of reduced structural asymmetries of either the SF or PT in schizophrenia, nor do they indicate a specific relationship to a propensity to experience AVHs. A modest correlation between leftward asymmetry of the SF and some positive symptomatology was found.

fMRI and cognitive dysfunction in schizophrenia

Despite being one of the most prevalent psychiatric conditions, SCHIZOPHRENIA is still poorly understood, with no clear objective biological marker. The advent of neuroimaging has enabled in vivo investigations to complement older techniques, and has revealed important insights. fMRI provides a means to assess the neurobiological theory that schizophrenia is caused by abnormal fronto-temporal lobe connections. In studies of language abnormalities, fMRI can explicitly assess the hypothesis that the normal lateralization of language is reversed in schizophrenia. Longitudinal fMRI studies, and studies examining the effects of medication, suggest that the technique has further potential to advance our understanding of this complex disorder.

The functional anatomy of auditory hallucinations in schizophrenia

We used continuous whole brain functional magnetic resonance imaging (fMRI) with a 3-T magnet to map the cerebral activation associated with auditory hallucinations in four subjects with schizophrenia. The subjects experienced episodes of hallucination whilst in the scanner so that periods of hallucination could be compared with periods of rest in the same individuals. Group analysis demonstrated shared areas of activation in right and left superior temporal gyri, left inferior parietal cortex and left middle frontal gyrus. When the data were examined on an individual basis, the temporal cortex and prefrontal cortex areas were activated during episodes of hallucination in all four subjects. These findings support the theory that auditory hallucination reflects abnormal activation of normal auditory pathways.

Serotonin(2A) receptors are reduced in the planum temporale from subjects with schizophrenia

[(3)H]ketanserin binding to 5HT(2A) receptors was measured in the left planum temporale (sensory speech cortex) from schizophrenic and non-schizophrenic (control) subjects using both particulate membranes and tissue sections. There was a significant decrease in the affinity of [(3)H]ketanserin binding to particulate membranes from schizophrenic subjects who were treated with phenothiazines up to death. Adding 2nM chlorpromazine to brain tissue from control subjects caused a similar decrease in the affinity of [(3)H]ketanserin binding to particulate membranes. This suggests that the decrease in affinity observed in the phenothiazine-treated subjects was due to residual drugs. In addition, there was a significant decrease in the density of [(3)H]ketanserin binding in both particulate membranes and tissue sections from schizophrenic subjects which did not appear to be due to residual antipsychotic drugs. Analysis of the laminar distribution of 5HT(2A) receptors showed that this decrease was greatest in cortical layer III. The decrease in the density of 5HT(2A) receptors was significant whether schizophrenic subjects were receiving phenothiazines or haloperidol at the time of death, and there was no correlation between the last recorded dose of antipsychotic drug and 5HT(2A) receptor density. These data suggest that a decrease in the density of 5HT(2A) receptors in the planum temporale may be associated with the pathology of schizophrenia.

Neuroimaging of hallucinations: a review of the literature

While hallucinations have been described for over two millennia, their cause remains unclear. Brain-based models suggest that abnormal cerebral excitation and a lack of normal cerebral inhibition may play primary roles, but evaluation of these hypotheses has been hampered by difficulty in studying the hallucinatory state. Recent advances in neuroimaging have provided researchers with tools to study a variety of mental states, including hallucinations. We review the literature regarding the structural and functional neural correlates of hallucinations. Despite small sample sizes and methodological differences, several studies describe similar results: hallucinations are associated with sensory modality-specific activation in cerebral areas involved in normal sensory processing. Furthermore, neural activation may be specifically related to distinct phenomenological features of the hallucinatory experience. Further work is needed to better understand the neural basis of hallucinations.

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.