The influence of impaired processing speed on cognition in first-episode antipsychotic-naïve schizophrenic patients

Breaking down processing speed: Motor and cognitive insights in first-episode psychosis and unaffected first-degree relatives

INTRODUCTION

Processing speed (PS) deficits represent a fundamental aspect of cognitive impairment, evident not only in schizophrenia but also in individuals undergoing their first episode of psychosis (FEP) and their unaffected first-degree relatives. Heterogeneity in tests assessing PS reflects the participation of motor and cognitive subcomponents to varying degrees. We aim to explore differences in performance of the subcomponents of PS in FEP patients, parents, siblings, and controls.

MATERIALS AND METHODS

Results from tests, including Trail Making Test part A and part B, Digit Symbol Coding Test, Grooved Pegboard Test, and Stroop Word and Stroop Color subtests, were obtained from 133 FEP patients, 146 parents, and 202 controls. Exploratory factor analysis (EFA) was employed in controls to establish the structure, followed by confirmatory factor analysis (CFA) to verify if the other groups share this structure.

RESULTS

EFA revealed a two-factor model: Factor 1 for the motor subcomponent and Factor 2 for the cognitive subcomponent. Subsequently, CFA indicated a good fit for the remaining groups with differences in the relationship between the factors.

CONCLUSIONS

Differences in the relationships of factors within a common structure suggest the involvement of different compensatory strategies among groups, providing insights into the underlying mechanisms of PS deficits in patients and relatives.

Exploring the latent cognitive structure in schizophrenia: implications for antipsychotic treatment responses

BACKGROUND

Individuals diagnosed with schizophrenia present diverse degrees and types of cognitive impairment, leading to variations in responses to antipsychotic treatments. Understanding the underlying cognitive structures is crucial for assessing this heterogeneity. Utilizing latent profile analysis (LPA) enables the delineation of latent categories of cognitive function. Integrating this approach with a dimensional perspective allows for the exploration of the relationship between cognitive function and treatment response.

METHODS

This study examined 647 patients from two distinct cohorts. Utilizing LPA within the discovery cohort (n = 333) and the replication cohort (n = 314), latent subtypes were identified categorically. The stability of cognitive structures was evaluated employing Latent Transition Analysis (LTA). The relationship between cognitive function and treatment response were investigated by comparing Positive and Negative Syndrome Scale (PANSS) reduction rates across diverse cognitive subtypes. Furthermore, dimensional insights were gained through correlation analyses between cognitive tests and PANSS reduction rates.

RESULTS

In terms of categorical, individuals diagnosed with schizophrenia can be categorized into three distinct subtypes: those 'without cognitive deficit', those 'with mild-moderate cognitive 'eficit', and those 'with moderate-severe cognitive deficit'. There are significant differences in PANSS reduction rates among patients belonging to these subtypes following antipsychotic treatment (p < 0.05). Furthermore, from a dimensional perspective, processing speed at baseline is positively correlated with PANSS score reduction rates at week 8/week 10 (p < 0.01).

CONCLUSIONS

Our findings have unveiled the latent subtypes of cognitive function in schizophrenia, illuminating the association between cognitive function and responses to antipsychotic treatment from both categorical and dimensional perspectives.

Reduced anterior callosal white matter in risk for psychosis associated with processing speed as a fundamental cognitive impairment

BACKGROUND

Previous research in psychotic disorders discovered associations between reduced integrity of white matter (WM) in the corpus callosum (CC) and impaired cognitive functions, suggesting processing speed as a central construct. However, it is still largely unexplored to what extent disruption in callosal WM is related to cognitive deficits during the risk stage prior to psychosis.

METHODS

To address this gap, we measured the WM integrity in CC by fractional anisotropy (FA) and assessed cognition in 60 clinical-high risk for psychosis (CHR) patients during adolescence/young adulthood and 38 healthy control (HC) subjects. We employed tract based spatial statistics to examine group differences and associations between CC-FA and processing speed, executive function, and spatial working memory.

RESULTS

We revealed deficits in processing speed, executive function, and spatial working memory of CHR patients, and reductions in FA of the genu and the body of the CC (p < 0.05, corrected for multiple comparisons) compared to HC. A mediation analysis using the combined sample (CHR + HC) showed that processing speed mediates the associations between the impaired CC structure and executive function and spatial working memory, respectively. Exploratory analyses between CC-FA and the cognitive domains located associations of processing speed in the genu and the body of CC with distinct spatial distributions of executive function and spatial working memory.

CONCLUSION

We suggest processing speed as a subordinate cognitive factor contributing to the associations between callosal WM, executive function and working memory. These results extend findings in psychotic disorders to the prior risk stage.

Neurocognitive subgroups among newly diagnosed patients with schizophrenia spectrum or bipolar disorders: A hierarchical cluster analysis

Studies across schizophrenia (SZ) and bipolar disorder (BD) indicate common transdiagnostic neurocognitive subgroups. However, existing studies of patients with long-term illness precludes insight into whether impairments result from effects of chronic illness, medication or other factors. This study aimed to investigate whether neurocognitive subgroups across SZ and BD can be demonstrated during early illness stages. Data from overlapping neuropsychological tests were pooled from cohort studies of antipsychotic-naïve patients with first-episode SZ spectrum disorders (n = 150), recently diagnosed BD (n = 189) or healthy controls (HC) (n = 280). Hierarchical cluster analysis was conducted to examine if transdiagnostic subgroups could be identified based on the neurocognitive profile. Patterns of cognitive impairments and patient characteristics across subgroups were examined. Patients could be clustered into two, three and four subgroups, of which the three-cluster solution (with 83% accuracy) was selected for posthoc analyses. This solution revealed a subgroup covering 39% of patients (predominantly BD) who were cognitively relatively intact, a subgroup of 33% of patients (more equal distributions of SZ and BD) displaying selective deficits, particularly in working memory and processing speed, and a subgroup of 28% (mainly SZ) with global impairments. The globally impaired group exhibited lower estimated premorbid intelligence than the other subgroups. Globally impaired BD patients also showed more functional disability than cognitively relatively intact patients. No differences were observed across subgroups in symptoms or medications. Neurocognitive results can be understood by clustering analysis with similar clustering solutions occurring across diagnoses. The subgroups were not explained by clinical symptoms or medication, suggesting neurodevelopmental origins.

Patterns of Impaired Neurocognitive Performance on the Global Neuropsychological Assessment, and Their Brain Structural Correlates in Recent-onset and Chronic Schizophrenia

Objective

Schizophrenia is associated with impairment in multiple cognitive domains. There is a paucity of research on the effect of prolonged illness duration (≥ 15 years) on cognitive performance along multiple domains. In this pilot study, we used the Global Neuropsychological Assessment (GNA), a brief cognitive battery, to explore the patterns of cognitive impairment in recent-onset (≤ 2 years) compared to chronic schizophrenia (≥ 15 years), and correlate cognitive performance with brain morphometry in patients and healthy adults.

Methods

We assessed cognitive performance in patients with recent-onset (n = 17, illness duration ≤ 2 years) and chronic schizophrenia (n = 14, duration ≥ 15 years), and healthy adults (n = 16) using the GNA and examined correlations between cognitive scores and gray matter volumes computed from T1-weighted magnetic resonance imaging images.

Results

We observed cognitive deficits affecting multiple domains in the schizophrenia samples. Selectively greater impairment of perceptual comparison speed was found in adults with chronic schizophrenia (p = 0.009, η2partial = 0.25). In the full sample (n = 47), perceptual comparison speed correlated significantly with gray matter volumes in the anterior and medial temporal lobes (TFCE, FWE p < 0.01).

Conclusion

Along with generalized deficit across multiple cognitive domains, selectively greater impairment of perceptual comparison speed appears to characterize chronic schizophrenia. This pattern might indicate an accelerated or premature cognitive aging. Anterior-medial temporal gray matter volumes especially of the left hemisphere might underlie the impairment noted in this domain in schizophrenia.

Extrapyramidal symptoms predict cognitive performance after first-episode psychosis

Extrapyramidal (EP) symptoms such as tremor, rigidity, and bradykinesia are common side effects of most antipsychotics, and may associate with impaired performance in neurocognitive testing. We studied EP symptoms in first-episode psychosis (FEP; n = 113). Cognitive testing and EP symptoms (three items of the Simpson-Angus Scale) were assessed at baseline and follow-up (mean follow-up time 12 months). Mild EP symptoms were present at treatment onset in 40% of the participants. EP symptoms were related with lower performance in neurocognitive testing at baseline and at follow-up, especially among those with nonaffective psychotic disorder, and especially in tasks requiring speed of processing. No associations between EP symptoms and social cognition were detected. In linear regression models, when positive and negative symptom levels and chlorpromazine equivalents were accounted for, baseline EP symptoms were associated with worse baseline global neurocognition and visuomotor performance. Baseline EP symptoms also longitudinally predicted global, verbal, and visuomotor cognition. However, there were no cross-sectional associations between EP symptoms and cognitive performance at follow-up. In sum, we found both cross-sectional and longitudinal associations between EP symptoms and neurocognitive task performance in the early course of psychosis. Those without EP symptoms at the start of treatment had higher baseline and follow-up neurocognitive performance. Even mild EP symptoms may represent early markers of long-term neurocognitive impairment.

Lifespan evolution of neurocognitive impairment in schizophrenia - A narrative review

Cognitive impairment is a well-recognized key feature of schizophrenia. Here we review the evidence on (1) the onset and sensitive periods of change in cognitive impairment before and after the first psychotic episode, and (2) heterogeneity in neurocognitive presentations across cognitive domains between and within individuals. Overall, studies suggest that mild cognitive impairment in individuals who develop schizophrenia or related disorders is already present during early childhood. Cross-sectional studies further suggest increasing cognitive impairments from pre- to post-psychosis onset, with the greatest declines between adolescence, the prodrome, and the first psychotic episode and with some variability between domains. Longitudinal studies with more than 10 years of observation time are scarce but support mild cognitive declines after psychosis onset until late adulthood. Whether and how much this cognitive decline exceeds normal aging, proceeds further in older patients, and is specific to certain cognitive domains and subpopulations of patients remains to be investigated. Finally, studies show substantial heterogeneity in cognitive performance in schizophrenia and suggest a variety of impairment profiles.

This review highlights a clear need for long-term studies that include a control group and individuals from adolescence to old age to better understand critical windows of cognitive change and their predictors. The available evidence stresses the importance of interventions that aim to counter cognitive decline during the prodromal years, as well as careful assessment of cognition in order to determine who will profit most from which cognitive training.

Association of depressive symptoms with cognitive impairment in patients with never-treated first-episode schizophrenia: Analysis of the Depression in Schizophrenia in China (DISC) study

OBJECTIVE

Depressive symptoms and cognitive dysfunction are common in patients with schizophrenia and depressive disorder. This study aimed at exploring whether and how depressive symptoms were correlated with neuro-cognitive impairment in patients with never-treated first-episode (NTFE) schizophrenia.

METHODS

The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was administered to 79 patients and 80 healthy controls to assess neuropsychological function. For all patients, the 17-item Hamilton Depression Rating Scale (HAMD-17) was adopted to evaluate depressive symptoms, and the Positive and Negative Syndrome Scale (PANSS) was utilized to assess psychopathological symptoms.

RESULTS

Thirty-nine patients (49.37%) met the criteria for comorbid depressive symptoms. The RBANS total and the four index scores in the patients were significantly lower than those in the healthy controls. Further, compared with patients without depressive symptoms, patients with depressive symptoms scored lower in attention index, but higher in PANSS general psychopathology and total scores. The HAMD-17 total score was significantly correlated with attention, PANSS total, and PANSS general psychopathology scores. Moreover, multiple regression analysis identified education and HAMD-17 score as the contributors to attention.

CONCLUSION

Our results suggest that the rate of depressive symptoms in NTFE schizophrenia is high, which is correlated with neuro-cognitive impairment, especially attention and psychopathology.

Generalized neurocognitive impairment in individuals at ultra-high risk for psychosis: The possible key role of slowed processing speed

OBJECTIVE

Widespread neurocognitive impairment is well-established in individuals at ultra-high risk (UHR) for developing psychoses, but it is unknown whether slowed processing speed may underlie impairment in other neurocognitive domains, as found in schizophrenia. The study delineated domain functioning in a UHR sample and examined if neurocognitive slowing might account for deficits across domains.

METHODS

The cross-sectional study included 50 UHR individuals with no (n = 38) or minimal antipsychotic exposure (n = 12; mean lifetime dose of haloperidol equivalent = 17.56 mg; SD = 13.04) and 50 matched healthy controls. Primary analyses compared group performance across neurocognitive domains before and after covarying for processing speed. To examine the specificity of processing speed effects, post hoc analyses examined the impact of the other neurocognitive domains and intelligence as covariates.

RESULTS

UHR individuals exhibited significant impairment across all neurocognitive domains (all ps ≤ .010), with medium to large effect sizes (Cohen's ds = -0.53 to -1.12). Only processing speed used as covariate eliminated significant between-group differences in all other domains, reducing unadjusted Cohen's d values with 68% on average, whereas the other domains used as covariates averagely reduced unadjusted Cohen's d values with 20% to 48%. When covarying each of the other domains after their shared variance with speed of processing was removed, all significant between-group domain differences remained (all ps ≤ .024).

CONCLUSION

Slowed processing speed may underlie generalized neurocognitive impairment in UHR individuals and represent a potential intervention target.

In- and outpatient lifestyle interventions on diet and exercise and their effect on physical and psychological health: a systematic review and meta-analysis of randomised controlled trials in patients with schizophrenia spectrum disorders and first episode of psychosis

Patients with non-affective psychosis often lead unhealthy lifestyles. We performed a systematic review and meta-analysis on non-pharmacological RCTs for improvement of diet and physical activity in non-affective psychosis patients, including first-episode psychosis. A variety of outcomes was analysed, including metabolic, psychopathology, cognitive, functional and quality of life outcomes. Fifty-nine studies were included. An improvement in anthropometric measurements (BMI, weight, waist circumference) was observed post-intervention, persisting after follow-up. Post-intervention benefit was found also for psychotic symptoms severity (also persisting after follow-up), many cognitive domains and physical and global functioning and quality of life. Conversely, no effect was observed in relation to most blood metabolites, blood pressure and non-psychotic psychopathology and spontaneous physical activity. Improvement was generally larger for interventions including exercise, especially moderate/vigorous aerobic exercise, but follow-up maintenance was greater for psychotherapy interventions. Sensitivity analyses limited to chronic stages of psychosis and low risk of bias studies produced comparable results. Further studies are needed to design optimized interventions in this vulnerable population.

Cognitive Remediation for Inpatients With Schizophrenia: Effects of a Brief and Intensive Training

Computer-assisted cognitive remediation (CACR) is a computer-based rehabilitation treatment aimed at improving cognition and at developing strategies that can be applied to various functional areas. Different protocols are currently used with great variability over the intensity and duration of treatments. In this study, we evaluated the effects of a brief and intensive CACR training (i.e., 15 sessions for 3 weeks) on cognitive domains, as well as the durability of cognitive gains and their generalization to functional areas, 3 months after CACR training. Thirty-eight patients with schizophrenia were recruited and assessed for psychopathology, cognitive performance, and functioning before the rehabilitative intervention. Patients were reassessed for cognition after CACR rehabilitation. Moreover, a subsample of 13 patients was evaluated for cognition and functioning 3 months after CACR completion. Results show significant improvements in multiple cognitive domains after CACR. Furthermore, 3 months after CACR completion, significant improvements were also detected in executive functions and daily functioning. This study suggests that a brief and intense CACR training is effective on cognitive and functional domains and that it could be feasible and affordable for health care services, thus offering patients the best options for fulfilling recovery goals.

White Matter Alterations Between Brain Network Hubs Underlie Processing Speed Impairment in Patients With Schizophrenia

Processing speed (PS) impairment is one of the most severe and common cognitive deficits in schizophrenia. Previous studies have reported correlations between PS and white matter diffusion properties, including fractional anisotropy (FA), in several fiber bundles in schizophrenia, suggesting that white matter alterations could underpin decreased PS. In schizophrenia, white matter alterations are most prevalent within inter-hub connections of the rich club. However, the spatial and topological characteristics of this association between PS and FA have not been investigated in patients. In this context, we tested whether structural connections comprising the rich club network would underlie PS impairment in 298 patients with schizophrenia or schizoaffective disorder and 190 healthy controls from the Australian Schizophrenia Research Bank. PS, measured using the digit symbol coding task, was largely (Cohen’s d = 1.33) and significantly (P < .001) reduced in the patient group when compared with healthy controls. Significant associations between PS and FA were widespread in the patient group, involving all cerebral lobes. FA was not associated with other cognitive measures of phonological fluency and verbal working memory in patients, suggesting specificity to PS. A topological analysis revealed that despite being spatially widespread, associations between PS and FA were over-represented among connections forming the rich club network. These findings highlight the need to consider brain network topology when investigating high-order cognitive functions that may be spatially distributed among several brain regions. They also reinforce the evidence that brain hubs and their interconnections may be particularly vulnerable parts of the brain in schizophrenia.

Cortical activation abnormalities in bipolar and schizophrenia patients in a combined oddball-incongruence paradigm

Patients with bipolar disorder and schizophrenia often suffer from severe cognitive impairment even during times of remission. This study investigated the pathomechanisms underlying their deficits in cognitive control. A combined oddball-incongruence fMRI task was applied to examine similarities and differences of neural activation patterns between patients and healthy controls. Bipolar and schizophrenia patients demonstrated hyperactivations in the intraparietal cortex during the oddball condition. Furthermore, bipolar patients revealed diagnosis-specific hyperactivation in the left middle frontal gyrus, precentral gyrus, anteroventral prefrontal cortex and orbitofrontal cortex regions compared to schizophrenia patients and healthy individuals. In comparison to healthy controls the patients showed hypoactivations in the inferior frontal junction and ventral pathway during the cognitively more demanding incongruence. Taken together, bipolar patients seem to recruit frontal and parietal areas during the oddball condition to compensate for potential deficits in their attentional network. During more challenging tasks, i.e., the incongruence condition, their compensatory mechanisms seem to collapse leading to hypoactivations in the same frontal areas as well as the ventral pathway.

Verbal memory measurement towards digital perspectives in first-episode psychosis: A review

BACKGROUND

Even in the early phases of psychotic spectrum illnesses such as schizophrenia, patients can experience cognitive decline or deficits prior to the onset of psychotic symptoms such as delusions and hallucinations. In this systematic review, we assessed which verbal memory assessments are most widely used in first-episode psychosis and may be applied via digital technologies (smartphone applications, etc.) for use in early detection.

METHODS

In November 2019, we searched for studies measuring verbal memory in first episode psychosis or schizophrenia over the past 10 years on PubMed and PsycINFO. We screened abstracts of these studies and excluded review studies. Full-texts of included studies were used to identify the verbal memory measurement tests, follow-up frequencies, and sample sizes.

RESULTS

We screened 233 reports and found that 120 original research studies measured verbal memory in first episode psychosis over the past 10 years. Four of these studies specified using a computer, 24 (20%) used a paper-pen format, 1(1%) used both, and 91 (76%) studies did not specify their administration tools or suggest there were offered in digital formats. Thirty-five (30%) studies had follow-up measurements of verbal memory, while 85 (70%) had only a single verbal memory measurement.

DISCUSSION

While many scales are commonly used to measure verbal memory in first episode psychosis, they are not often administered via digital technology. There is an emerging opportunity to administer these and other tests via digital technologies for expanding access to early detection of cognitive decline in clinical high risk and first-episode psychosis.

Resting-state hyperconnectivity within the default mode network impedes the ability to initiate cognitive performance in first-episode schizophrenia patients

Among multiple cognitive impairments present in schizophrenia, a decline in fast information processing is one of the most severe neuropsychological deficit. Reduced ability to efficiently launch a coherent cognitive activity might be a significant factor contributing to poor results in time-limited tasks obtained by schizophrenia patients. The aim of this study was to identify neurophysiological predictors of expected cognitive initiation failures in a group of first-episode schizophrenia individuals (SZ). To evaluate the effectiveness of initiation, a dynamic analysis of design fluency test was applied, assessing to what extent the productivity was focused within the first interval of the performance, what is a typical way healthy subjects execute this task. Resting-state EEG recordings were obtained from SZ patients (n = 34) and controls (n = 30) to examine functional connectivity between 84 intra-cortical current sources determined by eLORETA (exact low-resolution brain electromagnetic tomography) for six conventionally analyzed frequencies. The nonparametric randomization approach was used to identify hypo- and hyper-connections, i.e. synchronizations significantly differentiating the studied samples in terms of connectivity strength. Generally, SZ patients obtained poor outcomes in fluency test and dynamic analysis of performance confirmed the presence of initiation deficit in clinical sample, which was a single factor explaining the intergroup difference regarding the entire task. In the majority of frequencies, the arrangement of synchronizations in SZ group was dominated by hypo-connections, except for the theta band, in which the strength of synchronizations between posterior cingulate cortex, cuneus and precuneus was significantly higher for SZ group. These theta-band hyper-connections turned out to be significant predictors of cognitive initiation failure in the clinical sample. Additionally, theta hyper-connections correlated negatively with the total number of unique designs generated by patients, however, the strength of this correlation was weaker than regarding initiation index. The results of this study suggest that baseline hyperconnectivity within the posterior hub of the Default Mode Network, containing posterior cingulate gyrus and precuneus, might disturb effective cognitive outcome, not only by interfering with task-positive functional networks but also by delaying the starting phase of performance, which might be specifically deleterious for the execution of time-limited tests.

Advancing study of cognitive impairments for antipsychotic-naïve psychosis comparing high-income versus low- and middle-income countries with a focus on urban China: Systematic review of cognition and study methodology

BACKGROUND

Comparing the course of antipsychotic-naïve psychosis in low- and middle-income countries (LMIC) may help to illuminate core pathophysiologies associated with this condition. Previous reviews-primarily from high-income countries (HIC)-identified cognitive deficits in antipsychotic-naïve, first-episode psychosis, but did not examine whether individuals with psychosis with longer duration of untreated psychosis (DUP > 5 years) were included, nor whether LMIC were broadly represented.

METHOD

A comprehensive search of PUBMED from January 2002-August 2018 identified 36 studies that compared cognitive functioning in antipsychotic-naïve individuals with psychosis (IWP) and healthy controls, 20 from HIC and 16 from LMIC.

RESULTS

A key gap was identified in that LMIC study samples were primarily shorter DUP (<5 years) and were primarily conducted in urban China. Most studies matched cases and controls for age and gender but only 9 (24%) had sufficient statistical power for cognitive comparisons. Compared with healthy controls, performance of antipsychotic-naïve IWP was significantly worse in 81.3% (230/283) of different tests of cognitive domains assessed (90.1% in LMIC [118/131] and 73.7% [112/152] in HIC).

CONCLUSIONS

Most LMIC studies of cognition in antipsychotic-naïve IWP adopted standardized procedures and, like HIC studies, found broad-based impairments in cognitive functioning. However, these LMIC studies were often underpowered and primarily included samples typical of HIC: primarily male, young-adult, high-school educated IWP, in their first episode of illness with relatively short DUP (<5 years). To enhance understanding of the long-term natural course of cognitive impairments in untreated psychosis, future studies from LMIC should recruit community-dwelling IWP from rural areas where DUP may be longer.

Decreased processing speed might account for working memory span deficit in schizophrenia, and might mediate the associations between working memory span and clinical symptoms

Objective

Verbal working memory span is decreased in patients with schizophrenia, and this might contribute to impairment in higher cognitive functions as well as to the formation of certain clinical symptoms. Processing speed has been identified as a crucial factor in cognitive efficiency in this population. We tested the hypothesis that decreased processing speed underlies the verbal working memory deficit in patients and mediates the associations between working memory span and clinical symptoms.

Method

Forty-nine schizophrenia inpatients recruited from units for chronic and acute patients, and forty-five healthy participants, were involved in the study. Verbal working memory span was assessed by means of the letter-number span. The Digit Copy test was used to assess motor speed, and the Digit Symbol Substitution Test to assess cognitive speed.

Results

The working memory span was significantly impaired in patients (F(1,90) = 4.6, P < 0.05). However, the group difference was eliminated when either the motor or the cognitive speed measure was controlled (F(1,89) = 0.03, P = 0.86, and F(1,89) = 0.03, P = 0.88). In the patient group, working memory span was significantly correlated with negative symptoms (r = –0.52, P < 0.0001) and thought disorganisation (r = –0.34, P < 0.025) scores. Regression analyses showed that the association with negative symptoms was no longer significant when the motor speed measure was controlled (β = –0.12, P = 0.20), while the association with thought disorganisation was no longer significant when the cognitive speed measure was controlled (β = –0.10, P = 0.26).

Conclusions

Decrement in motor and cognitive speed plays a significant role in both the verbal working memory impairment observed in patients and the associations between verbal working memory impairment and clinical symptoms.

mGluR5 receptor availability is associated with lower levels of negative symptoms and better cognition in male patients with chronic schizophrenia

Consistent findings postulate disturbed glutamatergic function (more specifically a hypofunction of the ionotropic NMDA receptors) as an important pathophysiologic mechanism in schizophrenia. However, the role of the metabotropic glutamatergic receptors type 5 (mGluR5) in this disease remains unclear. In this study, we investigated their significance (using [¹¹C]ABP688) for psychopathology and cognition in male patients with chronic schizophrenia and healthy controls. In the patient group, lower mGluR5 binding potential (BP_ND) values in the left temporal cortex and caudate were associated with higher general symptom levels (negative and depressive symptoms), lower levels of global functioning and worse cognitive performance. At the same time, in both groups, mGluR5 BP_ND were significantly lower in smokers (F_[27,1] = 15.500; p = .001), but without significant differences between the groups. Our findings provide support for the concept that the impaired function of mGluR5 underlies the symptoms of schizophrenia. They further supply a new perspective on the complex relationship between tobacco addiction and schizophrenia by identifying glutamatergic neurotransmission—in particularly mGluR5—as a possible connection to a shared vulnerability.

Associations between P3a and P3b amplitudes and cognition in antipsychotic-naïve first-episode schizophrenia patients

BACKGROUND

Cognitive deficits are already present in early stages of schizophrenia. P3a and P3b event-related potentials (ERPs) are believed to underlie the processes of attention and working memory (WM), yet limited research has been performed on the associations between these parameters. Therefore, we explored possible associations between P3a/b amplitudes and cognition in a large cohort of antipsychotic-naïve, first-episode schizophrenia (AN-FES) patients and healthy controls (HC).

METHODS

Seventy-three AN-FES patients and 93 age- and gender-matched HC were assessed for their P3a/b amplitude with an auditory oddball paradigm. In addition, subjects performed several subtests from the Cambridge Neuropsychological Test Automated Battery (CANTAB).

RESULTS

AN-FES patients had significantly reduced P3a/b amplitudes, as well as significantly lower scores on all cognitive tests compared with HC. Total group correlations revealed positive associations between P3b amplitude and WM and sustained attention and negative associations with all reaction time measures. These associations appeared mainly driven by AN-FES patients, where we found a similar pattern. No significant associations were found between P3b amplitude and cognitive measures in our HC. P3a amplitude did not correlate significantly with any cognitive measures in either group, nor when combined.

CONCLUSIONS

Our results provide further evidence for P3a/b amplitude deficits and cognitive deficits in AN-FES patients, which are neither due to antipsychotics nor to disease progress. Furthermore, our data showed significant, yet weak associations between P3b and cognition. Therefore, our data do not supply evidence for deficient P3a/b amplitudes as direct underlying factors for cognitive deficits in schizophrenia.

Brain connectivity alterations in early psychosis: from clinical to neuroimaging staging

Early in the course of psychosis, alterations in brain connectivity accompany the emergence of psychiatric symptoms and cognitive impairments, including processing speed. The clinical-staging model is a refined form of diagnosis that places the patient along a continuum of illness conditions, which allows stage-specific interventions with the potential of improving patient care and outcome. This cross-sectional study investigates brain connectivity features that characterize the clinical stages following a first psychotic episode. Structural brain networks were derived from diffusion-weighted MRI for 71 early-psychosis patients and 76 healthy controls. Patients were classified into stage II (first-episode), IIIa (incomplete remission), IIIb (one relapse), and IIIc (two or more relapses), according to the course of the illness until the time of scanning. Brain connectivity measures and diffusion parameters (fractional anisotropy, apparent diffusion coefficient) were investigated using general linear models and sparse linear discriminant analysis (sLDA), studying distinct subgroups of patients who were at specific stages of early psychosis. We found that brain connectivity impairments were more severe in clinical stages following the first-psychosis episode (stages IIIa, IIIb, IIIc) than in first-episode psychosis (stage II) patients. These alterations were spatially diffuse but converged on a set of vulnerable regions, whose inter-connectivity selectively correlated with processing speed in patients and controls. The sLDA suggested that relapsing-remitting (stages IIIb, IIIc) and non-remitting (stage IIIa) patients are characterized by distinct dysconnectivity profiles. Our results indicate that neuroimaging markers of brain dysconnectivity in early psychosis may reflect the heterogeneity of the illness and provide a connectomics signature of the clinical-staging model.

From cognitive and clinical substrates to functional profiles: Disentangling heterogeneity in schizophrenia

The relationship between neurocognition and functioning among patients with schizophrenia is well documented. However, integrating neuropsychological, clinical and psychopathological data to better investigate functional outcome still constitutes a challenge. Artificial neural network-based modeling might help to better capture clinical heterogeneity by analyzing the non-linear relationships among multiple variables. Two hundred and fourteen clinically stabilized patients with schizophrenia were recruited and assessed for neurocognition, psychopathology and functioning. Artificial neural network analyses were conducted to yield significant predictors of functional outcome among clinical and cognitive variables and to build distinct functional Profiles, each characterized by a different medley of cognitive and clinical features. Twenty-two key predictors of daily functioning emerged, encompassing neurocognitive and clinical domains, with major roles for processing speed and attention. Four Profiles were constructed based on specific levels of functioning, each characterized by a distinct distribution of key clinical and neurocognitve measures. This study highlights the importance of a more in-depth investigation of cognitive and clinical heterogeneity. A better understanding of the building blocks of these Profiles would lead to more individualized rehabilitation treatments.

What specifically contributes to disturbed non-verbal fluency in patients with bipolar disorder: Ineffective performance initiation, slowed processing or lack of the execution strategy?

The study aimed at identifying the cognitive and clinical determinants of impaired design fluency in bipolar patients, with special reference to processing speed and performance strategy. A sample of bipolar disorder patients (BD, n = 45) and matched healthy controls (HC, n = 42) underwent the assessment of figural fluency, cognitive and manual speed, cognitive effort and affective state. An electronic version of design fluency test was applied, enabling assessment of performance speed, execution strategy and spontaneous fluctuations in production efficiency. Additional clinical variables were also controlled. BD patients produced significantly less unique designs, performed slower, utilized less effective strategy, their ability to concentrate designs production in the initial phase of performance was significantly reduced compared with HC. Regression analysis revealed that in BD patients design fluency main outcome was significantly predicted by slowed creation of designs and the number of hospitalizations, while in the HC group, the main fluency result was predicted only by the executive strategy indicators. Our study showed that non-verbal fluency in BD group was determined by essentially different neuropsychological functions than in healthy controls. Obtained findings confirm that cognitive slowdown should be an important goal of cognitive remediation and pharmacological interventions in bipolar disorder.

Exercise as an intervention for first-episode psychosis: a feasibility study

AIM

Exercise can improve psychiatric symptoms, neurocognitive functioning and physical health in schizophrenia. However, the effects in early psychosis have not been explored. This study aimed to assess the feasibility of an exercise intervention for early psychosis and to determine if it was associated with changes in physical and mental health.

METHODS

Thirty-one patients with first-episode psychosis (FEP) were recruited from early intervention services to a 10-week exercise intervention. The intervention group received individualized training programmes, aiming to achieve ≥90 min of moderate-to-vigorous activity each week, using exercise programmes tailored to individual preferences and needs. A comparison FEP sample from the same services (n = 7) received treatment as usual.

RESULTS

Rates of consent and retention in the exercise group were 94% and 81%, respectively. Participants achieved an average of 107 min of moderate-to-vigorous exercise per week. Positive and Negative Syndrome Scale total scores reduced by 13.3 points after 10 weeks of exercise, which was significantly greater than the treatment as usual comparison group (P = 0.010). The greatest differences were observed in negative symptoms, which reduced by 33% in the intervention group (P = 0.013). Significant improvements were also observed in psychosocial functioning and verbal short-term memory. Increases in cardiovascular fitness and processing speed were positively associated with the amounts of exercise achieved by participants.

CONCLUSION

Individualized exercise training could provide a feasible treatment option for improving symptomatic, neurocognitive and metabolic outcomes in FEP.

Cognitive impairments and low BDNF serum levels in first-episode drug-naive patients with schizophrenia

Evidence shows that BDNF may regulate activity-dependent forms of synaptic plasticity underlying learning and memory. Previous studies reported low BDNF levels and cognitive impairment in the early stage of schizophrenia. Our current study aimed to explore the association between serum BDNF and cognitive functions in first-episode drug-naïve (FEDN) patients with schizophrenia, which has been under-investigated. We recruited 80 FEDN patients and 80 healthy controls and examined the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and serum BDNF in both groups. Patient psychopathology was assessed using the Positive and Negative Syndrome Scale (PANSS). BDNF levels were significantly lower in patients compared to controls (p < 0.001). The RBANS total score and nearly all indexes (all p < 0.001) except for visuospatial/constructional index (p > 0.05) were significantly lower in patients than controls. No significant correlation was found between BDNF and any index or total scores of RBANS in either patients or healthy controls (all p > 0.05). However, the PANSS negative subscale score were negatively associated with both the immediate memory and language indexes (both p < 0.005). Our findings suggest that excessive cognitive impairments are present in the early stage of schizophrenia. Low BDNF may contribute to the pathogenesis of schizophrenia, but maybe not to its cognitive impairments.

D2/D3 dopamine receptor binding with [F-18]fallypride correlates of executive function in medication-naïve patients with schizophrenia

Converging evidence indicates that the prefrontal cortex is critically involved in executive control and that executive dysfunction is implicated in schizophrenia. Reduced dopamine D2/D3 receptor binding potential has been reported in schizophrenia, and the correlations with neuropsychological test scores have been positive and negative for different tasks. The aim of this study was to examine the relation between dopamine D2/D3 receptor levels with frontal and temporal neurocognitive performance in schizophrenia. Resting-state ¹⁸F-fallypride positron emission tomography was performed on 20 medication-naïve and 5 previously medicated for brief earlier periods patients with schizophrenia and 19 age- and sex-matched healthy volunteers. Striatal and extra-striatal dopamine D2/D3 receptor levels were quantified as binding potential using fallypride imaging. Magnetic resonance images in standard Talairach position and segmented into gray and white matter were co-registered to the fallypride images, and the AFNI stereotaxic atlas was applied. Two neuropsychological tasks known to activate frontal and temporal lobe function were chosen, specifically the Wisconsin Card Sorting Test (WCST) and the California Verbal Learning Test (CVLT). Images of the correlation coefficient between fallypride binding and WCST and CVLT performance showed a negative correlation in contrast to positive correlations in healthy volunteers. The results of this study demonstrate that lower fallypride binding potential in patients with schizophrenia may be associated with better performance. Our findings are consistent with previous studies that failed to find cognitive improvements with typical dopamine-blocking medications.

Planning performance in schizophrenia patients: a meta-analysis of the influence of task difficulty and clinical and sociodemographic variables

BACKGROUND

Despite a large body of research on planning performance in adult schizophrenia patients, results of individual studies are equivocal, suggesting either no, moderate or severe planning deficits. This meta-analysis therefore aimed to quantify planning deficits in schizophrenia and to examine potential sources of the heterogeneity seen in the literature.

METHOD

The meta-analysis comprised outcomes of planning accuracy of 1377 schizophrenia patients and 1477 healthy controls from 31 different studies which assessed planning performance using tower tasks such as the Tower of London, the Tower of Hanoi and the Stockings of Cambridge. A meta-regression analysis was applied to assess the influence of potential moderator variables (i.e. sociodemographic and clinical variables as well as task difficulty).

RESULTS

The findings indeed demonstrated a planning deficit in schizophrenia patients (mean effect size: ; 95% confidence interval 0.56-0.78) that was moderated by task difficulty in terms of the minimum number of moves required for a solution. The results did not reveal any significant relationship between the extent of planning deficits and sociodemographic or clinical variables.

CONCLUSIONS

The current results provide first meta-analytic evidence for the commonly assumed impairments of planning performance in schizophrenia. Deficits are more likely to become manifest in problem items with higher demands on planning ahead, which may at least partly explain the heterogeneity of previous findings. As only a small fraction of studies reported coherent information on sample characteristics, future meta-analyses would benefit from more systematic reports on those variables.

PICK1 Genetic Variation and Cognitive Function in Patients with Schizophrenia

The gene of protein interacting with C kinase 1 alpha (PICK1) has been implicated in schizophrenia, nevertheless, conflicting results existed. However, its role in cognitive function remains unclear. Besides, cognitive deficits impair the long-term outcome. We explored whether the polymorphisms of PICK1 (rs2076369, rs3952) affected cognitive functions in schizophrenic patients. We analyzed 302 patients and tested the differences of cognitive functions, clinical symptoms between genetic groups. We also used general linear model to analyze the effect of PICK1 genetic polymorphisms on cognitive functions. After adjustment for gender, age, education, the patients with rs2076369 G/T genotype showed better performance than T/T homozygotes in the summary score, global composite score, neurocognitive composite score, category fluency subtest, WAIS-III-Digit Symbol Coding subtest, working memory, WMS-III-Spatial Span (backward) subtest, MSCEIT-managing emotions branch (p = 0.038, 0.025, 0.046, 0.036, 0.025, 0.027, 0.035, 0.028, respectively). G/G homozygotes performed better than T/T in category fluency subtest (p = 0.049). A/A homozygotes of rs3952 performed better than G/G in trail making A subtest (p = 0.048). To our knowledge, this is the first study to indicate that PICK1 polymorphisms may associate with cognitive functions in schizophrenic patients. Further replication studies in healthy controls or other ethnic groups are warranted.

Processing speed is associated with differences in IQ and cognitive profiles between patients with schizophrenia and their healthy siblings

BACKGROUND

Processing speed turns out to be the central area of research on cognition in schizophrenia. So far the relationship between this dimension and the IQ level of patients and their healthy siblings has not been investigated.

AIM

To investigate the differences in cognitive speed in patients with schizophrenia and their healthy siblings, and to determine whether cognitive speed as a covariate affects differences in IQ and cognitive profiles between groups.

METHODS

Forty-seven inpatients diagnosed with schizophrenia according to DSM-IV (SCH) and their 36 healthy siblings (HSB) were tested with cognitive speed tasks according to Bartzokis et al. method and Wechsler Intelligence Scale. Additional control for the possible impact of antipsychotic drugs and selected demographic variables on the cognitive performance was taken into account.

RESULTS

The siblings scored significantly higher in the cognitive speed task (p < 0.01) than patients, the WAIS-R cognitive test profiles were also significantly different in two ways: between groups, and between single test results in each of the assessed groups. The interaction effect: ANOVA, F(10, 770) = 2.798, p = 0.002. Similarly, the Performance and Full Scale IQs were significantly different, at p < 0.01. After controlling for cognitive speed, all significant differences no longer exist: e.g. Full Scale IQ, p = 0.459.

CONCLUSIONS

Significant differences in cognitive speed between patients and their healthy siblings generate the differences in the cognitive profile assessed with Wechsler Intelligence Scale. Some problems of cognitive speed diagnosis and further research on the cognitive schizophrenia endophenotype were discussed.

Processing speed impairment in schizophrenia is mediated by white matter integrity

BACKGROUND

Processing speed predicts functional outcome and is a potential endophenotype for schizophrenia. Establishing the neural basis of processing speed impairment may inform the treatment and etiology of schizophrenia. Neuroimaging investigations in healthy subjects have linked processing speed to brain anatomical connectivity. However, the relationship between processing speed impairment and white matter (WM) integrity in schizophrenia is unclear.

METHOD

Individuals with schizophrenia and healthy subjects underwent diffusion tensor imaging (DTI) and completed a brief neuropsychological assessment that included measures of processing speed, verbal learning, working memory and executive functioning. Group differences in WM integrity, inferred from fractional anisotropy (FA), were examined throughout the brain and the hypothesis that processing speed impairment in schizophrenia is mediated by diminished WM integrity was tested.

RESULTS

WM integrity of the corpus callosum, cingulum, superior and inferior frontal gyri, and precuneus was reduced in schizophrenia. Average FA in these regions mediated group differences in processing speed but not in other cognitive domains. Diminished WM integrity in schizophrenia was accounted for, in large part, by individual differences in processing speed.

CONCLUSIONS

Cognitive impairment in schizophrenia was mediated by reduced WM integrity. This relationship was strongest for processing speed because deficits in working memory, verbal learning and executive functioning were not mediated by WM integrity. Larger sample sizes may be required to detect more subtle mediation effects in these domains. Interventions that preserve WM integrity or ameliorate WM disruption may enhance processing speed and functional outcome in schizophrenia.

Glutamate receptor 1 phosphorylation at serine 845 contributes to the therapeutic effect of olanzapine on schizophrenia-like cognitive impairments

Schizophrenia patients exhibit a wide range of impairments in cognitive functions. Clinically, atypical antipsychotic drugs (AAPs) such as olanzapine (OLZ) have a therapeutic effect on memory function among schizophrenia patients rather than typical antipsychotics, e.g., haloperidol. To date, however, little is known about the neuroplasticity mechanism underlying the effect of AAPs on the impairment of cognitive functions. Here, we treated schizophrenia rat models with a systematic injection of MK-801 (0.1mg/kg) and chose the drug OLZ as a tool to investigate the mechanisms of AAPs when used to alter cognitive function. The results showed that the systematic administration of MK-801 results in the impairment of spatial learning and memory as well as spatial working memory in a Morris water maze task. OLZ but not HAL improved these MK-801-induced cognitive dysfunctions. After MK-801 application, the hippocampal LTP was profoundly impaired. In conjunction with the results of the behavioral test, the administration of OLZ but not of HAL resulted in a significant reversal effect on the impaired LTP induced via MK-801 application. Furthermore, we found that OLZ but not HAL can upregulate the phosphorylation of GluR1 Ser845. These data suggest that the therapeutic effect of OLZ on cognitive dysfunctions may be due to its contribution to synaptic plasticity via the ability to upregulate the state of GluR1 Ser845 phosphorylation. We therefore suggest that the upregulated state of GluR1 Ser845 phosphorylation may be a promising target for developing novel therapeutics for treating schizophrenia.

Meta-analysis of cognitive performance in drug-naïve patients with schizophrenia

Cognitive deficits represent a significant characteristic of schizophrenia. However, a majority of the clinical studies have been conducted in antipsychotic drug treated patients. Thus, it remains unclear if significant cognitive impairments exist in the absence of medication. This is the first meta-analysis of cognitive findings in drug-naïve patients with schizophrenia. Cognitive data from 23 studies encompassing 1106 patients and 1385 controls published from 1992 to 2013 were included. Tests were to a large extent ordered in cognitive domains according to the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) battery. Analysis was performed with STATA using the random-effects model and heterogeneity as well as Egger's publication bias was assessed. Overall the results show that patients performed worse than healthy controls in all cognitive domains with medium to large effect sizes. Verbal memory, speed of processing and working memory were three of the domains with the greatest impairments. The pattern of results is in line with previous meta-analytic findings in antipsychotic treated patients. The present meta-analysis confirms the existence of significant cognitive impairments at the early stage of the illness in the absence of antipsychotic medication.

Relative stability of neurocognitive deficits in early onset schizophrenia spectrum patients

In contrast to the findings of progressive structural brain changes in adolescence, longitudinal studies of patients with early onset schizophrenia spectrum disorders (EOS) indicate that neurocognitive deficits are relatively stable over the first years. The aim of this study is to assess neurocognitive functions longitudinally in patients with EOS compared to healthy controls (HC) using the MATRICS Cognitive Consensus Battery (MCCB).

METHODS

Twenty patients with EOS and 41 HC were tested with the MCCB at baseline (T1) and after one (T2) and two years (T3). The mean age for the EOS group was 15.6 (SD=1.8) years, while the mean duration of illness was 1.7 (SD=1.4) years at T1.

RESULTS

The EOS group's neurocognitive performances indicate a stable deficit on most measures. Both the EOS and HC groups showed improved neurocognitive functioning over time on all measures except for the verbal learning domain. There was an interaction between the EOS and HC groups' performance over time on the Trail Making Test A (TMA), a subtest on the processing speed domain.

CONCLUSION

The longitudinal neurocognitive performances measured by the MCCB confirm previous findings of stable deficits in patients with EOS. It is premature to conclude whether the increases in neurocognitive performance reflect developmental processes in adolescence or may be explained by learning effects, or both. As opposed to the other tests in this domain, a stagnation in processing speed as measured by the TMA suggests that the TMA is a particularly sensitive measure of neurodevelopmental deviance in EOS.

TCF4 gene polymorphism and cognitive performance in patients with first episode psychosis

BACKGROUND

Single nucleotide polymorphisms in TCF4 gene have been consistently associated with schizophrenia in genome wide association studies, including the C allele of rs9960767. However, its exact role in modulating the schizophrenia phenotype is not known.

AIMS

To comprehensively investigate the relationship between rs9960767 risk allele (C) of TCF4 and cognitive performance in patients with first episode psychosis (FEP).

METHODS

173 patients with FEP received a comprehensive neurocognitive evaluation and were genotyped for rs9960767. Carriers of the risk allele (CA/CC) were compared to non-carriers (AA) using Multivariate Analysis of Covariance MANCOVA. Ethnicity, negative symptoms and substance abuse were included as covariates.

RESULTS

Carriers of the risk allele had a statistically significant lower performance in the cognitive domain of Reasoning/Problem-Solving compared to non-carriers (F1,172=4.4, p=.038). There were no significant genotype effects on the other cognitive domains or general cognition. This effect on the Reasoning/Problem-Solving domain remained significant even when controlling for IQ (F1,172=4.3, p=.039).

CONCLUSIONS

rs9960767 (C) of TCF4 appears to be associated with neurocognitive deficits in the Reasoning/Problem-Solving cognitive domain, in patients with FEP. A confirmation of this finding in a larger sample and including other TCF4 polymorphisms will be needed to gain further validity of this result.