Reduced task-related suppression during semantic repetition priming in schizophrenia

Few studies have reported the reduced suppression of brain activity within the default network in schizophrenia. The relationship, however, between task-specific activation and default network suppression, as well as impact of this relationship on brain function, is still not clear, and it has not been studied in schizophrenia so far. We used previously published data showing a relationship between semantic encoding and white matter integrity in schizophrenia (Jeong et al., 2009), and reanalyzed the data using an independent component analysis (ICA). Participants comprised 10 healthy control subjects and 10 patients with chronic schizophrenia who underwent an fMRI scan during which they performed the Levels of Processing paradigm. The semantic processing-related independent components were compared between two groups using tensor-ICA. An independent component of semantic repetition priming showed a significant difference between the two groups. The component consisted of both less activated and less suppressed regions within the patients' brains. The less activated regions included the bilateral inferior frontal gyri and the supramarginal gyri. The less suppressed regions included the medial frontal gyrus, the posterior cingulate gyrus, the precuneus and the right cerebellum. Our results suggest two components of semantic repetition priming deficit in schizophrenia: one related to weaker suppression of default network, mainly precuneus and medial frontal gyrus, the other related to weaker activation of regions directly involved in semantic repetition priming.     

A Brain‐wide association study of DISC1 genetic variants reveals a relationship with the structure and functional connectivity of the precuneus in schizophrenia

The Disrupted in Schizophrenia Gene 1 (DISC1) plays a role in both neural signaling and development and is associated with schizophrenia, although its links to altered brain structure and function in this disorder are not fully established. Here we have used structural and functional MRI to investigate links with six DISC1 single nucleotide polymorphisms (SNPs). We employed a brain‐wide association analysis (BWAS) together with a Jacknife internal validation approach in 46 schizophrenia patients and 24 matched healthy control subjects. Results from structural MRI showed significant associations between all six DISC1 variants and gray matter volume in the precuneus, post‐central gyrus and middle cingulate gyrus. Associations with specific SNPs were found for rs2738880 in the left precuneus and right post‐central gyrus, and rs1535530 in the right precuneus and middle cingulate gyrus. Using regions showing structural associations as seeds a resting‐state functional connectivity analysis revealed significant associations between all 6 SNPS and connectivity between the right precuneus and inferior frontal gyrus. The connection between the right precuneus and inferior frontal gyrus was also specifically associated with rs821617. Importantly schizophrenia patients showed positive correlations between the six DISC‐1 SNPs associated gray matter volume in the left precuneus and right post‐central gyrus and negative symptom severity. No correlations with illness duration were found. Our results provide the first evidence suggesting a key role for structural and functional connectivity associations between DISC1 polymorphisms and the precuneus in schizophrenia. Hum Brain Mapp 35:5414–5430, 2014. © 2014 Wiley Periodicals, Inc.     

Right‐hemispheric processing of non‐linguistic word features: Implications for mapping language recovery after stroke

Verbal stimuli often induce right‐hemispheric activation in patients with aphasia after left‐hemispheric stroke. This right‐hemispheric activation is commonly attributed to functional reorganization within the language system. Yet previous evidence suggests that functional activation in right‐hemispheric homologues of classic left‐hemispheric language areas may partly be due to processing nonlinguistic perceptual features of verbal stimuli. We used functional MRI (fMRI) to clarify the role of the right hemisphere in the perception of nonlinguistic word features in healthy individuals. Participants made perceptual, semantic, or phonological decisions on the same set of auditorily and visually presented word stimuli. Perceptual decisions required judgements about stimulus‐inherent changes in font size (visual modality) or fundamental frequency contour (auditory modality). The semantic judgement required subjects to decide whether a stimulus is natural or man‐made; the phonologic decision required a decision on whether a stimulus contains two or three syllables. Compared to phonologic or semantic decision, nonlinguistic perceptual decisions resulted in a stronger right‐hemispheric activation. Specifically, the right inferior frontal gyrus (IFG), an area previously suggested to support language recovery after left‐hemispheric stroke, displayed modality‐independent activation during perceptual processing of word stimuli. Our findings indicate that activation of the right hemisphere during language tasks may, in some instances, be driven by a “nonlinguistic perceptual processing” mode that focuses on nonlinguistic word features. This raises the possibility that stronger activation of right inferior frontal areas during language tasks in aphasic patients with left‐hemispheric stroke may at least partially reflect increased attentional focus on nonlinguistic perceptual aspects of language. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.     

Functional and anatomical connectivity abnormalities in left inferior frontal gyrus in schizophrenia

Functional studies in schizophrenia demonstrate prominent abnormalities within the left inferior frontal gyrus (IFG) and also suggest the functional connectivity abnormalities in language network including left IFG and superior temporal gyrus during semantic processing. White matter connections between regions involved in the semantic network have also been indicated in schizophrenia. However, an association between functional and anatomical connectivity disruptions within the semantic network in schizophrenia has not been established. Functional (using levels of processing paradigm) as well as diffusion tensor imaging data from 10 controls and 10 chronic schizophrenics were acquired and analyzed. First, semantic encoding specific activation was estimated, showing decreased activation within the left IFG in schizophrenia. Second, functional time series were extracted from this area, and left IFG specific functional connectivity maps were produced for each subject. In an independent analysis, tract‐based spatial statistics (TBSS) was used to compare fractional anisotropy (FA) values between groups, and to correlate these values with functional connectivity maps. Schizophrenia patients showed weaker functional connectivity within the language network that includes left IFG and left superior temporal sulcus/middle temporal gyrus. FA was reduced in several white matter regions including left inferior frontal and left internal capsule. Finally, left inferior frontal white matter FA was positively correlated with connectivity measures of the semantic network in schizophrenics, but not in controls. Our results indicate an association between anatomical and functional connectivity abnormalities within the semantic network in schizophrenia, suggesting further that the functional abnormalities observed in this disorder might be directly related to white matter disruptions. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.     

Altered intra- and interregional synchronization in the absence of the corpus callosum: a resting-state fMRI study

Agenesis of the corpus callosum (AgCC) can result in subtle to severe cognitive deficits. Individuals with impaired cognition often show abnormalities on resting-state functional magnetic resonance imaging (rs-fMRI). This study used rs-fMRI to investigate changes in regional homogeneity (ReHo) and functional connectivity (FC) among individuals with AgCC. AgCC individuals (n = 10) and age-, sex-, and education-matched healthy control subjects (n = 19) were included in this study. The ReHo values were calculated to represent spontaneous brain activity. The regions which showed altered ReHo were selected as seeds to compare FC with the whole brain between the AgCC group and the healthy control group. Compared with healthy control subjects, the AgCC individuals had increased ReHo in the left anterior cingulate gyrus, left rolandic operculum, and right precuneus and decreased ReHo in the right calcarine, right cingual gyrus and right cuneus gyrus. The right calcarine and the right lingual gyrus in the AgCC exhibited decreased FC with bilateral cuneus, superior occipital gyrus, Rolandic operculum, superior temporal gyrus, posterior central gyrus, and midcingulate gyrus.The right cuneus gyrus in the AgCC individuals exhibited decreased FC with the bilateral calcarine gyrus, left cuneus, and left superior occipital gyrus. Our study revealed several subareas within the visual cortex exhibited remarkable abnormalities of spontaneous brain activity and decreased FC with the higher-order cognitive cortex.The abnormalities of ReHo and FC in AgCC individuals may provide new insights into the neurological pathophysiology.     

Neural evidence for faster and further automatic spreading activation in schizophrenic thought disorder

It has been proposed that the loose associations characteristic of thought disorder in schizophrenia result from an abnormal increase in the automatic spread of activation through semantic memory. We tested this hypothesis by examining the time course of neural semantic priming using event-related potentials (ERPs). ERPs were recorded to target words that were directly related, indirectly related, and unrelated to their preceding primes, while thought-disordered (TD) and non-TD schizophrenia patients and healthy controls performed an implicit semantic categorization task under experimental conditions that encouraged automatic processing. By 300-400 milliseconds after target word onset, TD patients showed increased indirect semantic priming relative to non-TD patients and healthy controls, while the degree of direct semantic priming was increased in only the most severely TD patients. By 400-500 milliseconds after target word onset, both direct and indirect semantic priming were generally equivalent across the 3 groups. These findings demonstrate for the first time at a neural level that, under automatic conditions, activation across the semantic network spreads further within a shorter period of time in specific association with positive thought disorder in schizophrenia.     

La place de la compréhension des proverbes et des métaphores dans la compréhension des troubles du cours de la pensée dans la schizophrénie : apport de l’évaluation clinique,de l’imagerie cérébrale fonctionnelle et de la neurophysiologie

According to Bleuler (1911), language impairments were indicative of thought disorders, a fundamental feature of schizophrenia. The objectives of the present review are twofold: (1) to present the clinical interest of the use of the tests of proverbs and metaphors comprehension for the evaluation of the characteristics of thought disorders in schizophrenia, and to highlight the heterogeneity of the forms of their interpretations; (2) to present the results from neuroimaging and neurophysiological studies of metaphor comprehension in order to identify the neurocognitive mechanisms underlying metaphorical language comprehension of patients with schizophrenic disorders. Results from the reviewed clinical applications of proverbs tests showed that thought disorders in individuals with schizophrenia are illustrated by different forms of proverb interpretations: literal, concrete, idiosyncratic, over-inclusiveness and unconventional. Results from the reviewed brain imaging and neurophysiological studies showed that these different forms of figurative misinterpretations may be related to different neurocognitive mechanisms: concreteness appears to be related to the dysfunction of the left inferior frontal gyrus and inverted brain lateralization during metaphor processing in individuals with schizophrenia compared to healthy individuals. During novel metaphor comprehension, which is highly effortful, individuals with schizophrenia, relative to controls, demonstrate increased activation of the right precuneus, a region that mediates complex and highly integrated functions including retrieval of episodic memory and mental imagery. These results may suggest that individuals with schizophrenia use mental imagery to support comprehension of both literal and metaphoric language. Furthermore, it was demonstrated that over-inclusive thinking, which is exhibited by individuals with schizophrenia during figurative language comprehension, could be related to very early right hemispheric hyper-activation (when a left early activation is expected) and to reduced bilateral brain activity during semantic processing. Such as reversed brain activation may explain why the individuals with schizophrenia are relatively over reliant on early-stage coarse or large semantic processing and may be prone to form meanings that are idiosyncratic and highly unconventional.     

Genetic variation in G72 correlates with brain activation in the right middle temporal gyrus in a verbal fluency task in healthy individuals

The D ‐amino acid oxidase activator gene (G72) has been found associated with several psychiatric disorders such as schizophrenia, major depression, and bipolar disorder. Impaired performance in verbal fluency tasks is an often replicated finding in the mentioned disorders. In functional neuroimaging studies, this dysfunction has been linked to signal changes in prefrontal and lateral temporal areas and could possibly constitute an endophenotype. Therefore, it is of interest whether genes associated with the disorders, such as G72, modulate verbal fluency performance and its neural correlates. Ninety‐six healthy individuals performed a semantic verbal fluency task while brain activation was measured with functional MRI. All subjects were genotyped for two single nucleotide polymorphisms (SNP) in the G72 gene, M23 (rs3918342) and M24 (rs1421292), that have previously shown association with the above‐mentioned disorders. The effect of genotype on brain activation was assessed with fMRI during a semantic verbal fluency task. Although there were no differences in performance, brain activation in the right middle temporal gyrus (BA 39 ) and the right precuneus (BA 7) was positively correlated with the number of M24 risk alleles in the G72 gene. G72 genotype does modulate brain activation during language production on a semantic level in key language areas. These findings are in line with structural and functional imaging studies in schizophrenia, which showed alterations in the right middle temporal gyrus. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.     

Color Stroop and negative priming in schizophrenia: An fMRI study

Disturbances in selective attention represent a core characteristic of schizophrenia, whose neural underpinnings have yet to be fully elucidated. Consequently, we recorded brain activation using functional magnetic resonance imaging (fMRI) while 15 patients with schizophrenia and 15 age-matched controls performed a well-established measure of selective attention—the color Stroop negative priming task. We focused on two aspects of performance: overriding pre-potent responses (Stroop effect) and inhibition of prior negatively primed trials (negative priming effect). Behaviorally, controls demonstrated both significant Stroop and negative priming effects, while schizophrenic subjects only showed the Stroop effect. For the Stroop effect, fMRI indicated significantly greater activation in frontal regions–medial frontal gyrus/anterior cingulate gyrus and middle frontal gyrus for controls–but greater activation in medial parietal regions (posterior cingulate gyrus/precuneus) for patients. Negative priming elicited significant activation in right dorsolateral prefrontal cortex for both groups, but also in left dorsolateral prefrontal cortex for patients. These different patterns of fMRI activation may reflect faulty interaction in schizophrenia within networks of brain regions that are vital to selective attention.     

Attentional Modulation of Source Attribution in First-Episode Psychosis: A Functional Magnetic Resonance Imaging Study

Background: In patients with schizophrenia, the misattribution of self-generated events to an external source is associated with the presence of psychotic symptoms. The aim of this study was to investigate how this misattribution is influenced by dysfunction of attentional processing, which is also impaired in schizophrenia. Methods: Participants underwent functional Magnetic Resonance Imaging (fMRI) while listening to prerecorded speech. Their expectancies were manipulated using visual cues that were either congruent (valid) or incongruent (invalid) with the speech. The source (self/other) and the acoustic quality (undistorted/distorted) of the speech were also manipulated. Twenty patients with first-episode psychosis (FEP) and 20 matched healthy controls (HC) were tested. Results: When listening to self-generated speech preceded by an invalid (other speech) cue, relative to HC, FEP patients showed a trend to misidentify their own speech as that of another person. Analysis of fMRI data showed that FEP patients had reduced activation in the right middle temporal gyrus (MTG) and left precuneus (Pc) relative to HC. Within the FEP group, the level of activation in the right MTG was negatively correlated with the severity of their positive psychotic symptoms. Conclusions: Impaired attentional modulation in schizophrenia may contribute to the tendency for FEP patients to misattribute the source of self-generated material, and this may be mediated by the right MTG and Pc, regions that are involved in both self-referential processing and the integration of sensory information.Key words: psychosis, schizophrenia, speech, self-recognition, attention, top-down, bottom-up     

Neural dysfunction and violence in schizophrenia: an fMRI investigation

Contemporary theories and evidence implicate frontal lobe dysfunction in violent behaviour as well as in schizophrenia. We applied functional magnetic resonance imaging (fMRI) to investigate and compare brain activation during an 'n-back' working memory task in groups of men with (i) schizophrenia and a history of serious physical violence (VS; n=13), (ii) schizophrenia without a history of violence (NVS: n=12), (iii) antisocial personality disorder (APD) and a history of serious physical violence (n=10), and (iv) no history of violence or a mental disorder (n=13). We observed comparable performance in all four groups during the control (0-back) condition. Subtle working memory deficits were seen in the NVS and APD groups but severe deficits emerged in the VS group relative to the healthy group. The VS group showed activation deficit bilaterally in the frontal lobe and precuneus when compared to the healthy group, and in the right inferior parietal region when compared to the NVS group during the working memory load condition. Frontal (bilateral) as well as right inferior parietal activity was negatively associated with the ratings of violence across all schizophrenia patients, with the right parietal region showing this association most strongly. APD patients, relative to healthy subjects, showed activation deficit in the left frontal gyrus, anterior cingulate and precuneus. It is concluded that reduced functional response in the frontal and inferior parietal regions leads to serious violence in schizophrenia perhaps via impaired executive functioning.     

Abnormal object recall and anterior cingulate overactivation correlate with formal thought disorder in schizophrenia.

BACKGROUND: The neural basis of formal thought disorder (FTD) is unknown. An influential theory is that FTD results from impaired semantic memory processing. We explored the neural correlates of semantic memory retrieval in schizophrenia using an imaging task assessing semantic object recall. METHOD: Sixteen healthy control subjects and sixteen schizophrenia patients whose FTD symptoms were measured with the Thought Disorder Index completed a verbal object-recall task during functional magnetic resonance imaging. Participants viewed two words describing object features that either evoked (object recall) or did not evoke a semantic concept. RESULTS: Schizophrenia patients tended to overrecall objects for feature pairs that did not describe the same object. Functionally, rostral anterior cingulate cortex (ACC) activation in patients positively correlated with FTD severity during both correct recalled and overrecalled trials. Compared with control subjects, during object recalling, patients overactivated bilateral ACC, temporooccipital junctions, temporal poles and parahippocampi, right inferior frontal gyrus, and dorsolateral prefrontal cortex, but underactivated inferior parietal lobules. CONCLUSIONS: Our results support impaired semantic memory retrieval as underlying FTD pathophysiology. Schizophrenia patients showed abnormal activations of brain areas involved in semantic memory, verbal working memory, and initiation and suppression of conflicting responses, which were associated with semantic overrecall and FTD.     

Regional Homogeneity Brain Alterations in Schizophrenia: An Activation Likelihood Estimation Meta-Analysis

ObjectiveResting state functional magnetic resonance imaging (rsfMRI) provides a lot of evidence for local abnormal brain activity in schizophrenia, but the results are not consistent. Our aim is to find out the consistent abnormal brain regions of the patients with schizophrenia by using regional homogeneity (ReHo), and indirectly understand the degree of brain damage of the patients with drug-naive first episode schizophrenia (Dn-FES) and chronic schizophrenia. MethodsWe performed the experiment by activation likelihood estimation (ALE) software to analysis the differences between people with schizophrenia group (all schizophrenia group and chronic schizophrenia group) and healthy controls. ResultsThirteen functional imaging studies were included in quantitative meta-analysis. All schizophrenia group showed decreased ReHo in bilateral precentral gyrus (PreCG) and left middle occipital gyrus (MOG), and increased ReHo in bilateral superior frontal gyrus (SFG) and right insula. Chronic schizophrenia group showed decreased ReHo in bilateral MOG, right fusiform gyrus, left PreCG, left cerebellum, right precuneus, left medial frontal gyrus and left anterior cingulate cortex (ACC). No significant increased brain areas were found in patients with chronic schizophrenia. ConclusionOur findings suggest that patients with chronic schizophrenia have more extensive brain damage than FES, which may contribute to our understanding of the progressive pathophysiology of schizophrenia.     

Procedural learning in schizophrenia: a functional magnetic resonance imaging investigation

Procedural learning (PL) is a type of rule-based learning in which performance facilitation occurs with practice on task without the need for conscious awareness. Schizophrenic patients have often (though not invariably) been found to show impaired PL. We performed functional magnetic resonance imaging (fMRI) during a blocked, periodic sequence-learning task with groups of: (i) healthy subjects, and (ii) schizophrenic patients on conventional antipsychotics. Healthy subjects showed significant PL, but patients did not. In healthy subjects, PL was associated with increased activation in the striatum, thalamus, cerebellum, precuneus, medial frontal lobe, and cingulate gyrus. The power of activation in the thalamus, striatum, precuneus, cingulate gyrus and BA 6 was related to the magnitude of PL in these subjects. No regions, except the anterior inferior gyrus, were significantly activated in patients. The caudate nucleus, thalamus, precuneus, and sensorimotor regions were activated significantly differently between the two groups. The findings demonstrate the involvement of the striatum, cerebellum, thalamus, cingulate gyrus, precuneus, and sensorimotor regions in PL. Further fMRI studies of PL in normal subjects treated with conventional antipsychotics, drug na?ve patients, and patients given atypical antipsychotics would help to clarify the roles of schizophrenic disease processes and antipsychotic medication in impaired PL and associated brain abnormalities in schizophrenia.     

Effect of retrieval effort and switching demand on fMRI activation during semantic word generation in schizophrenia

Verbal fluency deficits in schizophrenia are difficult to interpret because the tasks are multi-factorial and groups differ in total words generated. We manipulated retrieval and switching demands by requiring alternation between over-learned sequences in which retrieval is relatively automatic (OS) and semantic categories requiring increased retrieval effort (SC). Controlled processing was also manipulated by including switching and non-switching conditions, and formal thought disorder (FTD) was assessed with the communication disorders index (CDI). The OS/SC semantic fluency paradigm was administered during fMRI to 13 patients with schizophrenia and 14 matched controls. Images were acquired on a 3 Tesla Siemens scanner using compressed image acquisition to allow for cued overt word production. Subjects alternated between OS, SC, OS-switch, SC-switch, and baseline blocks. Images were pre-processed in SPM-2, and a two-stage random effects analysis tested within and between group contrasts. There were no group performance differences. fMRI analysis did not reveal any group differences during the OS non-switching condition. Both groups produced expected activation in bilateral prefrontal and inferior parietal regions. However, during the SC condition patients had greater activation than controls in left prefrontal, right anterior cingulate, right superior temporal, bilateral thalamus, and left parietal regions. There was also evidence of patient over-activation in prefrontal, superior temporal, superior parietal, and visual association areas when a switching component was added. FTD was negatively correlated with BOLD response in the right anterior cingulate, cuneus and superior frontal gyrus during increased retrieval demand, and positively correlated with fMRI activation in the left lingual gyrus, right fusiform gyrus and left superior parietal lobule during increased switching demand. These results indicate that patients are able to successfully perform effortful semantic fluency tasks during non-speeded conditions. When retrieval is relatively automatic there does not appear to be an effect of schizophrenia on fMRI response. However, when retrieval and controlled processing demands increase, patients have greater activation than controls despite unimpaired task performance. This inefficient BOLD response may explain why patients are slower and less accurate on standard self-paced fluency tasks.     

抑郁症患者情绪图片刺激早期低频脑磁图研究

目的：探讨抑郁症患者给予视觉情绪图片刺激早期0～100ms、100～200ms、200～300ms3个时段8～30Hz的神经磁场激活特征。方法：8例抑郁症患者及12例健康右利手对照者,在给予国际情绪图片库（IAPS）正性、中性、负性情绪图片刺激同时记录脑磁图信号,使用SPM8b软件进行数据分析：设两样本t检验P〈0.01（未校正）和K值≥10个体素范围为差异有统计学意义。结果：与对照组相比,抑郁组在正性情绪图片刺激下,100～200ms内的左侧额下回,右侧的终板旁回、额内侧回、海马回激活增强。在中性情绪图片刺激下,抑郁组在0～100ms的右侧豆状核、岛叶、额上回,左内侧额叶,100～200ms内的右侧岛叶、豆状核壳核及屏状核,左侧额下回、额上回、颞上回,200～300ms内的右侧岛叶、豆状核、尾状核体激活增强。负性情绪图片刺激下抑郁组在0～100ms内的右侧颞上回、岛叶、尾状核头部、额中下回激活增强,100～200ms内的右侧额中回、尾状核体,200～300ms内右额下回激活增强。此外还比较一致的发现抑郁组在楔前叶、后扣带回等顶叶脑区激活降低。结论：抑郁个体起注意调节功能的顶叶脑区如楔前叶功能不足,对视觉皮质向前部脑区情绪信息颞叶底部传递通路抑制不足,腹侧前额皮质、岛叶过度的激活,可能是抑郁症的一个发病基础。     

Retrieving meaning after temporal lobe infarction: the role of the basal language area

During speech comprehension the auditory association cortex in the superior temporal cortex is involved in perceptual analysis of the speech signal, whereas the basal language area in the inferior temporal cortex mediates access to word meaning. Disruption of the interaction between the superior and inferior temporal cortices is one factor that may determine recovery from aphasic stroke. We used positron emission tomography to investigate semantic processing within inferior temporal cortex in control subjects and after infarction involving the superior temporal cortex. In the control group, semantic decision making on clear speech activated both anterior fusiform gyri. Chronic aphasic patients were impaired at the task and demonstrated reduced activation within the left anterior fusiform gyrus. A similar pattern of impaired performance and reduced left anterior fusiform gyrus activation was observed when control subjects heard perceptually degraded speech. Performance in both groups predicted activity in the right anterior fusiform gyrus and the temporal poles, where accuracy linearly correlated with activity. These results demonstrate that the function of the basal language area is sensitive to changes in the quality of perceptual input. In addition, different profiles of response observed in each hemisphere suggest distinct contributions of both left and right inferior temporal cortices to the semantic processing of speech.     

Alterations of theory of mind network activation in chronic cannabis users

Chronic cannabis use is associated with cognitive impairment and has been identified as a risk factor for schizophrenia. Patients with schizophrenia show profound deficits in social cognition such as the ability to attribute mental states to others, referred to as "theory of mind" (ToM). Aberrant activation of the ToM network has been demonstrated across different phases of schizophrenia, including at-risk stages. Accordingly, we aimed to investigate the ToM network in chronic cannabis users. Fifteen cannabis users received functional brain imaging during performance of a ToM cartoon story task. Findings were compared with 14 control subjects. Cannabis users showed less activation in the left parahippocampal gyrus, the right precuneus and cuneus, but greater activation in the left cuneus and the right anterior cingulate gyrus compared to healthy controls. These activation patterns resemble those found in at-risk populations, suggesting that cannabis use can affect the processing of social information similar to other risk factor constellations for psychosis.     

Resting-state brain entropy in schizophrenia

BackgroundThe human brain presents ongoing temporal fluctuations whose dynamic range indicates the capacity of information processing and can be approximately quantified with entropy. Using functional magnetic resonance imaging (fMRI), recent studies have shown a stable distribution pattern of temporal brain entropy (tBEN) in healthy subjects, which may be affected by neuropsychiatric diseases such as schizophrenia. Assessing tBEN may reciprocally provide a new tool to characterize those disorders.MethodsThe current study aimed to identify tBEN changes in schizophrenia patients using publicly available data from the Centers of Biomedical Research Excellence (COBRE) project. Forty-three schizophrenia patients and 59 sex- and age-matched healthy control subjects were included, and tBEN was calculated from their resting-state fMRI scans.ResultsCompared with healthy controls, patients showed decreased tBEN in the right middle prefrontal cortex, bilateral thalamus, right hippocampus and bilateral caudate and increased tBEN in the left lingual gyrus, left precuneus, right fusiform face area and right superior occipital gyrus. In schizophrenia patients, tBEN in the left cuneus and middle occipital gyrus was negatively correlated with the positive and negative syndrome scores (PANSS). Age of onset was inversely correlated with tBEN in the right fusiform gyrus and left insula.ConclusionOur findings demonstrate a detrimental tBEN reduction in schizophrenia that is related to clinical characteristics. The tBEN increase in a few regions might be a result of tBEN redistribution across the whole brain in schizophrenia.     

Functional MRI of verbal self-monitoring in schizophrenia: performance and illness-specific effects

Previous small-sample studies have shown altered frontotemporal activity in schizophrenia patients with auditory hallucinations and impaired monitoring of self-generated speech. We examined a large cohort of patients with schizophrenia (n = 63) and a representative group of healthy controls (n = 20) to disentangle performance, illness, and symptom-related effects in functional magnetic resonance imaging-detected brain abnormalities during monitoring of self- and externally generated speech in schizophrenia. Our results revealed activation of the thalamus (medial geniculate nucleus, MGN) and frontotemporal regions with accurate monitoring across all participants. Less activation of the thalamus (MGN, pulvinar) and superior-middle temporal and inferior frontal gyri occurred in poorly performing patients (1 standard deviation below controls' mean; n = 36), relative to the combined group of controls and well-performing patients. In patients, (1) greater deactivation of the ventral striatum and hypothalamus to own voice, combined with nonsignificant activation of the same regions to others' voice, associated positively with negative symptoms (blunted affect, emotional withdrawal, poor rapport, passive social avoidance) regardless of performance and (2) exaggerated activation of the right superior-middle temporal gyrus during undistorted, relative to distorted, feedback associated with both positive symptoms (hallucinations, persecution) and poor performance. A further thalamic abnormality characterized schizophrenia patients regardless of performance and symptoms. We conclude that hypoactivation of a neural network comprised of the thalamus and frontotemporal regions underlies impaired speech monitoring in schizophrenia. Positive symptoms and poor monitoring share a common activation abnormality in the right superior temporal gyrus during processing of degraded speech. Altered striatal and hypothalamic modulation to own and others' voice characterizes emotionally withdrawn and socially avoidant patients.