Modality specific neural correlates of auditory and somatic hallucinations

The insula: Leveraging cellular and systems-level research to better understand its roles in health and schizophrenia

Schizophrenia is a highly heterogeneous disorder characterized by a multitude of complex and seemingly non-overlapping symptoms. The insular cortex has gained increasing attention in neuroscience and psychiatry due to its involvement in a diverse range of fundamental human experiences and behaviors. This review article provides an overview of the insula's cellular and anatomical organization, functional and structural connectivity, and functional significance. Focusing on specific insula subregions and using knowledge gained from humans and preclinical studies of insular tracings in non-human primates, we review the literature and discuss the functional roles of each subregion, including in somatosensation, interoception, salience processing, emotional processing, and social cognition. Building from this foundation, we then extend these findings to discuss reported abnormalities of these functions in individuals with schizophrenia, implicating insular involvement in schizophrenia pathology. This review underscores the insula's vast role in the human experience and how abnormal insula structure and function could result in the wide-ranging symptoms observed in schizophrenia.

Is it really on your hand? Spontaneous sensations are not peripheral sensations - Evidence from able-bodied individuals and a phantom limb syndrome patient

Among other bodily signals, the perception of sensations arising spontaneously on the skin with no external triggers contributes to body awareness. The topic of spontaneous sensations (SPS) being quite recent in the literature, there is still a debate whether this phenomenon is elicited by peripheral cutaneous units' activity underlying tactile perception or originates directly from central mechanisms. In a first experiment, we figured that, if SPS depended on peripheral afferents, their perception on the glabrous hand should relate to the hand tactile sensitivity. On the contrary, we found no relationship at all, which led us to envisage the scenario of SPS in the absence of cutaneous units. In a second experiment, we present the case of Julie, a right-hand amputee that could perceive and report SPS arising on her phantom limb syndrome. We found that SPS distribution on the phantom limb followed the same gradient as that observed in control participants, unlike SPS perceived on the intact left hand. Those findings are crucial to the understanding of neural factors determining body awareness through SPS perception and provide insights into the existence of a precise neural gradient underlying somesthesis.

The hearing hippocampus

The hippocampus has a well-established role in spatial and episodic memory but a broader function has been proposed including aspects of perception and relational processing. Neural bases of sound analysis have been described in the pathway to auditory cortex, but wider networks supporting auditory cognition are still being established. We review what is known about the role of the hippocampus in processing auditory information, and how the hippocampus itself is shaped by sound. In examining imaging, recording, and lesion studies in species from rodents to humans, we uncover a hierarchy of hippocampal responses to sound including during passive exposure, active listening, and the learning of associations between sounds and other stimuli. We describe how the hippocampus' connectivity and computational architecture allow it to track and manipulate auditory information - whether in the form of speech, music, or environmental, emotional, or phantom sounds. Functional and structural correlates of auditory experience are also identified. The extent of auditory-hippocampal interactions is consistent with the view that the hippocampus makes broad contributions to perception and cognition, beyond spatial and episodic memory. More deeply understanding these interactions may unlock applications including entraining hippocampal rhythms to support cognition, and intervening in links between hearing loss and dementia.

Cues to body-related distortions and hallucinations? Spontaneous sensations correlate with EEG oscillatory activity recorded at rest in the somatosensory cortices

Body awareness may arise in the total absence of sensory input, as suggested by the spontaneous occurrence of normal and pathological (i.e., hallucinatory) bodily sensations. These phenomena may arise due to back-projections from higher-order cortical areas to the primary (SI) and secondary (SII) somatosensory cortices, and would appear to be reflected in cortical oscillatory activity in both SI and SII. Here, we set to investigate the relationship of SI and SII in SPS. Healthy participants underwent an EEG recording session at rest, and then completed an experiment on the perception of spontaneous sensations occurring on the hands. Cortical oscillatory activity was extracted from specified ROIs in the somatosensory cortices. The findings showed that (i) SPS perceived in the fingers correlated positively with alpha-band oscillations recorded in SI, and that (ii) SPS perceived in the palm correlated positively with gamma-band oscillations and negatively with beta-band oscillations recorded in SII. Apart from supporting the idea that the somatosensory cortices are involved in bodily awareness even in the absence of sensory input, these findings also suggest that default oscillatory activity in the somatosensory cortices reflects individual differences in bodily awareness. The results are interpreted in terms of neural and cognitive processes that may give rise to bodily awareness and modulate it, and their importance in understanding body perception distortions and bodily delusions and hallucinations is discussed.

Tactile and Somatic Hallucinations in a Muslim Population of Psychotic Patients

Background: Tactile and somatic hallucinations are distressing phenomena that have hardly been researched. The few studies that have been published focus on their occurrence in neurodegenerative disorders and substance use, and, surprisingly, not on schizophrenia spectrum disorders. Objective: To fill this gap in our knowledge, we sought to explore the phenomenological characteristics of tactile and somatic hallucinations in a group of psychotic Muslim patients. Since many Muslims attribute such experiences to jinn (invisible spirits) and jinn are often perceived in multiple sensory modalities, we not only charted the involvement of the tactile and somatic modalities but also their interrelatedness with hallucinations in other sensory modalities. Methods: We performed a cross-sectional study using a semi-structured interview and dedicated questionnaire. Results: Of the 42 Muslim inpatients mostly diagnosed with a schizophrenia spectrum disorder, 62% reported to suffer from tactile and/or somatic hallucinations. Their phenomenological characteristics varied, with 96% being multimodal in nature and 38% taking the form of full-blown entity/jinn encounters. In comparison to other entity experiences, the involvement of the tactile and somatic modalities was exceptionally high, as was the level of ensuing distress. Regarding the order of recruitment of the various sensory modalities, we suggest the involvement of an underlying stochastic process. Conclusion: Muslim patients with severe psychosis can have tactile and somatic hallucinations, of which a large number are multimodal or full-blown entity/jinn encounters, which are almost invariably appreciated as harrowing. On the basis of our findings we make recommendations for further research and clinical practice.

Localization of Early-Stage Visual Processing Deficits at Schizophrenia Spectrum Illness Onset Using Magnetoencephalography

Impairments in early-stage visual processing are observed in chronic psychosis. However, their presence, localization within the brain, and contribution to cognitive symptoms remain less well established early in disease course. The present study utilized magnetoencephalography (MEG) to examine sensory responses within primary visual cortex (V1). MEG was recorded from 38 individuals diagnosed with a schizophrenia spectrum illness at first psychotic episode (FESz) and 38 matched healthy controls (HC) during visual search tasks. The inverse solution for cortical activity contributing to the M100 visual evoked field was derived. Task performance and V1 activation were compared between groups. FESz exhibited a reduced V1 response relative to HC. This group deficit, however, was selective for the left hemisphere (LH). A similar interaction was observed for response time with FESz exhibiting slower responses to right visual field targets, a difference not observed among HC. Among FESz, larger LH V1 activity was associated with larger hallucination subscale scores on the Scale for the Assessment of Positive Symptoms. Early-stage visual processing deficits localized to V1 are present at disease onset in the schizophrenia spectrum. This impairment appears to be restricted to the LH, consistent with previous reports detailing a predominantly LH disease process in early psychosis, and activity within this region was associated with an increased experience of hallucinations. These findings detail the cortical responses contributing to visual processing impairments and their relationship with symptoms at disease onset, advancing our understanding of their developmental trajectory over the course of psychotic illness.

Differences between ketamine's short-term and long-term effects on brain circuitry in depression

Ketamine acts as a rapid clinical antidepressant at 25 min after injection with effects sustained for 7 days. As dissociative effects emerging acutely after injection are not entirely discernible from therapeutic action, we aimed to dissect the differences between short-term and long-term response to ketamine to elucidate potential imaging biomarkers of ketamine's antidepressant effect. We used a genetical model of depression, in which we bred depressed negative cognitive state (NC) and non-depressed positive cognitive state (PC) rat strains. Four parallel rat groups underwent stress-escape testing and a week later received either S-ketamine (12 NC, 13 PC) or saline (12 NC, 12 PC). We acquired resting-state functional magnetic resonance imaging time series before injection and at 30 min and 48 h after injection. Graph analysis was used to calculate brain network properties. We identified ketamine's distinct action over time in a qualitative manner. The rapid response entailed robust and strain-independent topological modifications in cognitive, sensory, emotion, and reward-related circuitry, including regions that exhibited correlation of connectivity metrics with depressive behavior, and which could explain ketamine's dissociative and antidepressant properties. At 48 h ketamine had mainly strain-specific action normalizing habenula, midline thalamus, and hippocampal connectivity measures in depressed rats. As these nodes mediate cognitive flexibility impaired in depression, action within this circuitry presumably reflects ketamine's procognitive effects induced only in depressed patients. This finding is especially valid, as our model represents cognitive aspects of depression. These empirically defined circuits explain ketamine's distinct action over time and might serve as translational imaging correlates of antidepressant response in preclinical testing.

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.

Self-touch: Contact durations and point of touch of spontaneous facial self-touches differ depending on cognitive and emotional load

Every human being spontaneously touches its eyes, cheeks, chin and mouth manifold every day. These spontaneous facial self-touches (sFST) are elicited with little or no awareness and are distinct from gestures and instrumental acts. Self-touch frequency has been shown to be influenced by negative affect and attention distraction and may be involved in regulating emotion and working memory functions. Yet, even though self-touch research dates back several decades fundamental aspects, like the temporal progression of sFST or the effects of executing hand and touched face area, have not yet been analyzed. For the first time, the present study measured sFST temporal aspects to the millisecond using accelerometers and EMG. Spontaneous self-touch was triggered in sixty participants who completed a delayed memory task of complex haptic relief stimuli while listening to distracting aversive sounds. We found that while both hands were used equally often and with the same overall movement times and contact durations, significant effects occurred for face area in both frequency and contact durations. Ergo the point of touch seems to have some relevance of its own, independently of which hand is used to perform it. The results show that not only frequency but also the point of touch and contact durations are influenced by cognitive and emotional demands. We argue that investigating the fundamental characteristics of sFST will further the understanding of cognitive focusing and attentional mechanisms.

The role of the inferior frontal gyrus in vicarious social touch: A transcranial direct current stimulation (tDCS) study

The neural mechanisms facilitating the experience of vicarious social touch are largely unknown. The right inferior frontal gyrus (rIFG) has been suggested as part of a simulation observation-execution neural network that plays a key role in the perception of tactile stimuli. Considering that vicarious social touch involves vicarious sharing of emotions, we hypothesized that emotional empathy, i.e., the ability to feel what another individual is feeling, modulates the neural responses to vicarious touch. To examine the role of the rIFG in vicarious touch and its modulation by levels of emotional empathy, we used anodal transcranial direct current stimulation (tDCS) on forty participants who observed photos depicting social touch, nonsocial touch or no touch during tDCS or sham stimulation. The results show that while participants with high levels of emotional empathy exhibited no change in ratings of vicarious social touch, participants with low levels of emotional empathy rate human touch as more emotional following anodal stimulation of the rIFG than following sham stimulation. These findings indicate that emotional responses to vicarious social touch are associated with rIFG activity and are modulated by levels of emotional empathy. This result has major therapeutic potential for individuals with low empathic abilities, such as those with ASD.

All in the mind? The neural correlates of unexplained physical symptoms

Physical symptoms with no medical explanation are commonly experienced by healthy people and those attending clinics. Psychiatrists see such patients in liaison settings and clinics for those with psychotic and affective disorders. The pathophysiology remains obscure; physical investigations are usually performed to exclude pathology rather than elucidate dysfunction. However, modern neuroimaging has allowed the study of nervous system structure and function. Although there are few diagnostically specific findings, patterns of association have emerged: where action is impeded (certain forms of conversion disorder and chronic fatigue syndrome) frontal systems of the brain are often implicated; when subjective awareness of the body is disturbed (passivity phenomena and anorexia nervosa) temporo-parietal cortices appear to be dysfunctional. The caudate nuclei (components of the frontal executive circuit) are implicated in a variety of syndromes (including body dysmorphic disorder, somatisation and chronic fatigue). The brain may be viewed as a cognitive neurobiological entity, crucially oriented towards action (for survival). Psychiatric syndromes that have an impact on bodily awareness signal dysfunction within systems representing that body and its performance in time and space.

fMRI capture of auditory hallucinations: Validation of the two-steps method

Our purpose was to validate a reliable method to capture brain activity concomitant with hallucinatory events, which constitute frequent and disabling experiences in schizophrenia. Capturing hallucinations using functional magnetic resonance imaging (fMRI) remains very challenging. We previously developed a method based on a two-steps strategy including (1) multivariate data-driven analysis of per-hallucinatory fMRI recording and (2) selection of the components of interest based on a post-fMRI interview. However, two tests still need to be conducted to rule out critical pitfalls of conventional fMRI capture methods before this two-steps strategy can be adopted in hallucination research: replication of these findings on an independent sample and assessment of the reliability of the hallucination-related patterns at the subject level. To do so, we recruited a sample of 45 schizophrenia patients suffering from frequent hallucinations, 20 schizophrenia patients without hallucinations and 20 matched healthy volunteers; all participants underwent four different experiments. The main findings are (1) high accuracy in reporting unexpected sensory stimuli in an MRI setting; (2) good detection concordance between hypothesis-driven and data-driven analysis methods (as used in the two-steps strategy) when controlled unexpected sensory stimuli are presented; (3) good agreement of the two-steps method with the online button-press approach to capture hallucinatory events; (4) high spatial consistency of hallucinatory-related networks detected using the two-steps method on two independent samples. By validating the two-steps method, we advance toward the possible transfer of such technology to new image-based therapies for hallucinations. Hum Brain Mapp 38:4966-4979, 2017. © 2017 Wiley Periodicals, Inc.

Brain Mechanisms of Reality Monitoring

Reality monitoring processes are necessary for discriminating between internally generated information and information that originated in the outside world. They help us to identify our thoughts, feelings, and imaginations, and to distinguish them from events we may have experienced or have been told about by someone else. Reality monitoring errors range from confusions between real and imagined experiences, that are byproducts of normal cognition, to symptoms of mental illness such as hallucinations. Recent advances support an emerging neurocognitive characterization of reality monitoring that provides insights into its underlying operating principles and neural mechanisms, the differing ways in which impairment may occur in health and disease, and the potential for rehabilitation strategies to be devised that might help those who experience clinically significant reality monitoring disruption.

The neural mechanisms of hallucinations: A quantitative meta-analysis of neuroimaging studies

Activation likelihood estimation meta-analysis of functional neuroimaging data was used to investigate the neural mechanisms underlying auditory-verbal and visual hallucinations (AVHs and VHs). Consistent activation across studies during AVHs, but not VHs, in Wernicke's and Broca's areas is consistent with involvement of speech and language processes in the experience of hearing voices when none are present. Similarly, greater activity in auditory cortex during AVHs and in visual cortex during VHs supports models proposing over-stimulation of sensory cortices in the generation of these perceptual anomalies. Activation across studies in the medial temporal lobe highlights a role for memory intrusions in the provision of content for AVHs, whereas insula activation may relate to the involvement of awareness and self-representation. Finally, activation in the paracingulate region of medial prefrontal cortex during AVHs is consistent with models implicating reality monitoring impairment in the misattribution of self-generated information as externally perceived. In the light of the results, the need for unified theoretical frameworks that account for the full range of hallucinatory experiences is discussed.

A Cognitive Neuroscience View of Voice-Processing Abnormalities in Schizophrenia: A Window into Auditory Verbal Hallucinations?

Auditory verbal hallucinations (AVH) are a core symptom of schizophrenia. Like "real" voices, AVH carry a rich amount of linguistic and paralinguistic cues that convey not only speech, but also affect and identity, information. Disturbed processing of voice identity, affective, and speech information has been reported in patients with schizophrenia. More recent evidence has suggested a link between voice-processing abnormalities and specific clinical symptoms of schizophrenia, especially AVH. It is still not well understood, however, to what extent these dimensions are impaired and how abnormalities in these processes might contribute to AVH. In this review, we consider behavioral, neuroimaging, and electrophysiological data to investigate the speech, identity, and affective dimensions of voice processing in schizophrenia, and we discuss how abnormalities in these processes might help to elucidate the mechanisms underlying specific phenomenological features of AVH. Schizophrenia patients exhibit behavioral and neural disturbances in the three dimensions of voice processing. Evidence suggesting a role of dysfunctional voice processing in AVH seems to be stronger for the identity and speech dimensions than for the affective domain.

Event-related potentials elicited by the Deutsch "high-low" word illusion in the patients with first-episode schizophrenia with auditory hallucinations

BACKGROUND

The exact cerebral structural and functional mechanisms under the auditory verbal hallucinations (AVHs) in schizophrenia are still unclear. The Deutsch "high-low" word illusion might trigger attentional responses mimicking those under AVHs.

METHODS

We therefore have invited 16 patients with first-episode, paranoid schizophrenia, and 16 age- and gender-matched healthy volunteers to undergo the "oddball" event-related potentials elicited by the illusion. The clinical characteristics of patients were measured with the positive and negative symptom scale.

RESULTS

Besides the longer reaction time to the illusion, the standard P2 latency was shortened, the N2 latency was prolonged, and both N1 and P3 amplitudes were reduced in patients. The P3 source analyses showed the activated bilateral temporal lobes, parietal lobe and cingulate cortex in both groups, left inferior temporal gyrus in controls, and left postcentral gyrus in schizophrenia. Moreover, the N1 amplitude was positively correlated with the paranoid score in patients.

CONCLUSIONS

Our results were in line with previous neurophysiological and neuroimaging reports of hallucination or auditory processing in schizophrenia, and illustrated a whole process of cerebral information processing from N1 to P3, indicating this illusion had triggered a dynamic cerebral response similar to that of the AVHs had engaged.

Cortical thickness and low insight into symptoms in enduring schizophrenia

Poor insight is a common, multidimensional phenomenon in patients with schizophrenia, associated with poorer outcomes and treatment non-adherence. Yet scant research has investigated the neuronal correlates of insight into symptoms (IS), a dimension of insight that may be particularly significant in enduring schizophrenia. Sixty-six patients with enduring schizophrenia (duration >4years) and 33 healthy controls completed MRI scanning and IQ, depression, and anxiety assessments. The Scale to Assess Insight-Expanded (SAI-E) measured insight into patients' four most prominent symptoms and patients were classified into two groups: low IS (0-2; n=33), and high IS (>2; n=33). We evaluated the association between cortical thickness (CT) and insight into symptoms using two methods: (1) a between-patients region-of-interest analysis in the insula, superior temporal gyrus (STG) and frontal lobe; and (2) a whole-brain exploratory regression between patient and controls. Brain regions were segmented using a neuroanatomical atlas and vertex-wise CT analyses were conducted with CIVET, covaried for age and sex. ROI analysis revealed thinner insula cortex in patients with low IS (p<0.05, surviving FDR correction). Patients with low IS also showed significantly thinner right insula, STG, and parahippocampal cortex compared to healthy controls (p<0.05, surviving FDR correction). Regions of observed CT reductions have been hypothesized to subserve self-monitoring, error awareness, and ability to identify hallucinations. Results highlight an important association between right insula abnormalities and impaired IS in schizophrenia. The diverse clinical presentation of patients further suggests an independent relationship between symptomology and insight-related differences in CT that has been previously unexplored in enduring schizophrenia.

Phenomenologically distinct psychotomimetic effects of ketamine are associated with cerebral blood flow changes in functionally relevant cerebral foci: a continuous arterial spin labelling study

RATIONALE

The N-methyl-D-aspartate (NMDA) receptor antagonist ketamine provides a pragmatic approach to address the link between glutamate-mediated changes in brain function and psychosis-like experiences. Most studies using PET or BOLD fMRI have assessed these symptoms broadly, which may limit inference about specific mechanisms.

OBJECTIVES

The objective of this study is to identify the cerebral blood flow (CBF) correlates of ketamine-induced psychopathology, focusing on individual psychotomimetic symptom dimensions, which may have separable neurobiological substrates.

METHODS

We measured validated psychotomimetic symptom factors following intravenous ketamine administration in 23 healthy male volunteers (10 given a lower dose and 13 a higher dose) and correlated ketamine-induced changes in symptoms with regional changes in CBF, measured non-invasively using arterial spin labelling (ASL).

RESULTS

The main effect of ketamine paralleled previous studies, with increases in CBF in anterior and subgenual cingulate cortex and decreases in superior and medial temporal cortex. Subjective effects were greater in the high-dose group. For this group, ketamine-induced anhedonia inversely related to orbitofrontal cortex CBF changes and cognitive disorganisation was positively correlated with CBF changes in posterior thalamus and the left inferior and middle temporal gyrus. Perceptual distortion was correlated with different regional CBF changes in the low- and high-dose groups.

CONCLUSIONS

Here, we provide evidence for the sensitivity of ASL to the effects of ketamine and the strength of subjective experience, suggesting plausible neural mechanisms for ketamine-induced anhedonia and cognitive disorganisation.

Common coding and dynamic interactions between observed, imagined, and experienced motor and somatosensory activity

Motor imagery and perception - considered generally as forms of motor simulation - share overlapping neural representations with motor production. While much research has focused on the extent of this "common coding," less attention has been paid to how these overlapping representations interact. How do imagined, observed, or produced actions influence one another, and how do we maintain control over our perception and behavior? In the first part of this review we describe interactions between motor production and motor simulation, and explore apparent regulatory mechanisms that balance these processes. Next, we consider the somatosensory system. Numerous studies now support a "sensory mirror system" comprised of neural representations activated by either afferent sensation or vicarious sensation. In the second part of this review we summarize evidence for shared representations of sensation and sensory simulation (including imagery and observed sensation), and suggest that similar interactions and regulation of simulation occur in the somatosensory domain as in the motor domain. We suggest that both motor and somatosensory simulations are flexibly regulated to support simulations congruent with our sensorimotor experience and goals and suppress or separate the influence of those that are not. These regulatory mechanisms are frequently revealed by cases of brain injury but can also be employed to facilitate sensorimotor rehabilitation.

Hearing disorders in brainstem lesions

Auditory processing can be disrupted by brainstem lesions. It is estimated that approximately 57% of brainstem lesions are associated with auditory disorders. However diseases of the brainstem usually involve many structures, producing a plethora of other neurologic deficits, often relegating "auditory symptoms in the background." Lesions below or within the cochlear nuclei result in ipsilateral auditory-processing abnormalities detected in routine testing; disorders rostral to the cochlear nuclei may result in bilateral abnormalities or may be silent. Lesions in the superior olivary complex and trapezoid body show a mixture of ipsilateral, contralateral, and bilateral abnormalities, whereas lesions of the lateral lemniscus, inferior colliculus, and medial geniculate body do not affect peripheral auditory processing and result in predominantly subtle contralateral abnormalities that may be missed by routine auditory testing. In these cases psychophysical methods developed for the evaluation of central auditory function should be employed (e.g., dichotic listening, interaural time perception, sound localization). The extensive connections of the auditory brainstem nuclei not only are responsible for binaural interaction but also assure redundancy in the system. This redundancy may explain why small brainstem lesions are sometimes clinically silent. Any disorder of the brainstem (e.g., neoplasms, vascular disorders, infections, trauma, demyelinating disorders, neurodegenerative diseases, malformations) that involves the auditory pathways and/or centers may produce hearing abnormalities.

Central mechanisms of itch

Itch is a complex sensory and emotional experience. Functional brain imaging studies have been performed to identify brain regions associated with this complex experience, and these studies reported that several brain regions are activated by itch stimuli. The possible roles of these regions in itch perception and difference in cerebral mechanism between healthy subjects and chronic itch patients are discussed in this review article. Additionally, the central itch modulation system and cerebral mechanisms of contagious itch, pleasurable sensation evoked by scratching have also been investigated in previous brain imaging studies. We also discuss how these studies advance our understanding of these mechanisms.

From tones in tinnitus to sensed social interaction in schizophrenia: how understanding cortical organization can inform the study of hallucinations and psychosis

The content, modality, and perceptual attributes of hallucinations and other psychotic symptoms may be related to neural representation at a single cell and population level in the cerebral cortex. A brief survey of some principles and examples of cortical representation and organization will be presented together with evidence for a correspondence between the neurobiology of brain areas activated at the time of a hallucination and the content of the corresponding hallucinatory and psychotic experiences. Contrasting the hallucinations of schizophrenia with other conditions, we highlight phenomenological aspects of hallucinations that are ignored in clinical practice but carry potentially important information about the brain regions and dysfunctions underlying them. Knowledge of cortical representation and organization are being used to develop animal models of hallucination and to test treatments that are now beginning to translate to the clinical domain.

Neuroprogression in schizophrenia: Pathways underpinning clinical staging and therapeutic corollaries

OBJECTIVE

Whilst dopaminergic dysfunction remains a necessary component involved in the pathogenesis of schizophrenia, our current pharmacological armoury of dopamine antagonists does little to control the negative symptoms of schizophrenia. This suggests other pathological processes must be implicated. This paper aims to elaborate on such theories.

METHODS

Data for this review were sourced from the electronic database PUBMED, and was not limited by language or date of publication.

RESULTS

It has been suggested that multiple 'hits' may be required to unveil the clinical syndrome in susceptible individuals. Such hits potentially first occur in utero, leading to neuronal disruption, epigenetic changes and the establishment of an abnormal inflammatory response. The development of schizophrenia may therefore potentially be viewed as a neuroprogressive response to these early stressors, driven on by changes in tryptophan catabolite (TRYCAT) metabolism, reactive oxygen species handling and N-methyl d-aspartate (NMDA) circuitry. Given the potential for such progression over time, it is prudent to explore the new treatment strategies which may be implemented before such changes become established.

CONCLUSIONS

Outside of the dopaminergic model, the potential pathogenesis of schizophrenia has yet to be fully elucidated, but common themes include neuropil shrinkage, the development of abnormal neuronal circuitry, and a chronic inflammatory state which further disrupts neuronal function. Whilst some early non-dopaminergic treatments show promise, none have yet to be fully studied in appropriately structured randomized controlled trials and they remain little more than potential attractive targets.

When doctors cry wolf: a systematic review of the literature on clinical lycanthropy

This paper provides an overview and critical reassessment of the cases of clinical lycanthropy reported in the medical literature from 1850 onwards. Out of 56 original case descriptions of metamorphosis into an animal, only 13 fulfilled the criteria of clinical lycanthropy proper. The remaining cases constituted variants of the overarching class of clinical zoanthropy. Forty-seven cases involved primary delusions, and nine secondary delusions on the basis of somatic and/or visual hallucinations which may well have affected the patients' sense of physical existence, also known as coenaesthesis. Cases of secondary delusions in particular warrant proper somatic and auxiliary investigations to rule out any underlying organic pathology, notably in somatosensory areas and those representing the body scheme.

Is Central Auditory Processing Disorder Present in Psychosis?

Purpose

The scope of this study was to trace central auditory processing issues in patients with first-episode psychosis using a psychoacoustic test battery approach.

Method

Patients ( n = 17) and volunteer control subjects ( n = 17) with no personal or family history of schizophrenia were included in the study on the basis of normal hearing sensitivity. The authors implemented a central auditory processing battery consisting of monaural and binaural tests with verbal and nonverbal stimuli.

Results

Perceptual deficits in both nonverbal and verbal auditory stimuli are reported in this study, with temporal central auditory processing deficits and a mean left-ear advantage documented in the patient group.

Conclusion

This study points to the possibility of the existence of central auditory processing deficits in first-episode psychosis leading to schizophrenia. Audiologists should be aware of the psychiatric research pointing to enhanced verbal memory as a result of auditory training, linking bottom-up remediation with top-down improvement.

Cortical grey matter and subcortical white matter brain microstructural changes in schizophrenia are localised and age independent: a case-control diffusion tensor imaging study

It is still unknown whether the structural brain impairments that characterize schizophrenia (SZ) worsen during the lifetime. Here, we aimed to describe age-related microstructural brain changes in cortical grey matter and subcortical white matter of patients affected by SZ. In this diffusion tensor imaging study, we included 69 patients diagnosed with SZ and 69 healthy control (HC) subjects, age and gender matched. We carried out analyses of covariance, with diagnosis as fixed factor and brain diffusion-related parameters as dependent variables, and controlled for the effect of education. White matter fractional anisotropy decreased in the entire age range spanned (18–65 years) in both SZ and HC and was significantly lower in younger patients with SZ, with no interaction (age by diagnosis) effect in fiber tracts including corpus callosum, corona radiata, thalamic radiations and external capsule. Also, grey matter mean diffusivity increased in the entire age range in both SZ and HC and was significantly higher in younger patients, with no age by diagnosis interaction in the left frontal operculum cortex, left insula and left planum polare and in the right temporal pole and right intracalcarine cortex. In individuals with SZ we found that localized brain cortical and white matter subcortical microstructural impairments appear early in life but do not worsen in the 18–65 year age range.

Fronto-thalamic volumetry markers of somatic delusions and hallucinations in schizophrenia

Although the psychotic phenomena of schizophrenia have been extensively investigated, somatic delusions and hallucinations have seldom been reported and their mechanisms are substantially unexplored. Here, we aimed to identify the brain structural correlates of somatic psychotic phenomena using combined volumetry and diffusivity structural neuroimaging techniques. Seventy-five individuals with a DSM-IV-TR diagnosis of schizophrenia and 75 healthy controls (HC) underwent a comprehensive clinical assessment, a high-resolution T1-weighted magnetic resonance imaging and a diffusion tensor imaging protocol using a 3T MRI scanner. Voxel-based volumetry and mean diffusivity (MD) of gray matter (GM) and fractional anisotropy (FA) of white matter (WM) of the whole brain were calculated for each subject. Reduced left fronto-insular GM volume was found in patients with somatic delusions compared with patients without somatic delusions and HC. Increased GM volume was found in the bilateral thalami, primarily in the right ventral-anterior thalamic nucleus projecting to the prefrontal-temporal cortices and the bilateral pars triangularis of the inferior frontal lobe, of patients with somatic hallucinations and HC compared with patients without somatic hallucinations. No differences emerged in GM MD and in WM FA between patients with and without psychotic somatic phenomena (i.e. delusions or hallucinations). These findings provide the first evidence that a frontal-thalamic structural perturbation mediates somatic psychotic phenomena in schizophrenia.

Exploring psychotic symptoms: a comparison of motor related neuronal activation during and after acute psychosis

BACKGROUND

Delusions and hallucinations are classic positive symptoms of schizophrenia. A contemporary cognitive theory called the 'forward output model' suggests that the misattribution of self-generated actions may underlie some of these types of symptoms, such as delusions of control - the experience of self-generated action being controlled by an external agency. In order to examine the validity of this suggestion, we performed a longitudinal functional magnetic resonance imaging (fMRI) study examining neuronal activation associated with motor movement during acute psychosis.

METHODS

We studied brain activation using fMRI during a motor task in 11 patients with schizophrenia and 9 healthy controls. The patient group was tested at two time points separated by 6-8 weeks.

RESULTS

At initial testing, the patient group had a mean Positive and Negative Syndrome Scale score of 56.3, and showed significantly increased activation within the left inferior parietal lobe (IPL) compared to controls. Patients reported significantly decreased positive symptoms at 6-8 week followup and IPL activation had returned to normal. Our results demonstrate that first-rank positive symptoms are associated with hyperactivation in the secondary somatosensory cortex (IPL).

CONCLUSIONS

These findings lend further credence to the theory that a dysfunction in the sensory feedback system located in the IPL, and which is thought to underlie our sense of agency, may contribute to the aetiology of delusions of control.

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.

Neurofunctional assessment in a stroke patient with musical hallucinations

We reported a case of an elderly female patient affected by musical hallucinations (MHs) as the unique symptom of a right temporal ischemic stroke. A functional magnetic resonance imaging examination was performed in the patient and in five age- and sex-matched normal controls (NC) to detect the complex neural substrate subserving MHs in such a context. Although an activation pattern involving the primary auditory cortex and the temporal associative areas bilaterally was found in the patient and NC, a significant increased activation mostly located in right temporal cortex (in the ischemic area), was observed in the patient. Further functional neuroimaging studies should be performed to detect the complex neural pathways underlying MHs and to find out differences between these hallucinations and real music perception.

Altered integrity of perisylvian language pathways in schizophrenia: relationship to auditory hallucinations

BACKGROUND

Functional neuroimaging supports the hypothesis that auditory verbal hallucinations (AVH) in schizophrenia result from altered functional connectivity between perisylvian language regions, although the extent to which AVH are also associated with an altered tract anatomy is less clear.

METHODS

Twenty-eight patients with schizophrenia subdivided into 17 subjects with a history of AVH and 11 without a history of hallucinations and 59 age- and IQ-matched healthy controls were recruited. The number of streamlines, fractional anisotropy (FA), and mean diffusivity were measured along the length of the arcuate fasciculus and its medial and lateral components.

RESULTS

Patients with schizophrenia had bilateral reduction of FA relative to controls in the arcuate fasciculi (p < .001). Virtual dissection of the subcomponents of the arcuate fasciculi revealed that these reductions were specific to connections between posterior temporal and anterior regions in the inferior frontal and parietal lobe. Also, compared with controls, the reduction in FA of these tracts was highest, and bilateral, in patients with AVH, but in patients without AVH, this reduction was reported only on the left.

CONCLUSIONS

These findings point toward a supraregional network model of AVH in schizophrenia. They support the hypothesis that there may be selective vulnerability of specific anatomical connections to posterior temporal regions in schizophrenia and that extensive bilateral damage is associated with a greater vulnerability to AVH. If confirmed by further studies, these findings may advance our understanding of the anatomical factors that are protective against AVH and predictive of a treatment response.

Hodological resonance, hodological variance, psychosis, and schizophrenia: a hypothetical model

Schizophrenia is a disorder with a large number of clinical, neurobiological, and cognitive manifestations, none of which is invariably present. However it appears to be a single nosological entity. This article considers the likely characteristics of a pathology capable of such diverse consequences. It is argued that both deficit and psychotic symptoms can be manifestations of a single pathology. A general model of psychosis is proposed in which the informational sensitivity or responsivity of a network ("hodological resonance") becomes so high that it activates spontaneously, to produce a hallucination, if it is in sensory cortex, or another psychotic symptom if it is elsewhere. It is argued that this can come about because of high levels of modulation such as those assumed present in affective psychosis, or because of high levels of baseline resonance, such as those expected in deafferentation syndromes associated with hallucinations, for example, Charles Bonnet. It is further proposed that schizophrenia results from a process (probably neurodevelopmental) causing widespread increases of variance in baseline resonance; consequently some networks possess high baseline resonance and become susceptible to spontaneous activation. Deficit symptoms might result from the presence of networks with increased activation thresholds. This hodological variance model is explored in terms of schizo-affective disorder, transient psychotic symptoms, diathesis-stress models, mechanisms of antipsychotic pharmacotherapy and persistence of genes predisposing to schizophrenia. Predictions and implications of the model are discussed. In particular it suggests a need for more research into psychotic states and for more single case-based studies in schizophrenia.

Brain anatomical abnormalities in high-risk individuals, first-episode, and chronic schizophrenia: an activation likelihood estimation meta-analysis of illness progression

OBJECTIVE

The present study reviewed voxel-based morphometry (VBM) studies on high-risk individuals with schizophrenia, patients experiencing their first-episode schizophrenia (FES), and those with chronic schizophrenia. We predicted that gray matter abnormalities would show progressive changes, with most extensive abnormalities in the chronic group relative to FES and least in the high-risk group.

METHOD

Forty-one VBM studies were reviewed. Eight high-risk studies, 14 FES studies, and 19 chronic studies were analyzed using anatomical likelihood estimation meta-analysis.

RESULTS

Less gray matter in the high-risk group relative to controls was observed in anterior cingulate regions, left amygdala, and right insula. Lower gray matter volumes in FES compared with controls were also found in the anterior cingulate and right insula but not the amygdala. Lower gray matter volumes in the chronic group were most extensive, incorporating similar regions to those found in FES and high-risk groups but extending to superior temporal gyri, thalamus, posterior cingulate, and parahippocampal gryus. Subtraction analysis revealed less frontotemporal, striatal, and cerebellar gray matter in FES than the high-risk group; the high-risk group had less gray matter in left subcallosal gyrus, left amygdala, and left inferior frontal gyrus compared with FES. Subtraction analysis confirmed lower gray matter volumes through ventral-dorsal anterior cingulate, right insula, left amygdala and thalamus in chronic schizophrenia relative to FES.

CONCLUSIONS

Frontotemporal brain structural abnormalities are evident in nonpsychotic individuals at high risk of developing schizophrenia. The present meta-analysis indicates that these gray matter abnormalities become more extensive through first-episode and chronic illness. Thus, schizophrenia appears to be a progressive cortico-striato-thalamic loop disorder.

The neuropsychology of hallucinations

Hallucinations are a psychopathological phenomenon with neuropsychological, neuroanatomical and pathophysiological correlates in specific brain areas. They can affect any of the senses, but auditory and visual hallucinations predominate. Verbal hallucinations reveal no gross organic lesions while visual hallucinations are connected to defined brain lesions. Functional neuroimaging shows impairments in modality specific sensory systems with the hyperactivity of the surrounding cerebral cortex. Disinhibition and expansion of the inner speech was noted with impaired internal monitoring in auditory verbal hallucinations. The subcortical areas and modal-specific associative cortex and cingulate cortex are essential for the occurrence of hallucinations.

The role of the insula in schizophrenia

Involvement of the insular cortex is a common finding in neuroanatomical studies of schizophrenia, yet its contribution to disease pathology remains unknown. This review describes the normal function of the insula and examines pathology of this region in schizophrenia. The insula is a cortical structure with extensive connections to many areas of the cortex and limbic system. It integrates external sensory input with the limbic system and is integral to the awareness of the body's state (interoception). Many deficits observed in schizophrenia involve these functions and may relate to insula pathology. Furthermore, reports describing deficits caused by lesions of the insula parallel deficits observed in schizophrenia. Examples of insula-related functions that are altered in schizophrenia include the processing of both visual and auditory emotional information, pain, and neuronal representations of the self. The last of these functions, processing representations of the self, plays a key role in discriminating between self-generated and external information, suggesting that insula dysfunction may contribute to hallucinations, a cardinal feature of schizophrenia.

Insight, grey matter and cognitive function in first-onset psychosis

BACKGROUND

Several studies have suggested that neuropsychological and structural brain deficits are implicated in poor insight. Few insight studies however have combined neurocognitive and structural neuroanatomical measures.

AIMS

Focusing on the ability to relabel psychotic symptoms as pathological, we examined insight, brain structure and neurocognition in first-onset psychosis.

METHOD

Voxel-based magnetic resonance imaging data were acquired from 82 individuals with psychosis and 91 controls assessed with a brief neuropsychological test battery. Insight was measured using the Schedule for the Assessment of Insight.

RESULTS

The principal analysis showed reduced general neuropsychological function was linked to poor symptom relabelling ability. A subsequent between-psychosis group analysis found those with no symptom relabelling ability had significant global and regional grey matter deficits primarily located at the posterior cingulate gyrus and right precuneus/cuneus.

CONCLUSIONS

The cingulate gyrus (as part of a midline cortical system) along with right hemisphere regions may be involved in illness and symptom self-appraisal in first-onset psychosis.

Hyperperfusion in primary somatosensory region related to somatic hallucination in the elderly

AIM

The purpose of the present study was to investigate the regional cerebral blood flow (rCBF) of patients with delusional disorder, somatic type (DDST) exhibiting somatic hallucination.

METHODS

Five patients diagnosed with DDST, as well as 20 control subjects, were examined. All subjects underwent technetium-99m ethyl cysteinate dimer brain perfusion single-photon emission computed tomography. Statistical analysis was performed with SPM5, using a two-sample t-test model to test the regional population effect on rCBF.

RESULTS

Patients with DDST had a significant increase in perfusion in the left post-central gyrus and the right paracentral lobule, both of which are involved in somatic sensory processing.

CONCLUSION

Somatic hallucination might be associated with increased perfusion in the primary somatosensory regions.

White matter abnormalities in first-episode schizophrenia: a combined structural MRI and DTI study

This study examined white matter volume change and integrity jointly in patients with first-episode schizophrenia using an empirically derived region of interest approach and novel Diffusion Tensor Imaging (DTI) geometric indices. Structural images from 103 individuals comprising of 39 patients with first-episode schizophrenia and 64 healthy controls were examined for regions of white matter volume change using voxel-based morphometry (VBM). These regions were then further interrogated for group differences employing geometric indices in addition to fractional anisotropy (FA).VBM analyses revealed that patients with first-episode schizophrenia had lower white matter volume in the right temporal-occipital region (p<0.005) corresponding to the inferior longitudinal fasciculus. Further analyses of diffusion anisotropy in the right temporal-occipital region revealed lower planar anisotropy, and higher linear anisotropy (p=0.012) in patients. FA in the implicated region was also found to be correlated with severity of delusions (r=0.47, p=0.004).We confirmed previous findings of lower white matter volume in the region of inferior longitudinal fasciculus. The presence of changes in geometric diffusion indices in the implicated white matter region suggested that pathophysiological processes which underlie cerebral white matter volume reduction may not be reflected by changes in FA. Further research is needed to better understand the nature of these white matter changes and its progression in schizophrenia over time.

Resting brain perfusion in alcohol-induced psychotic disorder: a comparison in patients with alcohol dependence, schizophrenia and healthy controls

INTRODUCTION

Alcohol-induced psychotic disorder (AIPD), also known as alcohol hallucinosis, is a rare complication of alcohol abuse. The underlying pathophysiology is poorly understood, and the disorder needs to be differentiated from alcohol withdrawal delirium and schizophrenia. No brain-imaging studies in AIPD have been reported to date. Case reports of brain imaging in AIPD suggest possible dysfunction in the thalamus, basal ganglia, frontal lobes and cerebellum. Our aim was to prospectively compare resting brain perfusion (rCBF) in patients with AIPD, uncomplicated alcohol dependence, schizophrenia and healthy volunteers.

METHODS

Single photon emission computed tomography (SPECT) was utilized to compare rCBF in patients with AIPD (n=19), schizophrenia (n=16), uncomplicated alcohol dependence (n=20) and healthy volunteers (n=19).

RESULTS

Increased rCBF was demonstrated in the right calcarine area in patients with AIPD compared to healthy volunteers, with a trend towards increased rCBF to the frontal and temporal lobes and the right pallidum. Decreased left sided rCBF to the putamen, parietal, mid-frontal and mid-temporal lobes and heterogenous flow to the cerebellum were demonstrated in patients with AIPD when compared to patients with uncomplicated alcohol dependence. The left posterior cingulate and right cerebellum showed higher and lower rCBF respectively in patients with AIPD compared to patients with schizophrenia.

CONCLUSION

Our findings implicate the right occipital lobe and possibly the cerebellum in the pathogenesis of AIPD and have similarities with those previously reported in alcohol withdrawal. Reduced rCBF to the frontal lobes, thalamus and basal ganglia in AIPD as suggested in previous case reports could not be confirmed.

The functional neuroanatomy of symptom dimensions in schizophrenia: a qualitative and quantitative review of a persistent question

One of the fundamental goals in understanding schizophrenia is linking the observable symptoms to the underlying unobservable pathophysiology. Given recent advances in medical imaging, researchers are increasingly investigating brain-behavior relationships to better understand the neural substrates of negative, positive, and disorganization symptoms in schizophrenia. This review focused on 25 task-related functional magnetic resonance imaging studies and found meaningful small to moderate associations between specific symptom dimensions and regional brain activity. Negative symptoms were related to the functioning of the ventrolateral prefrontal cortex and ventral striatum. Positive symptoms, particularly persecutory ideation, were related to functioning of the medial prefrontal cortex, amygdala, and hippocampus/parahippocampal region. Disorganization symptoms, although less frequently evaluated, were related to functioning of the dorsolateral prefrontal cortex. Surprisingly, no symptom domain had a consistent relationship with the middle or superior temporal regions. While a number of adaptations in experimental design and reporting standards can facilitate this work, current neuroimaging approaches appear to provide a number of consistent links between the manifest symptoms of schizophrenia and brain dysfunction.

Detection of irregular, transient fMRI activity in normal controls using 2dTCA: comparison to event-related analysis using known timing

When events occur spontaneously during the acquisition of a series of images, traditional modeling methods for detecting functional MRI activation detection cannot be employed. The two-dimensional temporal clustering algorithm, 2dTCA, has been shown to accurately detect random, transient activations in computer simulations without the use of known event timings. In this study we applied the 2dTCA technique to detect the timings and spatial locations of sparse, irregular, transient activations of the visual, auditory, and motor cortices in 12 normal controls. Experiments with one and two independent types of stimuli were employed. Event-related activation using known timing was compared with event-related activation using 2dTCA-detected timing in individuals and across groups. The 2dTCA algorithm detected the activation from all presented stimuli in every subject. When compared with block-design results using a measure of correlation between activation maps, no significant difference was found between the 2dTCA activation maps and the event-related maps using known timing across all subjects. Therefore, 2dTCA has the potential to be an accurate and more practical method for detection of spontaneous, transient events using fMRI.

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.

Relationship of auditory verbal hallucinations with cerebral asymmetry in patients with schizophrenia: an event-related fMRI study

The purpose of this study was to explore whether there are differences in cerebral asymmetry between subgroups of schizophrenic patients with or without auditory verbal hallucinations (AVHs) and normal controls by using event-related functional magnetic resonance imaging (efMRI). A total of 26 Chinese Han male patients with paranoid schizophrenia (diagnosed by DSM IV, including 13 patients with AVHs and 13 patients without) and 13 matched normal controls were recruited for the present study. The participants had been instructed to listen to short sentences from left or right side and to indicate laterality during efMRI scanning. Functional data were acquired using a 1.5T MR, and were analyzed using statistical parametric mapping. A random-effect model was employed to asses the difference in blood oxygen level dependent response between "left-sided" and "right-sided" conditions. The results from the present study have shown (1) within group comparisons: right precuneus and right superior parietal lobule were significantly activated showed significantly greater activation by left-sided voices than right-sided ones in controls. However, no significant difference in activation was found in any brain region between left and right-sided voices in either of the two patient subgroups, (2) between group comparisons: in comparison with AVHs patients, right middle frontal gyrus (MFG) was markedly activated when control subjects were differentiating right-sided voices. In comparison with patients without AVHs, right-side stimuli significantly activated bilateral MFG and left postcentral gyrus in control group. Furthermore, compared to the non-hallucination group, left Wernicke's area, including supramarginal gyrus, angular gyrus and superior temporal gyrus, was significantly activated by both left and right-sided voices in the hallucination group. In summary, auditory-related asymmetry in control subjects is attenuated in schizophrenic patients. The symptoms of AVHs in schizophrenia are possibly correlated with left hemispheric, particularly auditory and language-related areas dysfunction.

Development of 2dTCA for the detection of irregular, transient BOLD activity

The temporal clustering algorithm (TCA) has been developed in order to detect irregular, transient functional MRI (fMRI) activation signals when the timings of the stimuli are unknown. Unfortunately, such methods are also sensitive to signal changes caused by motion and physiological noise. We have developed a modified TCA technique, 2dTCA, which can detect multiple different timing patterns within a dataset so that signals of interest can be separated from artifacts and those of no interest. The objective of this work was to further develop the 2dTCA methods and evaluate their performance in simulated functional MRI datasets. Comparisons were made with TCA and a freely-distributed independent component analysis algorithm (ICA). We created two different sets of six computer-generated phantoms with one and two different simulated activation time courses present in 10 regions of interest. The phantoms also contained real subject rigid and nonrigid body motion and noise. Sensitivity of detection, defined as the true-positive activation rate at false-positive activation rates varying between 0.0001 and 0.01, was compared between methods. Additionally, specificity of detection of the irregular, transient signal of interest was assessed by comparing the number of signal time courses detected by each algorithm. The results suggest that the increased sensitivity of 2dTCA over TCA in detecting this particular signal of interest is comparable to the detection with ICA, but with fewer other signals detected. A few examples of the successful application of 2dTCA to the localization of interictal activity in preliminary studies of temporal lobe epilepsy are also described.

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.

Cognitive approaches to schizophrenia: theory and therapy

A theoretical analysis of schizophrenia based on a cognitive model integrates the complex interaction of predisposing neurobiological, environmental, cognitive, and behavioral factors with the diverse symptomatology. The impaired integrative function of the brain, as well as the domain-specific cognitive deficits, increases the vulnerability to aversive life experiences, which lead to dysfunctional beliefs and behaviors. Symptoms of disorganization result not only from specific neurocognitive deficits but also from the relative paucity of resources available for maintaining a set, adhering to rules of communication, and inhibiting intrusion of inappropriate ideas. Delusions are analyzed in terms of the interplay between active cognitive biases, such as external attributions, and resource-sparing strategies such as jumping to conclusions. Similarly, the content of hallucinations and the delusions regarding their origin and characteristics may be understood in terms of biased information processing. The interaction of neurocognitive deficits, personality, and life events leads to the negative symptoms characterized by negative social and performance beliefs, low expectancies for pleasure and success, and a resource-sparing strategy to conserve limited psychological resources. The comprehensive conceptualization creates the context for targeted psychological treatments.

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.