Structural and Functional Connectivity of Visual Cortex in Schizophrenia and Bipolar Disorder: A Graph-Theoretic Analysis

Visual processing abnormalities in schizophrenia (SZ) are poorly understood, yet predict functional outcomes in the disorder. Bipolar disorder (BD) may involve similar visual processing deficits. Converging evidence suggests that visual processing may be relatively normal at early stages of visual processing such as early visual cortex (EVC), but that processing abnormalities may become more pronounced by mid-level visual areas such as lateral occipital cortex (LO). However, little is known about the connectivity of the visual system in SZ and BD. If the flow of information to, from, or within the visual system is disrupted by reduced connectivity, this could help to explain perceptual deficits. In the present study, we performed a targeted analysis of the structural and functional connectivity of the visual system using graph-theoretic metrics in a sample of 48 SZ, 46 BD, and 47 control participants. Specifically, we calculated parallel measures of local efficiency for EVC and LO from both diffusion weighted imaging data (structural) and resting-state (functional) imaging data. We found no structural connectivity differences between the groups. However, there was a significant group difference in functional connectivity and a significant group-by-region interaction driven by reduced LO connectivity in SZ relative to HC, whereas BD was approximately intermediate to the other 2 groups. We replicated this pattern of results using a different brain atlas. These findings support and extend theoretical models of perceptual dysfunction in SZ, providing a framework for further investigation of visual deficits linked to functional outcomes in SZ and related disorders.

Effects of Transcranial Direct Current Stimulation on Visual Neuroplasticity in Schizophrenia

People with schizophrenia (SZ) exhibit visual processing abnormalities that affect their daily functioning and remediating these deficits might help to improve functioning. Transcranial direct current stimulation (tDCS) is a potential tool for perceptual enhancement for this purpose, though there are no reports of tDCS applied to visual cortex in SZ. In a within-subject, crossover design, we evaluated the effects of tDCS on visual processing in 27 SZ. All patients received anodal, cathodal, or sham stimulation over the central occipital region in 3 visits separated by 1 week. In each visit, a backward masking task and an electroencephalography measure of visual neuroplasticity were administered after tDCS. Neuroplasticity was assessed with visual evoked potentials before and after tetanizing visual high-frequency stimulation. Masking performance was significantly poorer in the anodal and cathodal conditions compared with sham. Both anodal and cathodal stimulation increased the amplitude of P1 but did not change the plasticity index. We found significant plasticity effects of tDCS for only one waveform for one stimulation condition (P2 for anodal tDCS) which did not survive correction for multiple comparisons. The reason for the lack of tDCS stimulation effects on plasticity may be because tDCS was not delivered simultaneously with the tetanizing visual stimulus. The present findings emphasize the need for more research on the relevant parameters for stimulation of visual processing regions in clinical populations.

People with schizophrenia do not show the normal benefits of social versus nonsocial attentional cues

OBJECTIVE

Schizophrenia is associated with impairments in social motivation. Social attention has been proposed as an underlying mechanism for social motivation. However, studies in schizophrenia have rarely examined social attention, and none of these studies examined the effects with rapidly presented stimuli.

METHOD

The current study examined whether individuals with schizophrenia have reduced social attention and whether reduced social attention was related to social motivation deficits (measured with the Clinical Assessment Interview for Negative Symptoms) and decreased social functioning (Role Functioning Scale). Thirty-seven outpatients with schizophrenia and 29 healthy participants completed a gaze cueing task with directional social cues (eye gaze) and nonsocial cues (arrows) at varying stimulus onset asynchronies.

RESULTS

As predicted, schizophrenia participants had reduced social attention relative to nonsocial attention, compared with healthy participants. Healthy participants were quicker to respond to social cues than nonsocial cues, but schizophrenia participants did not exhibit this same pattern. Schizophrenia participants showed higher accuracy when targets appeared in the same location as a directional cue (i.e., congruency) for nonsocial, but not social, cues. Contrary to expectations, reduced social attention was not significantly correlated with clinically rated social motivation deficits or decreased social functioning in the schizophrenia group.

CONCLUSION

These findings provide evidence for social attention deficits in schizophrenia, but without a clear mapping of its influence on social motivation. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Early Visual Processing Is Associated With Social Cognitive Performance in Recent-Onset Schizophrenia

BACKGROUND

Early-stage visual processing deficits are evident in chronic schizophrenia. Consistent with a cascade model of information processing, whereby early perceptual processes have downstream effects on higher-order cognition, impaired visual processing is associated with deficits in social cognition in this clinical population. However, the nature of this relationship in the early phase of illness is unknown. Here, we present data from a study of early visual processing and social cognitive performance in recent-onset schizophrenia (ROSz).

METHOD

Thirty-two people with ROSz and 20 healthy controls (HC) completed a visual backward masking task using stimuli of real world objects (Object Masking) to assess early-stage (i.e., 0-125 ms post-stimulus onset) visual processing. Subjects also completed two tasks of social cognition, one assessing relatively low-level processes of emotion identification (Emotion Biological Motion, EmoBio), and another assessing more complex, higher-order theory of mind abilities (The Awareness of Social Inference Test, TASIT). Group differences were tested with repeated measures ANOVAs and t-tests. Bivariate correlations and linear regressions tested the strength of associations between early-stage visual processing and social cognitive performance in ROSz.

RESULTS

For Object Masking, the mask interfered with object identification over a longer interval for ROSz than for HC [F (3.19, 159.35) = 8.51, p < 0.001]. ROSz were less accurate on the EmoBio task [t (50) = -3.36, p = 0.001] and on the TASIT compared to HC [F (1, 50) = 38.37, p < 0.001]. For the TASIT ROSz were disproportionately impaired on items assessing sarcasm detection [F (1, 50) = 4.30, p = 0.04]. In ROSz, better Object Masking performance was associated with better social cognitive performance [r EmoBio = 0.45, p < 0.01; r TASIT = 0.41, p < 0.02]. Regression analyses did not provide significant support for low-level social cognition mediating the relationship between visual processing and high-level social cognition.

CONCLUSION

Early-stage visual processing, low-level social cognition, and high-level social cognition were all significantly impaired in ROSz. Early-stage visual processing was associated with performance on the social cognitive tasks in ROSz, consistent with a cascade model of information processing. However, significant cascading effects within social cognition were not supported. These data suggest that interventions directed at early visual processing may yield downstream effects on social cognitive processes.

Reward processing in certain versus uncertain contexts in schizophrenia: An event-related potential (ERP) study

Disturbances in motivation are prominent in the clinical presentation of people with schizophrenia and might reflect a disturbance in reward processing. Recent advances in affective neuroscience have subdivided reward processing into distinct components, but there are two limitations of the prior work in schizophrenia. First, studies typically focus on only one component rather than on the unfolding of reward processing across multiple stages. Second, studies have not considered the impact of certainty effects, which represent an important contextual factor that impacts processing. We examined whether individuals with schizophrenia show the typical certainty effects across three phases of reward processing: cue evaluation, feedback anticipation, and feedback receipt. Electroencephalography from 74 healthy controls and 92 people with schizophrenia was recorded during a cued gambling task under conditions in which cues indicated forthcoming reward outcomes that were certain or uncertain. Controls demonstrated the expected certainty effects across each stage. Initial cue evaluation (cue P300) was intact in the schizophrenia group, but people with schizophrenia showed diminished certainty effects during feedback anticipation (stimulus-preceding negativity [SPN]) and receipt (feedback reward positivity [fRewP] and feedback P300). During feedback receipt, event-related potentials in people with schizophrenia were similar to controls for the uncertain context but larger than controls for the certain context. Essentially, people with schizophrenia appeared to process certain feedback as though it were uncertain. These findings show, for the first time, that the fundamental distinction between certain and uncertain contexts is altered in schizophrenia at a neural level. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Evaluating visual neuroplasticity with EEG in schizophrenia outpatients

Deficient neuroplasticity has been implicated in schizophrenia and can be examined with non-invasive methods in humans. High frequency visual stimulation (HFS) induces neuroplastic changes in visual evoked potential (VEP) components, similar to the tetanizing electrical stimulation that induces synaptic long-term potentiation (LTP). While visual HFS paradigms have been used in schizophrenia, the use of a single visual stimulus has precluded demonstration of whether the plasticity effects are specific to the stimulus presented during HFS (i.e., input specific). Additionally, test-retest reliability of VEP plasticity effects, an important consideration for applications of HFS paradigms in schizophrenia clinical trials, remains unknown. Accordingly, we administered a visual HFS paradigm to 38 schizophrenia patients and 27 healthy controls at baseline and two-weeks later. VEPs were elicited by horizontal and vertical line gratings before and after HFS; only one orientation was tetanized with HFS. Using a mass univariate permutation approach, we identified an input-specific cluster across groups that was broadly distributed over parietal-occipital areas between 108 and 183 ms. However, the groups did not differ in terms of the strength of plasticity effect. The test-retest reliability of the input-specific plasticity effect was modest over two weeks, suggesting that this HFS paradigm requires further development before it could be used to track plasticity change in clinical trials. Moreover, while the current HFS paradigm induced significant input-specific neuroplasticity, it did not replicate prior studies showing deficient neuroplasticity in schizophrenia. Accordingly, demonstration of deficient visual LTP-like neuroplasticity in schizophrenia may depend on paradigm parameters that remain to be fully elucidated.

Resilience in homeless veterans: Clinical and cognitive correlates

OBJECTIVE

Resilience is broadly defined as the ability to respond adaptively to challenges or adversity. It is unclear which clinical and cognitive factors are most closely related to resilience. Also, the dimensions that comprise resilience may differ among different groups, such as those who are homeless. The purpose of this study was to understand the relationships between resilience and clinical, cognitive, and functional variables among homeless veterans and to determine independent predictors of resilience.

METHOD

One hundred homeless veterans completed measures of resilience, defeatist beliefs, negative symptoms, psychotic and mood symptoms, social and nonsocial cognition, and community functioning. We examined associations between resilience and clinical, cognitive, and functional measures. We performed regression analyses to determine independent contributions of the variables to resilience.

RESULTS

Resilience was correlated with negative symptoms, defeatist beliefs, depression/anxiety symptoms, and social cognition. There were no significant correlations with nonsocial cognition or psychotic symptoms. Stepwise multiple linear regression showed that defeatist beliefs, motivational negative symptoms, expressive negative symptoms, and depression/anxiety symptoms made independent contributions. Resilience was correlated with community functioning in the domains of work, independent living, and social and family relationships. History of psychosis moderated the relationship between resilience and defeatist beliefs, which was stronger in those who had experienced psychosis.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

These findings suggest that resilience is an important construct to consider in homeless veterans, is related to other clinical factors such as defeatist beliefs and negative symptoms, and could be a valuable treatment target with the goal of improving functioning. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Evidence for intact stimulus-specific neural adaptation for visual objects in schizophrenia and bipolar disorder: An ERP study

People with schizophrenia (SZ) or bipolar disorder (BD) experience dysfunction in visual processing. Dysfunctional neural tuning, in which neurons and neuronal populations are selectively activated by specific features of visual stimuli, may contribute to these deficits. Few studies have examined this possibility and there are inconsistent findings of tuning deficits in the literature. We utilized an event-related potential (ERP) paradigm to examine neural adaptation for visual objects, a measure of neural tuning whereby neurons respond less strongly to the repeated presentation of the same stimulus. Seventy-seven SZ, 53 BD, and 49 healthy comparison participants (HC) were examined. In three separate conditions, pictures of objects were presented repeatedly: the same object (SS), different objects from the same category (e.g., two different vases; SD), or different objects from different categories (e.g., a barrel and a clock, DD). Mass-univariate cluster-based permutation analyses identified electrodes and time-windows in which there were significant differences between the SS vs. DD and the SD vs. DD conditions. Mean ERP amplitudes were extracted from these clusters and analyzed for group differences. Results revealed a significant condition difference over parieto-occipital electrodes for the SS-DD comparison between 109–164 ms and for the SD-DD comparison between 78–203 ms, with larger amplitudes in the DD compared to either SS or SD condition. However, there were no significant differences in the pattern of results between groups. Thus, while we found neural adaptation effects using this ERP paradigm, we did not find evidence of group differences. Our results suggest that people with SZ or BD may not exhibit deficits in neural tuning for processing of visual objects using this EEG task with rapidly presented stimuli. However, the results are inconsistent with other studies using different methodologies (e.g., fMRI, behavioral tasks) that have found tuning deficits in people with schizophrenia.

Parsing components of auditory predictive coding in schizophrenia using a roving standard mismatch negativity paradigm

BACKGROUND

Mismatch negativity (MMN) is an event-related potential (ERP) component reflecting auditory predictive coding. Repeated standard tones evoke increasing positivity ('repetition positivity'; RP), reflecting strengthening of the standard's memory trace and the prediction it will recur. Likewise, deviant tones preceded by more standard repetitions evoke greater negativity ('deviant negativity'; DN), reflecting stronger prediction error signaling. These memory trace effects are also evident in MMN difference wave. Here, we assess group differences and test-retest reliability of these indices in schizophrenia patients (SZ) and healthy controls (HC).

METHODS

Electroencephalography was recorded twice, 2 weeks apart, from 43 SZ and 30 HC, during a roving standard paradigm. We examined ERPs to the third, eighth, and 33rd standards (RP), immediately subsequent deviants (DN), and the corresponding MMN. Memory trace effects were assessed by comparing amplitudes associated with the three standard repetition trains.

RESULTS

Compared with controls, SZ showed reduced MMNs and DNs, but normal RPs. Both groups showed memory trace effects for RP, MMN, and DN, with a trend for attenuated DNs in SZ. Intraclass correlations obtained via this paradigm indicated good-to-moderate reliabilities for overall MMN, DN and RP, but moderate to poor reliabilities for components associated with short, intermediate, and long standard trains, and poor reliability of their memory trace effects.

CONCLUSION

MMN deficits in SZ reflected attenuated prediction error signaling (DN), with relatively intact predictive code formation (RP) and memory trace effects. This roving standard MMN paradigm requires additional development/validation to obtain suitable levels of reliability for use in clinical trials.

Motivational and cognitive correlates of community integration in homeless veterans entering a permanent supported housing program

Homelessness is a major public health problem, and serious mental illness (SMI) is highly prevalent in the homeless population. Although supported housing services-which provide permanent housing in the community along with case management-improve housing outcomes, community integration typically remains poor, and little is known about the underlying determinants of poor community integration postresidential placement. The general SMI literature has indicated that motivational and cognitive ability factors are key determinants of successful community integration, which provides a foundation for examining this issue. This study evaluated whether interview- and performance-based assessments of motivation, nonsocial and social-cognitive ability, and psychiatric symptoms were associated with community integration indices in 2 samples of homeless veterans either with (N = 96) or without (N = 80) a psychotic disorder who had recently been admitted to a supported housing program but who had not yet attained housing. Motivation indices, including experiential negative symptoms and defeatist performance attitudes, stood out as the most robust correlates (rs = -.30 to -.69) of community integration across both samples, particularly for social role participation. Demographics, general psychiatric symptoms, and nonsocial cognition showed generally weak relations with community integration, though social cognition showed a few relations. The consistent findings across samples point to the importance of motivational factors for understanding the determinants of poor community integration in this complex population. Further, interventions that target motivational challenges may have widespread usefulness for enhancing community integration outcomes beyond obtaining housing. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Reduced Neural Sensitivity to Social vs Nonsocial Reward in Schizophrenia

BACKGROUND

Human beings find social stimuli rewarding, which is thought to facilitate efficient social functioning. Although reward processing has been extensively studied in schizophrenia, a few studies have examined neural processes specifically involved in social reward processing. This study examined neural sensitivity to social and nonsocial rewards in schizophrenia.

METHODS

Twenty-seven patients with schizophrenia and 25 community controls completed a One-Armed Bandit Task, an implicit reinforcement learning task, in the scanner. There were 2 conditions with an identical trial structure, one with social rewards and the other with nonsocial rewards. The data were analyzed using a region of interest (ROI) approach, focusing on the ventral striatum, ventromedial prefrontal cortex, and anterior cingulate cortex.

RESULTS

Across all 3 ROIs, patients showed reduced activation for social rewards compared to controls. However, the 2 groups showed comparable levels of activation for nonsocial rewards. Within the patient group, levels of neural activation in these ROIs during the social reward condition were associated with better performance.

CONCLUSIONS

This study found reduced neural sensitivity in patients with schizophrenia in key reward-processing regions for social but not for nonsocial rewards. These findings suggest a relatively specific social reward-processing deficit in schizophrenia during an implicit reinforcement learning task.

A randomized controlled trial comparing a "bottom-up" and "top-down" approach to cognitive training in schizophrenia

The development of effective cognitive training (CT) interventions is critical for improving the daily lives of people with schizophrenia. At this point, it is unclear whether a so-called "bottom-up" or "top-down" CT approach is more beneficial for inducing cognitive gains and generalization in this population. The aims of this randomized controlled trial were to: 1) Compare the effects of these two types of training approaches on performance-based (MATRICS Consensus Cognitive Battery, MCCB) and neurophysiological (mismatch negativity, MMN) measures of cognition, and 2) Evaluate MMN as a potential predictor of treatment response. Ninety-nine patients with persistent schizophrenia (mean age of 51 and illness duration of 30 years) were randomly assigned in a 2:2:1 ratio to a "bottom-up" intervention that selectively targets basic auditory processing and verbal learning (Brain Fitness), a "top-down" intervention that targets a broad range of higher-order cognitive functions (COGPACK), or a control condition consisting of commercial computer games (Sporcle). Participants completed on average 30 h of training over 12 weeks. Despite demonstrated improvement on training tasks, we found no significant treatment effects on measures of neurocognition (MCCB), MMN, or functional capacity from either intervention. Interestingly, there was an association between an enhanced MMN response at 6 weeks and improved reasoning/problem solving at 12 weeks in the COGPACK group. Although this study had several methodological strengths, the results were mainly negative. It suggests that CT trials in schizophrenia should try to better understand mediators and moderators of treatment response to develop more personalized interventions.

fMRI evidence of aberrant neural adaptation for objects in schizophrenia and bipolar disorder

Functional magnetic resonance imaging (fMRI) adaptation (also known as fMRI repetition suppression) has been widely used to characterize stimulus selectivity in vivo, a fundamental feature of neuronal processing in the brain. We investigated whether SZ patients and BD patients show aberrant fMRI adaptation for object perception. About 52 SZ patients, 55 BD patients, and 53 community controls completed an object discrimination task with three conditions: the same object presented twice, two exemplars from the same category, and two exemplars from different categories. We also administered two functional localizer tasks. A region of interest analysis was employed to evaluate a priori hypotheses about the lateral occipital complex (LOC) and early visual cortex (EVC). An exploratory whole brain analysis was also conducted. In the LOC and EVC, controls showed the expected reduced fMRI responses to repeated presentation of the same objects compared with different objects (i.e., fMRI adaptation for objects, p < .001). SZ patients showed an adaptation effect that was significantly smaller compared with controls. BD patients showed a lack of fMRI adaptation. The whole brain analyses showed enhanced fMRI responses to repeated presentation of the same objects only in BD patients in several brain regions including anterior cingulate cortex. This study was the first to employ fMRI adaptation for objects in SZ and BD. The current findings provide empirical evidence of aberrant fMRI adaptation in the visual cortex in SZ and BD, but in distinctly different ways.

Understanding the Association Between Negative Symptoms and Performance on Effort-Based Decision-Making Tasks: The Importance of Defeatist Performance Beliefs

Effort-based decision-making paradigms are increasingly utilized to gain insight into the nature of motivation deficits. Research has shown associations between effort-based decision making and experiential negative symptoms; however, the associations are not consistent. The current study had two primary goals. First, we aimed to replicate previous findings of a deficit in effort-based decision making among individuals with schizophrenia on a test of cognitive effort. Second, in a large sample combined from the current and a previous study, we sought to examine the association between negative symptoms and effort by including the related construct of defeatist beliefs. The results replicated previous findings of impaired cognitive effort-based decision making in schizophrenia. Defeatist beliefs significantly moderated the association between negative symptoms and effort-based decision making such that there was a strong association between high negative symptoms and deficits in effort-based decision making, but only among participants with high levels of defeatist beliefs. Thus, our findings suggest the relationship between negative symptoms and effort performance may be understood by taking into account the role of defeatist beliefs, and finding that might explain discrepancies in previous studies.

ERP indices of performance monitoring and feedback processing in psychosis: A meta-analysis

BACKGROUND

Although individuals with, or at risk for, psychotic disorders often show difficulties with performance monitoring and feedback processing, findings from studies using event-related potentials (ERPs) to index these processes are not consistent. This meta-analytic review focused on studies of two different indexes of performance monitoring, the early error-related negativity (ERN; n = 25) and the later error positivity (Pe; n = 17), and one index of feedback processing, the feedback negativity (FN; n = 6).

METHODS

We evaluated whether individuals (1) with psychotic disorders, or (2) at heightened risk for these disorders differ from healthy controls in available studies of the ERN, Pe, and FN.

RESULTS

There was a significant, large ERN reduction in those with psychosis (g = -0.96) compared to controls, and a significant, moderate ERN reduction in those at-risk (g = -0.48). In contrast, there were uniformly non-significant, small between-group differences for Pe and FN (gs ≤ |0.16|).

CONCLUSIONS

The results reveal a differential pattern of impairment in psychosis. Early performance monitoring (ERN) impairments are substantial among those with psychotic disorders in general and may be a useful vulnerability indicator for these disorders. However, later performance monitoring (Pe) and basic feedback processing (FN) appear to be relatively spared in psychosis.

Pupillary responses to a cognitive effort task in schizophrenia

Effort-based decision making paradigms are increasingly utilized to gain insight into the nature of motivation deficits. Although these tasks are being used to assess effort and motivation in schizophrenia, little work has been done to confirm that effort-based decision making tasks validly manipulate effort. In the current study, we adapted the effort component a cognitive effort-based decision making task (the Deck Choice Effort Task) for use with pupillometric assessment. We sought to confirm with psychophysiology that cognitive effort is manipulated. We also examined correlations between physiological indicators of effort exertion and cognition and negative symptoms. The results confirmed manipulation of cognitive effort: there was a significant difference in pupillary responses between easy and difficult task conditions. Pupillary responses were also correlated with cognitive ability, and with negative symptoms when controlling for cognition. Thus, our findings offer physiological validation of an effort manipulation included in a cognitive effort-based decision making task for schizophrenia.

Aberrant patterns of neural activity when perceiving emotion from biological motion in schizophrenia

Social perceptual deficits in schizophrenia are well established. Recent work suggests that the ability to extract social information from bodily cues is reduced in patients. However, little is known about the neurobiological mechanisms underlying this deficit. In the current study, 20 schizophrenia patients and 16 controls completed two tasks using point-light animations during fMRI: a basic biological motion task and an emotion in biological motion task. The basic biological motion task was used to localize activity in posterior superior temporal sulcus (pSTS), a critical region for biological motion perception. During the emotion in biological motion task, participants viewed brief videos depicting happiness, fear, anger, or neutral emotions and were asked to decide which emotion was portrayed. Activity in pSTS and amygdala was interrogated during this task. Results indicated that patients showed overall reduced activation compared to controls in pSTS and at a trend level in amygdala across emotions, despite similar task performance. Further, a functional connectivity analysis revealed that controls, but not patients, showed significant positive connectivity between pSTS and left frontal regions as well as bilateral angular gyrus during the emotion in biological motion task. These findings indicate that schizophrenia patients show aberrant neural activity and functional connectivity when extracting complex social information from simple motion stimuli, which may contribute to social perception deficits in this disorder.

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Perception of social information from bodily cues is impaired in schizophrenia.

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We examined neural correlates of perception of emotion from biological motion.

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Activity in amygdala and posterior superior temporal sulcus was reduced in patients.

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pSTS functional connectivity with frontal and parietal regions was reduced in patients.

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Aberrant neural responses may contribute to social perceptual deficits in schizophrenia.

Single transcranial direct current stimulation in schizophrenia: Randomized, cross-over study of neurocognition, social cognition, ERPs, and side effects

Over the last decades, the treatment of schizophrenia has shifted fundamentally from a focus on symptom reduction to a focus on recovery and improving aspects of functioning. In this study, we examined the effect of transcranial direct current stimulation (tDCS) on social cognitive and nonsocial neurocognitive functions, as well as on electroencephalogram (EEG) measures, in individuals with schizophrenia. Thirty-seven individuals with schizophrenia were administered one of three different tDCS conditions (cathodal, anodal, and sham) per visit over the course of three visits, with approximately one week between each visit. Order of conditions was randomized and counterbalanced across subjects. For the active conditions, the electrode was placed over the left dorsolateral prefrontal cortex with the reference electrode over right supraorbital cortex. Current intensity was 2 mA and was maintained for two 20-minute sessions, with a one hour break between the sessions. Assessments were conducted immediately following each session, in a counterbalanced order of administration. No systematic effects were found across the social and nonsocial cognitive domains, and no significant effects were detected on event-related potentials (ERPs). The very small effect sizes, further validated by post-hoc power analyses (large Critical Ns), demonstrated that these findings were not due to lack of statistical power. Except for mild local discomfort, no significant side effects were reported. Findings demonstrate the safety and ease of administration of this procedure, but suggest that a single dose of tDCS over these areas does not yield a therapeutic effect on cognition in schizophrenia.

Trial registration: ClinicalTrials.gov NCT02539797.

Cortical Thickness of Functionally Defined Visual Areas in Schizophrenia and Bipolar Disorder

Patients with schizophrenia show specific abnormalities in visual perception, and patients with bipolar disorder may have related perceptual deficits. During tasks that highlight perceptual dysfunction, patients with schizophrenia show abnormal activity in visual brain areas, including the lateral occipital complex (LOC) and early retinotopic cortex. It is unclear whether the anatomical structure of those visual areas is atypical in schizophrenia and bipolar disorder. In members of those two patient groups and healthy controls, we localized LOC and early retinotopic cortex individually for each participant using functional magnetic resonance imaging (MRI), then measured the thickness of those regions of interest using structural MRI scans. In both regions, patients with schizophrenia had the thinnest cortex, controls had the thickest cortex, and bipolar patients had intermediate cortical thickness. A control region, motor cortex, did not show this pattern of group differences. The thickness of each visual region of interest was significantly correlated with performance on a visual object masking task, but only in schizophrenia patients. These findings suggest an anatomical substrate for visual processing abnormalities that have been found with both neural and behavioral measures in schizophrenia and other severe mental illnesses.

Hallucinations, neuroplasticity, and prediction errors in schizophrenia

Auditory hallucinations, a hallmark symptom of psychosis, are experienced by most people with a diagnosis of schizophrenia at some point in their illness. Auditory hallucinations can be understood as a failure in predictive coding, whereby abnormalities in sensory/perceptual processing combine with biased cognitive processes to result in a dampening of normal prediction error signaling. In this paper, we used a roving mismatch negativity (MMN) paradigm to optimize evaluation of prediction error signaling and short-term neuroplasticity in 30 people with schizophrenia (n = 16 with and n = 14 without recent auditory hallucinations) and 20 healthy comparison participants. The recent hallucinations group exhibited an abnormal roving MMN profile [F(2,27) = 3.98, p = 0.03], significantly reduced prediction error signaling [t(28) = -2.25, p = 0.03], and a trend for diminished short-term neuroplasticity [t(28) = 1.80, p = 0.08]. There were no statistically significant differences between the healthy comparison group and the combined schizophrenia group on any of the roving MMN indices. These findings are consistent with a predictive coding account of hallucinations in schizophrenia, which posits reduced prediction error signaling in those who are prone to hallucinations. These results also suggest that plasticity-mediated formation and online updating of predictive coding models may also be disrupted in individuals with recent hallucinations.

Social Disconnection in Schizophrenia and the General Community

Social disability is a defining characteristic of schizophrenia and a substantial public health problem. It has several components that are difficult to disentangle. One component, social disconnection, occurs extensively in the general community among nonhelp-seeking individuals. Social disconnection is an objective, long-standing lack of social/family relationships and minimal participation in social activities. It is associated with negative health effects, including early mortality, and is distinct from subjective loneliness. These 2 topics, social disability in schizophrenia and social disconnection in the general community, have generated entirely distinct research literatures that differ in their respective knowledge gaps and emphases. Specifically, the consequences of social disability in schizophrenia are unknown but its determinants (ie, nonsocial cognition, social cognition, and social motivation) have been well-examined. Conversely, the health consequences of social disconnection in the general community are well-established, but the determinants are largely unknown. Social disconnection is a condition that presents substantial public health concerns, exists within and outside of current psychiatric diagnostic boundaries, and may be related to the schizophrenia spectrum. A comparison of these 2 literatures is mutually informative and it generates intriguing research questions that can be critically evaluated.

The neural correlates of self-referential memory encoding and retrieval in schizophrenia

BACKGROUND

Enhanced memory for self-oriented information is known as the self-referential memory (SRM) effect. fMRI studies of the SRM effect have focused almost exclusively on encoding, revealing selective engagement of the medial prefrontal cortex (mPFC) during "self" relative to other processing conditions. Other critical areas for self-processing include ventrolateral prefrontal cortex (vlPFC), temporo-parietal junction (TPJ) and posterior cingulate/precuneus (PCC/PC). Previous behavioral studies show that individuals with schizophrenia fail to benefit from this memory boost. However, the neural correlates of this deficit, at either encoding or retrieval, are unknown.

METHODS

Twenty individuals with schizophrenia and 16 healthy controls completed an event-related fMRI SRM paradigm. During encoding, trait adjectives were judged in terms of structural features ("case" condition), social desirability ("other" condition), or as self-referential ("self" condition). Participants then completed an unexpected recognition test (retrieval phase). We examined BOLD activation during both encoding and retrieval within mPFC, vlPFC, TPJ, and PCC/PC regions-of-interest (ROIs).

RESULTS

During encoding, fMRI data indicated both groups had greater activation during the "self" relative to the "other" condition across ROIs. Controls showed this primarily in mPFC whereas patients showed this in PCC/PC. During retrieval, fMRI data indicated controls showed differentiation across ROIs between "self" and "other" conditions, but patients did not.

CONCLUSIONS

Results suggest regional differences in the neural processing of self-referential information in individuals with schizophrenia, perhaps because representation of the self is not as well established in patients relative to controls. The current study presents novel findings that add to the literature implicating impaired self-oriented processing in schizophrenia.