Cortical dysfunction in schizophrenia during auditory word and tone working memory demonstrated by functional magnetic resonance imaging

How does the macroenvironment influence brain and behaviour-a review of current status and future perspectives

The environment influences brain and mental health, both detrimentally and beneficially. Existing research has emphasised the individual psychosocial 'microenvironment'. Less attention has been paid to 'macroenvironmental' challenges, including climate change, pollution, urbanicity, and socioeconomic disparity. Notably, the implications of climate and pollution on brain and mental health have only recently gained prominence. With the advent of large-scale big-data cohorts and an increasingly dense mapping of macroenvironmental parameters, we are now in a position to characterise the relation between macroenvironment, brain, and behaviour across different geographic and cultural locations globally. This review synthesises findings from recent epidemiological and neuroimaging studies, aiming to provide a comprehensive overview of the existing evidence between the macroenvironment and the structure and functions of the brain, with a particular emphasis on its implications for mental illness. We discuss putative underlying mechanisms and address the most common exposures of the macroenvironment. Finally, we identify critical areas for future research to enhance our understanding of the aetiology of mental illness and to inform effective interventions for healthier environments and mental health promotion.

How does the macroenvironment influence brain and behaviour - a review of current status and future perspectives

The environment influences mental health, both detrimentally and beneficially. Current research has emphasized the individual psychosocial 'microenvironment'. Less attention has been paid to 'macro-environmental' challenges including climate change, pollution, urbanicity and socioeconomic disparity. With the advent of large-scale big-data cohorts and an increasingly dense mapping of macroenvironmental parameters, we are now in a position to characterise the relation between macroenvironment, brain, and behaviour across different geographic and cultural locations globally. This review synthesises findings from recent epidemiological and neuroimaging studies, aiming to provide a comprehensive overview of the existing evidence between the macroenvironment and the structure and functions of the brain, with a particular emphasis on its implications for mental illness. We discuss putative underlying mechanisms and address the most common exposures of the macroenvironment. Finally, we identify critical areas for future research to enhance our understanding of the aetiology of mental illness and to inform effective interventions for healthier environments and mental health promotion.

Orbitofrontal cortex conveys stimulus and task information to the auditory cortex

Auditory cortical neurons modify their response profiles in response to numerous external factors. During task performance, changes in primary auditory cortex (A1) responses are thought to be driven by top-down inputs from the orbitofrontal cortex (OFC), which may lead to response modification on a trial-by-trial basis. While OFC neurons respond to auditory stimuli and project to A1, the function of OFC projections to A1 during auditory tasks is unknown. Here, we observed the activity of putative OFC terminals in A1 in mice by using in vivo two-photon calcium imaging of OFC terminals under passive conditions and during a tone detection task. We found that behavioral activity modulates but is not necessary to evoke OFC terminal responses in A1. OFC terminals in A1 form distinct populations that exclusively respond to either the tone, reward, or error. Using tones against a background of white noise, we found that OFC terminal activity was modulated by the signal-to-noise ratio (SNR) in both the passive and active conditions and that OFC terminal activity varied with SNR, and thus task difficulty in the active condition. Therefore, OFC projections in A1 are heterogeneous in their modulation of auditory encoding and likely contribute to auditory processing under various auditory conditions.

Working memory and sensory memory in subclinical high schizotypy: An avenue for understanding schizophrenia?

The search for robust, reliable biomarkers of schizophrenia remains a high priority in psychiatry. Biomarkers are valuable because they can reveal the underlying mechanisms of symptoms and monitor treatment progress and may predict future risk of developing schizophrenia. Despite the existence of various promising biomarkers that relate to symptoms across the schizophrenia spectrum, and despite published recommendations encouraging multivariate metrics, they are rarely investigated simultaneously within the same individuals. In those with schizophrenia, the magnitude of purported biomarkers is complicated by comorbid diagnoses, medications and other treatments. Here, we argue three points. First, we reiterate the importance of assessing multiple biomarkers simultaneously. Second, we argue that investigating biomarkers in those with schizophrenia-related traits (schizotypy) in the general population can accelerate progress in understanding the mechanisms of schizophrenia. We focus on biomarkers of sensory and working memory in schizophrenia and their smaller effects in individuals with nonclinical schizotypy. Third, we note irregularities across research domains leading to the current situation in which there is a preponderance of data on auditory sensory memory and visual working memory, but markedly less in visual (iconic) memory and auditory working memory, particularly when focusing on schizotypy where data are either scarce or inconsistent. Together, this review highlights opportunities for researchers without access to clinical populations to address gaps in knowledge. We conclude by highlighting the theory that early sensory memory deficits contribute negatively to working memory and vice versa. This presents a mechanistic perspective where biomarkers may interact with one another and impact schizophrenia-related symptoms.

The alternations of nucleus accumbent in schizophrenia patients with auditory verbal hallucinations during low-frequency rTMS treatment

Low-frequency repetitive transcranial magnetic stimulation (rTMS) has been shown to reduce the severity of auditory verbal hallucinations (AVH) and induce beneficial functional and structural alternations of the brain in schizophrenia patients with AVH. The nucleus accumbens (NAcc) as an important component of the ventral striatum is implicated with the pathology in AVH. However, the induced characteristic patterns of NAcc by low-frequency rTMS in schizophrenia with AVH are seldom explored. We investigated the functional and structural characteristic patterns of NAcc by using seed-based functional connectivity (FC) analysis and gray matter volume (GMV) measurement in schizophrenia patients with AVH during 1 Hz rTMS treatment. Although low-frequency rTMS treatment did not affect the volumetric changes of NAcc, the abnormal FC patterns of NAcc, including increased FC of NAcc with the temporal lobes and decreased FC of NAcc with the frontal cortices in the pretreatment patients compared to healthy controls, were normalized or reversed after treatment. These FC changes were associated with improvements in clinical symptoms and neurocognitive functions. Our findings may extend our understanding of the NAcc in the pathology of schizophrenia with AVH and might be a biomarker of clinical effect for low-frequency rTMS treatment in schizophrenia.

Meta-Modal Information Flow: A Method for Capturing Multimodal Modular Disconnectivity in Schizophrenia

OBJECTIVE

Multimodal measurements of the same phenomena provide complementary information and highlight different perspectives, albeit each with their own limitations. A focus on a single modality may lead to incorrect inferences, which is especially important when a studied phenomenon is a disease. In this paper, we introduce a method that takes advantage of multimodal data in addressing the hypotheses of disconnectivity and dysfunction within schizophrenia (SZ).

METHODS

We start with estimating and visualizing links within and among extracted multimodal data features using a Gaussian graphical model (GGM). We then propose a modularity-based method that can be applied to the GGM to identify links that are associated with mental illness across a multimodal data set. Through simulation and real data, we show our approach reveals important information about disease-related network disruptions that are missed with a focus on a single modality. We use functional MRI (fMRI), diffusion MRI (dMRI), and structural MRI (sMRI) to compute the fractional amplitude of low frequency fluctuations (fALFF), fractional anisotropy (FA), and gray matter (GM) concentration maps. These three modalities are analyzed using our modularity method.

RESULTS

Our results show missing links that are only captured by the cross-modal information that may play an important role in disconnectivity between the components.

CONCLUSION

We identified multimodal (fALFF, FA and GM) disconnectivity in the default mode network area in patients with SZ, which would not have been detectable in a single modality.

SIGNIFICANCE

The proposed approach provides an important new tool for capturing information that is distributed among multiple imaging modalities.

Neural changes following cognitive remediation therapy for schizophrenia

Patients with schizophrenia experience cognitive impairments that relate to poorer social functioning even after amelioration of positive symptoms. Pharmacological treatment and cognitive remediation are the two important therapeutic approaches for cognitive impairment in schizophrenia. Cognitive remediation therapy (CRT) for schizophrenia improves cognitive functioning and induces neuroplasticity, but different approaches and durations of CRT and different neuroimaging devices have led to varying results in meta-analyses. The objective of this review was to explore the impact of CRT on neurobiology. Several studies have provided evidence of increased activation in the frontal brain regions, such as the prefrontal cortex, anterior cingulate cortex, and parietal and occipital regions during working memory or executive function tasks after CRT. Two studies have shown alterations in resting-state connectivity between the prefrontal cortex and temporal regions. Two studies have reported that CRT induces changes in gray matter volume in the hippocampus. Further, one study observed that patients who had received CRT had elevated fractional anisotropy in the basal ganglia. We conclude that neuroimaging studies assessing CRT in patients with schizophrenia showed functional, structural, and connectivity changes that were positively correlated with cognitive improvements despite heterogeneous CRT approaches. Future studies that combine multiple modalities are required to address the differences, effects of intrinsic motivation, and pharmacological augmentation of CRT. Further understanding of the biological basis might lead to predictions of the CRT response in patients with schizophrenia and contribute to identification of schizophrenia patients for future interventions.

Altered neural basis of self-reflective processing in schizophrenia: An fMRI study

BACKGROUND

Impaired self-awareness has often been described in schizophrenia. Recent neuroimaging studies examining the self-reflection processes in schizophrenia have produced inconsistent results.

METHOD

We examined the self-reflective neural network using self- and other-evaluation tasks in schizophrenia. Fifteen schizophrenia patients and fifteen age- and sex-matched healthy subjects underwent functional magnetic resonance imaging. Subjects were required to decide whether the sentence described their own personal trait (self-evaluation) and that of their close friends (other-evaluation).

RESULTS

Unlike normal control subjects, the schizophrenia patients did not have greater activation of the left posterior cingulate gyrus and hippocampus during self-evaluation than during other-evaluation. On the other hand, the schizophrenia patients had higher activation of the right superior frontal and right supramarginal gyri during self-evaluation than control subjects. Only the patient group exhibited hyperactivation in the left hippocampus and right external capsule associated with the other-evaluation task.

CONCLUSIONS

These findings provide evidence for an altered neural basis of self-reflective processing, which may underlie the self-awareness deficits in schizophrenia.

Identification of brain regions associated with working memory deficit in schizophrenia

Background: Schizophrenia, a severe psychological disorder, shows symptoms such as hallucinations and delusions. In addition, patients with schizophrenia often exhibit a deficit in working memory which adversely impacts the attentiveness and the behavioral characteristics of a person. Although several clinical efforts have already been made to study working memory deficit in schizophrenia, in this paper, we investigate the applicability of a machine learning approach for identification of the brain regions that get affected by schizophrenia leading to the dysfunction of the working memory. Methods: We propose a novel scheme for identification of the affected brain regions from functional magnetic resonance imaging data by deploying group independent component analysis in conjunction with feature extraction based on statistical measures, followed by sequential forward feature selection. The features that show highest accuracy during the classification between healthy and schizophrenia subjects are selected. Results: This study reveals several brain regions like cerebellum, inferior temporal gyrus, superior temporal gyrus, superior frontal gyrus, insula, and amygdala that have been reported in the existing literature, thus validating the proposed approach. We are also able to identify some functional changes in the brain regions, such as Heschl gyrus and the vermian area, which have not been reported in the literature involving working memory studies amongst schizophrenia patients. Conclusions: As our study confirms the results obtained in earlier studies, in addition to pointing out some brain regions not reported in earlier studies, the findings are likely to serve as a cue for clinical investigation, leading to better medical intervention.

Reading deficits in schizophrenia and their relationship to developmental dyslexia: A review

Although schizophrenia and developmental dyslexia are considered distinct disorders in terms of clinical presentation and functional outcome, they both involve disruption in the processes that support skilled reading, including language, auditory perception, visual perception, oculomotor control, and executive function. Further, recent work has proposed a common neurodevelopmental basis for the two disorders, as suggested by genetic and pathophysiological overlap. Thus, these lines of research suggest that reading may be similarly impacted in schizophrenia and dyslexia. In this review, we survey research on reading abilities in individuals with schizophrenia, and review the potential mechanisms underlying reading deficits in schizophrenia that may be shared with those implicated in dyslexia. Elucidating the relationship between reading impairment in schizophrenia and dyslexia could allow for a better understanding of the pathophysiological underpinnings of schizophrenia, and could facilitate remediation of cognitive deficits that impact day-to-day functioning.

Verbal working memory in schizophrenia: The role of syntax in facilitating serial recall

BACKGROUND

Deficits in verbal working memory (VWM) have consistently been observed in schizophrenia, ranging from impairments in capacity, encoding, to irregular semantic organisation. However, syntactic deficits are less well-characterised, despite its crucial role in language construction. This study examines the role of simple syntactic structure (basis of the "sentence superiority effect") in VWM of patients with psychotic disorders.

METHODS

Patients with schizophrenia-spectrum disorders (n=40) and healthy controls matched on age, sex and education (n=40) were administered an auditory serial recall task containing word lists with low semantic coherence and either syntactically familiar structure (noun-verb-noun sequence) or syntactically unfamiliar structure. Other neurocognitive measures, symptoms and social functioning of patients were also assessed.

RESULTS

A 4-way analysis of variance (group×version×list type×serial position) indicated that patients had significantly worse performance overall, suggesting a generalised verbal memory impairment. In addition, a significant interaction was found for list type and Group, demonstrating that healthy controls, but not patients, had superior performance in syntactically familiar word lists. A subgroup analysis of high-performing patients revealed that the interaction was not an artefact of poor verbal memory, but a selective deficit in syntactic facilitation.

CONCLUSIONS

Our findings may suggest segregated mechanisms for maintenance and computational aspects of VWM, and show that even simple syntactic structure facilitates recall of syntactically unfamiliar words lists. Additionally, schizophrenic patients show difficulty utilising syntactic information, which highlights the need to understand the neuropsychological basis of working memory and linguistic impairments in psychosis.

Neurobiology of early psychosis

Background

Neurobiological studies of the early course of psychoses, such as schizophrenia, allow investigation of pathophysiology without the confounds of illness chronicity and treatment.

Aims

To review the recent literature on the biology of the early course of psychoses.

Method

We carried out a critical appraisal of the recent findings in the neurobiology of early psychoses, using structural, functional and neurochemical imaging techniques.

Results

Brain structural alterations are present early in the illness and may predate symptom onset. Some changes, notably those in frontal and temporal lobes, can progress during the early phases of the illness. Functional and neurochemical brain abnormalities can also be seen in the premorbid and the early phases of the illness. Some, although not all, changes can be trait-like whereas some others might progress during the early years.

Conclusions

A better understanding of such changes, especially during the critical periods of the prodrome, around the transition to the psychotic phase and during the early phases of the illness is crucial for continued research into preventive intervention strategies.

Mechanisms of Working Memory Impairment in Schizophrenia

BACKGROUND

The neural correlates of working memory (WM) impairment in schizophrenia remain a key puzzle in understanding the cognitive deficits and dysfunction of dorsolateral prefrontal cortex observed in this disorder. We sought to determine whether patients with schizophrenia exhibit an alteration in the inverted-U relationship between WM load and activation that we recently observed in healthy individuals and whether this could account for WM deficits in this population.

METHODS

Medicated (n = 30) and unmedicated (n = 21) patients with schizophrenia and healthy control subjects (n = 45) performed the self-ordered WM task during functional magnetic resonance imaging. We identified regions exhibiting an altered fit to an inverted-U relationship between WM load and activation that were also predictive of WM performance.

RESULTS

A blunted inverted-U response was observed in left dorsolateral prefrontal cortex in patients and was associated with behavioral deficits in WM capacity. In addition, suppression of medial prefrontal cortex during WM was reduced in patients and was associated with poorer WM capacity in patients. Finally, activation of visual cortex in the cuneus was elevated in patients and associated with improved WM capacity. Together, these findings explained 55% of the interindividual variance in WM capacity when combined with diagnostic and medication status, which alone accounted for only 22% of the variance in WM capacity.

CONCLUSIONS

These findings identify a novel biomarker and putative mechanism of WM deficits in patients with schizophrenia, a reduction or flattening of the inverted-U relationship between activation and WM load observed in healthy individuals in left dorsolateral prefrontal cortex.

Testing the dual-pathway model for auditory processing in human cortex

Analogous to the visual system, auditory information has been proposed to be processed in two largely segregated streams: an anteroventral ("what") pathway mainly subserving sound identification and a posterodorsal ("where") stream mainly subserving sound localization. Despite the popularity of this assumption, the degree of separation of spatial and non-spatial auditory information processing in cortex is still under discussion. In the present study, a statistical approach was implemented to investigate potential behavioral dissociations for spatial and non-spatial auditory processing in stroke patients, and voxel-wise lesion analyses were used to uncover their neural correlates. The results generally provided support for anatomically and functionally segregated auditory networks. However, some degree of anatomo-functional overlap between "what" and "where" aspects of processing was found in the superior pars opercularis of right inferior frontal gyrus (Brodmann area 44), suggesting the potential existence of a shared target area of both auditory streams in this region. Moreover, beyond the typically defined posterodorsal stream (i.e., posterior superior temporal gyrus, inferior parietal lobule, and superior frontal sulcus), occipital lesions were found to be associated with sound localization deficits. These results, indicating anatomically and functionally complex cortical networks for spatial and non-spatial auditory processing, are roughly consistent with the dual-pathway model of auditory processing in its original form, but argue for the need to refine and extend this widely accepted hypothesis.

New perspectives on catecholaminergic regulation of executive circuits: evidence for independent modulation of prefrontal functions by midbrain dopaminergic and noradrenergic neurons

Cognitive functions associated with prefrontal cortex (PFC), such as working memory and attention, are strongly influenced by catecholamine [dopamine (DA) and norepinephrine (NE)] release. Midbrain dopaminergic neurons in the ventral tegmental area and noradrenergic neurons in the locus coeruleus are major sources of DA and NE to the PFC. It is traditionally believed that DA and NE neurons are homogeneous with highly divergent axons innervating multiple terminal fields and once released, DA and NE individually or complementarily modulate the prefrontal functions and other brain regions. However, recent studies indicate that both DA and NE neurons in the mammalian brain are heterogeneous with a great degree of diversity, including their developmental lineages, molecular phenotypes, projection targets, afferent inputs, synaptic connectivity, physiological properties, and behavioral functions. These diverse characteristics could potentially endow DA and NE neurons with distinct roles in executive function, and alterations in their responses to genetic and epigenetic risk factors during development may contribute to distinct phenotypic and functional changes in disease states. In this review of recent literature, we discuss how these advances in DA and NE neurons change our thinking of catecholamine influences in cognitive functions in the brain, especially functions related to PFC. We review how the projection-target specific populations of neurons in these two systems execute their functions in both normal and abnormal conditions. Additionally, we explore what open questions remain and suggest where future research needs to move in order to provide a novel insight into the cause of neuropsychiatric disorders related to DA and NE systems.

The effect of brain lesions on sound localization in complex acoustic environments

Localizing sound sources of interest in cluttered acoustic environments--as in the 'cocktail-party' situation--is one of the most demanding challenges to the human auditory system in everyday life. In this study, stroke patients' ability to localize acoustic targets in a single-source and in a multi-source setup in the free sound field were directly compared. Subsequent voxel-based lesion-behaviour mapping analyses were computed to uncover the brain areas associated with a deficit in localization in the presence of multiple distracter sound sources rather than localization of individually presented sound sources. Analyses revealed a fundamental role of the right planum temporale in this task. The results from the left hemisphere were less straightforward, but suggested an involvement of inferior frontal and pre- and postcentral areas. These areas appear to be particularly involved in the spectrotemporal analyses crucial for effective segregation of multiple sound streams from various locations, beyond the currently known network for localization of isolated sound sources in otherwise silent surroundings.

Neural correlates of sound localization in complex acoustic environments

Listening to and understanding people in a “cocktail-party situation” is a remarkable feature of the human auditory system. Here we investigated the neural correlates of the ability to localize a particular sound among others in an acoustically cluttered environment with healthy subjects. In a sound localization task, five different natural sounds were presented from five virtual spatial locations during functional magnetic resonance imaging (fMRI). Activity related to auditory stream segregation was revealed in posterior superior temporal gyrus bilaterally, anterior insula, supplementary motor area, and frontoparietal network. Moreover, the results indicated critical roles of left planum temporale in extracting the sound of interest among acoustical distracters and the precuneus in orienting spatial attention to the target sound. We hypothesized that the left-sided lateralization of the planum temporale activation is related to the higher specialization of the left hemisphere for analysis of spectrotemporal sound features. Furthermore, the precuneus − a brain area known to be involved in the computation of spatial coordinates across diverse frames of reference for reaching to objects − seems to be also a crucial area for accurately determining locations of auditory targets in an acoustically complex scene of multiple sound sources. The precuneus thus may not only be involved in visuo-motor processes, but may also subserve related functions in the auditory modality.

Heterogeneity of auditory verbal working memory in schizophrenia

The heterogeneity of schizophrenia remains an obstacle for understanding its pathophysiology. Studies using a tone discrimination screening test to classify patients have found evidence for 2 subgroups having either a specific deficit in verbal working memory (WM) or deficits in both verbal and nonverbal memory. This study aimed to (a) replicate in larger samples differences between these subgroups in auditory verbal WM; (b) evaluate their performance on tests of explicit memory and sustained attention; (c) determine the relation of verbal WM deficits to auditory hallucinations and other symptoms; and (d) examine medication effects. The verbal WM and tone discrimination performance did not differ between medicated (n = 45) and unmedicated (n = 38) patients. Patients with schizophrenia who passed the tone screening test (discriminators; n = 60) were compared with those who did not (nondiscriminators; n = 23) and healthy controls (n = 47). The discriminator subgroup showed poorer verbal WM than did controls and a deficit in verbal but not visual memory on the Wechsler Memory Scale-Revised (Wechsler, 1987), whereas the nondiscriminator subgroup showed overall poorer performance on both verbal and nonverbal tests and a marked deficit in sustained attention. Verbal WM deficits in discriminators were correlated with auditory hallucinations but not with negative symptoms. The results are consistent with a verbal memory deficit in a subgroup of schizophrenia having intact auditory perception, which may stem from dysfunction of language-related cortical regions, and a more generalized cognitive deficit in a subgroup having auditory perceptual and attentional dysfunction.

Dissociable systems of working memory for rhythm and melody

Specialized neural systems are engaged by the rhythmic and melodic components of music. Here, we used PET to measure regional cerebral blood flow (rCBF) in a working memory task for sequences of rhythms and melodies, which were presented in separate blocks. Healthy subjects, without musical training, judged whether a target rhythm or melody was identical to a series of subsequently presented rhythms or melodies. When contrasted with passive listening to rhythms, working memory for rhythm activated the cerebellar hemispheres and vermis, right anterior insular cortex, and left anterior cingulate gyrus. These areas were not activated in a contrast between passive listening to rhythms and a non-auditory control, indicating their role in the temporal processing that was specific to working memory for rhythm. The contrast between working memory for melody and passive listening to melodies activated mainly a right-hemisphere network of frontal, parietal, and temporal cortices: areas involved in pitch processing and auditory working memory. Overall, these results demonstrate that rhythm and melody have unique neural signatures not only in the early stages of auditory processing, but also at the higher cognitive level of working memory.

Task-specific modulation of human auditory evoked response in a delayed-match-to-sample task

In this study, we focus our investigation on task-specific cognitive modulation of early cortical auditory processing in human cerebral cortex. During the experiments, we acquired whole-head magnetoencephalography data while participants were performing an auditory delayed-match-to-sample (DMS) task and associated control tasks. Using a spatial filtering beamformer technique to simultaneously estimate multiple source activities inside the human brain, we observed a significant DMS-specific suppression of the auditory evoked response to the second stimulus in a sound pair, with the center of the effect being located in the vicinity of the left auditory cortex. For the right auditory cortex, a non-invariant suppression effect was observed in both DMS and control tasks. Furthermore, analysis of coherence revealed a beta band (12∼20 Hz) DMS-specific enhanced functional interaction between the sources in left auditory cortex and those in left inferior frontal gyrus, which has been shown to be involved in short-term memory processing during the delay period of DMS task. Our findings support the view that early evoked cortical responses to incoming acoustic stimuli can be modulated by task-specific cognitive functions by means of frontal–temporal functional interactions.

Stochastic tractography study of Inferior Frontal Gyrus anatomical connectivity in schizophrenia

BACKGROUND

Abnormalities within language-related anatomical structures have been associated with clinical symptoms and with language and memory deficits in schizophrenia. Recent studies suggest disruptions in functional connectivity within the Inferior Frontal Gyrus (IFG) network in schizophrenia. However, due to technical challenges, anatomical connectivity abnormalities within this network and their involvement in clinical and cognitive deficits have not been studied.

MATERIAL AND METHODS

Diffusion and anatomical scans were obtained from 23 chronic schizophrenia patients and 23 matched controls. The IFG was automatically segmented, and its white matter connections extracted and measured with newly-developed stochastic tractography tools. Correlations between anatomical structures and measures of semantic processing were also performed.

RESULTS

White Matter connections between the IFG and posterior brain regions followed two distinct pathways: dorsal and ventral. Both demonstrated left lateralization, but ventral pathway abnormalities were only found in schizophrenia. IFG volumes also showed left lateralization and abnormalities in schizophrenia. Further, despite similar laterality and abnormality patterns, IFG volumes and white matter connectivity were not correlated with each other in either group. Interestingly, measures of semantic processing correlated with white matter connectivity in schizophrenia and with gray matter volumes in controls. Finally, hallucinations were best predicted by both gray matter and white matter measures together.

CONCLUSIONS

Our results suggest abnormalities within the ventral IFG network in schizophrenia, with white matter abnormalities better predicting semantic deficits. The lack of a statistical relationship between coexisting gray and white matter deficits might suggest their different origin and the necessity for a multimodal approach in future schizophrenia studies.

Neural correlates of visuospatial working memory in the 'at-risk mental state'

BACKGROUND

Impaired spatial working memory (SWM) is a robust feature of schizophrenia and has been linked to the risk of developing psychosis in people with an at-risk mental state (ARMS). We used functional magnetic resonance imaging (fMRI) to examine the neural substrate of SWM in the ARMS and in patients who had just developed schizophrenia.

METHOD

fMRI was used to study 17 patients with an ARMS, 10 patients with a first episode of psychosis and 15 age-matched healthy comparison subjects. The blood oxygen level-dependent (BOLD) response was measured while subjects performed an object-location paired-associate memory task, with experimental manipulation of mnemonic load.

RESULTS

In all groups, increasing mnemonic load was associated with activation in the medial frontal and medial posterior parietal cortex. Significant between-group differences in activation were evident in a cluster spanning the medial frontal cortex and right precuneus, with the ARMS groups showing less activation than controls but greater activation than first-episode psychosis (FEP) patients. These group differences were more evident at the most demanding levels of the task than at the easy level. In all groups, task performance improved with repetition of the conditions. However, there was a significant group difference in the response of the right precuneus across repeated trials, with an attenuation of activation in controls but increased activation in FEP and little change in the ARMS.

CONCLUSIONS

Abnormal neural activity in the medial frontal cortex and posterior parietal cortex during an SWM task may be a neural correlate of increased vulnerability to psychosis.

Neuronal correlates of visual and auditory alertness in the DMT and ketamine model of psychosis

Deficits in attentional functions belong to the core cognitive symptoms in schizophrenic patients. Alertness is a nonselective attention component that refers to a state of general readiness that improves stimulus processing and response initiation. The main goal of the present study was to investigate cerebral correlates of alertness in the human 5HT(2A) agonist and N-methyl-D-aspartic acid (NMDA) antagonist model of psychosis. Fourteen healthy volunteers participated in a randomized double-blind, cross-over event-related functional magnetic resonance imaging (fMRI) study with dimethyltryptamine (DMT) and S-ketamine. A target detection task with cued and uncued trials in both the visual and the auditory modality was used. Administration of DMT led to decreased blood oxygenation level-dependent response during performance of an alertness task, particularly in extrastriate regions during visual alerting and in temporal regions during auditory alerting. In general, the effects for the visual modality were more pronounced. In contrast, administration of S-ketamine led to increased cortical activation in the left insula and precentral gyrus in the auditory modality. The results of the present study might deliver more insight into potential differences and overlapping pathomechanisms in schizophrenia. These conclusions must remain preliminary and should be explored by further fMRI studies with schizophrenic patients performing modality-specific alertness tasks.

ERP generator patterns in schizophrenia during tonal and phonetic oddball tasks: effects of response hand and silent count

Greater left than right reductions of P3 amplitude in schizophrenia during auditory oddball tasks have been interpreted as evidence of left-lateralized dysfunction. However, the contributions of methodological factors (response mode, stimulus properties, recording reference), which affect event-related potential (ERP) topographies, remain unclear. We recorded 31-channel ERPs from 23 schizophrenic patients and 23 age- and gender-matched healthy controls (all right-handed) during tonal and phonetic oddball tasks, varying response mode (left press, right press, silent count) within subjects. Performance accuracy was high in both groups but patients were slower. ERP generator patterns were summarized by temporal Principal Components Analysis (PCA; unrestricted Varimax) from reference-free current source density (CSD; spherical spline Laplacians) waveforms, which sharpen scalp topographies. CSD represents the magnitude of the radial current flow entering (source) and leaving (sink) the scalp. Both patients and controls showed asymmetric frontolateral and parietotemporal N2 sinks peaking at 240 ms and asymmetric parietal P3 sources (355 ms) for targets (tonal R > L, phonetic L > R), but frontocentral N2 sinks and parietal P3 sources were bilaterally reduced in patients. A response-related midfrontal sink and accompanying centroparietal source (560 ms) were highly comparable across groups. However, a superimposed left temporal source was larger for silent count compared to button press, and this difference was smaller in patients. In both groups, left or right press produced opposite, region-specific asymmetries originating from central sites, modulating the N2/P3 complex. The results suggest bilaterally reduced neural generators of N2 and P3 in schizophrenia during auditory oddball tasks, but both groups showed comparable topographic effects of task and response mode. However, additional working memory demands during silent count may partially overlap in time the generation of the N2/P3 complex and differentially affect the asymmetry of P3 subcomponents, particularly when employing conventional ERP measures.

An fMRI study of functional abnormalities in the verbal working memory system and the relationship to clinical symptoms in chronic schizophrenia

There has been evidence for functional abnormalities of the verbal working memory system in schizophrenia. Verbal working memory crucially involves the interplay between the anterior and posterior language systems, and previous studies have shown converging evidence for abnormalities in the posterior language system in schizophrenia. In this functional magnetic resonance imaging study, we measured cortical activity in chronic schizophrenic patients and matched healthy controls during auditory and visual verbal working memory tasks. We employed 1) regional analyses specifically targeting the posterior language system and 2) analyses of functional connectivity between anterior and posterior language regions. We performed these analyses separately for each memory stage and modality. In the regional analyses, the left sylvian-parietal-temporal (Spt) area consistently showed reduced activation during encoding and retrieval stages in schizophrenia. Magnitudes of activation in the left posterior superior temporal sulcus were correlated with the severity of delusions at every memory stage. Functional connectivity analyses revealed reduced connectivity between the left Spt and the anterior insula during the encoding of auditory words. In addition, the connectivity strength was correlated with the severity of auditory hallucinations. These findings identify abnormal components in the verbal working memory system and illustrate their possible overlap with the mechanisms of core schizophrenic symptoms.

Localization of cerebral functional deficits in treatment-naive, first-episode schizophrenia using resting-state fMRI

BACKGROUND

Spontaneous low-frequency fluctuations (LFF) in the blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal have been shown to reflect cerebral spontaneous neural activity, and the present study attempts to explore the functional changes in the regional brain in patients with schizophrenia using the amplitude of the BOLD signals.

METHODS

A total of 66 treatment-naïve, first-episode schizophrenia (FES) patients and 66 normal age- and sex-matched controls were recruited. Resting-state fMRIs were obtained using a gradient-echo echo-planar imaging sequence. The amplitude of LFF (ALFF) was calculated using REST software. Voxel-based analysis of the ALFF maps between control and patient groups was performed with twos-sample t-tests using SPM2.

RESULTS

Compared to the controls, the FES group showed significantly decreased ALFF in the medial prefrontal lobe (MPFC) and significant increases in the ALFF in the left and right putamen. Significant positive correlations were observed between ALFF values in the bilateral putamen in both the patient and control groups.

CONCLUSIONS

Alterations of the ALFF in the MPFC and putamen in FES observed in the present study suggest that the functional abnormalities of those areas are at an early stage of the disease.

A prospective open-label trial of extended-release carbamazepine monotherapy in children with bipolar disorder

OBJECTIVE

The aim of this study was to evaluate the safety and efficacy of extended release carbamazepine (CBZ-ER) monotherapy in the treatment of pediatric bipolar disorder (BD).

METHOD

This was an 8-week, open-label, prospective trial of CBZ-ER monotherapy (788 +/- 252 mg/day) to assess the effectiveness and tolerability of this compound in treating pediatric bipolar spectrum disorders. Assessments included the Young Mania Rating Scale (YMRS), Clinical Global Impressions-Improvement scale, Children's Depression Rating Scale, and Brief Psychiatric Rating Scale. Adverse events were assessed through spontaneous self-reports, vital signs weight monitoring, and laboratory analysis.

RESULTS

Of the 27 participating children with BD, 16 (59.%) completed the study. CBZ-ER treatment was associated with statistically significant, but modest, levels of improvement in mean YMRS scores (-10.1 +/- 10.2, p < 0.001) with end-point mean YMRS score (21.8 +/- 12.2) suggesting a lack of complete resolution of mania. CBZ-ER treatment also resulted in significant improvement in the severity of depressive, attention-deficit/hyperactivity disorder, and psychotic symptoms. With the exception of 2 participants who discontinued due to skin rash, CBZ-ER was well tolerated with marginal increase in body weight (0.8 +/- 2.5 kg, p = 0.04) and was not associated with any abnormal changes in laboratory parameters.

CONCLUSIONS

Open-label CBZ-ER treatment was beneficial for the treatment of BD in children. Future controlled trials are warranted.

Deficits in syntaxin 1 phosphorylation in schizophrenia prefrontal cortex

BACKGROUND

Schizophrenia has been described as a disease of the synapse. On the basis of previous studies reporting reductions in the levels and activity of CK2 (also know as casein kinase 2 or II) in the brain of subjects with schizophrenia, we hypothesized that CK2-mediated phosphorylation of the presynaptic protein syntaxin 1 (Stx 1) is deficient in schizophrenia. This in turn could affect the binding of Stx 1 to its protein partners and result in abnormal neurotransmitter release and synaptic transmission.

METHODS

We analyzed post mortem prefrontal cortex samples from 15 schizophrenia cases and matched controls by quantitative immunoblotting.

RESULTS

In addition to replicating previous findings of reduced CK2 levels, we show that as predicted, the deficit in CK2 correlates with a deficit in phospho-Stx 1. In contrast, we find that these deficits are not present in depression cases. Further, we show that the reduced levels of CK2 and phospho-Stx 1 are not due to treatment with antipsychotic drugs (APDs). In fact, APDs seem to increase both CK2 and phospho-Stx 1, suggesting that their therapeutic action may be associated with the reversal of these deficits. Finally, we show that lower phospho-Stx 1 levels are associated with reduced binding of Stx 1 to SNAP-25 and MUNC18 and decreased SNARE complex formation.

CONCLUSIONS

Our findings constitute the first report of altered phosphorylation of a key component for neurotransmitter release in humans and suggest that regulation of Stx 1 by CK2-mediated phosphorylation could play a role in the pathophysiology of schizophrenia.

Executive function, neural circuitry, and genetic mechanisms in schizophrenia

After decades of research aimed at elucidating the pathophysiology and etiology of schizophrenia, it has become increasingly apparent that it is an illness knowing few boundaries. Psychopathological manifestations extend across several domains, impacting multiple facets of real-world functioning for the affected individual. Even within one such domain, arguably the most enduring, difficult to treat, and devastating to long-term functioning-executive impairment-there are not only a host of disrupted component processes, but also a complex underlying dysfunctional neural architecture. Further, just as implicated brain structures (eg, dorsolateral prefrontal cortex) through postmortem and neuroimaging techniques continue to show alterations in multiple, interacting signaling pathways, so too does evolving understanding of genetic risk factors suggest multiple molecular entry points to illness liability. With this expansive network of interactions in mind, the present chapter takes a systems-level approach to executive dysfunction in schizophrenia, by identifying key regions both within and outside of the frontal lobes that show changes in schizophrenia and are important in cognitive control neural circuitry, summarizing current knowledge of their relevant functional interactions, and reviewing emerging links between schizophrenia risk genetics and characteristic executive circuit aberrancies observed with neuroimaging methods.

Temporally anticorrelated brain networks during working memory performance reveal aberrant prefrontal and hippocampal connectivity in patients with schizophrenia

Functional neuroimaging studies on cognitive dysfunction in schizophrenia have suggested regional brain activation changes in the dorsolateral prefrontal cortex and the medial temporal lobe. However, less is known about the functional coupling of these areas during cognitive performance. In this study, we used functional magnetic resonance imaging, a verbal working memory (WM) task and multivariate statistical techniques to investigate the functional coupling of temporally anticorrelated neural networks during cognitive processing in patients with schizophrenia (n=16) compared to healthy controls (n=16). Independent component analysis identified 18 independent components (ICs) among which two ICs were selected for further analyses. These ICs included temporally anticorrelated networks which were most highly associated with the delay period of the task in both healthy controls and patients with schizophrenia. Functional network abnormalities in patients with schizophrenia were detected within a "task-positive" lateral frontoparietal network, where increased functional connectivity was found in bilateral dorsolateral prefrontal regions. In addition, aberrant functional coupling of the hippocampal cortex in patients with schizophrenia was detected within a "task-negative" medial frontotemporal network. In patients with schizophrenia, functional connectivity indices in the left dorsolateral prefrontal cortex and the right hippocampal cortex were positively correlated with accuracy during the WM task, while the connectivity strength in the right dorsolateral prefrontal cortex was negatively correlated with measures of symptom severity. These data suggest that within two temporally anticorrelated network states, patients with schizophrenia exhibit increased and persistent dorsolateral prefrontal and hippocampal connectivity during WM performance.

Symptomatic and functional correlates of regional brain physiology during working memory processing in patients with recent onset schizophrenia

Patients with schizophrenia show altered patterns of functional activation during working memory processing; specifically, high-performing patients appear to hyper-activate and low-performing patients appear to hypo-activate when compared with controls. It remains unclear how these individual differences in neurophysiological activation relate to the clinical presentation of the syndrome. In this functional magnetic resonance imaging (fMRI) study, the relationship is examined using partial least squares (PLS), a multivariate statistical technique that selects underlying latent variables based on the covariance between two sets of variables, in this case, clinical variables and regional fMRI activations during a verbal working memory task. The PLS analysis extracted two latent variables, and the significance of these associations was confirmed through permutation. Lower levels of activation during task performance across frontal and parietal regions of interest in the left hemisphere were found to covary with poorer role functioning and greater severity of negative and disorganized symptoms, while lower activation in right frontal and subcortical regions of interest was found to covary with better social functioning and fewer positive symptoms. These results suggest that appropriately lateralized patterns of functional activation during working memory processing are related to the severity of negative and disorganized symptoms and to the level of role and social functioning in schizophrenia.

Meta-analysis of 41 functional neuroimaging studies of executive function in schizophrenia

CONTEXT

Prefrontal cortical dysfunction is frequently reported in schizophrenia. It remains unclear whether this represents the coincidence of several prefrontal region- and process-specific impairments or a more unitary dysfunction in a superordinate cognitive control network. Whether these impairments are properly considered reflective of hypofrontality vs hyperfrontality remains unresolved.

OBJECTIVES

To test whether common nodes of the cognitive control network exhibit altered activity across functional neuroimaging studies of executive cognition in schizophrenia and to evaluate the direction of these effects.

DATA SOURCES

PubMed database.

STUDY SELECTION

Forty-one English-language, peer-reviewed articles published prior to February 2007 were included. All reports used functional neuroimaging during executive function performance by adult patients with schizophrenia and reported whole-brain analyses in standard stereotactic space. Tasks primarily included the delayed match-to-sample, N-back, AX-CPT, and Stroop tasks.

DATA EXTRACTION

Activation likelihood estimation modeling reported activation maxima as the center of a 3-dimensional gaussian function in the meta-analysis, with statistical thresholding and correction for multiple comparisons.

DATA SYNTHESIS

In within-group analyses, healthy controls and patients activated a similarly distributed cortical-subcortical network, prominently including the dorsolateral prefrontal cortex (PFC), ventrolateral PFC, anterior cingulate cortex (ACC), and thalamus. In between-group analyses, patients showed reduced activation in the left dorsolateral PFC, rostral/dorsal ACC, left thalamus (with significant co-occurrence of these areas), and inferior/posterior cortical areas. Increased activation was observed in several midline cortical areas. Activation within groups varied modestly by task.

CONCLUSIONS

Healthy adults and schizophrenic patients activate a qualitatively similar neural network during executive task performance, consistent with the engagement of a general-purpose cognitive control network, with critical nodes in the dorsolateral PFC and ACC. Nevertheless, patients with schizophrenia show altered activity with deficits in the dorsolateral PFC, ACC, and mediodorsal nucleus of the thalamus. Increases in activity are evident in other PFC areas, which could be compensatory in nature.

Neural mechanisms of auditory discrimination of long-duration tonal patterns: a neural modeling and fMRI study

Language perception comprises mechanisms of perception and discrimination of auditory stimuli. An important component of auditory perception and discrimination concerns auditory objects. Many interesting auditory objects in our environment are of relatively long duration; however, the temporal window of integration of auditory cortex neurons processing these objects is very limited. Thus, it is necessary to make active use of short-term memory in order to construct and temporarily store long-duration objects. We sought to understand the mechanisms by which the brain manipulates long-duration tonal patterns, temporarily stores the segments of those patterns, and integrates them into an auditory object. We extended a previously constructed model of auditory recognition of short-duration tonal patterns by expanding the prefrontal cortically-based short-term memory module of the previous model into a memory buffer with multiple short-term memory submodules and by adding a gating module. The gating module distributes the segments of the input pattern to separate locations of the extended prefrontal cortex in an orderly fashion, allowing a subsequent comparison of the stored segments against the segments of a second pattern. In addition to simulating behavioral data and electrical activity of neurons, our model also produces simulations of the blood oxygen level dependent (BOLD) signal as obtained in fMRI studies. The results of these simulations provided us with predictions that we tested in an fMRI experiment with normal volunteers. This fMRI experiment used the same task and similar stimuli to that of the model. We compared simulated data with experimental values. We found that two brain areas, the right precentral gyrus and the left medial frontal gyrus, correlated well with our simulations of the memory gating module. Other fMRI studies of auditory perception and discrimination have also found correlation of fMRI activation of those areas with similar tasks and thus provide further support to our findings.

Visuospatial working memory in children and adolescents with 22q11.2 deletion syndrome; an fMRI study

22q11.2 deletion syndrome (22q11DS) is a genetic disorder associated with a microdeletion of chromosome 22q11. In addition to high rates of neuropsychiatric disorders such as schizophrenia and attention deficit hyperactivity disorder, children with 22q11DS have a specific neuropsychological profile with particular deficits in visuospatial and working memory. However, the neurobiological substrate underlying these deficits is poorly understood. We investigated brain function during a visuospatial working memory (SWM) task in eight children with 22q11DS and 13 healthy controls, using fMRI. Both groups showed task-related activation in dorsolateral prefrontal cortex (DLPFC) and bilateral parietal association cortices. Controls activated parietal and occipital regions significantly more than those with 22q11DS but there was no significant between-group difference in DLPFC. In addition, while controls had a significant age-related increase in the activation of posterior brain regions and an age-related decrease in anterior regions, the 22q11DS children showed the opposite pattern. Genetically determined differences in the development of specific brain systems may underpin the cognitive deficits in 22q11DS, and may contribute to the later development of neuropsychiatric disorders.

Re-evaluating dorsolateral prefrontal cortex activation during working memory in schizophrenia

Previous neuroimaging studies of working memory (WM) in schizophrenia have generated conflicting findings of hypo- and hyper-frontality, discrepancies potentially driven by differences in task difficulty and/or performance. This study proposes and tests a new model of the performance-activation relationship in schizophrenia by combining changes by load with overall individual differences in performance. Fourteen patients with recent-onset schizophrenia and eighteen controls underwent functional magnetic resonance imaging while performing a parametric verbal WM task. Group level differences followed a linear "cross-over" pattern, such that in controls, activation in the dorsolateral prefrontal cortex (DLPFC) increased as performance decreased, while patients showed the opposite. Overall, low performing patients were hypoactive and high performing patients hyperactive relative to controls. However, patients and controls showed similar functions of activation by load in which activation rises with task difficulty but levels off or slightly decreases at higher loads. Moreover, across all loads and at their own WM capacity, higher performing patients showed greater DLPFC activation than controls, while lower performing patients activated least. This study establishes a novel framework for predicting the relationship between functional activation and WM performance by combining changes of activation by WM load occurring within each subject with the overall differences in activation associated with general WM performance. Essentially, increasing task difficulty correlates asymptotically with increasing activation in all subjects, but depending on their behavioral performance, patients show overall hyper- versus hypofrontality, a pattern potentially derived from individual differences in underlying cellular changes that may relate to levels of functional disability.

FMRI indices of auditory attention in schizophrenia

The present study sought to identify abnormalities in activation in several brain regions in response to an auditory attention task in patients with schizophrenia. Ten patients and twenty healthy control participants were examined using Functional Magnetic Resonance Imaging (FMRI) measures acquired during an auditory attention task. Region of interest analyses of activation of targeted regions implicated in attention included: anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC), hippocampus, parahippocampal gyrus (PHG), and superior temporal gyrus (STG). The results indicated over-activation in patients with schizophrenia. While the control group showed notable coherence in activation within and across hemispheres the schizophrenia group showed relatively less coherence overall that was only present in the right hemisphere. These findings suggest that patients with schizophrenia show both an over-engagement of brain regions during attention task as well as a lack of communication among neural regions involved.

The primate cortical auditory system and neural representation of conspecific vocalizations

Over the past decade, renewed interest in the auditory system has resulted in a surge of anatomical and physiological research in the primate auditory cortex and its targets. Anatomical studies have delineated multiple areas in and around primary auditory cortex and demonstrated connectivity among these areas, as well as between these areas and the rest of the cortex, including prefrontal cortex. Physiological recordings of auditory neurons have found that species-specific vocalizations are useful in probing the selectivity and potential functions of acoustic neurons. A number of cortical regions contain neurons that are robustly responsive to vocalizations, and some auditory responsive neurons show more selectivity for vocalizations than for other complex sounds. Demonstration of selectivity for vocalizations has prompted the question of which features are encoded by higher-order auditory neurons. Results based on detailed studies of the structure of these vocalizations, as well as the tuning and information-coding properties of neurons sensitive to these vocalizations, have begun to provide answers to this question. In future studies, these and other methods may help to define the way in which cells, ensembles, and brain regions process communication sounds. Moreover, the discovery that several nonprimary auditory cortical regions may be multisensory and responsive to vocalizations with corresponding facial gestures may change the way in which we view the processing of communication information by the auditory system.

Canonical Correlation Analysis for Feature-Based Fusion of Biomedical Imaging Modalities and Its Application to Detection of Associative Networks in Schizophrenia

Typically data acquired through imaging techniques such as functional magnetic resonance imaging (fMRI), structural MRI (sMRI), and electroencephalography (EEG) are analyzed separately. However, fusing information from such complementary modalities promises to provide additional insight into connectivity across brain networks and changes due to disease. We propose a data fusion scheme at the feature level using canonical correlation analysis (CCA) to determine inter-subject covariations across modalities. As we show both with simulation results and application to real data, multimodal CCA (mCCA) proves to be a flexible and powerful method for discovering associations among various data types. We demonstrate the versatility of the method with application to two datasets, an fMRI and EEG, and an fMRI and sMRI dataset, both collected from patients diagnosed with schizophrenia and healthy controls. CCA results for fMRI and EEG data collected for an auditory oddball task reveal associations of the temporal and motor areas with the N2 and P3 peaks. For the application to fMRI and sMRI data collected for an auditory sensorimotor task, CCA results show an interesting joint relationship between fMRI and gray matter, with patients with schizophrenia showing more functional activity in motor areas and less activity in temporal areas associated with less gray matter as compared to healthy controls. Additionally, we compare our scheme with an independent component analysis based fusion method, joint-ICA that has proven useful for such a study and note that the two methods provide complementary perspectives on data fusion.

Age-associated differences in cognitive performance in older community dwelling schizophrenia patients: differential sensitivity of clinical neuropsychological and experimental information processing tests

Cognitive dysfunction is a common feature of schizophrenia and deficits are present before the onset of psychosis, and are moderate to severe by the time of the first episode. Controversy exists over the course of cognitive dysfunction after the first episode. This study examined age-associated differences in performance on clinical neuropsychological (NP) and information processing tasks in a sample of geriatric community living schizophrenia patients (n=172). Compared to healthy control subjects (n=70), people with schizophrenia did not differ on NP tests across age groups but showed evidence for age-associated cognitive worsening on the more complex components of an information-processing test. Age-related changes in cognitive function in schizophrenia may be a function of both the course of illness and the processing demands of the cognitive measure of interest. Tests with fixed difficulty, such as clinical NP tests, may differ in their sensitivity from tests for which parametric difficulty manipulations can be performed.

The cognitive neuroscience of working memory: relevance to CNTRICS and schizophrenia

Working memory is one of the central constructs in cognitive science and has received enormous attention in the theoretical and empirical literature. Similarly, working memory deficits have long been thought to be among the core cognitive deficits in schizophrenia, making it a ripe area for translation. This article provides a brief overview of the current theories and data on the psychological and neural mechanisms involved in working memory, which is a summary of the presentation and discussion on working memory that occurred at the first Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) meeting (Washington, D.C.). At this meeting, the consensus was that the constructs of goal maintenance and interference control were the most ready to be pursued as part of a translational cognitive neuroscience effort at future CNTRICS meetings. The constructs of long-term memory reactivation, capacity, and strategic encoding were felt to be of great clinical interest but requiring more basic research. In addition, the group felt that the constructs of maintenance over time and updating in working memory had growing construct validity at the psychological and neural levels but required more research in schizophrenia before these should be considered as targets for a clinical trials setting.

Theory of mind and schizophrenia: a positron emission tomography study of medication-free patients

BACKGROUND

"Theory of mind" (TOM) refers to the ability to attribute mental states (ie, beliefs and goals) to one's self and others and to recognize that behaviors are guided by these mental states. This capacity, critical for social competence, is impaired in schizophrenia. We undertook a study of TOM in a group of patients with schizophrenia and healthy controls.

METHOD

We used positron emission tomography to identify the neural circuits recruited during a verbal task that required participants to attribute mental states to a character in a story of their creation. The comparison task consisted of reading aloud a neutral story, controlling for the speech component of the task.

RESULTS

Patients and controls generated the same percentage of TOM utterances. However, the two groups had markedly different patterns of brain activation. Compared with controls, patients had a lower blood flow in multiple regions in the left hemisphere including the frontal and visual association cortices, posterior hippocampus, and insula. The flow was also lower in contralateral areas in the lateral cerebellum and vermis, thalamus, and posterior insula. On the other hand, the flow was higher in the patients predominantly in the right hemisphere, including multiple frontal and parietal regions, insula, visual association cortex, and pulvinar.

DISCUSSION

The areas of lower flow are consistent with previous studies indicating impairment in recruiting cortical-cerebellar circuitry in schizophrenia. The areas of higher flow may reflect a need to draw on the right hemisphere to compensate for deficits in left hemisphere networks that include frontal cortex, anterior cingulate, cerebellum, and thalamus.

Differentiating cortical patterns of cognitive dysfunction in schizophrenia and posttraumatic stress disorder

Comparative studies are needed to determine whether the cognitive impairments found in various psychiatric disorders are specific to those disorders, or are a more universal consequence of mental illness. This study compares the patterns of cognitive dysfunction in two conditions characterized by working memory dysfunction, schizophrenia and posttraumatic stress disorder (PTSD). Three matched groups (Schizophrenia, PTSD, Control) of 16 subjects had event related potentials recorded, using a 27 electrode array, while they performed a working memory auditory target detection task. Both disorders were associated with impaired task performance, with greater impairment in schizophrenia. Reduction in N1 amplitude was found only in schizophrenia, and an increase in target N2 amplitude and latency was found only in PTSD. Both patient groups showed a reduction in the amplitude of the non-target and target P3, but the groups were distinguished by a reduction in non-target parietal P3 amplitude in the schizophrenia group and a reduction in target P3 amplitude over the left posterior parietal region in the PTSD Group. This study demonstrates that there are specific patterns of cognitive dysfunction associated with schizophrenia and with PTSD.

Dysfunctional and compensatory prefrontal cortical systems, genes and the pathogenesis of schizophrenia

Cognitive deficits are critical determinants of schizophrenia morbidity. In this review, we offer a mechanistic perspective regarding schizophrenia-related changes observed in prefrontal cortical networks engaged in working memory. A body of earlier work converges on aberrations in putative macrocircuit stability and functional efficiency as the underlying pathophysiology of the cognitive deficits in schizophrenia. In parsing the dysfunctional prefrontal cortical dynamics of schizophrenia, recent functional magnetic resonance imaging and electoencephalography works suggest that in the context of reduced capacity for executive aspects of working memory, patients engage a larger network of cortical regions consistent with an interplay between reduced signal-to-noise components and the recruitment of compensatory networks. The genetic programming underlying these systems-level cortical interactions has been examined under the lens of certain schizophrenia susceptibility genes, especially catechol-o-methyltransferase (COMT) and GRM3. Variation in COMT, which presumably impacts on cortical dopamine signaling, translates into variable neural strategies for working memory and altering patterns of intracortical functional correlations. GRM3, which impacts on synaptic glutamate, interacts with COMT and exaggerates the genetic dissection of cortical processing strategies. These findings reveal novel insights into the modulation and parcellation of working memory processing in cortical assemblies and provide a mechanistic link between susceptibility genes and cortical pathophysiology related to schizophrenia.

Cognitive impairment and in vivo metabolites in first-episode neuroleptic-naive and chronic medicated schizophrenic patients: a proton magnetic resonance spectroscopy study

Involvement of the prefrontal cortex in schizophrenia has been implicated by neuropsychological, as well as neuropathological and imaging studies. Reductions of N-acetylaspartate (NAA), an in vivo marker of neuronal integrity, have repeatedly been detected in the frontal lobes of patients with schizophrenia by proton magnetic resonance spectroscopy (1H-MRS). In chronic medicated patients, a positive correlation between NAA levels of the prefrontal cortex and cognitive functioning has been observed, but to date, there have been no studies in first-episode neuroleptic-naive patients. In this study, single-voxel 1H-MRS was used to investigate neuronal function of the dorsolateral prefrontal cortex in 15 first-episode and 20 chronic schizophrenic patients. Outcomes were compared to 20 age-matched healthy controls to assess the relationship between prefrontal metabolism and neuropsychological performance. Patients with chronic schizophrenia had significant reductions of NAA, glutamate/glutamine, and choline levels compared to first-episode patients and healthy controls. Furthermore, creatine and phosphocreatine were significantly reduced in both patient groups compared to healthy controls. In the neuropsychological tests, chronic schizophrenic patients performed significantly poorer in the Auditory Verbal Learning Task (AVLT) compared to first-episode patients. In both patient groups, NAA levels of the left frontal lobe significantly correlated with performances in verbal learning and memory. These results corroborate data from recent structural and spectroscopic imaging studies of the frontal lobes in schizophrenia, in which cortical gray matter reductions after onset of symptoms as well as reduced levels of NAA in chronic, but not in first-episode schizophrenic patients have been reported.