Event-related fMRI of frontotemporal activity during word encoding and recognition in schizophrenia

Neuroimaging features of cognitive impairments in schizophrenia and major depressive disorder

Cognitive dysfunctions are one of the key symptoms of schizophrenia (SZ) and major depressive disorder (MDD), which exist not only during the onset of diseases but also before the onset, even after the remission of psychiatric symptoms. With the development of neuroimaging techniques, these non-invasive approaches provide valuable insights into the underlying pathogenesis of psychiatric disorders and information of cognitive remediation interventions. This review synthesizes existing neuroimaging studies to examine domains of cognitive impairment, particularly processing speed, memory, attention, and executive function in SZ and MDD patients. First, white matter (WM) abnormalities are observed in processing speed deficits in both SZ and MDD, with distinct neuroimaging findings highlighting WM connectivity abnormalities in SZ and WM hyperintensity caused by small vessel disease in MDD. Additionally, the abnormal functions of prefrontal cortex and medial temporal lobe are found in both SZ and MDD patients during various memory tasks, while aberrant amygdala activity potentially contributes to a preference to negative memories in MDD. Furthermore, impaired large-scale networks including frontoparietal network, dorsal attention network, and ventral attention network are related to attention deficits, both in SZ and MDD patients. Finally, abnormal activity and volume of the dorsolateral prefrontal cortex (DLPFC) and abnormal functional connections between the DLPFC and the cerebellum are associated with executive dysfunction in both SZ and MDD. Despite these insights, longitudinal neuroimaging studies are lacking, impeding a comprehensive understanding of cognitive changes and the development of early intervention strategies for SZ and MDD. Addressing this gap is critical for advancing our knowledge and improving patient prognosis.

Functional magnetic resonance imaging in schizophrenia: current evidence, methodological advances, limitations and future directions

Functional neuroimaging emerged with great promise and has provided fundamental insights into the neurobiology of schizophrenia. However, it has faced challenges and criticisms, most notably a lack of clinical translation. This paper provides a comprehensive review and critical summary of the literature on functional neuroimaging, in particular functional magnetic resonance imaging (fMRI), in schizophrenia. We begin by reviewing research on fMRI biomarkers in schizophrenia and the clinical high risk phase through a historical lens, moving from case-control regional brain activation to global connectivity and advanced analytical approaches, and more recent machine learning algorithms to identify predictive neuroimaging features. Findings from fMRI studies of negative symptoms as well as of neurocognitive and social cognitive deficits are then reviewed. Functional neural markers of these symptoms and deficits may represent promising treatment targets in schizophrenia. Next, we summarize fMRI research related to antipsychotic medication, psychotherapy and psychosocial interventions, and neurostimulation, including treatment response and resistance, therapeutic mechanisms, and treatment targeting. We also review the utility of fMRI and data-driven approaches to dissect the heterogeneity of schizophrenia, moving beyond case-control comparisons, as well as methodological considerations and advances, including consortia and precision fMRI. Lastly, limitations and future directions of research in the field are discussed. Our comprehensive review suggests that, in order for fMRI to be clinically useful in the care of patients with schizophrenia, research should address potentially actionable clinical decisions that are routine in schizophrenia treatment, such as which antipsychotic should be prescribed or whether a given patient is likely to have persistent functional impairment. The potential clinical utility of fMRI is influenced by and must be weighed against cost and accessibility factors. Future evaluations of the utility of fMRI in prognostic and treatment response studies may consider including a health economics analysis.

Postnatal Phencyclidine-Induced Deficits in Decision Making Are Ameliorated by Optogenetic Inhibition of Ventromedial Orbitofrontal Cortical Glutamate Neurons

Background

The orbitofrontal cortex (OFC) is essential for decision making, and functional disruptions within the OFC are evident in schizophrenia. Postnatal phencyclidine (PCP) administration in rats is a neurodevelopmental manipulation that induces schizophrenia-relevant cognitive impairments. We aimed to determine whether manipulating OFC glutamate cell activity could ameliorate postnatal PCP-induced deficits in decision making.

Methods

Male and female Wistar rats (n = 110) were administered saline or PCP on postnatal days 7, 9, and 11. In adulthood, we expressed YFP (yellow fluorescent protein) (control), ChR2 (channelrhodopsin-2) (activation), or eNpHR 3.0 (enhanced halorhodopsin) (inhibition) in glutamate neurons within the ventromedial OFC (vmOFC). Rats were tested on the probabilistic reversal learning task once daily for 20 days while we manipulated the activity of vmOFC glutamate cells. Behavioral performance was analyzed using a Q-learning computational model of reinforcement learning.

Results

Compared with saline-treated rats expressing YFP, PCP-treated rats expressing YFP completed fewer reversals, made fewer win-stay responses, and had lower learning rates. We induced similar performance impairments in saline-treated rats by activating vmOFC glutamate cells (ChR2). Strikingly, PCP-induced performance deficits were ameliorated when the activity of vmOFC glutamate cells was inhibited (halorhodopsin).

Conclusions

Postnatal PCP-induced deficits in decision making are associated with hyperactivity of vmOFC glutamate cells. Thus, normalizing vmOFC activity may represent a potential therapeutic target for decision-making deficits in patients with schizophrenia.

Evidence that the frontal pole has a significant role in the pathophysiology of schizophrenia

Different regions of the cortex have been implicated in the pathophysiology of schizophrenia. Recently published data suggested there are many more changes in gene expression in the frontal pole (Brodmann's Area (BA) 10) compared to the dorsolateral prefrontal cortex (BA 9) and the anterior cingulate cortex (BA 33) from patients with schizophrenia. These data argued that the frontal pole is significantly affected by the pathophysiology of schizophrenia. The frontal pole is a region necessary for higher cognitive functions and is highly interconnected with many other brain regions. In this review we summarise the growing body of evidence to support the hypothesis that a dysfunctional frontal pole, due at least in part to its widespread effects on brain function, is making an important contribution to the pathophysiology of schizophrenia. We detail the many structural, cellular and molecular abnormalities in the frontal pole from people with schizophrenia and present findings that argue the symptoms of schizophrenia are closely linked to dysfunction in this critical brain region.

Disruptions in white matter microstructure associated with impaired visual associative memory in schizophrenia-spectrum illness

Episodic memory ability relies on hippocampal-prefrontal connectivity. However, few studies have examined relationships between memory performance and white matter (WM) microstructure in hippocampal-prefrontal pathways in schizophrenia-spectrum disorder (SSDs). Here, we investigated these relationships in individuals with first-episode psychosis (FEP) and chronic schizophrenia-spectrum disorders (SSDs) using tractography analysis designed to interrogate the microstructure of WM tracts in the hippocampal-prefrontal pathway. Measures of WM microstructure (fractional anisotropy [FA], radial diffusivity [RD], and axial diffusivity [AD]) were obtained for 47 individuals with chronic SSDs, 28 FEP individuals, 52 older healthy controls, and 27 younger healthy controls. Tractography analysis was performed between the hippocampus and three targets involved in hippocampal-prefrontal connectivity (thalamus, amygdala, nucleus accumbens). Measures of WM microstructure were then examined in relation to episodic memory performance separately across each group. Both those with FEP and chronic SSDs demonstrated impaired episodic memory performance. However, abnormal WM microstructure was only observed in individuals with chronic SSDs. Abnormal WM microstructure in the hippocampal-thalamic pathway in the right hemisphere was associated with poorer memory performance in individuals with chronic SSDs. These findings suggest that disruptions in WM microstructure in the hippocampal-prefrontal pathway may contribute to memory impairments in individuals with chronic SSDs but not FEP.

Continuous theta-burst stimulation over the right dorsolateral prefrontal cortex disrupts fear memory reconsolidation in humans

Continuous theta-burst stimulation (cTBS), a non-invasive brain stimulation technique, can induce long-lasting changes in synaptic plasticity, vital for memory reconsolidation. For this study, a total of 170 participants completed four experiments by a randomized controlled design. Succeeding fear conditioning, the subjects received cTBS over the right dorsolateral prefrontal cortex (dlPFC) or vertex (control) with or without exposure to the conditioned stimulus to reactivate the original fear memory, and then underwent fear response tests. Compared with cTBS over the vertex and without memory reactivation, only cTBS over the right dlPFC after reactivation decreased the fear response for both recent and remote fear memories. This procedure was effective only during the reconsolidation window. The disruptive effect of cTBS over the right dlPFC on fear memory reconsolidation was delay-dependent. These findings demonstrate that cTBS time-dependently and delay-dependently prevents the return of fear and may have clinical potential for treating fear-related disorders.

MicroRNAs in the Onset of Schizophrenia

Mounting evidence implicates microRNAs (miRNAs) in the pathology of schizophrenia. These small noncoding RNAs bind to mRNAs containing complementary sequences and promote their degradation and/or inhibit protein synthesis. A single miRNA may have hundreds of targets, and miRNA targets are overrepresented among schizophrenia-risk genes. Although schizophrenia is a neurodevelopmental disorder, symptoms usually do not appear until adolescence, and most patients do not receive a schizophrenia diagnosis until late adolescence or early adulthood. However, few studies have examined miRNAs during this critical period. First, we examine evidence that the miRNA pathway is dynamic throughout adolescence and adulthood and that miRNAs regulate processes critical to late neurodevelopment that are aberrant in patients with schizophrenia. Next, we examine evidence implicating miRNAs in the conversion to psychosis, including a schizophrenia-associated single nucleotide polymorphism in MIR137HG that is among the strongest known predictors of age of onset in patients with schizophrenia. Finally, we examine how hemizygosity for DGCR8, which encodes an obligate component of the complex that synthesizes miRNA precursors, may contribute to the onset of psychosis in patients with 22q11.2 microdeletions and how animal models of this disorder can help us understand the many roles of miRNAs in the onset of schizophrenia.

On the Role of Bilateral Brain Hypofunction and Abnormal Lateralization of Cortical Information Flow as Neural Underpinnings of Conventional Metaphor Processing Impairment in Schizophrenia: An fMRI and EEG Study

Figurative language processing (e.g. metaphors) is commonly impaired in schizophrenia. In the present study, we investigated the neural activity and propagation of information within neural circuits related to the figurative speech, as a neural substrate of impaired conventional metaphor processing in schizophrenia. The study included 30 schizophrenia outpatients and 30 healthy controls, all of whom were assessed with a functional Magnetic Resonance Imaging (fMRI) and electroencephalography (EEG) punchline-based metaphor comprehension task including literal (neutral), figurative (metaphorical) and nonsense (absurd) endings. The blood oxygenation level-dependent signal was recorded with 3T MRI scanner and direction and strength of cortical information flow in the time course of task processing was estimated with a 64-channel EEG input for directed transfer function. The presented results revealed that the behavioral manifestation of impaired figurative language in schizophrenia is related to the hypofunction in the bilateral fronto-temporo-parietal brain regions (fMRI) and various differences in effective connectivity in the fronto-temporo-parietal circuit (EEG). Schizophrenia outpatients showed an abnormal pattern of connectivity during metaphor processing which was related to bilateral (but more pronounced at the left hemisphere) hypoactivation of the brain. Moreover, we found reversed lateralization patterns, i.e. a rightward-shifted pattern during metaphor processing in schizophrenia compared to the control group. In conclusion, the presented findings revealed that the impairment of the conventional metaphor processing in schizophrenia is related to the bilateral brain hypofunction, which supports the evidence on reversed lateralization of the language neural network and the existence of compensatory recruitment of alternative neural circuits in schizophrenia.

Strategies to solve the reverse inference fallacy in future MRI studies of schizophrenia: a review

Few advances in schizophrenia research have been translated into clinical practice, despite 60 years of serum biomarkers studies and 50 years of genetic studies. During the last 30 years, neuroimaging studies on schizophrenia have gradually increased, partly due to the beautiful prospect that the pathophysiology of schizophrenia could be explained entirely by the Human Connectome Project (HCP). However, the fallacy of reverse inference has been a critical problem of the HCP. For this reason, there is a dire need for new strategies or research "bridges" to further schizophrenia at the biological level. To understand the importance of research "bridges," it is vital to examine the strengths and weaknesses of the recent literature. Hence, in this review, our team has summarized the recent literature (1995-2018) about magnetic resonance imaging (MRI) of schizophrenia in terms of regional and global structural and functional alterations. We have also provided a new proposal that may supplement the HCP for studying schizophrenia. As postulated, despite the vast number of MRI studies in schizophrenia, the lack of homogeneity between the studies, along with the relatedness of schizophrenia with other neurological disorders, has hindered the study of schizophrenia. In addition, the reverse inference cannot be used to diagnose schizophrenia, further limiting the clinical impact of findings from medical imaging studies. We believe that multidisciplinary technologies may be used to develop research "bridges" to further investigate schizophrenia at the single neuron or neuron cluster levels. We have postulated about future strategies for overcoming the current limitations and establishing the research "bridges," with an emphasis on multimodality imaging, molecular imaging, neuron cluster signals, single transmitter biomarkers, and nanotechnology. These research "bridges" may help solve the reverse inference fallacy and improve our understanding of schizophrenia for future studies.

Normalization of mediotemporal and prefrontal activity, and mediotemporal-striatal connectivity, may underlie antipsychotic effects of cannabidiol in psychosis

BACKGROUND

Recent evidence suggests that cannabidiol (CBD), a non-intoxicating ingredient present in cannabis extract, has an antipsychotic effect in people with established psychosis. However, the effect of CBD on the neurocognitive mechanisms underlying psychosis is unknown.

METHODS

Patients with established psychosis on standard antipsychotic treatment were studied on separate days at least one week apart, to investigate the effects of a single dose of orally administered CBD (600 mg) compared to a matched placebo (PLB), using a double-blind, randomized, PLB-controlled, repeated-measures, within-subject cross-over design. Three hours after taking the study drug participants were scanned using a block design functional magnetic resonance imaging (fMRI) paradigm, while performing a verbal paired associate learning task. Fifteen psychosis patients completed both study days, 13 completed both scanning sessions. Nineteen healthy controls (HC) were also scanned using the same fMRI paradigm under identical conditions, but without any drug administration. Effects of CBD on brain activation measured using the blood oxygen level-dependent hemodynamic response fMRI signal were studied in the mediotemporal, prefrontal, and striatal regions of interest.

RESULTS

Compared to HC, psychosis patients under PLB had altered prefrontal activation during verbal encoding, as well as altered mediotemporal and prefrontal activation and greater mediotemporal-striatal functional connectivity during verbal recall. CBD attenuated dysfunction in these regions such that activation under its influence was intermediate between the PLB condition and HC. CBD also attenuated hippocampal-striatal functional connectivity and caused trend-level symptom reduction in psychosis patients.

CONCLUSIONS

This suggests that normalization of mediotemporal and prefrontal dysfunction and mediotemporal-striatal functional connectivity may underlie the antipsychotic effects of CBD.

Neural Signatures of Memory Encoding in Schizophrenia Are Modulated by Antipsychotic Treatment

There is no pharmacological treatment to remediate cognitive impairment in schizophrenia (SZ). It is imperative to characterize underlying pathologies of memory processing in order to effectively develop new treatments. In this longitudinal study, we combined functional magnetic resonance imaging during a memory encoding task with proton MR spectroscopy to measure hippocampal glutamate + glutamine (Glx). Seventeen SZ were scanned while unmedicated and after 6 weeks of treatment with risperidone and compared to a group of matched healthy controls (HC) scanned 6 weeks apart. Unmedicated patients showed reduced blood oxygen level dependent (BOLD) response in several regions, including the hippocampus, and greater BOLD response in regions of the default mode network (DMN) during correct memory encoding. Post hoc contrasts from significant group by time interactions indicated reduced hippocampal BOLD response at baseline with subsequent increase following treatment. Hippocampal Glx was not different between groups at baseline, but at week 6, hippocampal Glx was significantly lower in SZ compared to HC. Finally, in unmedicated SZ, higher hippocampal Glx predicted less deactivation of the BOLD response in regions of the DMN. Using 2 brain imaging modalities allowed us to concurrently investigate different mechanisms involved in memory encoding dysfunction in SZ. Hippocampal pathology during memory encoding stems from decreased hippocampal recruitment and faulty deactivation of the DMN, and hippocampal recruitment during encoding can be modulated by antipsychotic treatment. High Glx in unmedicated patients predicted less deactivation of the DMN; these results suggest a mechanism by which faulty DMN deactivation, a hallmark of pathological findings in SZ, is achieved.

The Visual Word Form Area compensates for auditory working memory dysfunction in schizophrenia

Auditory working memory impairments feature prominently in schizophrenia. However, the existence of altered and perhaps compensatory neural dynamics, sub-serving auditory working memory, remains largely unexplored. We compared the dynamics of induced high gamma power (iHGP) across cortex in humans during speech-sound working memory in individuals with schizophrenia (SZ) and healthy comparison subjects (HC) using magnetoencephalography (MEG). SZ showed similar task performance to HC while utilizing different brain regions. During encoding of speech sounds, SZ lacked the correlation of iHGP with task performance in posterior superior temporal gyrus (STGp) that was observed in healthy subjects. Instead, SZ recruited the visual word form area (VWFA) during both stimulus encoding and response preparation. Importantly, VWFA activity during encoding correlated with the magnitude of SZ hallucinations, task performance and an independent measure of verbal working memory. These findings suggest that VWFA plasticity is harnessed to compensate for STGp dysfunction in schizophrenia patients with hallucinations.

The muscarinic M1 receptor modulates associative learning and memory in psychotic disorders

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Psychosis characterised by different M₁ sensitivity in learning and memory.

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Greater limbic-temporal hyperactivity in response to biperiden in psychosis.

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Hippocampal M₁ binding predicted limbic-temporal hyperactivation underlying learning.

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M₁ agonist may normalise functional response underlying learning & memory in psychosis.

Background

Psychotic disorders are characterized by prominent deficits in associative learning and memory for which there are currently no effective treatments. Functional magnetic resonance imaging (fMRI) studies in psychotic disorders have identified deficits in fronto-temporal activation during associative learning and memory. The underlying pathology of these findings remains unclear. Postmortem data have suggested these deficits may be related to loss of muscarinic M₁ receptor mediated signaling. This is supported by an in-vivo study showing improvements in these symptoms after treatment with the experimental M_1/4 receptor agonist xanomeline. The current study tests whether reported deficits in fronto-temporal activation could be mediated by loss of M₁ receptor signaling in psychotic disorders.

Methods

Twenty-six medication-free subjects diagnosed with a psychotic disorder and 29 age-, gender-, and IQ-matched healthy controls underwent two functional magnetic resonance imaging (fMRI) sessions, one under placebo and one under selective M₁ antagonist biperiden, while performing the paired associated learning task. M₁ binding potentials (BP_ND) were measured in the dorsolateral prefrontal cortex (DLPFC) and hippocampus using ¹²³I-IDEX single photon emission computed tomography.

Results

In the subjects with psychotic disorders DLPFC hypoactivation was only found in the memory phase of the task. In both learning and memory phases of the task, M₁ antagonism by biperiden elicited significantly greater hyperactivation of the parahippocampal gyrus and superior temporal gyrus in subjects with a psychotic disorders compared to controls. Greater hyperactivation of these areas after biperiden was associated with greater hippocampal M₁ receptor binding during learning, with no association found with M₁ receptor binding in the DLPFC. M₁ receptor binding in the DLPFC was related to greater functional sensitivity to biperiden of the cingulate gyrus during the memory phase.

Conclusion

The current study is the first to show differences in M₁ receptor mediated functional sensitivity between subjects with a psychotic disorder and controls during a paired associate learning and memory task. Results point to subjects with psychotic disorders having a loss of M₁ receptor reserve in temporal-limbic areas.

Intervention-specific patterns of cortical function plasticity during auditory encoding in people with schizophrenia

Schizophrenia is a neurocognitive illness characterized by behavioral and neural impairments in both early auditory processing and higher order verbal working memory. Previously we have shown intervention-specific cognitive performance improvements with computerized, targeted training of auditory processing (AT) when compared to a computer games (CG) control intervention that emphasized visual processing. To investigate spatiotemporal changes in patterns of neural activity specific to the AT intervention, the current study used magnetoencephalography (MEG) imaging to derive induced high gamma band oscillations (HGO) during auditory encoding, before and after 50 h (∼10 weeks) of exposure to either the AT or CG intervention. During stimulus encoding, AT intervention-specific changes in high gamma activity occurred in left middle frontal and left middle-superior temporal cortices. In contrast, CG intervention-specific changes were observed in right medial frontal and supramarginal gyri during stimulus encoding, and in bilateral temporal cortices during response preparation. These data reveal that, in schizophrenia, intensive exposure to either training of auditory processing or exposure to visuospatial activities produces significant but complementary patterns of cortical function plasticity within a distributed fronto-temporal network. These results underscore the importance of delineating the specific neuroplastic effects of targeted behavioral interventions to ensure desired neurophysiological changes and avoid unintended consequences on neural system functioning.

Examination of relational memory in multidimensional schizotypy

We report the first study to examine the association of positive, negative, and disorganized schizotypy with relational memory. Relational memory refers to memory for relations among multiple elements of an experience, and this form of episodic memory is different from memory for individual elements themselves. Using a cornerstone task from the neurocognitive literature that is designed specifically to assess relational memory, we found that negative schizotypy, but not positive or disorganized schizotypy, is associated with impaired relational memory performance. The deficit was observed both in poorer accuracy and slower response time. The results demonstrate the importance of examining schizotypy as a multidimensional construct, and indicate that using a total schizotypy score both obscures the nature of the association with various dimensions of schizotypy and also explains only half of the variance accounted for by taking into consideration the multidimensionality of schizotypy. These results add to previous findings that negative schizotypy is associated with a wide array of episodic memory deficits linked to impairment in retrieval and processing of contextual information.

Altered Brain Activation During Memory Retrieval Precedes and Predicts Conversion to Psychosis in Individuals at Clinical High Risk

Memory deficits are a hallmark of psychotic disorders such as schizophrenia. However, whether the neural dysfunction underlying these deficits is present before the onset of illness and potentially predicts conversion to psychosis is unclear. In this study, we investigated brain functional alterations during memory processing in a sample of 155 individuals at clinical high risk (including 18 subjects who later converted to full psychosis) and 108 healthy controls drawn from the second phase of the North American Prodrome Longitudinal Study (NAPLS-2). All participants underwent functional magnetic resonance imaging with a paired-associate memory paradigm at the point of recruitment and were clinically followed up for approximately 2 years. We found that at baseline, subjects at high risk showed significantly higher activation during memory retrieval in the prefrontal, parietal, and bilateral temporal cortices (PFWE < .035). This effect was more pronounced in converters than nonconverters and was particularly manifested in unmedicated subjects (P < .001). The hyperactivation was significantly correlated with retrieval reaction time during scan in converters (P = .009) but not in nonconverters and controls, suggesting an exaggerated retrieval effort. These findings suggest that hyperactivation during memory retrieval may mark processes associated with conversion to psychosis, and such measures have potential as biomarkers for psychosis prediction.

Memory and cognition in schizophrenia

Episodic memory deficits are consistently documented as a core aspect of cognitive dysfunction in schizophrenia patients, present from the onset of the illness and strongly associated with functional disability. Over the past decade, research using approaches from experimental cognitive neuroscience revealed disproportionate episodic memory impairments in schizophrenia (Sz) under high cognitive demand relational encoding conditions and relatively unimpaired performance under item-specific encoding conditions. These specific deficits in component processes of episodic memory reflect impaired activation and connectivity within specific elements of frontal-medial temporal lobe circuits, with a central role for the dorsolateral prefrontal cortex (DLPFC), relatively intact function of ventrolateral prefrontal cortex and variable results in the hippocampus. We propose that memory deficits can be understood within the broader context of cognitive deficits in Sz, where impaired DLPFC-related cognitive control has a broad impact across multiple cognitive domains. The therapeutic implications of these findings are discussed.

Aberrant attentive and inattentive brain activity to auditory negative words, and its relation to persecutory delusion in patients with schizophrenia

BACKGROUND AND PURPOSE

Previous research has suggested that deficits in emotion recognition are involved in the pathogenesis of persecutory delusion in schizophrenia. Although disruption in auditory and language processing is crucial in the pathophysiology of schizophrenia, the neural basis for the deficits in emotion recognition of auditorily presented language stimuli and its relation to persecutory delusion have not yet been clarified.

PATIENTS AND METHODS

The current functional magnetic resonance imaging study used a dichotic listening task for 15 patients with schizophrenia and 23 healthy controls matched for age, sex, parental socioeconomic background, handedness, dexterous ear, and intelligence quotient. The participants completed a word recognition task on the attended side in which a word with emotionally valenced content (negative/neutral) was presented to one ear and a different neutral word was presented to the other ear. Participants selectively attended to either ear.

RESULTS

The whole brain analysis detected the aberrant neural activity in the right inferior frontal gyrus in the patients with schizophrenia compared to that in the controls (P<0.05, false discovery rate-corrected). Brain activity in the right pars triangularis of the inferior frontal gyrus was significantly reduced when negatively valenced words were presented to the right ear, whereas the activity of the same region was significantly enhanced when these words were presented to the left ear, irrespective of the attended ear, in the participants with schizophrenia compared to the controls. Furthermore, this diminished brain response to auditorily presented negatively valenced words significantly correlated with severe positive symptoms (r=-0.67, P=0.006) and delusional behavior (r=-0.62, P=0.014) in the patients with schizophrenia.

CONCLUSION

The present results indicate that the significantly impaired brain activity in response to auditorily presented negatively valenced words in the right pars triangularis of the inferior frontal gyrus is associated with the pathogenesis of positive symptoms such as persecutory delusion.

Associative Memory Impairments Are Associated With Functional Alterations Within the Memory Network in Schizophrenia Patients and Their Unaffected First-Degree Relatives: An fMRI Study

Memory impairments are a major characteristic of schizophrenia (SZ). In the current study, we used an associative memory task to test the hypothesis that SZ patients and first-degree relatives have altered functional patterns in comparison to healthy controls. We analyzed the fMRI activation pattern during the presentation of a face-name task in 27 SZ patients, 23 first-degree relatives, and 27 healthy controls. In addition, we performed correlation analyses between individual psychopathology, accuracy and reaction time of the task and the beta scores of the functional brain activations. We observed a lower response accuracy and increased reaction time during the retrieval of face-name pairs in SZ patients compared with controls. Deficient performance was accompanied by abnormal functional activation patterns predominantly in DMN regions during encoding and retrieval. No significant correlation between individual psychopathology and neuronal activation during encoding or retrieval of face-name pairs was observed. Findings of first-degree relatives indicated slightly different functional pattern within brain networks in contrast to controls without significant differences in the behavioral task. Both the accuracy of memory performance as well as the functional activation pattern during retrieval revealed alterations in SZ patients, and, to a lesser degree, in relatives. The results are of potential relevance for integration within a comprehensive model of memory function in SZ. The development of a neurophysiological model of cognition in psychosis may help to clarify and improve therapeutic options to improve memory and functioning in the illness.

Amplitude of low-frequency fluctuations in childhood-onset schizophrenia with or without obsessive-compulsive symptoms: a resting-state functional magnetic resonance imaging study

INTRODUCTION

Childhood-onset schizophrenia with obsessive-compulsive symptoms (COSO) and without obsessive-compulsive symptoms (COS) share considerable overlap in clinical features and genetic risk factors. However, the extent of brain functional abnormalities in COSO and COS is poorly understood.

MATERIAL AND METHODS

A total of 51 first-episode childhood schizophrenic patients and 30 healthy age- and sex-matched controls were recruited. We used the Yale-Brown Obsessive Compulsive Scale to divide patients into COSO (n = 21) and COS (n = 30) groups. Resting-state functional magnetic resonance imaging images were obtained using a gradient-echo echo-planar imaging sequence. Voxel-based analysis of amplitude of low-frequency fluctuation (ALFF) maps between the two groups was performed.

RESULTS

The COS group showed significantly increased ALFF in the right caudate body, middle temporal gyrus and inferior parietal lobule (p < 0.05), while showing decreased ALFF in the left cerebellum posterior lobe (p < 0.05). The COSO group showed significantly increased ALFF in the left and right frontal lobe, cerebellum posterior lobe and precuneus (p < 0.05). When comparing the two groups, COSO showed significantly higher ALFF in the left cerebellum posterior lobe, frontal lobe, supramarginal gyrus, precuneus, right inferior frontal gyrus and medial frontal gyrus (p < 0.05). Interestingly, significantly lower ALFF was found in the right fusiform gyrus, corpus callosum and inferior parietal lobule in the group of patients with obsessive-compulsive symptoms (p < 0.05).

CONCLUSIONS

Our findings increase the understanding of the pathophysiology of schizophrenia and may provide imaging evidence for early diagnosis of COSO or COS.

Localization and Elimination of Attentional Dysfunction in Schizophrenia During Visual Search

Theories of the locus of visual selective attention dysfunction in schizophrenia propose that the deficits arise from either an inability to maintain working memory representations that guide attention, or difficulty focusing lower-level visual attention mechanisms. However, these theoretical accounts neglect the role of long-term memory representations in controlling attention. Here, we show that the control of visual attention is impaired in people with schizophrenia, and that this impairment is driven by an inability to shift top-down attentional control from working memory to long-term memory across practice. Next, we provide converging evidence for the source of attentional impairments in long-term memory by showing that noninvasive electrical stimulation of medial frontal cortex normalizes long-term memory related neural signatures and patients' behavior. Our findings suggest that long-term memory structures may be a source of impaired attentional selection in schizophrenia when visual attention is taxed during the processing of multi-object arrays.

Effects of High-Frequency Transcranial Magnetic Stimulation for Cognitive Deficit in Schizophrenia: A Meta-Analysis

Objective: Repetitive transcranial magnetic stimulation (rTMS) has been applied to dorsolateral prefrontal cortex (DLPFC) to improve cognitive function of patients with schizophrenia (SZs). The aim of this meta-analysis was to evaluate whether a high-frequency rTMS course could enhance cognitive function in SZs. Methods: Studies published in PubMed, Cochrane Library, Embase, ScienceDirect, and Web of science were searched until April 2018. The search terms included: "repetitive transcranial magnetic stimulation" or "Rtms," "SZ," or "schizophrenia," and "neuro-cognition" or "neurocognitive performance" or "cognitive effects" or "cognitive" or "cognition" or "working memory" or "executive function" or "language function" or "processing speed," After screening the literatures according to inclusion and exclusion criteria, extracting data, and evaluating the methodological quality of the included studies, a meta-analysis was performed using RevMan 5.3 software (The Cochrane Collaboration, USA). Results: A total of 9 studies on cognitive dysfunction of SZs were included and involved 351 patients. A significant efficacy of high-frequency rTMS on working memory in SZs was found compared to sham stimulation [p = 0.009, standardized mean difference (SMD) = 0.34]. Specifically, rTMS treatment positioned on the left DLPFC, with a total pluses <30,000 was more significantly more effective in improving the working memory (SMD = 0.33, p = 0.03). No improvement was found in other cognitive domains such as executive function, attention, processing speed, and language function. For the follow-up observations, high-frequency rTMS had long-lasting sustained effects on working memory (SMD = 0.45, p = 0.01) and language function (SMD = 0.77, p = 0.02) in SZs. Conclusions: High-frequency rTMS over the left DLPFC with a total pulses <30,000 stimulation could significantly improve working memory in SZs for an extended period of time.

Theoretical Modeling of Cognitive Dysfunction in Schizophrenia by Means of Errors and Corresponding Brain Networks

The current evidence of cognitive disturbances and brain alterations in schizophrenia does not provide the plausible explanation of the underlying mechanisms. Neuropsychological studies outlined the cognitive profile of patients with schizophrenia, that embodied the substantial disturbances in perceptual and motor processes, spatial functions, verbal and non-verbal memory, processing speed and executive functioning. Standardized scoring in the majority of the neurocognitive tests renders the index scores or the achievement indicating the severity of the cognitive impairment rather than the actual performance by means of errors. At the same time, the quantitative evaluation may lead to the situation when two patients with the same index score of the particular cognitive test, demonstrate qualitatively different performances. This may support the view why test paradigms that habitually incorporate different cognitive variables associate weakly, reflecting an ambiguity in the interpretation of noted cognitive constructs. With minor exceptions, cognitive functions are not attributed to the localized activity but eventuate from the coordinated activity in the generally dispersed brain networks. Functional neuroimaging has progressively explored the connectivity in the brain networks in the absence of the specific task and during the task processing. The spatio-temporal fluctuations of the activity of the brain areas detected in the resting state and being highly reproducible in numerous studies, resemble the activation and communication patterns during the task performance. Relatedly, the activation in the specific brain regions oftentimes is attributed to a number of cognitive processes. Given the complex organization of the cognitive functions, it becomes crucial to designate the roles of the brain networks in relation to the specific cognitive functions. One possible approach is to identify the commonalities of the deficits across the number of cognitive tests or, common errors in the various tests and identify their common "denominators" in the brain networks. The qualitative characterization of cognitive performance might be beneficial in addressing diffuse cognitive alterations presumably caused by the dysconnectivity of the distributed brain networks. Therefore, in the review, we use this approach in the description of standardized tests in the scope of potential errors in patients with schizophrenia with a subsequent reference to the brain networks.

Brain Responses at Encoding Predict Limited Verbal Memory Retrieval by Persons with Schizophrenia

Objective

Special attention has been given to verbal memory deficits in schizophrenia because they are apparent in healthy biological relatives of affected individuals, indicating a link to genetic risk for the disorder. Despite a growing consensus that encoding abnormalities contribute to poor verbal memory in the disorder, few studies have directly examined how neural responses during encoding contribute to later memory performance.

Method

We evaluated event-related potentials (ERPs) during encoding of verbal material by patients with schizophrenia, healthy first-degree biological relatives of patients, and healthy controls. The extent to which N1, N400, and anterior and parietal Late Positive Components (LPCs) explained encoding accuracy and later memory of material was investigated.

Results

Encoding accuracy was associated with asymmetry in anterior LPCs toward right frontal brain regions and was most evident in relatives. N1 was abnormal at encoding in schizophrenia and differentially accounted for later memory performance. In controls better recall of verbal material was predicted by a larger early occipital (N1) encoding response; however, in patients with schizophrenia smaller N1 encoding responses were related to better recall. Interestingly, better recognition of verbal material across groups was also predicted by smaller N1 amplitudes during encoding of word stimuli.

Conclusion

Separable patterns of electrophysiological response during encoding appear to differentially support recall and recognition of material from memory. Similar patterns of electrophysiological response across patient and relative groups suggest that those who carry genetic liability for schizophrenia share deviations in the neural activity related to encoding of material into episodic memory.

Neuroscience-informed computer-assisted cognitive training in schizophrenia

Schizophrenia is a heterogeneous psychiatric syndrome characterized by psychosis. It is also a neurodevelopmental disorder. In the earliest phases of the illness, at-risk individuals exhibit subtle, nonspecific symptoms, including cognitive dysfunction and progressive brain volumetric loss. Generally, schizophrenia is characterized by abnormal/inefficient neural system operations and neural oscillatory activity, as well as functional disconnectivity across frontal-temporo parietal and frontal-subcortical networks; it thus may best be described as a widespread neural oscillatory connectomopathy. Despite earlier views of schizophrenia as an inevitably progressive neurodegenerative disease, emerging evidence indicates that endogenous neuroplastic capacity is retained. An active area of research is directed at understanding how best to harness this learning-induced neuroplasticity to enhance neural system functioning, improve cognition, and prevent-and possibly even reverse-disease progression. In this review, we present an overview of results from the most widely used computer-assisted cognitive-training programs in schizophrenia, contrasting a broad neuropsychological rehabilitation approach with a targeted cognitive-training approach. We then review studies on the neurobiological effects of these two training methods. Finally, we discuss future directions with a focus on the "oscillatory connectome" as a key area of investigation for developing the most precise and scientifically informed treatment approaches for this illness.

Aberrant neural networks for the recognition memory of socially relevant information in patients with schizophrenia

INTRODUCTION

Patients with schizophrenia exhibit several cognitive deficits, including memory impairment. Problems with recognition memory can hinder socially adaptive behavior. Previous investigations have suggested that altered activation of the frontotemporal area plays an important role in recognition memory impairment. However, the cerebral networks related to these deficits are not known. The aim of this study was to elucidate the brain networks required for recognizing socially relevant information in patients with schizophrenia performing an old-new recognition task.

METHODS

Sixteen patients with schizophrenia and 16 controls participated in this study. First, the subjects performed the theme-identification task during functional magnetic resonance imaging. In this task, pictures depicting social situations were presented with three words, and the subjects were asked to select the best theme word for each picture. The subjects then performed an old-new recognition task in which they were asked to discriminate whether the presented words were old or new. Task performance and neural responses in the old-new recognition task were compared between the subject groups. An independent component analysis of the functional connectivity was performed.

RESULTS

The patients with schizophrenia exhibited decreased discriminability and increased activation of the right superior temporal gyrus compared with the controls during correct responses. Furthermore, aberrant network activities were found in the frontopolar and language comprehension networks in the patients.

CONCLUSIONS

The functional connectivity analysis showed aberrant connectivity in the frontopolar and language comprehension networks in the patients with schizophrenia, and these aberrations possibly contribute to their low recognition performance and social dysfunction. These results suggest that the frontopolar and language comprehension networks are potential therapeutic targets in patients with schizophrenia.

Converging effects of diverse treatment modalities on frontal cortex in schizophrenia: A review of longitudinal functional magnetic resonance imaging studies

OBJECTIVES

A variety of treatment options exist for schizophrenia, but the effects of these treatments on brain function are not clearly understood. To facilitate the development of more effective treatment strategies, it is important to identify how brain function in schizophrenia patients is affected by the diverse therapeutic approaches that are currently available. The aim of the present article is to systematically review the evidence for functional brain changes associated with different treatment modalities for schizophrenia.

METHODS

We searched PubMed for longitudinal functional MRI (fMRI) studies reporting on the effects of antipsychotic medications (APM), repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), cognitive remediation therapy (CRT) and cognitive behavioral therapy for psychosis (CBTp) on brain function in schizophrenia.

RESULTS

Thirty six studies fulfilled the inclusion criteria. Functional alterations were observed in diverse brain regions. Across intervention modalities, changes in fMRI parameters were reported most commonly in frontal brain regions including prefrontal cortex, anterior cingulate and inferior frontal cortex.

CONCLUSIONS

We conclude that current treatments for schizophrenia commonly induce functional brain alterations in frontal brain regions. However, interpretability is limited by inconsistency in task and region of interest selection, and failures to replicate. Further task independent fMRI studies examining treatment effects with whole brain analysis are needed to deepen our insights.

Functional neuroanatomical correlates of episodic memory impairment in early phase psychosis

Studies have demonstrated that episodic memory (EM) is often preferentially disrupted in schizophrenia. The neural substrates that mediate EM impairment in this illness are not fully understood. Several functional magnetic resonance imaging (fMRI) studies have employed EM probe tasks to elucidate the neural underpinnings of impairment, though results have been inconsistent. The majority of EM imaging studies have been conducted in chronic forms of schizophrenia with relatively few studies in early phase patients. Early phase schizophrenia studies are important because they may provide information regarding when EM deficits occur and address potential confounds more frequently observed in chronic populations. In this study, we assessed brain activation during the performance of visual scene encoding and recognition fMRI tasks in patients with earlyphase psychosis (n = 35) and age, sex, and race matched healthy control subjects (n = 20). Patients demonstrated significantly lower activation than controls in the right hippocampus and left fusiform gyrus during scene encoding and lower activation in the posterior cingulate, precuneus, and left middle temporal cortex during recognition of target scenes. Symptom levels were not related to the imaging findings, though better cognitive performance in patients was associated with greater right hippocampal activation during encoding. These results provide evidence of altered function in neuroanatomical circuitry subserving EM early in the course of psychotic illness, which may have implications for pathophysiological models of this illness.

Impact of schizophrenia on anterior and posterior hippocampus during memory for complex scenes

Objectives

Hippocampal dysfunction has been proposed as a mechanism for memory deficits in schizophrenia. Available evidence suggests that the anterior and posterior hippocampus could be differentially affected. Accordingly, we used fMRI to test the hypothesis that activity in posterior hippocampus is disproportionately reduced in schizophrenia, particularly during spatial memory retrieval.

Methods

26 healthy participants and 24 patients with schizophrenia from the UC Davis Early Psychosis Program were studied while fMRI was acquired on a 3 Tesla Siemens scanner. During encoding, participants were oriented to critical items through questions about item features (e.g., “Does the lamp have a square shade?”) or spatial location (e.g., “Is the lamp on the table next to the couch?”). At test, participants determined whether scenes were changed or unchanged. fMRI analyses contrasted activation in a priori regions of interest (ROI) in anterior and posterior hippocampus during correct recognition of item changes and spatial changes.

Results

As predicted, patients with schizophrenia exhibited reduced activation in the posterior hippocampus during detection of spatial changes but not during detection of item changes. Unexpectedly, patients exhibited increased activation of anterior hippocampus during detection of item changes. Whole brain analyses revealed reduced fronto-parietal and striatal activation in patients for spatial but not for item change trials.

Conclusions

Results suggest a gradient of hippocampal dysfunction in which posterior hippocampus – which is necessary for processing fine-grained spatial relationships – is underactive, and anterior hippocampus – which may process context more globally - is overactive.

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Patients with schizophrenia show impaired memory for spatial relationships amongst objects in scenes.

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Patients have less posterior hippocampal activation during spatial memory and more anterior hippocampal activation during item memory.

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This gradient of hippocampal dysfunction in schizophrenia, suggests that it should not be examined as a unitary structure in future studies.

White matter correlates of episodic memory encoding and retrieval in schizophrenia

Episodic memory (EM) impairments in schizophrenia (SZ) are predictive of functional outcome and are a potential endophenotype of the disorder. The current study investigated the neuroanatomical correlates of EM encoding and retrieval in SZ with structural magnetic resonance and diffusion tensor imaging (DTI) measures in 22 patients with SZ and 22 age- and gender-matched healthy controls. Tract-based Spatial Statistics (TBSS) was used to investigate microstructural alterations in white matter (WM), while FreeSurfer surface-based analysis was used to determine abnormalities in grey matter (GM) and WM volumetrics and cortical thickness. Compared to controls, patients demonstrated GM deficits in temporal and parietal regions and lower fractional anisotropy (FA) of WM in diffuse brain regions. Patients also demonstrated reduced functioning in both encoding and retention of auditory-verbal EM. Among patients but not controls, EM encoding correlated with WM volume in the orbitofrontal cortex and increased radial diffusivity in the fornix, whereas EM retrieval correlated with WM volume in posterior parietal cortex. These findings suggest a differential role for frontal and parietal WM in EM encoding and retrieval processes, while myelin integrity of the fornix may play a specific role in mediating EM encoding processes in SZ.

Quantifying Individual Brain Connectivity with Functional Principal Component Analysis for Networks

In typical functional connectivity studies, connections between voxels or regions in the brain are represented as edges in a network. Networks for different subjects are constructed at a given graph density and are summarized by some network measure such as path length. Examining these summary measures for many density values yields samples of connectivity curves, one for each individual. This has led to the adoption of basic tools of functional data analysis, most commonly to compare control and disease groups through the average curves in each group. Such group differences, however, neglect the variability in the sample of connectivity curves. In this article, the use of functional principal component analysis (FPCA) is demonstrated to enrich functional connectivity studies by providing increased power and flexibility for statistical inference. Specifically, individual connectivity curves are related to individual characteristics such as age and measures of cognitive function, thus providing a tool to relate brain connectivity with these variables at the individual level. This individual level analysis opens a new perspective that goes beyond previous group level comparisons. Using a large data set of resting-state functional magnetic resonance imaging scans, relationships between connectivity and two measures of cognitive function-episodic memory and executive function-were investigated. The group-based approach was implemented by dichotomizing the continuous cognitive variable and testing for group differences, resulting in no statistically significant findings. To demonstrate the new approach, FPCA was implemented, followed by linear regression models with cognitive scores as responses, identifying significant associations of connectivity in the right middle temporal region with both cognitive scores.

Following the Spreading of Brain Structural Changes in Alzheimer's Disease: A Longitudinal, Multimodal MRI Study

BACKGROUND

Longitudinal MRI studies in Alzheimer's disease (AD) are one of the most reliable way to track brain changes along the course of the disease.

OBJECTIVE

To investigate the evolution of grey matter (GM) atrophy and white matter (WM) damage in AD patients, and to assess the relationships of MRI changes with baseline clinical and cognitive variables and their evolution over time.

METHODS

Clinical, neuropsychological, and MRI assessments (T1-weighted and diffusion tensor [DT]-MRI) were obtained from 14 patients with AD at baseline and after a 16 ± 3 month period. Lumbar puncture was obtained at study entry. At baseline, AD patients were compared to 37 controls. GM atrophy progression was assessed with tensor-based morphometry and GM volumes of interest, and WM damage progression using tract-based spatial statistics and tractography.

RESULTS

At baseline, patients showed cortical atrophy in the medial temporal and parietal regions and a widespread pattern of WM damage involving the corpus callosum, cingulum, and temporo-occipital, parietal, and frontal WM tracts. During follow up, AD patients showed total GM atrophy, while total WM volume did not change. GM tissue loss was found in frontal, temporal, and parietal regions. In addition, AD patients showed a progression of WM microstructural damage to the corpus callosum, cingulum, fronto-parietal and temporo-occipital connections bilaterally. Patients with higher baseline cerebrospinal fluid total tau showed greater WM integrity loss at follow up. GM and WM changes over time did not correlate with each other nor with cognitive evolution.

CONCLUSION

In AD, GM atrophy and WM tract damage are likely to progress, at least partially, independently. This study suggests that a multimodal imaging approach, which includes both T1-weighted and DT MR imaging, may provide additional markers to monitor disease progression.

Aberrant Hippocampal Connectivity in Unmedicated Patients With Schizophrenia and Effects of Antipsychotic Medication: A Longitudinal Resting State Functional MRI Study

To better characterize hippocampal pathophysiology in schizophrenia, we conducted a longitudinal study evaluating hippocampal functional connectivity during resting state, using seeds prescribed in its anterior and posterior regions. We enrolled 34 unmedicated patients with schizophrenia or schizoaffective disorder (SZ) and 34 matched healthy controls. SZ were scanned while off medication, then were treated with risperidone for 6 weeks and re-scanned (n = 22). Group differences in connectivity, as well as changes in connectivity over time, were assessed on the group's participant level functional connectivity maps. We found significant dysconnectivity with anterior and posterior hippocampal seeds in unmedicated SZ. Baseline connectivity between the hippocampus and anterior cingulate cortex, caudate nucleus, auditory cortex and calcarine sulcus in SZ predicted subsequent response to antipsychotic medications. These same regions demonstrated changes over the 6-week treatment trial that were correlated with symptomatic improvement. Our findings implicate several neural networks relevant to clinical improvement with antipsychotic medications.

Association between impaired brain activity and volume at the sub-region of Broca's area in ultra-high risk and first-episode schizophrenia: A multi-modal neuroimaging study

Recent studies have suggested that functional abnormalities in Broca's area, which is important in language production (speech and thoughts before speech), play an important role in the pathophysiology of schizophrenia. While multi-modal approaches have proved useful in revealing the specific pathophysiology of psychosis, the association of functional abnormalities with gray matter volume (GMV) here in subjects with an ultra-high risk (UHR) of schizophrenia, those with first-episode schizophrenia (FES), and healthy controls has yet to be clarified. Therefore, the relationship between cortical activity measured using functional near-infrared spectroscopy (fNIRS) during a verbal fluency task, and GMV in the Broca's area assessed using a manual tracing in magnetic resonance imaging (MRI), which considers individual structural variation, was examined for 57 subjects (23 UHR/18 FES/16 controls). The UHR and FES group showed significantly reduced brain activity compared to control group in the left pars triangularis (PT) (P=.036, .003, respectively). Furthermore in the FES group, the reduced brain activity significantly positively correlated with the volume in the left PT (B=0.29, P=.027), while significant negative association was evident for all subjects (B=-0.18, P=.010). This correlation remained significant after adjusting for antipsychotics dosage, and voxel-wise analysis could not detect any significant correlation between impaired cortical activity and volume. The significant relationship between neural activity and GMV in the left PT may reflect a specific pathophysiology related to the onset of schizophrenia.

Disrupted amplitude of low-frequency fluctuations in antipsychotic-naïve adolescents with early-onset schizophrenia

Evidence points to a crucial role for altered neural oscillations and synchrony in the pathophysiology of schizophrenia. Previous resting state functional magnetic resonance imaging (fMRI) studies found aberrant amplitudes of low-frequency oscillations in adult patients with schizophrenia. Whether the abnormality is also present in adolescents with early-onset schizophrenia (EOS) is largely unknown. We recruited 39 adolescents with a first episode of EOS and 31 age- and education- matched healthy controls. Resting state fMRI was obtained using an echo-planar imaging sequence. Voxel-wise amplitude of low-frequency (0.01-0.08Hz) fluctuations (ALFF) was compared between groups. We investigated seed-based functional connectivity between significantly disturbed ALFF regions and whole brain voxels in all participants. EOS participants exhibited significantly increased ALFF values in the orbitofrontal cortex (OFC) and decreased ALFF in the ventral precuneus compared with controls. Decreased ALFF values in the precuneus of EOS showed a significant negative correlation with negative symptom scores on the Positive and Negative Syndrome Scale. Disturbed functional connectivity mainly occurred between the orbitofrontal cortex and the temporal cortex in EOS. These findings demonstrate abnormal spontaneous neuronal activity and functional connectivity in the frontal and parietal cortex of EOS. Aberrant ALFF in the precuneus might be a biomarker of EOS.

Neuroscience-informed Auditory Training in Schizophrenia: A Final Report of the Effects on Cognition and Serum Brain-Derived Neurotrophic Factor

Objective

We previously reported the interim effects in a per protocol analysis of a randomized controlled trial of an innovative neuroscience-informed computerized cognitive training approach in schizophrenia. Here we report the effects of training on behavioral outcome measures in our final sample using an intent-to-treat analysis. We also report the effects on serum brain-derived neurotrophic factor (BDNF).

Method

Eighty-seven clinically stable participants with schizophrenia were randomly assigned to either targeted auditory training (AT, N=46) or a computer games control condition (CG, N=41). Participants were assessed on neurocognition, symptoms and functional outcome at baseline and after 50 hours of intervention delivered over 10 weeks. Serum BDNF was assessed at baseline, at 2 weeks, and at 10 weeks.

Results

After the intervention, AT participants showed significant gains in global cognition, speed of processing, verbal learning, and verbal memory, relative to CG participants, with no changes in symptoms or functioning. At baseline, schizophrenia participants had significantly lower-than-normal serum BDNF. AT participants showed a significant increase in serum BDNF compared to CG participants, and “normalized” levels by post training.

Conclusions

Participants with chronic schizophrenia made significant cognitive gains after 50 hours of intensive computerized training delivered as a stand-alone treatment, but no improvement in symptoms or functioning. Serum BDNF levels were significantly increased, and may serve as a peripheral biomarker for the effects of training. Future research must focus on: 1) Methods of integrating cognitive training with psychosocial treatments; 2) A deeper understanding of underlying neurophysiology in order to enhance critical mechanisms of action.

A Possible Common Neurophysiologic Basis for MDD, Bipolar Disorder, and Schizophrenia: Lessons from Electrophysiology

There is ample electrophysiological evidence of attention dysfunction in the EEG/ERP signal of major depressive disorder (MDD), bipolar disorder, and schizophrenia. The reduced attention-related ERP waves show much similarity between MDD, bipolar disorder, and schizophrenia, raising the question whether there are similarities in the neurophysiologic process that underlies attention dysfunction in these pathologies. The present work suggests that there is such a unified underlying neurophysiologic process, which results in reduced attention in the three pathologies. Naturally, as these pathologies involve different clinical manifestations, we expect differences in their underlying neurophysiology. These differences and their subtle manifestation in the ERP marker for attention are also discussed. MDD, bipolar disorder, and schizophrenia are just three of multiple neuropsychiatric disorders, which involve changes in the EEG/ERP manifestations of attention. Further work should expand the basic model presented here to offer comprehensive modeling of these multiple disorders and to emphasize similarities and dissimilarities of the underlying neurophysiologic processes.

Verbal memory impairments in schizophrenia associated with cortical thinning

Verbal memory (VM) represents one of the most affected cognitive domains in schizophrenia. Multiple studies have shown that schizophrenia is associated with cortical abnormalities, but it remains unclear whether these are related to VM impairments. Considering the vast literature demonstrating the role of the frontal cortex, the parahippocampal cortex, and the hippocampus in VM, we examined the cortical thickness/volume of these regions. We used a categorical approach whereby 27 schizophrenia patients with 'moderate to severe' VM impairments were compared to 23 patients with 'low to mild' VM impairments and 23 healthy controls. A series of between-group vertex-wise GLM on cortical thickness were performed for specific regions of interest defining the parahippocampal gyrus and the frontal cortex. When compared to healthy controls, patients with 'moderate to severe' VM impairments revealed significantly thinner cortex in the left frontal lobe, and the parahippocampal gyri. When compared to patients with 'low to mild' VM impairments, patients with 'moderate to severe' VM impairments showed a trend of thinner cortex in similar regions. Virtually no differences were observed in the frontal area of patients with 'low to mild' VM impairments relative to controls. No significant group differences were observed in the hippocampus. Our results indicate that patients with greater VM impairments demonstrate significant cortical thinning in regions known to be important in VM performance. Treating VM deficits in schizophrenia could have a positive effect on the brain; thus, subgroups of patients with more severe VM deficits should be a prioritized target in the development of new cognitive treatments.

A Hierarchical Generative Framework of Language Processing: Linking Language Perception, Interpretation, and Production Abnormalities in Schizophrenia

Language and thought dysfunction are central to the schizophrenia syndrome. They are evident in the major symptoms of psychosis itself, particularly as disorganized language output (positive thought disorder) and auditory verbal hallucinations (AVHs), and they also manifest as abnormalities in both high-level semantic and contextual processing and low-level perception. However, the literatures characterizing these abnormalities have largely been separate and have sometimes provided mutually exclusive accounts of aberrant language in schizophrenia. In this review, we propose that recent generative probabilistic frameworks of language processing can provide crucial insights that link these four lines of research. We first outline neural and cognitive evidence that real-time language comprehension and production normally involve internal generative circuits that propagate probabilistic predictions to perceptual cortices - predictions that are incrementally updated based on prediction error signals as new inputs are encountered. We then explain how disruptions to these circuits may compromise communicative abilities in schizophrenia by reducing the efficiency and robustness of both high-level language processing and low-level speech perception. We also argue that such disruptions may contribute to the phenomenology of thought-disordered speech and false perceptual inferences in the language system (i.e., AVHs). This perspective suggests a number of productive avenues for future research that may elucidate not only the mechanisms of language abnormalities in schizophrenia, but also promising directions for cognitive rehabilitation.

Altered prefrontal activity and connectivity predict different cognitive deficits in schizophrenia

BACKGROUND

Cognitive dysfunction is considered a core feature of schizophrenia, and impaired performances in episodic memory (EM) and executive function (EF) tasks are consistently reported in schizophrenia patients. Traditional fMRI and EEG studies have helped identifying brain areas, including the prefrontal cortex (PFC), involved in these tasks. However, it is unclear whether intrinsic defects in prefrontal function per se contribute to poor performance in schizophrenia, given the presence of confounds like reduced motivation and psychotic symptoms. TMS/hd-EEG measurements are obtained without cognitive effort, and can be calculated in any cortical area.

METHODS

We performed TMS/hd-EEG recordings in parietal, motor, premotor, and PFC in healthy individuals (N=20) and schizophrenia patients (N=20). Source modeling of TMS-evoked responses was performed, and measures of cortical activity (significant current density, SCD) and connectivity (significant current scattering, SCS) were computed. Patients with schizophrenia also performed Penn Word memory delayed (CPWd) and Penn Conditional Exclusion Test (PCET). CPWd evaluates EM and involves primarily PFC, whereas PCET reflects EF and implicates PFC with other brain regions.

FINDINGS

We found no difference in SCD and SCS after TMS of parietal/motor cortices, whereas those parameters were reduced in premotor/prefrontal areas in schizophrenia patients. In PFC, where these measures were most defective, SCD was negatively correlated with performance in CPWd whereas higher SCS values were associated with more errors in PCET.

CONCLUSION

These findings indicate that schizophrenia patients have intrinsic defects in both activity and connectivity of PFC, and that these defects are specifically associated with impairments in cognitive abilities.

Effective connectivity during episodic memory retrieval in schizophrenia participants before and after antipsychotic medication

BACKGROUND

Impairment in episodic memory is one of the most robust findings in schizophrenia. Disruptions of fronto-temporal functional connectivity that could explain some aspects of these deficits have been reported. Recent work has identified abnormal hippocampal function in unmedicated patients with schizophrenia (SZ), such as increased metabolism and glutamate content that are not always seen in medicated SZ. For these reasons, we hypothesized that altered fronto-temporal connectivity might originate from the hippocampus and might be partially restored by antipsychotic medication.

METHODS

Granger causality methods were used to evaluate the effective connectivity between frontal and temporal regions in 21 unmedicated SZ and 20 matched healthy controls (HC) during performance of an episodic memory retrieval task. In 16 SZ, effective connectivity between these regions was evaluated before and after 1-week of antipsychotic treatment.

RESULTS

In HC, significant effective connectivity originating from the right hippocampus to frontal regions was identified. Compared to HC, unmedicated SZ showed significant altered fronto-temporal effective connectivity, including reduced right hippocampal to right medial frontal connectivity. After 1-week of antipsychotic treatment, connectivity more closely resembled the patterns observed in HC, including increased effective connectivity from the right hippocampus to frontal regions.

CONCLUSIONS

These results support the notion that memory disruption in schizophrenia might originate from hippocampal dysfunction and that medication restores some aspects of fronto-temporal dysconnectivity. Patterns of fronto-temporal connectivity could provide valuable biomarkers to identify new treatments for the symptoms of schizophrenia, including memory deficits.

Amphetamine sensitisation and memory in healthy human volunteers: a functional magnetic resonance imaging study

Amphetamine sensitisation (AS) is an established animal model of the hypersensitivity to psychostimulants seen in patients with schizophrenia. AS also models the dysregulation of mesolimbic dopamine signalling which has been implicated in the development of psychotic symptoms. Recent data suggest that the enhanced excitability of mesolimbic dopamine neurons in AS is driven by a hyperactivity of hippocampal (subiculum) neurons, consistent with a strong association between hippocampal dysfunction and schizophrenia. While AS can be modelled in human volunteers, its functional consequences on dopaminoceptive brain regions (i.e. striatum and hippocampus) remains unclear. Here we describe the effects of a sensitising dosage pattern of dextroamphetamine on the neural correlates of motor sequence learning in healthy volunteers, within a randomised, double-blind, parallel-groups design. Behaviourally, sensitisation was characterised by enhanced subjective responses to amphetamine but did not change performance (i.e. learning rate) during an explicit sequence learning task. In contrast, functional magnetic resonance imaging (fMRI) measurements showed that repeated intermittent amphetamine exposure was associated with increased blood-oxygen-level dependent (BOLD) signal within the medial temporal lobe (MTL) (subiculum/entorhinal cortex) and midbrain, in the vicinity of the substantia nigra/ventral tegmental area (SN/VTA) during sequence encoding. Importantly, MTL hyperactivity correlated with the sensitisation of amphetamine-induced attentiveness. The MTL-midbrain hyperactivity reported here mirrors observations in sensitised rodents and is consistent with contemporary models of schizophrenia and behavioural sensitisation. These findings of meso-hippocampal hyperactivity during AS thus link pathophysiological concepts of dopamine dysregulation to cognitive models of psychosis.

Hippocampal integrity and neurocognition in first-episode schizophrenia: a multidimensional study

OBJECTIVES

Impairments in memory and executive function are key components of schizophrenia. These disturbances have been linked to several subcortical and cortical networks. For example, anatomical and functional changes in the hippocampus have been linked to deficits in these cognitive domains. However, the association between hippocampal morphometry, neurochemistry and function is controversial. Therefore, we aimed to investigate the relationship between hippocampal anomalies and their functional relevance.

METHODS

Fifty-seven first-episode schizophrenia patients (FE-SZ) and 61 healthy control subjects (HC) participated in this study. Hippocampal volumes were investigated using structural magnetic resonance imaging (sMRI) and hippocampal neurochemistry was determined using proton magnetic resonance spectroscopy (1H MRS). Verbal memory was used as a hippocampus-dependent cognitive task whereas working memory and cognitive flexibility assessed frontal lobe function.

RESULTS

FE-SZ presented smaller volumes of the left hippocampus, with a significant correlation between left hippocampal volume and verbal memory performance (immediate recall). There was also an inverse correlation between neurochemical ratios (NAA/Cho and Cho/Cr) and verbal memory (delayed recognition). Tests of cognitive flexibility and working memory were not correlated with MRI and 1H MRS values. Compared to HC, FE-SZ demonstrated reduced performance in all of the assessed neurocognitive domains.

CONCLUSIONS

These results point to a relationship between verbal memory and hippocampal integrity in schizophrenia patients which might be independent from deficits in other memory domains. Disturbed verbal memory functions in FE-SZ might be linked specifically to hippocampal function.

A genome-wide supported variant in CACNA1C influences hippocampal activation during episodic memory encoding and retrieval

The alpha 1C subunit of the L-type voltage-gated calcium channel (CACNA1C) gene is one of the best replicated susceptibility loci for bipolar disorder, schizophrenia and major depression. It is involved in learning, memory and brain plasticity. Genetic studies using functional magnetic resonance imaging (fMRI) reported evidence of association with the CACNA1C single nucleotide polymorphism rs1006737 with functional correlates of episodic memory encoding and retrieval, especially activations in the hippocampus. These results, however, are inconsistent with regard to the magnitude and directionality of effect. In the present study, brain activation was measured with fMRI during an episodic memory encoding and retrieval task using neutral faces in two independent samples of 94 and 111 healthy subjects, respectively. Within whole brain analyses, a main effect of genotype emerged mainly in the right hippocampus during encoding as well as retrieval within the first sample: Carriers of the minor allele (A) exhibited lower activations compared to G/G allele carriers. This effect could be replicated within the second sample, however, only for the retrieval condition. The results strengthen findings that rs1006737 is associated with neural systems related to memory processes in hippocampal regions which are detectable in healthy subjects.

Altered language network activity in young people at familial high-risk for schizophrenia

BACKGROUND

Abnormalities in language and language neural circuitry are observed in schizophrenia (SZ). Similar, but less pronounced language deficits are also seen in young first-degree relatives of people with SZ, who are at higher familial risk (FHR) for the disorder than the general population. The neural underpinnings of these deficits in people with FHR are unclear.

METHODS

Participants were 43 people with FHR and 32 comparable controls. fMRI scans were collected while participants viewed associated and unrelated word pairs, and performed a lexical decision task. fMRI analyses conducted in SPM8 examined group differences in the modulation of hemodynamic activity by semantic association.

RESULTS

There were no group differences in demographics, IQ or behavioral semantic priming, but FHR participants had more schizotypal traits than controls. Controls exhibited the expected suppression of hemodynamic activity to associated versus unrelated word pairs. Compared to controls, FHR participants showed an opposite pattern of hemodynamic modulation to associated versus unrelated word pairs, in the left inferior frontal gyrus (IFG), right superior and middle temporal gyrus (STG) and the left cerebellum. Group differences in activation were significant, FWE-corrected for multiple comparisons (p<0.05). Activity within the IFG during the unrelated condition predicted schizotypal symptoms in FHR participants.

CONCLUSIONS

FHR for SZ is associated with abnormally increased neural activity to semantic associates within an inferior frontal/temporal network. This might increase the risk of developing unusual ideas, perceptions and disorganized language that characterize schizotypal traits, potentially predicting which individuals are at greater risk to develop a psychotic disorder.

Extent of cortical involvement in amyotrophic lateral sclerosis--an analysis based on cortical thickness

Background

Besides the defining involvement of upper and lower motor neurons, the involvement of extramotor structures has been increasingly acknowledged in amyotrophic lateral sclerosis (ALS).

Methods

Here we investigated a group of 14 mildly to moderately affected ALS patients and 14 age-matched healthy control participants using cortical thickness analysis. Cortical thickness was determined from high resolution 3D T1 magnetic resonance images and involved semiautomatic segmentation in grey and white matter, cortical alignment and determination of thickness using the Laplace method. In addition to a whole-cortex analysis a region of interest approach was applied.

Results

ALS patients showed regions of significant cortical thinning in the pre- and postcentral gyri bilaterally. Further regions of cortical thinning included superior and inferior parietal lobule, angular and supramarginal gyrus, insula, superior frontal, temporal and occipital regions, thus further substantiating extramotor involvement in ALS. A relationship between cortical thickness of the right superior frontal cortex and clinical severity (assessed by the ALS functional rating scale) was also demonstrated.

Conclusions

Cortical thickness is reduced in ALS not only in motor areas but in widespread non-motor cortical areas. Cortical thickness is related to clinical severity.

Brain functional connectivity of male patients in remission after the first episode of schizophrenia

OBJECTIVES

Abnormal task-related activation and connectivity is present in schizophrenia. The aim of this study was the analysis of functional networks in schizophrenia patients in remission after the first episode.

EXPERIMENTAL DESIGN

Twenty-nine male patients in remission after the first episode of schizophrenia and 22 healthy controls underwent examination by functional magnetic resonance during verbal fluency tasks (VFT). The functional connectivity of brain networks was analyzed using independent component analysis.

RESULTS

The patients showed lower activation of the salience network during VFT. They also showed lower deactivation of the default mode network (DMN) during VFT processing. Spectral analysis of the component time courses showed decreased power in slow frequencies of signal fluctuations in the salience and DMNs and increased power in higher frequencies in the left frontoparietal cortex reflecting higher fluctuations of the network activity. Moreover, there was decreased similarity of component time courses in schizophrenia—the patients had smaller negative correlation between VFT activated and deactivated networks, and smaller positive correlations between DMN subcomponents.

CONCLUSIONS

There is still an abnormal functional connectivity of several brain networks in remission after the first episode of schizophrenia. The effect of different treatment modalities on brain connectivity, together with temporal dynamics of this functional abnormality should be the objective of further studies to assess its potential as a marker of disease stabilization.

Memory deficits in schizophrenia: a selective review of functional magnetic resonance imaging (FMRI) studies

Schizophrenia is a complex chronic mental illness that is characterized by positive, negative and cognitive symptoms. Cognitive deficits are most predictive of long-term outcomes, with abnormalities in memory being the most robust finding. The advent of functional magnetic resonance imaging (fMRI) has allowed exploring neural correlates of memory deficits in vivo. In this article, we will give a selective review of fMRI studies probing brain regions and functional networks that are thought to be related to abnormal memory performance in two memory systems prominently affected in schizophrenia; working memory and episodic memory. We revisit the classic "hypofrontality" hypothesis of working memory deficits and explore evidence for frontotemporal dysconnectivity underlying episodic memory abnormalities. We conclude that fMRI studies of memory deficits in schizophrenia are far from universal. However, the current literature does suggest that alterations are not isolated to a few brain regions, but are characterized by abnormalities within large-scale brain networks.

Limbic hyperactivity associated to verbal memory deficit in schizophrenia

In schizophrenia there seems to be an inefficient activation of prefrontal and hippocampal regions. Patients tend to show worse cognitive performance in functions subserved by those regions as compared to healthy controls in spite of higher regional activation. However, the association between activation abnormalities and cognitive deficits remains without being understood. In the present study, we compared cerebral perfusion using single-photon emission tomography (SPECT) in patients and controls to study the association between activation patterns and cognitive performance in this disease. The SPECT studies were simultaneously obtained with an electrophysiological recording during a P300 paradigm to elicit P3a and P3b components. We included 23 stable patients with paranoid schizophrenia and 29 healthy controls that underwent clinical and cognitive assessments. Patients with schizophrenia showed an increased perfusion in the right hippocampus with respect to healthy controls, they also displayed a statistically significant inverse association between perfusion in the left hippocampus and verbal memory performance. Healthy controls showed an inverse association between perfusion in the left dorsolateral prefrontal (DLPFC) region and working memory performance. P3b but not P3a amplitude was significantly lower in patients. The limbic overactivation in the patients may contribute to their cognitive deficits in verbal memory.