Hyperfocusing in schizophrenia: Evidence from interactions between working memory and eye movements

Pre-stimulus EEG phase coherence predicts visual target detection failures in schizophrenia: A pilot study

Impaired visual target detection is a common finding in schizophrenia that is linked to poor functional outcomes. However, the neural mechanisms that contribute to this deficit remain unclear. Recent research in healthy samples has identified relationships between the phase of pre-stimulus electroencephalographic (EEG) activity in the alpha band (8-12 Hz) or theta band (4-7 Hz) and the likelihood of visual target detection with and without attentional cueing, but these effects have not yet been explored in schizophrenia. We performed a study to investigate such effects in schizophrenia (n = 19) and healthy participants (n = 14), using a visual target detection task with attentional cues. We found significant relationships between pre-stimulus EEG phase properties and visual target detection in both groups, but also clear differences in the effects as a function of frequency, group, and attentional cueing. Alpha-band phase effects were relatively uniform across groups and conditions. By contrast, theta-band phase effects showed differences by group and attentional condition which could be consistent with attentional hyperfocusing in the schizophrenia group. Thus, our results elucidate a novel neural mechanism that may help to explain known impairments affecting both visual target detection and attention in schizophrenia.

Aberrant hyperfocusing in schizophrenia indicated by elevated theta phase-gamma amplitude coupling

OBJECTIVE

We aimed to investigate electroencephalographic (EEG) markers of aberrant hyperfocusing, a novel framework of impaired selective attention, in schizophrenia patients by using theta phase-gamma amplitude coupling (TGC).

METHODS

Fifty-four schizophrenia patients and 73 healthy controls (HCs) underwent EEG recording during an auditory oddball paradigm. For the standard and target conditions, TGC was calculated using the source signals from 25 brain regions of interest (ROIs) related to attention networks and sensory processing; TGC values were then compared across groups and conditions using two-way analysis of covariance. Correlations of altered TGC with performance on the Trail Making Test Parts A and B (TMT-A/B), were explored.

RESULTS

Compared to HCs, schizophrenia patients showed elevated TGC in the left inferior frontal gyrus (IFG) and superior temporal gyrus in the standard condition but not in the target condition. Correlation analyses revealed that the TGC in the left IFG was positively correlated with the TMT-A/B completion times.

CONCLUSIONS

Aberrant hyperfocusing, as reflected by elevated TGC in attention-related brain regions, was related to behavioral performance on the TMT-A/B in schizophrenia patients.

SIGNIFICANCE

This study suggests that TGC is a electrophysiological marker for aberrant hyperfocusing of attentional processes that may result in cognitive impairments in schizophrenia patients.

Working-Memory-Guided Attention Competes with Exogenous Attention but Not with Endogenous Attention

Recent research has extensively investigated working memory (WM)-guided attention, which is the phenomenon of attention being directed towards information in the external environment that matches the content stored in WM. While prior studies have focused on the potential influencing factors of WM-guided attention, little is known about the nature of it. This attention system exhibits characteristics of two classical distinct attention systems: exogenous attention and endogenous attention, as it can operate automatically like exogenous attention yet persist for a long time and be modulated by cognitive resources like endogenous attention. Thus, the current study aimed to explore the mechanism of WM-guided attention by testing whether it competed with exogenous attention, endogenous attention, or both. Two experiments were conducted within a classic WM-guided attention paradigm. Experiment 1 included an exogenous cue and revealed an interaction between WM-guided attention and exogenous attention. Experiment 2 replaced the exogenous cue with an endogenous cue and demonstrated that endogenous attention had no impact on WM-guided attention. These findings indicate that WM-guided attention shares mechanisms with exogenous attention to some extent while operating in parallel with endogenous attention.

The flickering spotlight of visual attention: Characterizing abnormal object-based attention in schizophrenia

Schizophrenia is associated with deficits in both object perception and visual attention. However, few studies in schizophrenia have investigated object-based attention, which is dissociable from other forms of visuospatial attention. Recent research in healthy populations has shown that the 'spotlight' of sustained visual attention flickers in a rhythmic, oscillatory fashion at specific frequencies in the 4-12 Hz range. In healthy samples, this oscillatory signature has been used to investigate spatiotemporal dynamics of object-based attention, showing that the attentional spotlight spreads to uncued locations within cued objects, and also periodically alternates focus between cued and uncued objects. In this study, we adapted a performance-based visual object cueing task to investigate object-based attention in individuals with a schizophrenia diagnosis and healthy controls. In controls, spatiotemporal patterns of object-based attention closely resembled those reported in previous studies of healthy individuals. In the schizophrenia group, the oscillatory signature of attention also appeared in the location of the cue and on uncued objects, similar to the effects in controls. Indeed, the oscillatory signature of attention at the spatial location of the cue was stronger in the schizophrenia group than in controls. However, attention did not spread across the cued object in schizophrenia; rather, attention appeared to remain hyperfocused at the spatial location of the cue. These findings provide the first evidence that visual attention has oscillatory characteristics in schizophrenia, as in the general population. The results also show that the fundamental process of attentional spreading which underlies object-based attention is abnormal in schizophrenia.

Load-dependent functional connectivity deficits during visual working memory in first-episode psychosis

INTRODUCTION

Aberrant network connectivity is a core deficit in schizophrenia and may underlie many of its associated cognitive deficits. Previous work in first-episode schizophrenia spectrum illness (FESz) suggests preservation of working memory network function during low-load conditions with dysfunction emerging as task complexity increases. This study assessed visual network connectivity and its contribution to load-dependent working memory impairments.

METHODS

Magnetoencephalography was recorded from 35 FESz and 28 matched controls (HC) during a lateralized change detection task. Impaired alpha desynchronization was previously identified within bilateral dorsal occipital (Occ) regions. Here, whole-brain alpha-band connectivity was examined using phase-locking (PLV) and bilateral Occ as connectivity seeds. Load effects on connectivity were assessed across participants, and PLV modulation within networks was compared between groups.

RESULTS

Occ exhibited significant load modulated connectivity with six regions (FDR-corrected). HC exhibited PLV enhancement with load in all connections. FESz failed to show PLV modulation between right Occ and left inferior frontal gyrus, lateral occipito-temporal sulcus, and anterior intermediate parietal sulcus. Smaller PLVs in all three network connections during both memory load conditions were associated with increased reality distortion in FESz (FDR-corrected.) CONCLUSION: Examination of functional connectivity across the visual working memory network in FESz revealed an inability to enhance communication between perceptual and executive networks in response to increasing cognitive demands. Furthermore, the degree of network communication impairment was associated with positive symptoms. These findings provide insights into the nature of brain dysconnectivity and its contribution to symptoms in early psychosis and identify potential targets for future interventions.

Attention in Schizophrenia

Attention is clearly a core area of cognitive dysfunction in schizophrenia, but the concept of "attention" is complex and multifaceted. This chapter focuses on three different aspects of attentional function that are of particular interest in schizophrenia. First, we discuss the evidence that schizophrenia involves a reduction in global alertness, leading to an inward focusing of attention and a neglect of external stimuli and tasks. Second, we discuss the control of attention, the set of processes that allow general goals to be translated into shifts of attention toward task-relevant information. When a goal is adequately represented, people with schizophrenia often show no deficit in using the goal to direct attention in the visual modality unless challenged by stimuli that strongly activate the magnocellular processing pathway. Finally, we discuss the implementation of selection, the processes that boost relevant information and suppress distractors once attention has been directed to a given source of information. Although early evidence indicated an impairment in selection, more recent evidence indicating that people with schizophrenia actually focus their attention more narrowly and more intensely that healthy individuals (hyperfocusing). However, this hyperfocused attention may be directed toward goal-irrelevant information, creating the appearance of impaired attentional filtering.

Atypical attentional filtering of visual information in youth with chromosome 22q11.2 deletion syndrome as indexed by event-related potentials

BACKGROUND

Youth with chromosome 22q11.2 deletion syndrome (22q) face one of the highest genetic risk factors for the development of schizophrenia. Previous research suggests impairments in attentional control and potential interactions with elevated anxiety and reduced adaptive functioning may increase the risk for developing psychosis in this population. Here, we examined how variations in attentional control relate to the presence or severity of psychosis-proneness symptoms in these individuals.

METHODS

To achieve this, we measured attentional control in youth (12-18 years) with 22q (N = 35) compared to a typically developing group (N = 45), using a flanker task (the Distractor Target task) while measuring neural activity with event-related potentials.

RESULTS

Similar to previous findings observed in people with schizophrenia, greater attentional capture by, and reduced suppression of, non-target flanker stimuli characterized participants with 22q and was indexed by the N2pc (N2-posterior-contralateral) and PD (distractor positivity) components. Although we observed no relationships between these components and measures of psychosis-proneness in youth with 22q, these individuals endorsed a relatively low incidence of positive symptoms overall.

CONCLUSIONS

Our results provide neural evidence of an attentional control impairment in youth with 22q that suggests these individuals experience sustained attentional focus on irrelevant information and reduced suppression of distracting stimuli in their environment. Impairments in attentional control might be a valid biomarker of the potential to develop attenuated positive symptoms or frank psychosis in high-risk individuals long before the age at which such symptoms typically arise. The evaluation of such a hypothesis, and the preventive potential for the putative biomarker, should be the focus of future studies.

Atypically larger variability of resource allocation accounts for visual working memory deficits in schizophrenia

Working memory (WM) deficits have been widely documented in schizophrenia (SZ), and almost all existing studies attributed the deficits to decreased capacity as compared to healthy control (HC) subjects. Recent developments in WM research suggest that other components, such as precision, also mediate behavioral performance. It remains unclear how different WM components jointly contribute to deficits in schizophrenia. We measured the performance of 60 SZ (31 females) and 61 HC (29 females) in a classical delay-estimation visual working memory (VWM) task and evaluated several influential computational models proposed in basic science of VWM to disentangle the effect of various memory components. We show that the model assuming variable precision (VP) across items and trials is the best model to explain the performance of both groups. According to the VP model, SZ exhibited abnormally larger variability of allocating memory resources rather than resources or capacity per se. Finally, individual differences in the resource allocation variability predicted variation of symptom severity in SZ, highlighting its functional relevance to schizophrenic pathology. This finding was further verified using distinct visual features and subject cohorts. These results provide an alternative view instead of the widely accepted decreased-capacity theory and highlight the key role of elevated resource allocation variability in generating atypical VWM behavior in schizophrenia. Our findings also shed new light on the utility of Bayesian observer models to characterize mechanisms of mental deficits in clinical neuroscience.

Working memory is a core cognitive function related to a broad range of cognitive domains such as problem-solving, attention, executive control, and IQ. Although working memory deficits have been well-documented in schizophrenia, the underlying mechanisms remain unclear. Conventional working memory theories attribute working memory deficits in schizophrenia to their reduced memory capacity, overlooking the potential roles of other memory components, such as precision. In this study, we take the approach of computational psychiatry and use computational modeling to uncover the major determinants of working memory deficits. We assess working memory performance of a large cohort of participants (60 schizophrenia patients and 61 demographic matched healthy controls) and evaluate multiple mainstream computational models of visual working memory. The variable precision model turns out to be the best model for both groups. We further find that the poorer performance of schizophrenia patients arises from heterogeneous distribution of memory resources when encoding items in memory. This resource allocation variability can also predict symptom severity in schizophrenia. Our study highlights the use of computational models in psychiatric researches.

Impaired Filtering and Hyperfocusing: Neural Evidence for Distinct Selective Attention Abnormalities in People with Schizophrenia

Although schizophrenia is classically thought to involve impaired attentional filtering, people with schizophrenia (PSZ) exhibit a more intense and more exclusive attentional focus than healthy control subjects (HCS) in many tasks. To resolve this contradiction, this functional magnetic resonance imaging study tested the impact of attentional control demands on the modulation of stimulus-induced activation in the fusiform face area and parahippocampal place area when participants (43 PSZ and 43 HCS) were looking for a target face versus house. Stimuli were presented individually, or as face-house overlays that challenged attentional control. Responses were slower for house than face stimuli and when prioritizing houses over faces in overlays, suggesting a difference in salience. Blood-oxygen-level-dependent activity reflected poorer attentional selectivity in PSZ than HCS when attentional control was challenged most, that is, when stimuli were overlaid and the task required detecting the lower-salience house target. By contrast, attentional selectivity was exaggerated in PSZ when control was challenged least, that is, when stimuli were presented sequentially and the task required detecting the higher-salience face target. These findings are consistent with 2 distinct attentional abnormalities in schizophrenia leading to impaired and exaggerated selection under different conditions: attentional control deficits, and hyperfocusing once attention has been directed toward a stimulus.

Oculomotor inhibition and location priming in schizophrenia

Schizophrenia is widely thought to involve elevated distractibility, which may reflect a general impairment in top-down inhibitory processes. Schizophrenia also appears to involve increased priming of previously performed actions. Here, we used a highly refined eye-tracking paradigm that makes it possible to concurrently assess distractibility, inhibition, and priming. In both healthy control subjects (HCS, N = 41) and people with schizophrenia (PSZ, N = 46), we found that initial saccades were actually less likely to be directed toward a salient "singleton" distractor than toward less salient distractors, reflecting top-down suppression of the singleton. Remarkably, this oculomotor suppression effect was as strong or stronger in PSZ than in HCS, indicating intact inhibitory control. In addition, saccades were frequently directed to the location of the previous-trial target in both groups, but this priming effect was much stronger in PSZ than in HCS. Indeed, PSZ directed gaze toward the location of the previous-trial target as often as they directed gaze to the location of the current-trial target. These results demonstrate that-at least in the context of visual search-PSZ are no more distractable than HCS and are fully capable of inhibiting salient-but-irrelevant stimuli. However, PSZ do exhibit exaggerated priming, focusing on recently attended locations even when this is not beneficial for goal attainment. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Hyperfocus: the forgotten frontier of attention

'Hyperfocus' is a phenomenon that reflects one's complete absorption in a task, to a point where a person appears to completely ignore or 'tune out' everything else. Hyperfocus is most often mentioned in the context of autism, schizophrenia, and attention deficit hyperactivity disorder, but research into its effect on cognitive and neural functioning is limited. We propose that hyperfocus is a critically important aspect of cognition, particularly with regard to clinical populations, and that it warrants significant investigation. Hyperfocus, though ostensibly self-explanatory, is poorly defined within the literature. In many cases, hyperfocus goes undefined, relying on the assumption that the reader inherently knows what it entails. Thus, there is no single consensus to what constitutes hyperfocus. Moreover, some studies do not refer to hyperfocus by name, but describe processes that may be related. In this paper, we review how hyperfocus (as well as possibly related phenomena) has been defined and measured, the challenges associated with hyperfocus research, and assess how hyperfocus affects both neurotypical and clinical populations. Using this foundation, we provide constructive criticism about previously used methods and analyses. We also propose an operational definition of hyperfocus for researchers to use moving forward.

Lateralized evoked responses in parietal cortex demonstrate visual short-term memory deficits in first-episode schizophrenia

Working memory dysfunction may be central to neurocognitive deficits in schizophrenia. Maintenance of visual information in working memory, or visual short-term memory (vSTM), is linked to general cognitive dysfunction and predicts functional outcome. Lateralized change-detection tasks afford investigation of the contralateral delay activity (CDA), a useful tool for investigating vSTM dysfunction. Previous work suggests "hyperfocusing" of attention in schizophrenia, such that CDA is increased when a single item is maintained in vSTM but reduced for multiple items. If observed early in the disease, vSTM dysfunction may be a key feature of schizophrenia or target for intervention. We investigated CDA during lateralized vSTM of one versus three items using sensor-level electroencephalography and source-level magnetoencephalography in 26 individuals at their first episode of schizophrenia-spectrum psychosis (FESz) and 26 matched healthy controls. FESz were unable to modulate CDA with increased memory load - high-load CDA was reduced and low-load CDA was increased compared to controls. Further, sources of CDA in posterior parietal cortex were reduced in FESz and indices of working memory were correlated with neurocognitive deficits and symptom severity. These results support working memory maintenance dysfunction as a central and early component to the disorder. Targeted intervention focusing on vSTM deficits may be warranted to alleviate downstream effects of this disability.

Increased repulsion of working memory representations in schizophrenia

Computational neuroscience models propose that working memory (WM) involves recurrent excitatory feedback loops that maintain firing over time along with lateral inhibition that prevents the spreading of activity to other feature values. In behavioral paradigms, this lateral inhibition appears to cause a repulsion of WM representations away from each other and from other strong sources of input. Recent computational models of schizophrenia have proposed that reduction in the strength of inhibition relative to strength of excitation may underlie impaired cognition, and this leads to the prediction that repulsion effects should be reduced in people with schizophrenia spectrum disorders (PSZ) relative to healthy control subjects (HCS). We tested this hypothesis in 2 experiments measuring WM repulsion effects. In Experiment 1, 45 PSZ and 32 HCS remembered the location of a single object relative to a centrally presented visual landmark and reported this location after a short delay. The reported location was repelled away from the landmark in both groups, but this repulsion effect was increased rather than decreased in PSZ relative to HCS. In Experiment 2, 41 PSZ and 34 HCS remembered 2 sequentially presented orientations and reported each orientation after a short delay. The reported orientations were biased away from each other in both groups, and this repulsion effect was again more pronounced in PSZ than in HCS. Contrary to the widespread hypothesis of reduced inhibition in schizophrenia, we provide robust evidence from 2 experiments showing that the behavioral performance of PSZ exhibited an exaggeration rather than a reduction of competitive inhibition. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Antisaccade Deficits in Schizophrenia Can Be Driven by Attentional Relevance of the Stimuli

The antisaccade task is considered a test of cognitive control because it creates a conflict between the strong bottom-up signal produced by the cue and the top-down goal of shifting gaze to the opposite side of the display. Antisaccade deficits in schizophrenia are thought to reflect impaired top-down inhibition of the prepotent bottom-up response to the cue. However, the cue is also a highly task-relevant stimulus that must be covertly attended to determine where to shift gaze. We tested the hypothesis that difficulty in overcoming the attentional relevance of the cue, rather than its bottom-up salience, is key in producing impaired performance in people with schizophrenia (PSZ). We implemented 3 versions of the antisaccade task in which we varied the bottom-up salience of the cue while holding its attentional relevance constant. We found that difficulty in performing a given antisaccade task-relative to a prosaccade version using the same stimuli-was largely independent of the cue's bottom-up salience. The magnitude of impairment in PSZ relative to control subjects was also independent of bottom-up salience. The greatest impairment was observed in a version where the cue lacked bottom-up salience advantage over other locations. These results indicate that the antisaccade deficit in PSZ does not reflect an impairment in overcoming bottom-up salience of the cue, but PSZ are instead impaired at overcoming its attentional relevance. This deficit may still indicate an underlying inhibitory control impairment but could also reflect a hyperfocusing of attentional resources on the cue.

Reduced Dorsal Visual Oscillatory Activity During Working Memory Maintenance in the First-Episode Schizophrenia Spectrum

Cognitive deficits in people with schizophrenia are among the hardest to treat and strongly predict functional outcome. The ability to maintain sensory precepts in memory over a short delay is impacted early in the progression of schizophrenia and has been linked to reliable neurophysiological markers. Yet, little is known about the mechanisms of these deficits. Here, we investigated possible neurophysiological mechanisms of impaired visual short-term memory (vSTM, aka working memory maintenance) in the first-episode schizophrenia spectrum (FESz) using magnetoencephalography (MEG). Twenty-eight FESz and 25 matched controls performed a lateralized change detection task where they were cued to selectively attend and remember colors of circles presented in either the left or right peripheral visual field over a 1 s delay. Contralateral alpha suppression (CAS) during the delay period was used to assess selective attention to cued visual hemifields held in vSTM. Delay-period CAS was compared between FESz and controls and between trials presenting one vs three items per visual hemifield. CAS in dorsal visual cortex was reduced in FESz compared to controls in high-load trials, but not low-load trials. Group differences in CAS were found beginning 100 ms after the disappearance of the memory set, suggesting deficits were not due to the initial deployment of attention to the cued visual hemifield prior to stimulus presentation. CAS was not greater for high-load vs low-load trials in FESz subjects, although this effect was prominent in controls. Further, lateralized gamma (34-40 Hz) power emerged in dorsal visual cortex prior to the onset of CAS in controls but not FESz. Gamma power in this cluster differed between groups at both high and low load. CAS deficits observed in FESz were correlated with change detection accuracy, working memory function, estimated IQ, and negative symptoms. Our results implicate deficits in CAS in trials requiring broad, but not narrow, focus of attention to spatially distributed objects maintained in vSTM in FESz, possibly due to reduced ability to broadly distribute visuospatial attention (alpha) or disruption of object-location binding (gamma) during encoding/consolidation. This early pathophysiology may shed light upon mechanisms of emerging working memory deficits that are intrinsic to schizophrenia.

Cognitive effort-avoidance in patients with schizophrenia can reflect Amotivation: an event-related potential study

BACKGROUND

Amotivation is regarded as a core negative symptom in patients with schizophrenia. There are currently no objective methods for assessing and measuring amotivation in the scientific literature, only a trend towards assessing motivation using effort-orientated, decision-making tasks. However, it remains inconclusive as to whether cognitive effort-avoidance in patients with schizophrenia can reflect their amotivation. Therefore, this study aimed to find out whether cognitive effort-avoidance in patients with schizophrenia can reflect their amotivation.

METHODS

In total, 28 patients with schizophrenia and 27 healthy controls were selected as participants. The demand selection task (DST) was adapted according to the feedback-based Guilty Knowledge Test (GKT) delayed response paradigm, which was combined with the mean amplitude of contingent negative variation (CNV), considered as the criterion of motivation.

RESULTS

Our results showed that: (1) patients with schizophrenia showed a lower CNV amplitude for the target stimuli compared to the probe stimuli, whereas the control group showed the opposite trend (P < 0.05); (2) among patients with schizophrenia, the high cognitive effort-avoidance group showed a smaller CNV amplitude for the target stimuli compared to the probe stimuli, whereas the low cognitive effort avoidance group showed a higher CNV amplitude for the target stimuli compared to the probe stimuli; the opposite trend was observed in the control group (P < 0.05).

CONCLUSION

These findings support the claim that CNV amplitude can be used as a criterion for detecting amotivation in patients with schizophrenia. Within the context of the DST, the high and low cognitive effort-avoidance of patients with schizophrenia can reflect their state of amotivation; patients with high cognitive effort-avoidance showed severe amotivation.

Impaired attentional modulation of sensorimotor control and cortical excitability in schizophrenia

Impairments in attentional, working memory and sensorimotor processing have been consistently reported in schizophrenia. However, the interaction between cognitive and sensorimotor impairments and the underlying neural mechanisms remains largely uncharted. We hypothesized that altered attentional processing in patients with schizophrenia, probed through saccadic inhibition, would partly explain impaired sensorimotor control and would be reflected as altered task-dependent modulation of cortical excitability and inhibition. Twenty-five stabilized patients with schizophrenia, 17 unaffected siblings and 25 healthy control subjects were recruited. Subjects performed visuomotor grip force-tracking alone (single-task condition) and with increased cognitive load (dual-task condition). In the dual-task condition, two types of trials were randomly presented: trials with visual distractors (requiring inhibition of saccades) or trials with addition of numbers (requiring saccades and addition). Both dual-task trial types required divided visual attention to the force-tracking target and to the distractor or number. Gaze was measured during force-tracking tasks, and task-dependent modulation of cortical excitability and inhibition were assessed using transcranial magnetic stimulation. In the single-task, patients with schizophrenia showed increased force-tracking error. In dual-task distraction trials, force-tracking error increased further in patients, but not in the other two groups. Patients inhibited fewer saccades to distractors, and the capacity to inhibit saccades explained group differences in force-tracking performance. Cortical excitability at rest was not different between groups and increased for all groups during single-task force-tracking, although, to a greater extent in patients (80%) compared to controls (40%). Compared to single-task force-tracking, the dual-task increased cortical excitability in control subjects, whereas patients showed decreased excitability. Again, the group differences in cortical excitability were no longer significant when failure to inhibit saccades was included as a covariate. Cortical inhibition was reduced in patients in all conditions, and only healthy controls increased inhibition in the dual-task. Siblings had similar force-tracking and gaze performance as controls but showed altered task-related modulation of cortical excitability and inhibition in dual-task conditions. In patients, neuropsychological scores of attention correlated with visuomotor performance and with task-dependant modulation of cortical excitability. Disorganization symptoms were greatest in patients with weakest task-dependent modulation of cortical excitability. This study provides insights into neurobiological mechanisms of impaired sensorimotor control in schizophrenia showing that deficient divided visual attention contributes to impaired visuomotor performance and is reflected in impaired modulation of cortical excitability and inhibition. In siblings, altered modulation of cortical excitability and inhibition is consistent with a genetic risk for cortical abnormality.

Cortical hyperactivation at low working memory load: A primary processing abnormality in people with schizophrenia?

A frequent finding when studying substrates of working memory (WM) deficits in people with schizophrenia (PSZ) is task-induced hyperactivation relative to healthy control subjects (HCS) when WM load is low. Hyperactivation accompanying similar performance is commonly attributed to cognitive deficits rendering relatively easy operations more resource-consuming. To test if hyperactivation at low load really is secondary to cognitive impairment in PSZ, we re-analyzed functional MRI data showing left posterior parietal cortex (PPC) hyperactivation in PSZ when holding a single color-item in WM. In subgroups matched for the number of items successfully stored in WM (K) by excluding the highest-performing HCS and lowest-performing PSZ, performance was almost identical across all set sizes (1-7). While BOLD activation at the larger set sizes did not differ between groups, PSZ still robustly hyperactivated left PPC when a single item had to be maintained. The same pattern was observed in subgroups matched for model-based estimates of WM capacity or attentional lapse rate. Given that in the K-matched subsamples PSZ performed as well as HCS even in the most challenging load conditions and that no BOLD signal difference was seen at high loads, it is implausible that PSZ over-recruited WM-related neural structures because they were more challenged by maintaining a single item in WM. Instead, the findings are consistent with a primary schizophrenia-related processing abnormality as proposed by the hyperfocusing hypothesis, which suggests that an abnormally narrow but intense focusing of processing resources is central to many aspects of impaired cognition in PSZ.

People with schizophrenia show enhanced cognitive costs of maintaining a single item in working memory

BACKGROUND

Working memory (WM) deficits are seen as a core deficit in schizophrenia, implicated in the broad cognitive impairment seen in the illness. Here we examine the impact of WM storage of a single item on the operation of other cognitive systems.

METHODS

We studied 37 healthy controls (HCS) and 43 people with schizophrenia (PSZ). Each trial consisted of a sequence of two potential target stimuli, T1 and T2. T1 was a letter presented for 100 ms. After delays of 100-800 ms, T2 was presented. T2 was a 1 or a 2 and required a speeded response. In one condition, subjects were instructed to ignore T1 but respond to T2. In another condition, they were required to report T1 after making their speeded response to T2 (i.e. to make a speeded T2 response while holding T1 in WM).

RESULTS

PSZ were dramatically slowed at responding to T2 when T1 was held in WM. A repeated measures ANOVA yielded main effects of group, delay, and condition with a group by condition interaction (p's < 0.001). Across delays, the slowing of the T2 response when required to hold T1 in memory, relative to ignoring T1, was nearly 3 times higher in PSZ than HCS (633 v. 219 ms).

CONCLUSIONS

Whereas previous studies have focused on reduced storage capacity, the present study found that PSZ are impaired at performing tasks while they are successfully maintaining a single item in WM. This may play a role in the broad cognitive impairment seen in PSZ.

Increased influence of a previously attended feature in people with schizophrenia

Everyday functioning requires the appropriate allocation of visual attention, which is achieved through multiple mechanisms of attentional guidance. Traditional theories have focused on top-down and bottom-up factors, but implicit learning from recent experience ("selection history") also has a substantial impact on attentional allocation. The present experiment examined the influence of intertrial priming on attentional guidance in people with schizophrenia and matched control subjects. Participants searched for a color pop-out target, which switched randomly between a red target among blue distractors and a blue target among red distractors. We found that performance on the current trial was more influenced by the previous-trial target color in people with schizophrenia than in control subjects. Moreover, this implicit priming effect was greater in individuals with lower working memory capacity (as measured in a separate task). These results suggest that intertrial priming has an exaggerated impact on attentional guidance in people with schizophrenia and that this is associated with other aspects of impaired cognition. Overall, these results are consistent with the hyperfocusing hypothesis, which proposes that a single underlying attentional abnormality may explain a range of atypical effects across perception, attention, and cognition in schizophrenia. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Assessing the information content of ERP signals in schizophrenia using multivariate decoding methods

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This study took multivariate decoding methods that are widely used to assess the nature of neural representations in neurotypical people and applied them to a comparison of people with schizophrenia and matched control subjects.

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Participants performed a visual working memory task that required remembering 1–5 items from one side of the display and ignoring an equal number of items on the other side of the display.

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We attempted to decode which side was being held in working memory from the scalp distribution of the ERP activity during the delay period of the working memory task, and we found greater decoding accuracy in people with schizophrenia than in control subjects when a single item was being held in memory.

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These results support the hyperfocusing hypothesis of cognitive dysfunction in schizophrenia, and they provide an important proof of concept for applying multivariate decoding methods to comparisons of neural representations in psychiatric and non-psychiatric populations.

Multivariate pattern classification (decoding) methods are commonly employed to study mechanisms of neurocognitive processing in typical individuals, where they can be used to quantify the information that is present in single-participant neural signals. These decoding methods are also potentially valuable in determining how the representation of information differs between psychiatric and non-psychiatric populations. Here, we examined ERPs from people with schizophrenia (PSZ) and healthy control subjects (HCS) in a working memory task that involved remembering 1, 3, or 5 items from one side of the display and ignoring the other side. We used the spatial pattern of ERPs to decode which side of the display was being held in working memory. One might expect that decoding accuracy would be inevitably lower in PSZ as a result of increased noise (i.e., greater trial-to-trial variability). However, we found that decoding accuracy was greater in PSZ than in HCS at memory load 1, consistent with previous research in which memory-related ERP signals were larger in PSZ than in HCS at memory load 1. We also observed that decoding accuracy was strongly related to the ratio of the memory-related ERP activity and the noise level. In addition, we found similar noise levels in PSZ and HCS, counter to the expectation that PSZ would exhibit greater trial-to-trial variability. Together, these results demonstrate that multivariate decoding methods can be validly applied at the individual-participant level to understand the nature of impaired cognitive function in a psychiatric population.

The Hyperfocusing Hypothesis: A New Account of Cognitive Dysfunction in Schizophrenia

Impairments in basic cognitive processes such as attention and working memory are commonly observed in people with schizophrenia and are predictive of long-term outcome. In this review, we describe a new theory-the hyperfocusing hypothesis-which provides a unified account of many aspects of impaired cognition in schizophrenia. This hypothesis proposes that schizophrenia involves an abnormally narrow but intense focusing of processing resources. This hyperfocusing impairs the ability of people with schizophrenia to distribute attention among multiple locations, decreases the number of representations that can simultaneously be maintained in working memory, and causes attention to be abnormally captured by irrelevant inputs that share features with active representations. Evidence supporting the hyperfocusing hypothesis comes from a variety of laboratory tasks and from both behavioral and electrophysiological measures of processing. In many of these tasks, people with schizophrenia exhibit supranormal effects of task manipulations, which cannot be explained by a generalized cognitive deficit or by nonspecific factors such as reduced motivation or poor task comprehension. In addition, the degree of hyperfocusing in these tasks is often correlated with the degree of impairment in measures of broad cognitive function, which are known to be related to long-term outcome. Thus, the mechanisms underlying hyperfocusing may be a good target for new treatments targeting cognitive deficits in schizophrenia.

Is Attentional Filtering Impaired in Schizophrenia?

Recent evidence suggests that schizophrenia involves hyperfocusing, an unusually narrow but intense focusing of processing resources. This appears to contradict the classic idea that schizophrenia involves an impairment in the ability to focus on relevant information and filter irrelevant information. Here, we review one set of studies suggesting that attentional filtering is impaired in people with schizophrenia and another set of studies suggesting that attentional filtering is unimpaired or even enhanced in these individuals. Considerable evidence supports both conclusions, and we propose 3 potential ways of reconciling the conflicting evidence. First, impaired attentional filtering may occur primarily during periods of active psychosis, with hyperfocusing being a part of the broad pattern of cognitive impairment that persists independent of the level of positive symptoms. Second, schizophrenia may involve hyperfocusing in the visual modality and impaired attentional filtering in the auditory modality. Third, attention may be directed toward irrelevant inputs as a result of impaired executive control, and hyperfocusing on those inputs may be functionally equivalent to a failure of attentional filtering. Given the widespread clinical observations and first-person reports of impaired attentional filtering in schizophrenia, it will be important for future research to test these possibilities.

Altered spatial profile of distraction in people with schizophrenia

Attention is critical for effective processing of incoming information and has long been identified as a potential area of dysfunction in people with schizophrenia (PSZ). In the realm of visual processing, both spatial attention and feature-based attention are involved in biasing selection toward task-relevant stimuli and avoiding distraction. Evidence from multiple paradigms has suggested that PSZ may hyperfocus and have a narrower "spotlight" of spatial attention. In contrast, feature-based attention seems largely preserved, with some suggestion of increased processing of stimuli sharing the target-defining feature. In the current study, we examined the spatial profile of feature-based distraction using a task in which participants searched for a particular color target and attempted to ignore distractors that varied in distance from the target location and either matched or mismatched the target color. PSZ differed from healthy controls in terms of interference from peripheral distractors that shared the target-color presented 200 ms before a central target. Specifically, PSZ showed an amplified gradient of spatial attention, with increased distraction to near distractors and less interference to far distractors. Moreover, consistent with hyperfocusing, individual differences in this spatial profile were correlated with positive symptoms, such that those with greater positive symptoms showed less distraction by target-colored distractors near the task-relevant location. (PsycINFO Database Record

Visuospatial task-related prefrontal activity is correlated with negative symptoms in schizophrenia

Control of attention is thought to be specifically impaired in schizophrenia due to abnormal function in the prefrontal cortex (PFC). The PFC plays a critical role in the identification of relevant stimuli and the development of appropriate biases for the identified signals, including selection of an appropriate attentional 'zoom'. We examined how demands associated with changes in attentional requirements in a Sustained Attention Task (SAT) may contribute to differences in functional involvement of the PFC and relation to clinical status. A group of 24 individuals with schizophrenia and 16 healthy controls (N = 40) performed the SAT and a visuospatial condition (vSAT) while activity in the bilateral anterior PFC was monitored using functional Near Infrared Spectroscopy (fNIRS). The results confirm that the right frontopolar region plays a role in control of attention for both patients and healthy controls. However, patients with schizophrenia exhibited a general attentional deficit and inefficient right-medial PFC activation. Additionally, we observed a strong regional association between left Middle Frontal Gyrus (MFG) activity during the vSAT task and the PANSS score driven by the negative symptom subscale. The presence of aberrant activation differences within the left-MFG region may describe a dysregulation of attentional networks linked to the clinical expression of negative and general symptoms.

Comparison of automatic visual attention in schizophrenia, bipolar disorder, and major depression: Evidence from P1 event-related component

AIM

The ability to discern commonalities and differences in the neurobiology of functional psychoses represents a key element to unmasking shared vulnerability across different psychiatric conditions. The present study sought to compare the automatic visual attention mechanisms in three psychiatric disorders considered to distribute along the continuum of psychosis severity: schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD). To this end, the visual P1 event-related potential component, a cortical correlate of automatic visual attention, was measured during an ecological task based on visual word pair presentation.

METHODS

Four samples of participants, 18 SCZ, 20 BD, 28 MDD, and 30 healthy controls, were recruited and submitted to the same procedure and stimuli. The P1 evoked by visual word presentation was recorded through a 38-electrode electroencephalography cap. Words were presented on a computer screen serially as pairs, and participants had to decide whether they rhymed or not.

RESULTS

P1 was larger at posterior sites in SCZ compared with BD, healthy control, and MDD participants. BD patients showed the lowest P1 compared with all other groups. Positive Pearson's correlations were found in SCZ patients between P1 amplitude on left posterior sites and both hallucination severity and worse task performance.

CONCLUSION

The three investigated psychiatric samples showed different automatic visual attention patterns: SCZ patients exhibited the greatest cognitive impairment correlated with the amplitude of P1, MDD patients revealed a normal component, and BD showed a compensated euthymic response different from results of past literature in untreated patients.

Oculomotor capture reveals trial-by-trial neural correlates of attentional guidance by contents of visual working memory

Evidence from attentional and oculomotor capture, contingent capture, and other paradigms suggests that mechanisms supporting human visual working memory (VWM) and visual attention are intertwined. Features held in VWM bias guidance toward matching items even when those features are task irrelevant. However, the neural basis of this interaction is underspecified. Prior examinations using fMRI have primarily relied on coarse comparisons across experimental conditions that produce varying amounts of capture. To examine the neural dynamics of attentional capture on a trial-by-trial basis, we applied an oculomotor paradigm that produced discrete measures of capture. On each trial, subjects were shown a memory item, followed by a blank retention interval, then a saccade target that appeared to the left or right. On some trials, an irrelevant distractor appeared above or below fixation. Once the saccade target was fixated, subjects completed a forced-choice memory test. Critically, either the target or distractor could match the feature held in VWM. Although task irrelevant, this manipulation produced differences in behavior: participants were more likely to saccade first to an irrelevant VWM-matching distractor compared with a non-matching distractor - providing a discrete measure of capture. We replicated this finding while recording eye movements and scanning participants' brains using fMRI. To examine the neural basis of oculomotor capture, we separately modeled the retention interval for capture and non-capture trials within the distractor-match condition. We found that frontal activity, including anterior cingulate cortex and superior frontal gyrus regions, differentially predicted subsequent oculomotor capture by a memory-matching distractor. Other regions previously implicated as involved in attentional capture by VWM-matching items showed no differential activity across capture and non-capture trials, even at a liberal threshold. Our findings demonstrate the power of trial-by-trial analyses of oculomotor capture as a means to examine the underlying relationship between VWM and attentional guidance systems.

Strategic predictors of performance in a divided attention task

In this study we investigate the strategies of subjects in a complex divided attention task. We conducted a series of experiments with ten participants and evaluated their performance. After an extensive analysis, we identified four strategic measures that justify the achievement of the participants, by highlighting the individual differences and predicting performance in a regression analysis using generalized estimating equations. Selecting the more urgent task and user action between multiple simultaneous possibilities form two of the strategic decisions, respectively. The third one refers to choosing a response within the same task when the opportunity is present. The fourth and most important measure of strategy involves thinking ahead and executing an action before a situation would become critical. This latter one has the effect of reducing later cognitive load or timing constraints and it is shown to explain almost as much variance in performance as the other three, more straightforward predictors together. In addition to determining these strategic predictors, we also show how manipulating task difficulty induces a shift in strategy, thus impairing human performance in the rehearsed task. The results of this study indicate that considerable differences in the divided attention ability of normal subjects can be identified early and with simple measurements. The importance of describing and analyzing strategies is also emphasized, which can substantially influence performance in complex tasks and may serve training needs.

Prenatal kynurenine treatment in rats causes schizophrenia-like broad monitoring deficits in adulthood

RATIONALE

Elevated brain kynurenic acid (KYNA) levels are implicated in the pathology and neurodevelopmental pathogenesis of schizophrenia. In rats, embryonic treatment with kynurenine (EKyn) causes elevated brain KYNA levels in adulthood and cognitive deficits reminiscent of schizophrenia.

OBJECTIVES

Growing evidence suggests that people with schizophrenia have a narrowed attentional focus, and we aimed at establishing whether these abnormalities may be related to KYNA dysregulation.

METHODS

To test whether EKyn rats display broad monitoring deficits, kynurenine was added to the chow of pregnant Wistar dams on embryonic days 15-22. As adults, 20 EKyn and 20 control rats were trained to stable performance on the five-choice serial reaction time task, requiring the localization of 1-s light stimuli presented randomly across five apertures horizontally arranged along a curved wall, equating the locomotor demands of reaching each hole.

RESULTS

EKyn rats displayed elevated omission errors and reduced anticipatory responses relative to control rats, indicative of a lower response rate, and showed reduced locomotor activity. The ability to spread attention broadly was measured by parsing performance by stimulus location. Both groups displayed poorer stimulus detection with greater target location eccentricity, but this effect was significantly more pronounced in the EKyn group. Specifically, the groups differed in the spatial distribution of correct but not incorrect responses. This pattern cannot be explained by differences in response rate and is indicative of a narrowed attentional focus.

CONCLUSIONS

The findings suggest a potential etiology of broad monitoring deficits in schizophrenia, which may constitute a core cognitive deficit.

Clinical correlates of saccadic eye movement in antipsychotic-naïve schizophrenia

Some aspects of saccadic performance have been found to be abnormal in chronic schizophrenia. The majority of this research has, however, been performed on patients treated with long-term antipsychotic medication. Very few studies have examined saccadic performance in antipsychotic-naïve/free patients. There are also very few studies describing the relationship between saccadic performance and clinical symptoms, particularly in antipsychotic free patients. In this study, we compared pro and antisaccade performance in a large sample of antipsychotic-naïve/free schizophrenia patients (N = 45) with healthy controls (N = 57). Clinical symptoms were assessed using Scale for Assessment of Positive Symptoms (SAPS) and Negative Symptoms (SANS). In the antisaccade task, patients made significantly more errors, and their correct antisaccades had smaller amplitudes in comparison to healthy controls. Higher error rates were associated with increased severity of hallucinations. In the prosaccade task, patients had less accurate final eye positions, and made saccades with slower latency and reduced amplitude compared to the healthy controls. These observations in schizophrenia patients without the potential confounds of antipsychotic treatment suggest intrinsic link between saccadic deficits and schizophrenia pathogenesis. The relationship between antisaccade errors and hallucination severity supports the potential link between hallucinations and deficits in inhibitory control.

What Can Different Motor Circuits Tell Us About Psychosis? An RDoC Perspective

Signs of motor dysfunction are evidenced across a range of psychiatric disorders including schizophrenia. Historically, these features have been neglected but emerging theoretical and methodological advancements have shed new light on the utility of considering movement abnormalities. Indeed, the National Institute of Mental Health Research Domain Criteria initiative has recently met to develop a Motor Systems Domain. This reflects a growing appreciation for the enhanced reliability and validity that can come along with evaluating disturbances relevant to psychiatric illnesses from multiple levels of analysis, and conceptualizing these domains with respect to the complexity of their role in a broader integrated system (ie, weighing contributions and interactions between the cognitive, affective, and motor domains). This article discusses motor behaviors and seeks to explain how research into basal ganglia, cerebellar, and cortico-motor circuit function/dysfunction, grounded in brain circuit-motor behavior relationships, can elucidate our understanding of pathophysiology, provide vital links to other key systems of interest, significantly improve identification and classification, and drive development of targeted individualized treatments.

Electrophysiological Evidence for Hyperfocusing of Spatial Attention in Schizophrenia

A recently proposed hyperfocusing hypothesis of cognitive dysfunction in schizophrenia proposes that people with schizophrenia (PSZ) tend to concentrate processing resources more narrowly but more intensely than healthy control subjects (HCS). The present study tests a key prediction of this hypothesis, namely, that PSZ will hyperfocus on information presented at the center of gaze. This should lead to greater filtering of peripheral stimuli when the task requires focusing centrally but reduced filtering of central stimuli when the task requires attending broadly in the periphery. These predictions were tested in a double oddball paradigm, in which frequent standard stimuli and rare oddball stimuli were presented at central and peripheral locations while event-related potentials were recorded. Participants were instructed to discriminate between the standard and oddball stimuli at either the central location or at the peripheral locations. PSZ and HCS showed opposite patterns of spatial bias at the level of early sensory processing, as assessed with the P1 component: PSZ exhibited stronger sensory suppression of peripheral stimuli when the task required attending narrowly to the central location, whereas HCS exhibited stronger sensory suppression of central stimuli when the task required attending broadly to the peripheral locations. Moreover, PSZ exhibited a stronger stimulus categorization response than HCS, as assessed with the P3b component, for central stimuli when the task required attending to the peripheral region. These results provide strong evidence of hyperfocusing in PSZ, which may provide a unified mechanistic account of multiple aspects of cognitive dysfunction in schizophrenia.SIGNIFICANCE STATEMENT Schizophrenia clearly involves impaired attention, but attention is complex, and delineating the precise nature of attentional dysfunction in schizophrenia has been difficult. The present study tests a new hyperfocusing hypothesis, which proposes that people with schizophrenia (PSZ) tend to concentrate processing resources more intensely but more narrowly than healthy control subjects (HCS). Using electrophysiological measures of sensory and cognitive processing, we found that PSZ were actually superior to HCS in focusing attention at the point of gaze and filtering out peripheral distractors when the task required a narrow focusing of attention. This finding of superior filtering in PSZ supports the hyperfocusing hypothesis, which may provide the mechanism underlying a broad range of cognitive impairments in schizophrenia.

Hyperfocusing of attention on goal-related information in schizophrenia: Evidence from electrophysiology

Schizophrenia clearly involves impairments of attention, but the precise nature of these impairments has been difficult to determine. One possibility is that the deficit in attention is a secondary consequence of a deficit in goal maintenance. However, recent research suggests that people with schizophrenia (PSZ) actually focus attention more strongly on objects containing goal-relevant features. To test these competing hypotheses, we recorded event-related potentials (ERPs) from PSZ (N = 20) and healthy control subjects (HCS; N = 20) while they looked for a particular target color at fixation and tried to ignore lateral distractors that sometimes matched the target color (target-color distractors). Goal maintenance was made trivially easy by the continual presentation of a goal reminder. We found that HCS were able to successfully suppress target-color distractors (leading to a distractor positivity ERP component), whereas PSZ focused attention on these items (leading to an N2-posterior-contralateral ERP component). This suggests that, when maintaining a task set, PSZ engage in aberrant focusing of attention, or hyperfocusing, on goal-relevant features. (PsycINFO Database Record

Hyperdeactivation of the Default Mode Network in People With Schizophrenia When Focusing Attention in Space

When studying selective attention in people with schizophrenia (PSZ), a counterintuitive but replicated finding has been that PSZ display larger performance benefits than healthy control subjects (HCS) by cues that predicts the location of a target stimulus relative to non-predictive cues. Possible explanations are that PSZ hyperfocus attention in response to predictive cues, or that an inability to maintain a broad attentional window impairs performance when the cue is non-predictive. Over-recruitment of regions involved in top-down focusing of spatial attention in response to predictive cues would support the former possibility, and an inappropriate recruitment of these regions in response to non-predictive cues the latter. We probed regions of the dorsal attention network while PSZ (N = 20) and HCS (N = 20) performed a visuospatial attention task. A central cue either predicted at which of 4 peripheral locations a target signal would appear, or it gave no information about the target location. As observed previously, PSZ displayed a larger reaction time difference between predictive and non-predictive cue trials than HCS. Activity in frontoparietal and occipital regions was greater for predictive than non-predictive cues. This effect was almost identical between PSZ and HCS. There was no sign of over-recruitment when the cue was predictive, or of inappropriate recruitment when the cue was non-predictive. However, PSZ differed from HCS in their cue-dependent deactivation of the default mode network. Unexpectedly, PSZ displayed significantly greater deactivation than HCS in predictive cue trials, which may reflect a tendency to expend more processing resources when focusing attention in space.

Can cognitive behaviour therapy beneficially influence arousal mechanisms in psychosis?

Cognitive behavioural therapy for psychosis (CBTp) is an approved adjunct therapy for patients with psychotic disorders; however, we do not fully understand the neurobiological effects that this therapy may exert. Arousal, as measured by electroencephalography (EEG), provides a useful electrophysiological marker for assessing psychotic disorders. EEG studies may therefore serve as a useful measure for assessing the underlying effects of CBTp in psychotic disorders.