Left-Dominant Temporal-Frontal Hypercoupling in Schizophrenia Patients With Hallucinations During Speech Perception

Background:

Task-based functional neuroimaging studies of schizophrenia have not yet replicated the increased coordinated hyperactivity in speech-related brain regions that is reported with symptom-capture and resting-state studies of hallucinations. This may be due to suboptimal selection of cognitive tasks.

Methods:

In the current study, we used a task that allowed experimental manipulation of control over verbal material and compared brain activity between 23 schizophrenia patients (10 hallucinators, 13 nonhallucinators), 22 psychiatric (bipolar), and 27 healthy controls. Two conditions were presented, one involving inner verbal thought (in which control over verbal material was required) and another involving speech perception (SP; in which control verbal material was not required).

Results:

A functional connectivity analysis resulted in a left-dominant temporal-frontal network that included speech-related auditory and motor regions and showed hypercoupling in past-week hallucinating schizophrenia patients (relative to nonhallucinating patients) during SP only.

Conclusions:

These findings replicate our previous work showing generalized speech-related functional network hypercoupling in schizophrenia during inner verbal thought and SP, but extend them by suggesting that hypercoupling is related to past-week hallucination severity scores during SP only, when control over verbal material is not required. This result opens the possibility that practicing control over inner verbal thought processes may decrease the likelihood or severity of hallucinations.Key words: schizophrenia, inner speech, speech perception, functional magnetic resonance imaging, functional connectivity     

Cerebral activity associated with auditory verbal hallucinations: a functional magnetic resonance imaging case study

Among the many theories that have been advanced to explain the mechanism by which auditory verbal hallucinations (AVH) arise, 2 that have received a degree of empirical support are: the hypothesis that AVHs arise from misinterpreted inner speech and the proposal that they arise from aberrant activation of the primary auditory cortex. To test these hypotheses, we were fortunate to be able to study the interesting and rare case of a woman with schizophrenia who experienced continuous AVH which disappeared when she listened to loud external speech. Functional magnetic resonance imaging (fMRI) was used to measure the patient's brain activity in the temporal and inferior frontal regions during the AVHs and while the she was listening to external speech. The brain activity of a matched control subject was also recorded under the same experimental conditions. AVHs were associated with increased metabolic activity in the left primary auditory cortex and the right middle temporal gyrus. Our results suggest a possible interaction between these areas during AVHs and also that the hypotheses of defective internal monitoring and aberrant activation are not mutually exclusive. Potential limitations to the generalization of our results are discussed.     

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.     

Cortical interactions during the experience of auditory verbal hallucinations

Auditory verbal hallucinations (AVHs), the perception of voices in the absence of auditory stimuli, are common and distressing symptoms reported by 50%-80% of patients with schizophrenia. However, the results in a number of imaging and electrophysiological studies on the origins of AVH are not consistent, and the underlying pathophysiology remains unclear. The authors enrolled a group of schizophrenia patients and normal-control subjects, age 18-45 years. Two patient groups participated in the study; 1) a group of 8 patients with drug-resistant spontaneous AVHs; and 2) a group of 7 patients whose AVHs were successfully controlled with neuroleptic medication; along with 16 normal-control subjects. The entire sample had EEG recording done, with the AVH group told to press a button when they experienced a hallucination, and the other two groups randomly told when to press the button. In the AVH group, hallucinations were longer in the "eyes-closed" than "eyes-open" condition. There was spreading phase-coupling in the AVH group, intra- and inter-hemispherically, at left and right frontal and temporal areas, under both eyes-closed and eyes-open condition, during the experience of AVH. There was a statistically significant increase of α-band frequency-specific synchrony maximum values in the AVH group. AVHs are considered to be complex features, and, as such, they reflect abnormal functional connectivity in multiple related regions in both intra- and inter-hemispherical brain sites, primarily defined by phase-integration.     

Parietal memory network and default mode network in first‐episode drug‐naïve schizophrenia: Associations with auditory hallucination

Atypical spontaneous activities in resting‐state networks may play a role in auditory hallucinations (AHs), but networks relevant to AHs are not apparent. Given the debating role of the default mode network (DMN) in AHs, a parietal memory network (PMN) may better echo cognitive theories of AHs in schizophrenia, because PMN is spatially adjacent to the DMN and more relevant to memory processing or information integration. To examine whether PMN is more relevant to AHs than DMN, we characterized these intrinsic networks in AHs with 59 first‐episode, drug‐naïve schizophrenics (26 AH+ and 33 AH?) and 60 healthy participants in resting‐state fMRI. We separated the PMN, DMN, and auditory network (AN) using independent component analysis, and compared their functional connectivity across the three groups. We found that only AH+ patients displayed dysconnectivity in PMN, both AH+ and AH? patients exhibited dysfunctions of AN, but neither patient group showed abnormal connectivity within DMN. The connectivity of PMN significantly correlated with memory performance of the patients. Further region‐of‐interest analyses confirmed that the connectivity between the core regions of PMN, the left posterior cingulate gyrus and the left precuneus, was significantly lower only in the AH+ group. In exploratory correlation analysis, this functional connectivity metric significantly correlated with the severity of AH symptoms. The results implicate that compared to the DMN, the PMN is more relevant to the AH symptoms in schizophrenia, and further provides a more precise potential brain modulation target for the intervention of AH symptoms.     

Network analysis of auditory hallucinations in nonpsychotic individuals

Background: Auditory verbal hallucinations (AVH) are a cardinal feature of schizophrenia and can severely disrupt behavior and decrease quality of life. Identification of areas with high functional connectivity (so‐called hub regions) that are associated with the predisposition to hallucinate may provide potential targets for neuromodulation in the treatment of AVH. Methods: Resting‐state fMRI scans during which no hallucinations had occurred were acquired from 29 nonpsychotic individuals with AVH and 29 matched controls. These nonpsychotic individuals with AVH provide the opportunity to study AVH without several confounds associated with schizophrenia, such as antipsychotic medication use and other symptoms related to the illness. Hub regions were identified by assessing weighted connectivity strength and betweenness centrality across groups using a permutation analysis. Results: Nonpsychotic individuals with AVH exhibited increased functioning as hub regions in the temporal cortices and the posterior cingulate/precuneus, which is an important area in the default mode network (DMN), compared to the nonhallucinating controls. In addition, the right inferior temporal gyrus, left paracentral lobule and right amygdala were less important as a hub region in the AVH group. Conclusions: These results suggest that the predisposition to hallucinate may be related to aberrant functioning of the DMN and the auditory cortices. Hum Brain Mapp 35:1436–1445, 2014. © 2013 Wiley Periodicals, Inc.     

Auditory verbal hallucinations and dysfunction of the neural substrates of speech

OBJECTIVE: to evaluate the neural substrate of auditory verbal hallucinations (AVH), the correlation between AVH and subvocal speech (hereafter SVS), and the relationship between speech and AVH. METHOD: we reviewed the papers found by an electronic literature search on hallucinations and speech. The review was extended to the papers cited in these publications and to classical works. RESULTS: there is no conclusive evidence of structural abnormality of the speech perception area in hallucinating schizophrenic patients. However there is evidence of electrophysiological abnormalities of the auditory and speech perception cortices. Functional imaging data are inconsistent, yet point to the left superior temporal gyrus as one of the neural substrates for AVH. There is also evidence that SVS could accompany the experience of AVH. CONCLUSION: there is evidence that dysfunction of brain areas responsible for speech generation is a fundamental mechanism for generating AVH in schizophrenia. It results in a secondary activation of Wernicke's area (speech perception) and Broca's area (speech expression). The first leading to the experience of hallucinations, and the second, eventually, gives rise to a variable degree of vocal muscle activity detectable by EMG, and/or faint vocalizations detectable by sensitive microphones placed at proximity of the larynx. Direct stimulation or disease of Wernicke's area produces AVH without SVS.     

Abnormal interhemispheric and intrahemispheric functional connectivity dynamics in drug‐naïve first‐episode schizophrenia patients with auditory verbal hallucinations

Numerous studies indicate altered static local and long‐range functional connectivity of multiple brain regions in schizophrenia patients with auditory verbal hallucinations (AVHs). However, the temporal dynamics of interhemispheric and intrahemispheric functional connectivity patterns remain unknown in schizophrenia patients with AVHs. We analyzed resting‐state functional magnetic resonance imaging data for drug‐naïve first‐episode schizophrenia patients, 50 with AVHs and 50 without AVH (NAVH), and 50 age‐ and sex‐matched healthy controls. Whole‐brain functional connectivity was decomposed into ipsilateral and contralateral parts, and sliding‐window analysis was used to calculate voxel‐wise interhemispheric and intrahemispheric dynamic functional connectivity density (dFCD). Finally, the correlation analysis was performed between abnormal dFCD variance and clinical measures in the AVH and NAVH groups. Compared with the NAVH group and healthy controls, the AVH group showed weaker interhemispheric dFCD variability in the left middle temporal gyrus (p < .01; p < .001), as well as stronger interhemispheric dFCD variability in the right thalamus (p < .001; p < .001) and right inferior temporal gyrus (p < .01; p < .001) and stronger intrahemispheric dFCD variability in the left inferior frontal gyrus (p < .001; p < .01). Moreover, abnormal contralateral dFCD variability of the left middle temporal gyrus correlated with the severity of AVHs in the AVH group (r = −.319, p = .024). The findings demonstrate that abnormal temporal variability of interhemispheric and intrahemispheric dFCD in schizophrenia patients with AVHs mainly focus on the temporal and frontal cortices and thalamus that are pivotal components of auditory and language pathways.     

Auditory/Verbal hallucinations, speech perception neurocircuitry, and the social deafferentation hypothesis.

Auditory/verbal hallucinations (AVHs) are comprised of spoken conversational speech seeming to arise from specific, nonself speakers. One hertz repetitive transcranial magnetic stimulation (rTMS) reduces excitability in the brain region stimulated. Studies utilizing 1-Hz rTMS delivered to the left temporoparietal cortex, a brain area critical to speech perception, have demonstrated statistically significant improvements in AVHs relative to sham simulation. A novel mechanism of AVHs is proposed whereby dramatic pre-psychotic social withdrawal prompts neuroplastic reorganization by the "social brain" to produce spurious social meaning via hallucinations of conversational speech. Preliminary evidence supporting this hypothesis includes a very high rate of social withdrawal emerging prior to the onset of frank psychosis in patients who develop schizophrenia and AVHs. Moreover, reduced AVHs elicited by temporoparietal 1-Hz rTMS are likely to reflect enhanced long-term depression. Some evidence suggests a loss of long-term depression following experimentally-induced deafferentation. Finally, abnormal cortico-cortical coupling is associated with AVHs and also is a common outcome of deafferentation. Auditory/verbal hallucinations (AVHs) of spoken speech or "voices" are reported by 60-80% of persons with schizophrenia at various times during the course of illness. AVHs are associated with high levels of distress, functional disability, and can lead to violent acts. Among patients with AVHs, these symptoms remain poorly or incompletely responsive to currently available treatments in approximately 25% of cases. For patients with AVHs who do respond to antipsychotic drugs, there is a very high likelihood that these experiences will recur in subsequent episodes. A more precise characterization of underlying pathophysiology may lead to more efficacious treatments.     

Misattribution of speech and impaired connectivity in patients with auditory verbal hallucinations

Several studies report that patients with schizophrenia who experience auditory verbal hallucinations (AVH) tend to misidentify their own speech as that of somebody else. We tested the hypothesis that this tendency is associated with poor functional integration within the network of regions that mediate the evaluation of speech. Using functional magnetic resonance imaging, we measured brain responses from 11 schizophrenics with AVH, 10 schizophrenics without AVH, and 10 healthy controls. Stimuli comprised prerecorded words, which varied for their source (self, alien) and acoustic quality (undistorted, distorted). Participants had to indicate whether each word was spoken in their own or another person's voice via a button press. Using dynamic causal modeling, we estimated the impact of one region over another ("effective connectivity") and how this was modulated by source and distortion. In controls and in patients without AVH, the connectivity between left superior temporal and anterior cingulate cortex was significantly greater for alien- than for self-generated speech; in contrast, the reverse trend was found in schizophrenic patients with AVH. In conclusion, when patients with AVH appraise their own speech we find impaired functional integration between left superior temporal and anterior cingulate cortex. Although this finding is based on external rather than internal speech, the same mechanism may contribute to the faulty appraisal of inner speech that putatively underlies AVH.     

Nicotine and the hallucinating brain: effects on mismatch negativity (MMN) in schizophrenia

Elevated smoking rates have been noted in schizophrenia, and it has been hypothetically attributed to nicotine's ameliorating abnormal brain processes in this illness. There is some preliminary evidence that nicotine may alter pre-attentive auditory change detection, as indexed by the EEG-derived mismatch negativity (MMN), but no previous study has examined what role auditory verbal hallucinations (AVH) may have on these effects. The objective of this study was to examine MMN-indexed acoustic change detection in schizophrenia (SZ) following nicotine administration and elucidate its association with AVH. Using a modified multi-feature paradigm, MMNs to duration, frequency and intensity deviants were recorded in 12 schizophrenia outpatients (SZ) with persistent AVHs following nicotine (6mg) and placebo administration. Electrical activity was recorded from 32 scalp electrodes; MMN amplitudes and latencies for each deviant were compared between treatments and were correlated with trait (PSYRATS) and state measures of AVH severity and Positive and Negative Syndrome Scale (PANSS) ratings. Nicotine administration resulted in a shortened latency for intensity MMN. Additionally, nicotine-related change in MMN amplitude was correlated with nicotine-related change in subjective measures of hallucinatory state. In summary, nicotine did not affect MMN amplitudes in schizophrenia patients with persistent AVHs, however this study reports accelerated auditory change detection to intensity deviants with nicotine in this group. Additionally, nicotine appeared to induce a generalized activation of the auditory cortex in schizophrenia, resulting in a concurrent increase in intensity MMN amplitude and subjective clarity of AVHs.     

Auditory verbal hallucinations and the interhemispheric auditory pathway in chronic schizophrenia

Objectives. The interhemispheric auditory pathway has been shown to play a crucial role in the processing of acoustic stimuli, and alterations of structural and functional connectivity between bilateral auditory areas are likely relevant to the pathogenesis of auditory verbal hallucinations (AVHs). The aim of this study was to examine this pathway in patients with chronic schizophrenia regarding their lifetime history of AVHs. Methods. DTI scans were acquired from 33 healthy controls (HC), 24 schizophrenia patients with a history of AVHs (LT-AVH) and nine schizophrenia patients without any lifetime hallucinations (N-LT-AVH). The interhemispheric auditory fibre bundles were extracted using streamline tractography. Subsequently, diffusivity indices, namely Fractional Anisotropy (FA), Trace, Mode, Axial and Radial diffusivity, were calculated. Results. FA was decreased over the entire pathway in LT-AVH compared with N-LT-AVH. Moreover, LT-AVH displayed decreased FA and Mode as well as increased radial diffusivity in the midsagittal section of the fibre tract. Conclusions. These findings indicate complex microstructural changes in the interhemispheric auditory pathway of schizophrenia patients with a history of AVHs. Alterations appear to be absent in patients who have never hallucinated.     

Dysregulation of working memory and default‐mode networks in schizophrenia using independent component analysis,an fBIRN and MCIC study

Deficits in working memory (WM) are a consistent neurocognitive marker for schizophrenia. Previous studies have suggested that WM is the product of coordinated activity in distributed functionally connected brain regions. Independent component analysis (ICA) is a data‐driven approach that can identify temporally coherent networks that underlie fMRI activity. We applied ICA to an fMRI dataset for 115 patients with chronic schizophrenia and 130 healthy controls by performing the Sternberg Item Recognition Paradigm. Here, we describe the first results using ICA to identify differences in the function of WM networks in schizophrenia compared to controls. ICA revealed six networks that showed significant differences between patients with schizophrenia and healthy controls. Four of these networks were negatively task‐correlated and showed deactivation across the posterior cingulate, precuneus, medial prefrontal cortex, anterior cingulate, inferior parietal lobules, and parahippocampus. These networks comprise brain regions known as the default‐mode network (DMN), a well‐characterized set of regions shown to be active during internal modes of cognition and implicated in schizophrenia. Two networks were positively task‐correlated, with one network engaging WM regions such as bilateral DLPFC and inferior parietal lobules while the other network engaged primarily the cerebellum. Our results suggest that DLPFC dysfunction in schizophrenia might be lateralized to the left and intrinsically tied to other regions such as the inferior parietal lobule and cingulate gyrus. Furthermore, we found that DMN dysfunction in schizophrenia exists across multiple subnetworks of the DMN and that these subnetworks are individually relevant to the pathophysiology of schizophrenia. In summary, this large multsite study identified multiple temporally coherent networks, which are aberrant in schizophrenia versus healthy controls and suggests that both task‐correlated and task‐anticorrelated networks may serve as potential biomarkers. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.     

Auditory Verbal Hallucinations and Brain Dysconnectivity in the Perisylvian Language Network: A Multimodal Investigation

Neuroimaging studies of schizophrenia have indicated that the development of auditory verbal hallucinations (AVHs) is associated with altered structural and functional connectivity within the perisylvian language network. However, these studies focussed mainly on either structural or functional alterations in patients with chronic schizophrenia. Therefore, they were unable to examine the relationship between the 2 types of measures and could not establish whether the observed alterations would be expressed in the early stage of the illness.We used diffusion tensor imaging and functional magnetic resonance imaging to examine white matter integrity and functional connectivity within the left perisylvian language network of 46 individuals with an at risk mental state for psychosis or a first episode of the illness, including 28 who had developed AVH group and 18 who had not (nonauditory verbal hallucination [nAVH] group), and 22 healthy controls. Inferences were made at P < .05 (corrected). The nAVH group relative to healthy controls showed a reduction of both white matter integrity and functional connectivity as well as a disruption of the normal structure−function relationship along the fronto-temporal pathway. For all measures, the AVH group showed intermediate values between healthy controls and the nAVH group. These findings seem to suggest that, in the early stage of the disorder, a significant impairment of fronto-temporal connectivity is evident in patients who do not experience AVHs. This is consistent with the hypothesis that, whilst mild disruption of connectivity might still enable the emergence of AVHs, more severe alterations may prevent the occurrence of the hallucinatory experience.Key words: connectivity, auditory verbal hallucinations, psychosis     

Connectivity patterns during music listening: Evidence for action‐based processing in musicians

Musical expertise is visible both in the morphology and functionality of the brain. Recent research indicates that functional integration between multi‐sensory, somato‐motor, default‐mode (DMN), and salience (SN) networks of the brain differentiates musicians from non‐musicians during resting state. Here, we aimed at determining whether brain networks differentially exchange information in musicians as opposed to non‐musicians during naturalistic music listening. Whole‐brain graph‐theory analyses were performed on participants' fMRI responses. Group‐level differences revealed that musicians' primary hubs comprised cerebral and cerebellar sensorimotor regions whereas non‐musicians' dominant hubs encompassed DMN‐related regions. Community structure analyses of the key hubs revealed greater integration of motor and somatosensory homunculi representing the upper limbs and torso in musicians. Furthermore, musicians who started training at an earlier age exhibited greater centrality in the auditory cortex, and areas related to top‐down processes, attention, emotion, somatosensory processing, and non‐verbal processing of speech. We here reveal how brain networks organize themselves in a naturalistic music listening situation wherein musicians automatically engage neural networks that are action‐based while non‐musicians use those that are perception‐based to process an incoming auditory stream. Hum Brain Mapp 38:2955–2970, 2017. © 2017 Wiley Periodicals, Inc.     

Auditory verbal hallucinations in schizophrenia as aberrant lateralized speech perception: evidence from dichotic listening

We report evidence that auditory verbal hallucinations (AVH) in schizophrenia patients are perceptual distortions lateralized to the left hemisphere. We used a dichotic listening task with repeated presentations of consonant-vowel syllables, a different syllable in the right and left ear. This task produces more correct reports for the right ear syllable in healthy individuals, indicative of left hemisphere speech processing focus. If AVHs are lateralized to the left hemisphere language receptive areas, then this should interfere with correct right ear reports in the dichotic task, which would result in significant negative correlations with severity of AVHs. We correlated the right and left ear correct reports with the PANSS hallucination symptom, and a randomly selected negative symptom, in addition to the sum total of the positive and negative symptoms, in 160 patients with schizophrenia. The results confirmed the predictions with significant negative correlations for the right ear scores with the PANSS hallucination item, and for the sum total of positive symptoms, while all other correlations were close to zero. The results are unambiguous evidence for AVHs as aberrant speech perceptions originating in the left hemisphere.     

Are auditory-verbal hallucinations associated with auditory affective processing deficits?

We investigated whether the presence of auditory-verbal hallucinations (AVH) was associated with impaired auditory affect perception. Controls, schizophrenia patients with a history of AVH (AVH) or with no history of AVH (NAVH) completed four perceptual auditory affect tasks. The tasks used either non-verbal/non-semantic or verbal/semantic stimuli. AVH patients showed significant impairments on a non-verbal task requiring the recognition of environmental sounds, this was particularly so for the affective stimuli and not the neutral valance stimuli. Thus, confirming auditory affect deficits in AVH patients. AVH patients also showed reduced right ear performance on a dichotic listening task. Conversely, both patient groups showed impairments on auditory affect tasks that used verbal/semantic stimuli; as these tasks require proficient semantic processing we speculated that significant semantic impairments in schizophrenia masked the additional auditory affect deficits present in the AVH group. The overall results support the notion that patients with AVH have increased liability for auditory affect perception deficits.     

Investigation of the neural substrates of voice recognition in Chinese schizophrenic patients with auditory verbal hallucinations: an event-related functional MRI study

Objective: Auditory hallucinations (AVHs), like real auditory perceptions, are often perceived as familiar voices. Given that neural correlates of AVHs involve the auditory cortex, it is likely that those brain regions responsible for recognition of voice identity are invoked during AVHs. Method: Schizophrenic patients with (n = 13) and without (n = 13) auditory hallucinations, and 13 healthy subjects performed a voice recognition task during functional magnetic resonance imaging at 1.5 T. In the task using prerecorded vocal stimuli, they classified voice as familiar and unfamiliar. Results: Under the familiar minus unfamiliar contrasts, cerebral activation pattern is different in the three groups and patients with auditory hallucinations showed less activation in the right temporal lobe than controls. Conclusion: Voice recognition was impaired in patients with AVHs. Our results support that auditory association cortices play a role in the perception of AVHs.     

Aberrations in the arcuate fasciculus are associated with auditory verbal hallucinations in psychotic and in non‐psychotic individuals

The pathophysiology of auditory verbal hallucinations (AVH) is still unclear. Cognitive as well as electrophysiological studies indicate that a defect in sensory feedback (corollary discharge) may contribute to the experience of AVH. This could result from disruption of the arcuate fasciculus, the major tract connecting frontal and temporo‐parietal language areas. Previous diffusion tensor imaging studies indeed demonstrated abnormalities of this tract in schizophrenia patients with AVH. It is, however, difficult to disentangle specific associations with AVH in this patient group as many other factors, such as other positive and negative symptoms, medication or halted education could likewise have affected tract integrity. We therefore investigated AVH in relative isolation and studied a group of non‐psychotic individuals with AVH as well as patients with AVH and non‐hallucinating matched controls. We compared tract integrity of the arcuate fasiculus and of three other control tracts, between 35 non‐psychotic individuals with AVH, 35 schizophrenia patients with AVH, and 36 controls using diffusion tensor imaging and magnetization transfer imaging. Both groups with AVH showed an increase in magnetization transfer ratio (MTR) in the arcuate fasciculus, but not in the other control tracts. In addition, a general decrease in fractional anisotropy (FA) for almost all bundles was observed in the patient group, but not in the non‐psychotic individuals with AVH. As increased MTR in the arcuate fasciculus was present in both hallucinating groups, a specific association with AVH seems plausible. Decreases in FA, on the other hand, seem to be related to other disease processes of schizophrenia. Hum Brain Mapp, 2013. © 2011 Wiley Periodicals, Inc.     

About the mechanisms of auditory verbal hallucinations: a positron emission tomographic study

OBJECTIVE: Auditory verbal hallucinations (AVHs) likely result from disorders, as yet unspecified, of the neural mechanisms of language. Here we examine the functional neuroanatomy of single-word reading in patients with and without a history of AVH. METHOD: Eighteen medicated schizophrenia patients (8 with AVH and 10 without AVH) and 12 healthy control subjects were scanned with PET (15)O-water technique under 2 conditions: reading aloud English nouns and passively looking at English nouns without reading them. RESULTS: The contrast between the 2 conditions shows higher activation in Wernicke's area during the reading condition in the patient group and a reversed laterality index for the supplementary motor area in the AVH group. CONCLUSIONS: These findings provide indications about the possible mechanisms of AVH. We suggest that the abnormal laterality of the supplementary motor area activity accounts for the failure to attribute speech generated by one's own brain to one's self and that the activation of Wernicke's area accounts for the perceptual nature (hearing) of the patient's experience.