Working memory constrains abstraction in schizophrenia

The Social Route to Abstraction: Interaction and Diversity Enhance Performance and Transfer in a Rule-Based Categorization Task

Capacities for abstract thinking and problem-solving are central to human cognition. Processes of abstraction allow the transfer of experiences and knowledge between contexts helping us make informed decisions in new or changing contexts. While we are often inclined to relate such reasoning capacities to individual minds and brains, they may in fact be contingent on human-specific modes of collaboration, dialogue, and shared attention. In an experimental study, we test the hypothesis that social interaction enhances cognitive processes of rule-induction, which in turn improves problem-solving performance. Through three sessions of increasing complexity, individuals and groups were presented with a problem-solving task requiring them to categorize a set of visual stimuli. To assess the character of participants' problem representations, after each training session, they were presented with a transfer task involving stimuli that differed in appearance, but shared relations among features with the training set. Besides, we compared participants' categorization behaviors to simulated agents relying on exemplar learning. We found that groups performed superior to individuals and agents in the training sessions and were more likely to correctly generalize their observations in the transfer phase, especially in the high complexity session, suggesting that groups more effectively induced underlying categorization rules from the stimuli than individuals and agents. Crucially, variation in performance among groups was predicted by semantic diversity in members' dialogical contributions, suggesting a link between social interaction, cognitive diversity, and abstraction.

Construction of a computerized adaptive test (CAT-CCNB) for efficient neurocognitive and clinical psychopathology assessment

BACKGROUND

Traditional paper-and-pencil neurocognitive evaluations and semi-structured mental health interviews can take hours to administer and score. Computerized assessment has decreased that burden substantially, and contemporary psychometric tools such as item response theory and computerized adaptive testing (CAT) allow even further abbreviation.

NEW METHOD

The goal of this paper was to describe the application of CAT and related methods to the Penn Computerized Neurocognitive Battery (CNB) and a well-validated clinical assessment in order to increase efficiency in assessment and relevant domain coverage. To calibrate item banks for CAT, N = 5053 participants (63% female; mean age 45 years, range 18-80) were collected from across the United States via crowdsourcing, providing item parameters that were then linked to larger item banks and used in individual test construction. Tests not amenable to CAT were abbreviated using complementary short-form methods.

RESULTS

The final "CAT-CCNB" battery comprised 21 cognitive tests (compared to 14 in the original) and five adaptive clinical scales (compared to 16 in the original).

COMPARISON WITH EXISTING METHODS

This new battery, derived with contemporary psychometric approaches, provides further improvements over existing assessments that use collections of fixed-length tests developed for stand-alone administration. The CAT-CCNB provides an improved version of the CNB that shows promise as a maximally efficient tool for neuropsychiatric assessment.

CONCLUSIONS

We anticipate CAT-CCNB will help satisfy the clear need for broad yet efficient measurement of cognitive and clinical domains, facilitating implementation of large-scale, "big science" approaches to data collection, and potential widespread clinical implementation.

Impact of daytime spectral tuning on cognitive function

Light at night can improve alertness and cognition. Exposure to daytime light, however, has yielded less conclusive results. In addition to direct effects, daytime light may also mitigate the impact of nocturnal light exposure on alertness. To examine the impact of daytime lighting on daytime cognitive performance, and evening alertness, we studied nine healthy individuals using a within subject crossover design. On four visits, participants were exposed to one of four lighting conditions for 10 h (dim fluorescent, room fluorescent, broad-spectrum LED, standard white LED; the latter three conditions were matched for 100 lx) followed by an exposure to bright evening light. Cognitive performance, subjective and objective measures of alertness were regularly obtained. While daytime alertness was not impacted by light exposure, the broad-spectrum LED light improved several aspects of daytime cognition. The impact of evening light on alertness was not mitigated by the pre-exposure to different daytime lighting conditions. Results suggest that daytime exposure to white light with high melanopic efficacy has the potential to improve daytime cognitive function and that such improvements are likely to be direct rather than a consequence of light-induced changes in alertness.

Acceptability of the Cognition Test Battery in Astronaut and Astronaut-Surrogate Populations

BACKGROUND

Sustained high levels of astronaut cognitive performance are a prerequisite for mission success. A neuropsychological battery of 10 brief cognitive tests (Cognition) covering a range of cognitive domains was specifically developed for high performing astronauts to objectively assess cognitive performance. Extended mission durations require repeated cognitive testing and thus high acceptability of the Cognition software to the astronaut population. The aim of this qualitative study was to evaluate acceptability of Cognition to astronauts and astronaut surrogate populations.

METHODS

Cognition was administered repeatedly to N=87 subjects (mean age ±SD 35.1 ±8.7 years, 52.8% male) on a laptop or iPad across five individual studies on the International Space Station or in space analog environments on Earth. Following completion of each study, participants were interviewed regarding their experience using Cognition in a semi-structured debrief. Participant comments were analyzed using a qualitative conventional content analysis approach.

RESULTS

The majority of participants' comments (86.1%) were coded as positive or neutral in valence, with most positive comments relating to software usability, engagement, and overall design. Among the 10 Cognition tests, subjects liked the Visual Object Learning Test most (28 likes, 32.2% of participants), while the Emotion Recognition Test was liked least (44 dislikes, 50.6% of participants). Some subjects (36.8%) were frustrated with the level of difficulty of some of the 10 Cognition tests, especially during early administrations, which was by design to avoid ceiling effects in repeated administrations of high-performers. Technical difficulties were rare (20.7% of participants), and most often observed in environments with restricted internet access. Most participants (82.3% of those who commented) liked the feedback provided by Cognition after each test, which includes a graph showing performance history.

CONCLUSION

Cognition was found to be acceptable to astronaut and astronaut-surrogate populations across a variety of settings and mission durations. Participant feedback provided was used to further improve Cognition and increase its acceptability during sustained space missions.

The progression of disorder-specific brain pattern expression in schizophrenia over 9 years

Age plays a crucial role in the performance of schizophrenia vs. controls (SZ-HC) neuroimaging-based machine learning (ML) models as the accuracy of identifying first-episode psychosis from controls is poor compared to chronic patients. Resolving whether this finding reflects longitudinal progression in a disorder-specific brain pattern or a systematic but non-disorder-specific deviation from a normal brain aging (BA) trajectory in schizophrenia would help the clinical translation of diagnostic ML models. We trained two ML models on structural MRI data: an SZ-HC model based on 70 schizophrenia patients and 74 controls and a BA model (based on 561 healthy individuals, age range = 66 years). We then investigated the two models’ predictions in the naturalistic longitudinal Northern Finland Birth Cohort 1966 (NFBC1966) following 29 schizophrenia and 61 controls for nine years. The SZ-HC model’s schizophrenia-specificity was further assessed by utilizing independent validation (62 schizophrenia, 95 controls) and depression samples (203 depression, 203 controls). We found better performance at the NFBC1966 follow-up (sensitivity = 75.9%, specificity = 83.6%) compared to the baseline (sensitivity = 58.6%, specificity = 86.9%). This finding resulted from progression in disorder-specific pattern expression in schizophrenia and was not explained by concomitant acceleration of brain aging. The disorder-specific pattern’s progression reflected longitudinal changes in cognition, outcomes, and local brain changes, while BA captured treatment-related and global brain alterations. The SZ-HC model was also generalizable to independent schizophrenia validation samples but classified depression as control subjects. Our research underlines the importance of taking account of longitudinal progression in a disorder-specific pattern in schizophrenia when developing ML classifiers for different age groups.

Recovery of consciousness and cognition after general anesthesia in humans

Understanding how the brain recovers from unconsciousness can inform neurobiological theories of consciousness and guide clinical investigation. To address this question, we conducted a multicenter study of 60 healthy humans, half of whom received general anesthesia for 3 hr and half of whom served as awake controls. We administered a battery of neurocognitive tests and recorded electroencephalography to assess cortical dynamics. We hypothesized that recovery of consciousness and cognition is an extended process, with differential recovery of cognitive functions that would commence with return of responsiveness and end with return of executive function, mediated by prefrontal cortex. We found that, just prior to the recovery of consciousness, frontal-parietal dynamics returned to baseline. Consistent with our hypothesis, cognitive reconstitution after anesthesia evolved over time. Contrary to our hypothesis, executive function returned first. Early engagement of prefrontal cortex in recovery of consciousness and cognition is consistent with global neuronal workspace theory.

Effects of head-down tilt bed rest plus elevated CO2 on cognitive performance

Microgravity and elevated CO2 levels are two important environmental spaceflight stressors that can adversely affect astronaut cognitive performance and jeopardize mission success. This study investigated the effects of 6° head-down tilt bed rest (HDBR) with (n = 11 participants, 30-day HDBR) and without (n = 8 participants, 60-day HDBR) elevated ambient (3.73 mmHg) CO2 concentrations on cognitive performance. Participants of both groups performed all 10 tests of NASA's Cognition battery and a brief alertness and mood survey repeatedly before, during, and after the HDBR period. Test scores were adjusted for practice and stimulus set effects. Concentrating on the first 30 days of HDBR, a modest but statistically significant slowing across a range of cognitive domains was found in both groups (controls: -0.37 SD; 95% CI -0.48, -0.27; adjusted P < 0.0001; CO2: -0.25 SD; 95% CI -0.34, -0.16; adjusted P < 0.001), most prominently for sensorimotor speed. These changes were observed early during HDBR and did not further deteriorate or improve with increasing time in HDBR. The study found similar cognitive effects of HDBR irrespective of CO2 levels, suggesting that elevated CO2 neither ameliorated nor worsened the HDBR effects. In both groups, cognitive performance after 15 days of recovery was statistically indistinguishable from pre-HDBR performance. However, subjects undergoing 60 days of HDBR rated themselves as feeling more sleepy, tired, physically exhausted, stressed, and unhealthy during recovery compared to their 30-day counterparts.NEW AND NOTEWORTHY This study investigated the effects of prolonged head-down tilt bed rest with and without elevated (3.73 mmHg) levels of ambient CO2 on cognitive performance across a range of cognitive domains and is one of the few studies investigating combined effects of environmental stressors prevalent in spaceflight. The study showed moderate declines in cognitive speed induced by head-down tilt bed rest and suggests that exposure to elevated levels of ambient CO2 did not modify this effect.

Continuous and Intermittent Artificial Gravity as a Countermeasure to the Cognitive Effects of 60 Days of Head-Down Tilt Bed Rest

Environmental and psychological stressors can adversely affect astronaut cognitive performance in space. This study used a 6° head-down tilt bed rest (HDBR) paradigm to simulate some of the physiologic changes induced by microgravity. Twenty-four participants (mean ± SD age 33.3 ± 9.2 years, N = 16 men) spent 60 consecutive days in strict HDBR. They were studied in three groups of eight subjects each. One group served as Control, whereas the other two groups received either a continuous or intermittent artificial gravity (AG) countermeasure of 30 min centrifugation daily (1 g acceleration at the center of mass and 2 g at the feet). Participants performed all 10 tests of NASA’s Cognition battery and a brief alertness and mood survey repeatedly before, during, and after the HDBR period. Test scores were adjusted for practice and stimulus set difficulty effects. A modest but statistically significant slowing across a range of cognitive domains was found in all three groups during HDBR compared to baseline, most consistently for sensorimotor speed, whereas accuracy was unaffected. These changes were observed early during HDBR and did not further worsen or improve with increasing time in HDBR, except for emotion recognition performance. With increasing time spent in HDBR, participants required longer time to decide which facial emotion was expressed. They were also more likely to select categories with negative valence over categories with neutral or positive valence. Except for workload, which was rated lower in the Control group, continuous or intermittent AG did not modify the effect of HDBR on cognitive performance or subjective responses. Participants expressed several negative survey responses during HDBR relative to baseline, and some of the responses further deteriorated during recovery, which highlights the importance of adequate medical and psychological support during extended duration HDBR studies. In conclusion, 60 days of HDBR were associated with moderate cognitive slowing and changes in emotion recognition performance, but these effects were not mitigated by either continuous or intermittent exposure to AG for 30 min daily.

A Pilot Study of Cognitive Impairment in Longstanding Electroconvulsive Therapy-treated Schizophrenia Patients Versus Controls

BACKGROUND

Electroconvulsive therapy (ECT), though reliable and effective, is controversial due to its media portrayal as a treatment with severe side effects. Electroconvulsive therapy is mainly given to patients suffering from affective disorders and treatment-resistant schizophrenia. Although past research assessed the amount and duration of memory loss due to ECT, little is known about its influence on cognition for patients suffering from schizophrenia, whose cognitive decline is an inherent part of their illness. We aimed to test whether maintenance ECT causes cognitive decline among elderly schizophrenia patients.

METHODS

Twenty elderly (age >65 years) patients suffering from schizophrenia and schizoaffective disorder who received maintenance ECT were matched with 20 controls suffering from the same illnesses that have never been treated with ECT. The match was based on age, sex, and illness duration. The participants were evaluated using the Montreal Cognitive Assessment for cognitive decline and a Positive and Negative Syndrome Scale (PANSS) for illness severity.

RESULTS

A lower score in the abstraction subscale was found in the maintenance ECT population (P = 0.002), without significant differences in the total Montreal Cognitive Assessment and the delayed-recall subscale scores. In the treatment group, a correlation was found between an impairment in naming and positive symptoms in the PANSS score (r = -0.45) and between abstraction impairment and negative symptoms (r = -0.56) and total PANSS score (r = -0.497).

CONCLUSIONS

Maintenance ECT does not worsen existing global cognitive deficits or delayed recall in elderly schizophrenia patients. The abstraction impairment was possibly due to the higher disease burden of the patients referred to ECT.

Changes in Subjective Motivation and Effort During Sleep Restriction Moderate Interindividual Differences in Attentional Performance in Healthy Young Men

PURPOSE

The effects of sleep restriction on subjective alertness, motivation, and effort vary among individuals and may explain interindividual differences in attention during sleep restriction. We investigated whether individuals with a greater decrease in subjective alertness or motivation, or a greater increase in subjective effort (versus other participants), demonstrated poorer attention when sleep restricted.

PARTICIPANTS AND METHODS

Fifteen healthy men (M±SD, 22.3±2.8 years) completed a study with three nights of 10-hour time in bed (baseline), five nights of 5-hour time in bed (sleep restriction), and two nights of 10-hour time in bed (recovery). Participants completed a 10-minute psychomotor vigilance task (PVT) of sustained attention and rated alertness, motivation, and effort every two hours during wake (range: 3-9 administrations on a given day). Analyses examined performance across the study (first two days excluded) moderated by per-participant change in subjective alertness, motivation, or effort from baseline to sleep restriction. For significant interactions, we investigated the effect of study day² (day*day) on the outcome at low (mean-1 SD) and high (mean+1 SD) levels of the moderator (N = 15, all analyses).

RESULTS

False starts increased across sleep restriction in participants who reported lower (mean-1 SD) but not preserved (mean+1 SD) motivation during sleep restriction. Lapses increased across sleep restriction regardless of change in subjective motivation, with a more pronounced increase in participants who reported lower versus preserved motivation. Lapses increased across sleep restriction in participants who reported higher (mean+1 SD) but not preserved (mean-1 SD) effort during sleep restriction. Change in subjective alertness did not moderate the effects of sleep restriction on attention.

CONCLUSION

Vigilance declines during sleep restriction regardless of change in subjective alertness or motivation, but individuals with reduced motivation exhibit poorer inhibition. Individuals with preserved subjective alertness still perform poorly during sleep restriction, while those reporting additional effort demonstrate impaired vigilance.

Cognition Test Battery Performance Is Associated with Simulated 6df Spacecraft Docking Performance

INTRODUCTION: Environmental and operational stressors commonly encountered in spaceflight can affect astronaut cognitive performance. It is currently unclear how performance decrements on test batteries that assess individual cognitive domains translate to complex operational performance.METHODS: N 30 healthy adults (mean SD age 33.5 7.1 yr, range 2548 yr; 16 men) with demographic characteristics similar to astronauts performed all 10 tests of the Cognition test battery as well as a simulated 6 degrees-of-freedom (6df) spacecraft docking task 15 times. Performance on 60 Cognition outcome variables was rank-correlated with 6df docking performance individually as well as in models containing up to 12 predictors after accounting for sex, age, and study design effects.RESULTS: Average response time on the Digit Symbol Substitution Test (DSST)a measure of processing speed requiring complex scanning, visual tracking, and working memorywas the best individual predictor of 6df docking performance (unadjusted r 0.550; semipartial cross-validated R² 0.244). Furthermore, higher levels of spatial orientation efficiency and vigilant attention, lower levels of impulsivity, and faster response speed were associated with higher 6df performance, while sensorimotor speed, memory, and risk decision making were less relevant. After semipartial cross-validation, a model with three Cognition outcomes (DSST average response time, Abstract Matching accuracy, and conservative response bias on the Fractal 2-Back test) explained 30% of the variance in 6df performance.CONCLUSIONS: This study demonstrates direct links between performance on tests designed to assess specific cognitive domains and complex operational docking performance.Basner M, Moore TM, Hermosillo E, Nasrini J, Dinges DF, Gur RC, Johannes B. Cognition test battery performance is associated with simulated 6df spacecraft docking performance. Aerosp Med Hum Perform. 2020; 91(11):861867.

Navigating Increasing Levels of Relational Complexity: Perceptual, Analogical, and System Mappings

Relational thinking involves comparing abstract relationships between mental representations that vary in complexity; however, this complexity is rarely made explicit during everyday comparisons. This study explored how people naturally navigate relational complexity and interference using a novel relational match-to-sample (RMTS) task with both minimal and relationally directed instruction to observe changes in performance across three levels of relational complexity: perceptual, analogy, and system mappings. Individual working memory and relational abilities were examined to understand RMTS performance and susceptibility to interfering relational structures. Trials were presented without practice across four blocks, and participants received feedback after each attempt to guide learning. Experiment 1 instructed participants to select the target that best matched the sample, whereas Experiment 2 additionally directed participants' attention to same and different relations. Participants in Experiment 2 demonstrated improved performance when solving analogical mappings, suggesting that directing attention to relational characteristics affected behavior. Higher performing participants-those with above-chance performance on the final block of system mappings-solved more analogical RMTS problems and had greater visuospatial working memory, abstraction, verbal analogy, and scene analogy scores compared to lower performers. Lower performers were less dynamic in their performance across blocks and demonstrated negative relationships between analogy and system mapping accuracy, suggesting increased interference between these relational structures. Participant performance on RMTS problems did not change monotonically with relational complexity, suggesting that increases in relational complexity places nonlinear demands on working memory. We argue that competing relational information causes additional interference, especially in individuals with lower executive function abilities.

Cognition test battery: Adjusting for practice and stimulus set effects for varying administration intervals in high performing individuals

INTRODUCTION

Practice effects associated with the repeated administration of cognitive tests often confound true therapeutic or experimental effects. Alternate test forms help reduce practice effects, but generating stimulus sets with identical properties can be difficult. The main objective of this study was to disentangle practice and stimulus set effects for Cognition, a battery of 10 brief cognitive tests specifically designed for high-performing populations with 15 unique versions for repeated testing. A secondary objective was to investigate the effects of test-retest interval on practice effects.

METHODS

The 15 versions of Cognition were administered in three groups of 15-16 subjects (total N = 46, mean±SD age 32.5 ± 7.2 years, range 25-54 years, 23 male) in a randomized but balanced fashion with administration intervals of ≥10 days, ≤5 days, or 4 times per day. Mixed effect models were used to investigate linear and logarithmic trends across repeated administrations in key speed and accuracy outcomes, whether these trends differed significantly between administration interval groups, and whether stimulus sets differed significantly in difficulty.

RESULTS

Protracted, non-linear practice effects well beyond the second administration were observed for most of the 10 Cognition tests both in accuracy and speed, but test-retest administration interval significantly affected practice effects only for 3 out of the 10 tests and only in the speed domain. Stimulus set effects were observed for the 6 Cognition tests that use unique sets of stimuli. Factors were established that allow for correcting for both practice and stimulus set effects.

CONCLUSIONS

Practice effects are pronounced and probably under-appreciated in cognitive testing. The correction factors established in this study are a unique feature of the Cognition battery that can help avoid masking practice effects, address noise generated by differences in stimulus set difficulty, and facilitate interpretation of results from studies with repeated assessments.

Neurocognitive and linguistic correlates of positive and negative formal thought disorder: A meta-analysis

Executive dysfunction and language impairment are the most prominent neuropsychological models of formal thought disorder (FTD) in schizophrenia. However, available studies have provided contradictory findings regarding the accuracy of these models. Furthermore, specific neurocognitive underpinnings of positive FTD (PosFTD) and negative FTD (NegFTD) are not clear. Following the systematic review of schizophrenia studies, a random-effects meta-analysis of the relationship between FTD and neurocognition/language in schizophrenia was conducted in 52 reports including 2805 patients. Neurocognition was significantly associated with both PosFTD (r = -0.21, CI = -0.14 to -0.27) and NegFTD (r = -0.24, CI = -0.18 to -0.30). Both PosFTD (r = ranged from -0.18 to -0.27) and NegFTD (r = ranged from -0.19 to -0.23) were significantly correlated with verbal memory, visual memory, attention, and processing speed. In meta-analyses of executive functions, PosFTD was significantly associated with working memory (r = -0.21), planning (r = -0.19), and inhibition (r = -0.21) and NegFTD was significantly associated with planning (r = -0.27), fluency (r = -0.27), and working memory (r = -0.24). In meta-analyses of linguistic variables, PosFTD was associated with deficits in syntactic comprehension (r = -0.27) and semantic processing (r = -0.18). In contrast, NegFTD was associated only with semantic comprehension (r = -0.21). Both PosFTD and NegFTD were significantly associated with executive dysfunction, neurocognitive deficits and semantic dysfunction but syntactic deficits were more specific to PosFTD. There were also some distinct patterns of relationships between the pattern of executive dysfunction and types of FTD. Fluency deficit was associated more strongly with NegFTD and poor inhibition was more specifically related to PosFTD. Current findings suggest that neurocognitive and linguistic correlates of PosFTD and NegFTD might be partly different.

Effects of acute exposures to carbon dioxide on decision making and cognition in astronaut-like subjects

Acute exposure to carbon dioxide (CO₂) concentrations below those found on the International Space Station are reported to deteriorate complex decision-making. Effective decision-making is critical to human spaceflight, especially during an emergency response. Therefore, effects of acutely elevated CO₂ on decision-making competency and various cognitive domains were assessed in astronaut-like subjects by the Strategic Management Simulation (SMS) and Cognition test batteries. The double-blind cross-over study included 22 participants at the Johnson Space Center randomly assigned to one of four groups. Each group was exposed to a different sequence of four concentrations of CO₂ (600, 1200, 2500, 5000 ppm). Subjects performed Cognition before entering the chamber, 15 min and 2.5 h after entering the chamber, and 15 min after exiting the chamber. The SMS was administered 30 min after subjects entered the chamber. There were no clear dose–response patterns for performance on either SMS or Cognition. Performance on most SMS measures and aggregate speed, accuracy, and efficiency scores across Cognition tests were lower at 1200 ppm than at baseline (600 ppm); however, at higher CO₂ concentrations performance was similar to or exceeded baseline for most measures. These outcomes, which conflict with those of other studies, likely indicate differing characteristics of the various subject populations and differences in the aggregation of unrecognized stressors, in addition to CO₂, are responsible for disparate outcomes among studies. Studies with longer exposure durations are needed to verify that cognitive impairment does not develop over time in crew-like subjects.

The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight

To understand the health impact of long-duration spaceflight, one identical twin astronaut was monitored before, during, and after a 1-year mission onboard the International Space Station; his twin served as a genetically matched ground control. Longitudinal assessments identified spaceflight-specific changes, including decreased body mass, telomere elongation, genome instability, carotid artery distension and increased intima-media thickness, altered ocular structure, transcriptional and metabolic changes, DNA methylation changes in immune and oxidative stress-related pathways, gastrointestinal microbiota alterations, and some cognitive decline postflight. Although average telomere length, global gene expression, and microbiome changes returned to near preflight levels within 6 months after return to Earth, increased numbers of short telomeres were observed and expression of some genes was still disrupted. These multiomic, molecular, physiological, and behavioral datasets provide a valuable roadmap of the putative health risks for future human spaceflight.

Effects of −12° head-down tilt with and without elevated levels of CO2 on cognitive performance: the SPACECOT study

Microgravity and elevated levels of CO2 are two common environmental stressors in spaceflight that may affect cognitive performance of astronauts. In this randomized, double-blind, crossover trial (SPACECOT), 6 healthy males (mean ± SD age: 41 ± 5 yr) were exposed to 0.04% (ambient air) and 0.5% CO2 concentrations during 26.5-h periods of −12° head-down tilt (HDT) bed rest with a 1-wk washout period between exposures. Subjects performed the 10 tests of the Cognition Test Battery before and on average 0.1, 5.2, and 21.0 h after the initiation of HDT bed rest. HDT in ambient air induced a change in response strategy, with increased response speed (+0.19 SD; P = 0.0254) at the expense of accuracy (−0.19 SD; P = 0.2867), resulting in comparable cognitive efficiency. The observed effects were small and statistically significant for cognitive speed only. However, even small declines in accuracy can potentially cause errors during mission-critical tasks in spaceflight. Unexpectedly, exposure to 0.5% CO2 reversed the response strategy changes observed under HDT in ambient air. This was possibly related to hypercapnia-induced cerebrovascular reactivity that favors cortical regions in general and the frontal cortex in particular, or to the CNS arousing properties of mildly to moderately increased CO2 levels. There were no statistically significant time-in-CO2 effects for any cognitive outcome. The small sample size and the small effect sizes are major limitations of this study and its findings. The results should not be generalized beyond the group of investigated subjects until they are confirmed by adequately powered follow-up studies.

NEW & NOTEWORTHY Simulating microgravity with exposure to 21 h of −12° head-down tilt bed rest caused a change in response strategy on a range of cognitive tests, with a statistically significant increase in response speed at the expense of accuracy. Cognitive efficiency was not affected. The observed speed-accuracy tradeoff was small but may nevertheless be important for mission-critical tasks in spaceflight. Importantly, the change in response strategy was reversed by increasing CO2 concentrations to 0.5%.

Cognitive and Neurophysiological Recovery Following Electroconvulsive Therapy: A Study Protocol

Electroconvulsive therapy (ECT) employs the elective induction of generalizes seizures as a potent treatment for severe psychiatric illness. As such, ECT provides an opportunity to rigorously study the recovery of consciousness, reconstitution of cognition, and electroencephalographic (EEG) activity following seizures. Fifteen patients with major depressive disorder refractory to pharmacologic therapy will be enrolled (Clinicaltrials.gov, NCT02761330). Adequate seizure duration will be confirmed following right unilateral ECT under etomidate anesthesia. Patients will then undergo randomization for the order in which they will receive three sequential treatments: etomidate + ECT, ketamine + ECT, and ketamine + sham ECT. Sessions will be repeated in the same sequence for a total of six treatments. Before each session, sensorimotor speed, working memory, and executive function will be assessed through a standardized cognitive test battery. After each treatment, the return of purposeful responsiveness to verbal command will be determined. At this point, serial cognitive assessments will begin using the same standardized test battery. The presence of delirium and changes in depression severity will also be ascertained. Sixty-four channel EEG will be acquired throughout baseline, ictal, and postictal epochs. Mixed-effects models will correlate the trajectories of cognitive recovery, clinical outcomes, and EEG metrics over time. This innovative research design will answer whether: (1) time to return of responsiveness will be prolonged with ketamine + ECT compared with ketamine + sham ECT; (2) time of restoration to baseline function in each cognitive domain will take longer after ketamine + ECT than after ketamine + sham ECT; (3) postictal delirium is associated with delayed restoration of baseline function in all cognitive domains; and (4) the sequence of reconstitution of cognitive domains following the three treatments in this study is similar to that occurring after an isoflurane general anesthetic (NCT01911195). Sub-studies will assess the relationships of cognitive recovery to the EEG preceding, concurrent, and following individual ECT sessions. Overall, this study will lead the development of biomarkers for tailoring the cogno-affective recovery of patients undergoing ECT.

Lifetime use of psychiatric medications and cognition at 43years of age in schizophrenia in the Northern Finland Birth Cohort 1966

BACKGROUND

Higher lifetime antipsychotic exposure has been associated with poorer cognition in schizophrenia. The cognitive effects of adjunctive psychiatric medications and lifetime trends of antipsychotic use remain largely unclear. We aimed to study how lifetime and current benzodiazepine and antidepressant medications, lifetime trends of antipsychotic use and antipsychotic polypharmacy are associated with cognitive performance in midlife schizophrenia.

METHODS

Sixty participants with DSM-IV schizophrenia from the Northern Finland Birth Cohort 1966 were examined at 43years of age with an extensive cognitive test battery. Cumulative lifetime and current use of psychiatric medications were collected from medical records and interviews. The associations between medication and principal component analysis-based cognitive composite score were analysed using linear regression.

RESULTS

Lifetime cumulative DDD years of benzodiazepine and antidepressant medications were not significantly associated with global cognition. Being without antipsychotic medication (for minimum 11months) before the cognitive examination was associated with better cognitive performance (P=0.007) and higher lifetime cumulative DDD years of antipsychotics with poorer cognition (P=0.020), when adjusted for gender, onset age and lifetime hospital treatment days. Other lifetime trends of antipsychotic use, such as a long antipsychotic-free period earlier in the treatment history, and antipsychotic polypharmacy, were not significantly associated with cognition.

CONCLUSIONS

Based on these naturalistic data, low exposure to adjunctive benzodiazepine and antidepressant medications does not seem to affect cognition nor explain the possible negative effects of high dose long-term antipsychotic medication on cognition in schizophrenia.

Protocol for the Reconstructing Consciousness and Cognition (ReCCognition) Study

Important scientific and clinical questions persist about general anesthesia despite the ubiquitous clinical use of anesthetic drugs in humans since their discovery. For example, it is not known how the brain reconstitutes consciousness and cognition after the profound functional perturbation of the anesthetized state, nor has a specific pattern of functional recovery been characterized. To date, there has been a lack of detailed investigation into rates of recovery and the potential orderly return of attention, sensorimotor function, memory, reasoning and logic, abstract thinking, and processing speed. Moreover, whether such neurobehavioral functions display an invariant sequence of return across individuals is similarly unknown. To address these questions, we designed a study of healthy volunteers undergoing general anesthesia with electroencephalography and serial testing of cognitive functions (NCT01911195). The aims of this study are to characterize the temporal patterns of neurobehavioral recovery over the first several hours following termination of a deep inhaled isoflurane general anesthetic and to identify common patterns of cognitive function recovery. Additionally, we will conduct spectral analysis and reconstruct functional networks from electroencephalographic data to identify any neural correlates (e.g., connectivity patterns, graph-theoretical variables) of cognitive recovery after the perturbation of general anesthesia. To accomplish these objectives, we will enroll a total of 60 consenting adults aged 20-40 across the three participating sites. Half of the study subjects will receive general anesthesia slowly titrated to loss of consciousness (LOC) with an intravenous infusion of propofol and thereafter be maintained for 3 h with 1.3 age adjusted minimum alveolar concentration of isoflurane, while the other half of subjects serves as awake controls to gauge effects of repeated neurobehavioral testing, spontaneous fatigue and endogenous rest-activity patterns.

From neurocognition to community participation in serious mental illness: the intermediary role of dysfunctional attitudes and motivation

BACKGROUND

Evidence for a relationship between neurocognition and functional outcome in important areas of community living is robust in serious mental illness research. Dysfunctional attitudes (defeatist performance beliefs and asocial beliefs) have been identified as intervening variables in this causal chain. This study seeks to expand upon previous research by longitudinally testing the link between neurocognition and community participation (i.e. time in community-based activity) through dysfunctional attitudes and motivation.

METHOD

Adult outpatients with serious mental illness (N = 175) participated, completing follow-up assessments approximately 6 months after initial assessment. Path analysis tested relationships between baseline neurocognition, emotion perception, functional skills, dysfunctional attitudes, motivation, and outcome (i.e. community participation) at baseline and follow-up.

RESULTS

Path models demonstrated two pathways to community participation. The first linked neurocognition and community participation through functional skills, defeatist performance beliefs, and motivation. A second pathway linked asocial beliefs and community participation, via a direct path passing through motivation. Model fit was excellent for models predicting overall community participation at baseline and, importantly, at follow-up.

CONCLUSIONS

The existence of multiple pathways to community participation in a longitudinal model supports the utility of multi-modal interventions for serious mental illness (i.e. treatment packages that build upon individuals' strengths while addressing the array of obstacles to recovery) that feature dysfunctional attitudes and motivation as treatment targets.

Lifetime antipsychotic medication and cognitive performance in schizophrenia at age 43 years in a general population birth cohort

This naturalistic study analysed the association between cumulative lifetime antipsychotic dose and cognition in schizophrenia after an average of 16.5 years of illness. Sixty participants with schizophrenia and 191 controls from the Northern Finland Birth Cohort 1966 were assessed at age 43 years with a neurocognitive test battery. Cumulative lifetime antipsychotic dose-years were collected from medical records and interviews. The association between antipsychotic dose-years and a cognitive composite score based on principal component analysis was analysed using linear regression. Higher lifetime antipsychotic dose-years were significantly associated with poorer cognitive composite score, when adjusted for gender, onset age and lifetime hospital treatment days. The effects of typical and atypical antipsychotics did not differ. This is the first report of an association between cumulative lifetime antipsychotic dose and global cognition in midlife schizophrenia. Based on these data, higher lifetime antipsychotic dose-years may be associated with poorer cognitive performance at age 43 years. Potential biases related to the naturalistic design may partly explain the results; nonetheless, it is possible that large antipsychotic doses harm cognition in schizophrenia in the long-term.

Functional Connectivity of Cognitive Brain Networks in Schizophrenia during a Working Memory Task

Task-based connectivity studies facilitate the understanding of how the brain functions during cognition, which is commonly impaired in schizophrenia (SZ). Our aim was to investigate functional connectivity during a working memory task in SZ. We hypothesized that the task-negative (default mode) network and the cognitive control (frontoparietal) network would show dysconnectivity. Twenty-five SZ patient and 31 healthy control scans were collected using the customized 3T Siemens Skyra MRI scanner, previously used to collect data for the Human Connectome Project. Blood oxygen level dependent signal during the 0-back and 2-back conditions were extracted within a network-based parcelation scheme. Average functional connectivity was assessed within five brain networks: frontoparietal (FPN), default mode (DMN), cingulo-opercular (CON), dorsal attention (DAN), and ventral attention network; as well as between the DMN or FPN and other networks. For within-FPN connectivity, there was a significant interaction between n-back condition and group (p = 0.015), with decreased connectivity at 0-back in SZ subjects compared to controls. FPN-to-DMN connectivity also showed a significant condition × group effect (p = 0.003), with decreased connectivity at 0-back in SZ. Across groups, connectivity within the CON and DAN were increased during the 2-back condition, while DMN connectivity with either CON or DAN were decreased during the 2-back condition. Our findings support the role of the FPN, CON, and DAN in working memory and indicate that the pattern of FPN functional connectivity differs between SZ patients and control subjects during the course of a working memory task.

The neural underpinnings of cognitive flexibility and their disruption in psychotic illness

Schizophrenia (SZ) has long been associated with a variety of cognitive deficits, including reduced cognitive flexibility. More recent findings, however, point to tremendous inter-individual variability among patients on measures of cognitive flexibility/set-shifting. With an eye toward shedding light on potential sources of variability in set-shifting abilities among SZ patients, I examine the neural substrates of underlying probabilistic reversal learning (PRL) - a paradigmatic measure of cognitive flexibility - as well as neuromodulatory influences upon these systems. Finally, I report on behavioral and neuroimaging studies of PRL in SZ patients, discussing the potentially influences of illness profile and antipsychotic medications on cognitive flexibility in SZ.

Spectral EEG abnormalities during vibrotactile encoding and quantitative working memory processing in schizophrenia

Schizophrenia is associated with a number of cognitive impairments such as deficient sensory encoding or working memory processing. However, it is largely unclear how dysfunctions on these various levels of cortical processing contribute to alterations of stimulus-specific information representation. To test this, we used a well-established sequential frequency comparison paradigm, in which sensory encoding of vibrotactile stimuli can be assessed via frequency-specific steady-state evoked potentials (SSEPs) over primary somatosensory cortex (S1). Further, we investigated the maintenance of frequency information in working memory (WM) in terms of parametric power modulations of induced beta-band EEG oscillations. In the present study schizophrenic patients showed significantly less pronounced SSEPs during vibrotactile stimulation than healthy controls. In particular, inter-trial phase coherence was reduced. While maintaining vibrotactile frequencies in WM, patients showed a significantly weaker prefrontal beta-power modulation compared to healthy controls. Crucially, patients exhibited no general disturbances in attention, as inferred from a behavioral test and from alpha-band event-related synchronization. Together, our results provide novel evidence that patients with schizophrenia show altered neural correlates of stimulus-specific sensory encoding and WM maintenance, suggesting an early somatosensory impairment as well as alterations in the formation of abstract representations of task-relevant stimulus information.

Predictors of Long-Term Change in Adult Cognitive Performance: Systematic Review and Data from the Northern Finland Birth Cohort 1966

OBJECTIVE

Several social life events and challenges have an impact on cognitive development. Our goal was to analyze the predictors of change in cognitive performance in early midlife in a general population sample. Additionally, systematic literature review was performed.

METHOD

The study sample was drawn from the Northern Finland Birth Cohort 1966 at the ages of 34 and 43 years. Primary school performance, sociodemographic factors and body mass index (BMI) were used to predict change in cognitive performance measured by the California Verbal Learning Test, Visual Object Learning Test, and Abstraction Inhibition and Working Memory task. Analyses were weighted by gender and education, and p-values were corrected for multiple comparisons using Benjamini-Hochberg procedure (B-H).

RESULTS

Male gender predicted decrease in episodic memory. Poor school marks of practical subjects, having no children, and increase in BMI were associated with decrease in episodic memory, though non-significantly after B-H. Better school marks, and higher occupational class were associated with preserved performance in visual object learning. Higher vocational education predicted preserved performance in visual object learning test, though non-significantly after B-H. Likewise, having children predicted decreased performance in executive functioning but non-significantly after B-H.

CONCLUSIONS

Adolescent cognitive ability, change in BMI and several sociodemographic factors appear to predict cognitive changes in early midlife. The key advantage of present study is the exploration of possible predictors of change in cognitive performance among general population in the early midlife, a developmental period that has been earlier overlooked.

Development and Validation of the Cognition Test Battery for Spaceflight

BACKGROUND

Sustained high-level cognitive performance is of paramount importance for the success of space missions, which involve environmental, physiological, and psychological stressors that may affect brain functions. Despite subjective symptom reports of cognitive fluctuations in spaceflight, the nature of neurobehavioral functioning in space has not been clarified.

METHODS

We developed a computerized cognitive test battery (Cognition) that has sensitivity to multiple cognitive domains and was specifically designed for the high-performing astronaut population. Cognition consists of 15 unique forms of 10 neuropsychological tests that cover a range of cognitive domains, including emotion processing, spatial orientation, and risk decision making. Cognition is based on tests known to engage specific brain regions as evidenced by functional neuroimaging. Here we describe the first normative and acute total sleep deprivation data on the Cognition test battery as well as several efforts underway to establish the validity, sensitivity, feasibility, and acceptability of Cognition.

RESULTS

Practice effects and test-retest variability differed substantially between the 10 Cognition tests, illustrating the importance of normative data that both reflect practice effects and differences in stimulus set difficulty in the population of interest. After one night without sleep, medium to large effect sizes were observed for 3 of the 10 tests addressing vigilant attention (Cohen's d = 1.00), cognitive throughput (d = 0.68), and abstract reasoning (d = 0.65).

CONCLUSIONS

In addition to providing neuroimaging-based novel information on the effects of spaceflight on a range of cognitive functions, Cognition will facilitate comparing the effects of ground-based analogues to spaceflight, increase consistency across projects, and thus enable meta-analyses.

Neurocognition as a predictor of outcome in schizophrenia in the Northern Finland Birth Cohort 1966

The purpose of this study was to study neurocognitive performance as a predictor of outcomes in midlife schizophrenia. There is a lack of studies with unselected samples and a long follow-up. The study is based on the prospective, unselected population-based Northern Finland Birth Cohort 1966. The study includes 43 individuals with schizophrenia and 73 controls, whose neurocognitive performance was assessed twice, at 34 and 43 years. At both time points we used identical neurocognitive tests to assess verbal and visual memory and executive functions. Our main aim was to analyse neurocognitive performance at 34 years as a predictor of clinical, vocational and global outcomes at 43 years. Additionally, the analysis addressed cross-sectional associations between cognitive performance and clinical, vocational and global measures at 43 years. The assessment of outcomes was performed in the schizophrenia group only. In the longitudinal analysis poorer visual memory predicted poorer vocational outcome and poorer long-term verbal memory predicted poorer global outcome. In the cross-sectional analysis poorer visual memory and lower composite score of neurocognition were associated with poorer global outcome. No individual neurocognitive test or the composite score of these predicted remission. These data indicate that neurocognition, especially memory function, is an important determinant of long-term functional outcome in midlife schizophrenia.

Poor premorbid school performance, but not severity of illness, predicts cognitive decline in schizophrenia in midlife

Neurocognitive dysfunction is common in schizophrenia but its course and determinants remain uncertain. Our aim was to analyse if premorbid school performance and the severity of illness and functioning predict change in cognition in schizophrenia in a general population sample. The sample included cases with schizophrenia spectrum disorder from the Northern Finland Birth Cohort 1966. Data on school marks at the age of 16 years, educational level at the age of 34 years, severity of symptoms and occupational functioning around first episode and after years of illness were gained from national registers, hospital notes and interviews. Change of verbal and visual learning and memory and executive functioning were examined between ages 34 and 43 years. The number of cases varied in analyses from 29 to 41, depending on missing data in particular cognitive tests. Lower school marks at age 16 years and lower education at age 34 years predicted more decline of cognition. Measures of severity of illness or functioning were not associated statistically significantly with change of cognition. Premorbid school performance, but not later course of schizophrenia, related to change of cognition in midlife. Poor premorbid scholastic performance and post-onset cognitive decline may represent related processes as part of an endophenotype of schizophrenia.

Brain structure-function associations in multi-generational families genetically enriched for bipolar disorder

Recent theories regarding the pathophysiology of bipolar disorder suggest contributions of both neurodevelopmental and neurodegenerative processes. While structural neuroimaging studies indicate disease-associated neuroanatomical alterations, the behavioural correlates of these alterations have not been well characterized. Here, we investigated multi-generational families genetically enriched for bipolar disorder to: (i) characterize neurobehavioural correlates of neuroanatomical measures implicated in the pathophysiology of bipolar disorder; (ii) identify brain-behaviour associations that differ between diagnostic groups; (iii) identify neurocognitive traits that show evidence of accelerated ageing specifically in subjects with bipolar disorder; and (iv) identify brain-behaviour correlations that differ across the age span. Structural neuroimages and multi-dimensional assessments of temperament and neurocognition were acquired from 527 (153 bipolar disorder and 374 non-bipolar disorder) adults aged 18-87 years in 26 families with heavy genetic loading for bipolar disorder. We used linear regression models to identify significant brain-behaviour associations and test whether brain-behaviour relationships differed: (i) between diagnostic groups; and (ii) as a function of age. We found that total cortical and ventricular volume had the greatest number of significant behavioural associations, and included correlations with measures from multiple cognitive domains, particularly declarative and working memory and executive function. Cortical thickness measures, in contrast, showed more specific associations with declarative memory, letter fluency and processing speed tasks. While the majority of brain-behaviour relationships were similar across diagnostic groups, increased cortical thickness in ventrolateral prefrontal and parietal cortical regions was associated with better declarative memory only in bipolar disorder subjects, and not in non-bipolar disorder family members. Additionally, while age had a relatively strong impact on all neurocognitive traits, the effects of age on cognition did not differ between diagnostic groups. Most brain-behaviour associations were also similar across the age range, with the exception of cortical and ventricular volume and lingual gyrus thickness, which showed weak correlations with verbal fluency and inhibitory control at younger ages that increased in magnitude in older subjects, regardless of diagnosis. Findings indicate that neuroanatomical traits potentially impacted by bipolar disorder are significantly associated with multiple neurobehavioural domains. Structure-function relationships are generally preserved across diagnostic groups, with the notable exception of ventrolateral prefrontal and parietal association cortex, volumetric increases in which may be associated with cognitive resilience specifically in individuals with bipolar disorder. Although age impacted all neurobehavioural traits, we did not find any evidence of accelerated cognitive decline specific to bipolar disorder subjects. Regardless of diagnosis, greater global brain volume may represent a protective factor for the effects of ageing on executive functioning.

Similar verbal memory impairments in schizophrenia and healthy aging. Implications for understanding of neural mechanisms

Memory is impaired in schizophrenia patients but it is not clear whether this is specific to the illness and whether different types of memory (verbal and nonverbal) or memories in different cognitive domains (executive, object recognition) are similarly affected. To study relationships between memory impairments and schizophrenia we compared memory functions in 77 schizophrenia patients, 58 elderly healthy individuals and 41 young healthy individuals. Tests included verbal associative and logical memory and memory in executive and object recognition domains. We compared relationships of memory functions to each other and to other cognitive functions including psychomotor speed and verbal and spatial working memory. Compared to the young healthy group, schizophrenia patients and elderly healthy individuals showed similar severe impairment in logical memory and in the ability to learn new associations (NAL), and similar but less severe impairment in spatial working memory and executive and object memory. Verbal working memory was significantly more impaired in schizophrenia patients than in the healthy elderly. Verbal episodic memory impairment in schizophrenia may share common mechanisms with similar impairment in healthy aging. Impairment in verbal working memory in contrast may reflect mechanisms specific to schizophrenia. Study of verbal explicit memory impairment tapped by the NAL index may advance understanding of abnormal hippocampus dependent mechanisms common to schizophrenia and aging.

Linking the developmental and degenerative theories of schizophrenia: association between infant development and adult cognitive decline

Neurodevelopmental and neurodegenerative theories may be viewed as incompatible accounts that compete to explain the pathogenesis of schizophrenia. However, it is possible that neurodevelopmental and neurodegenerative processes could both reflect common underlying causal mechanisms. We hypothesized that cognitive dysfunction would gradually deteriorate over time in schizophrenia and the degree of this deterioration in adulthood would be predicted by an infant measure of neurodevelopment. We aimed to examine the association between age of learning to stand in infancy and deterioration of cognitive function in adulthood. Participants were nonpsychotic control subjects (n = 76) and participants with schizophrenia (n = 36) drawn from the Northern Finland 1966 Birth Cohort study. The schizophrenia group showed greater deterioration in abstraction with memory than controls, but there were no differences between schizophrenia and controls in rate of change of other cognitive measures. Age of learning to stand in infancy significantly inversely predicted later deterioration of abstraction with memory in adult schizophrenia (later infant development linked to greater subsequent cognitive deterioration during adulthood), possibly suggesting a link between abnormal neurodevelopmental and neurodegenerative processes in schizophrenia.

Executive function processes mediate the impact of working memory impairment on intelligence in schizophrenia

OBJECTIVE

The study investigated working memory, executive functions (conceptualized as response inhibition, updating, and shifting), and intelligence in schizophrenia, using structural equation modelling to determine the relationship between working memory and intelligence, testing whether specific executive functions act as a mediator for the association.

METHOD

One hundred and twenty-five individuals diagnosed with schizophrenia and 64 healthy participants were included in the study, tested using measures of working memory, intelligence and executive functioning. Structural equation modelling (SEM) was used to estimate direct and indirect associations between main measures.

RESULTS

The schizophrenia group had significantly lower working memory, executive function and intelligence than the healthy group. The relationship between working memory and intelligence was significantly mediated by inhibition, updating and shifting functions.

CONCLUSION

The study indicates a mediating role of executive functions in determining the association between working memory and intellectual function in schizophrenia. It is further proposed that in people with schizophrenia, cognitive remediation approaches targeting working memory through executive functioning may in turn improve intellectual function generally.

Reduced mediodorsal thalamic volume and prefrontal cortical spindle activity in schizophrenia

BACKGROUND

We recently found marked deficits in sleep spindles, non-rapid eye movement (NREM) sleep oscillations that are generated within the thalamus and then amplified and sustained in the cortex, in patients with schizophrenia compared to both healthy and psychiatric controls. Here, we investigated the thalamic and cortical contributions to these sleep spindle deficits.

METHODS

Anatomical volume of interest analysis (i.e., thalamic volumes) and electroencephalogram (EEG) source modeling (i.e., spindle-related cortical currents) were performed in patients with schizophrenia and healthy comparison subjects.

FINDINGS

Schizophrenia patients had reduced mediodorsal (MD) thalamic volumes, especially on the left side, compared to healthy controls, whereas whole thalami and lateral geniculate nuclei did not differ between groups. Furthermore, left MD volumes were strongly correlated with the number of scalp-recorded spindles in an anterior frontal region, and cortical currents underlying these anterior frontal spindles were localized in the prefrontal cortex, in Brodmann area (BA) 10. Finally, prefrontal currents at the peak of spindle activity were significantly reduced in schizophrenia patients and correlated with their performance in an abstraction/working memory task.

CONCLUSION

Altogether, these findings point to deficits in a specific thalamo-cortical circuitry in schizophrenia, which is associated with some cognitive deficits commonly reported in those patients.

Longitudinal changes in total brain volume in schizophrenia: relation to symptom severity, cognition and antipsychotic medication

Studies show evidence of longitudinal brain volume decreases in schizophrenia. We studied brain volume changes and their relation to symptom severity, level of function, cognition, and antipsychotic medication in participants with schizophrenia and control participants from a general population based birth cohort sample in a relatively long follow-up period of almost a decade. All members of the Northern Finland Birth Cohort 1966 with any psychotic disorder and a random sample not having psychosis were invited for a MRI brain scan, and clinical and cognitive assessment during 1999-2001 at the age of 33-35 years. A follow-up was conducted 9 years later during 2008-2010. Brain scans at both time points were obtained from 33 participants with schizophrenia and 71 control participants. Regression models were used to examine whether brain volume changes predicted clinical and cognitive changes over time, and whether antipsychotic medication predicted brain volume changes. The mean annual whole brain volume reduction was 0.69% in schizophrenia, and 0.49% in controls (p = 0.003, adjusted for gender, educational level, alcohol use and weight gain). The brain volume reduction in schizophrenia patients was found especially in the temporal lobe and periventricular area. Symptom severity, functioning level, and decline in cognition were not associated with brain volume reduction in schizophrenia. The amount of antipsychotic medication (dose years of equivalent to 100 mg daily chlorpromazine) over the follow-up period predicted brain volume loss (p = 0.003 adjusted for symptom level, alcohol use and weight gain). In this population based sample, brain volume reduction continues in schizophrenia patients after the onset of illness, and antipsychotic medications may contribute to these reductions.

Multisystem component phenotypes of bipolar disorder for genetic investigations of extended pedigrees

IMPORTANCE

Genetic factors contribute to risk for bipolar disorder (BP), but its pathogenesis remains poorly understood. A focus on measuring multisystem quantitative traits that may be components of BP psychopathology may enable genetic dissection of this complex disorder, and investigation of extended pedigrees from genetically isolated populations may facilitate the detection of specific genetic variants that affect BP as well as its component phenotypes.

OBJECTIVE

To identify quantitative neurocognitive, temperament-related, and neuroanatomical phenotypes that appear heritable and associated with severe BP (bipolar I disorder [BP-I]) and therefore suitable for genetic linkage and association studies aimed at identifying variants contributing to BP-I risk.

DESIGN, SETTING, AND PARTICIPANTS

Multigenerational pedigree study in 2 closely related, genetically isolated populations: the Central Valley of Costa Rica and Antioquia, Colombia. A total of 738 individuals, all from Central Valley of Costa Rica and Antioquia pedigrees, participated; among them, 181 have BP-I.

MAIN OUTCOMES AND MEASURES

Familial aggregation (heritability) and association with BP-I of 169 quantitative neurocognitive, temperament, magnetic resonance imaging, and diffusion tensor imaging phenotypes.

RESULTS

Of 169 phenotypes investigated, 126 (75%) were significantly heritable and 53 (31%) were associated with BP-I. About one-quarter of the phenotypes, including measures from each phenotype domain, were both heritable and associated with BP-I. Neuroimaging phenotypes, particularly cortical thickness in prefrontal and temporal regions as well as volume and microstructural integrity of the corpus callosum, represented the most promising candidate traits for genetic mapping related to BP based on strong heritability and association with disease. Analyses of phenotypic and genetic covariation identified substantial correlations among the traits, at least some of which share a common underlying genetic architecture.

CONCLUSIONS AND RELEVANCE

To our knowledge, this is the most extensive investigation of BP-relevant component phenotypes to date. Our results identify brain and behavioral quantitative traits that appear to be genetically influenced and show a pattern of BP-I association within families that is consistent with expectations from case-control studies. Together, these phenotypes provide a basis for identifying loci contributing to BP-I risk and for genetic dissection of the disorder.

Pathways to similar executive impairment: comparison of schizophrenia patients and healthy aging individuals

Executive impairment is prominent in schizophrenia, in conditions such as Parkinson's disease and dementia and in healthy aging. Identifying processes that critically constrain executive function can advance investigation of their biological basis and treatment planning. Recent findings that elderly healthy individuals showed similar impairment on conditional exclusion task as schizophrenia patients raised the question whether similar processes are impaired. To test this we compared 56 schizophrenia patients, 57 elderly and 77 young healthy individuals on three executive tests: conditional exclusion, abstraction and inhibition and tests of working memory and psychomotor speed. Schizophrenia patients performed worse than elderly healthy on abstraction, inhibition and verbal working memory. They were similarly impaired on Penn Conditional Exclusion Test (PCET) outcome measures but differed in performance characteristics. Schizophrenia patients needed relatively more trials to learn the first PCET category than the second or the third. This correlated with other cognitive impairments, particularly in working memory. Elderly healthy individuals found it most difficult to learn the last category. The two groups showed different error patterns. We propose that schizophrenia patients have particular difficulty in early (probabilistic) learning ("what to do") while aging individuals have selective impairment in executive integration. These constitute distinct targets for customized treatment in the two conditions.

Distinct structural alterations independently contributing to working memory deficits and symptomatology in paranoid schizophrenia

Schizophrenia is considered a brain disease with a quite heterogeneous clinical presentation. Studies in schizophrenia have yielded a wide array of correlations between structural and functional brain changes and clinical and cognitive symptoms. Reductions of grey matter volume (GMV) in the prefrontal and temporal cortex have been described which are crucial for the development of positive and negative symptoms and impaired working memory (WM). Associations between GMV reduction and positive and negative symptoms as well as WM impairment were assessed in schizophrenia patients (symptomatology in 34, WM in 26) and compared to healthy controls (36 total, WM in 26). GMV was determined by voxel-based morphometry and its relation to positive and negative symptoms as well as WM performance was assessed. In schizophrenia patients, reductions of GMV were evident in anterior cingulate cortex, ventrolateral prefrontal cortex (VLPFC), superior temporal cortex, and insula. GMV reductions in the superior temporal gyrus (STG) were associated with positive symptom severity as well as WM impairment. Furthermore, the absolute GMV of VLPFC was strongly related to negative symptoms. These predicted WM performance as well as processing speed. The present results support the assumption of two distinct pathomechanisms responsible for impaired WM in schizophrenia: (1) GMV reductions in the VLPFC predict the severity of negative symptoms. Increased negative symptoms in turn are associated with a slowing down of processing speed and predict an impaired WM. (2) GMV reductions in the temporal and mediofrontal cortex are involved in the development of positive symptoms and impair WM performance, too.

Impairment in associative memory in healthy aging is distinct from that in other types of episodic memory

There is evidence that age related changes in episodic memory are heterogeneous and result from diverse pathologies. To test this, we examined performance of healthy high-functioning younger (N=41, ages 18-60 y) and older (N=58, ages 61-83 y) individuals in tests of associative memory, logical memory and memory in executive and object-recognition domains. We compared their relationships to each other and to other cognitive functions, including, psychomotor speed and verbal and spatial working memory. Older individuals showed significantly greater reduction in an index of the ability to learn new associations (NAL) than for memory in executive and object-recognition domains. Age-related reduction in NAL and in logical memory was of similar severity, but the two measures showed only moderate correlation when age and other cognitive functions were controlled for. NAL shows an age-related pattern of change distinct from memory in executive and object-recognition domains and from logical (item) memory. We propose that in healthy well-functioning individuals, NAL taps processes which support binding of newly learned association in context of accumulating information, a key function of the hippocampus. NAL may thus serve as a selective marker of complex, hippocampus-based, cognitive functions in studies of normal cognitive aging and of its possible relationship to early dementia.

Concordance between chart review and structured interview assessments of schizophrenic symptoms

BACKGROUND

It is unclear whether direct structured interviews are able to capture the full range of psychopathology in schizophrenia, as is required in diagnostic assessments or clinical ratings. We examined agreement between symptom ratings derived from direct patient interviews and from review of casenotes.

METHODS

The study sample comprised 1021 schizophrenic subjects collected as part of the Irish Case-Control Study of Schizophrenia. Diagnostic interviews used a modified version of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition. Symptoms were rated by the interviewer. In addition, the Casenote Rating Scale was used to rate symptoms based on medical record information. For each negative and positive symptom, we calculated the Pearson correlation between the interview and the casenote rating. Using the mean of the interview and casenote rating for each symptom, exploratory factor analysis using Varimax rotation was performed.

RESULTS

Three factors were extracted in factor analysis: positive, negative, and Schneiderian symptoms. The highest correlations between interview and casenote ratings were for negative symptoms, in which all symptoms were significantly correlated. Positive and Schneiderian symptoms were significantly correlated with the exception of thought insertion, thought withdrawal, voices speaking in sentences, and somatic hallucinations. Significant correlations were generally moderate (0.2-0.55).

CONCLUSION

Most schizophrenic symptoms, especially negative symptoms, can be assessed by direct interviews as the sole source of information with moderate reliability. However, the presence of some Schneiderian and possibly less prevalent positive symptoms may be difficult to determine without a review of records, which may include longitudinal observations and information from multiple observers.

Computerized cognitive training restores neural activity within the reality monitoring network in schizophrenia

Schizophrenia patients suffer from severe cognitive deficits, such as impaired reality monitoring. Reality monitoring is the ability to distinguish the source of internal experiences from outside reality. During reality monitoring tasks, schizophrenia patients make errors identifying "I made it up" items, and even during accurate performance, they show abnormally low activation of the medial prefrontal cortex (mPFC), a region that supports self-referential cognition. We administered 80 hr of computerized training of cognitive processes to schizophrenia patients and found improvement in reality monitoring that correlated with increased mPFC activity. In contrast, patients in a computer games control condition did not show any behavioral or neural improvements. Notably, recovery in mPFC activity after training was associated with improved social functioning 6 months later. These findings demonstrate that a serious behavioral deficit in schizophrenia, and its underlying neural dysfunction, can be improved by well-designed computerized cognitive training, resulting in better quality of life.

Computerized neurocognitive test performance in schizophrenia: a lifespan analysis

OBJECTIVE

Computerized neurocognitive batteries based on advanced behavioral neuroscience methods are increasingly used in large-scale clinical and genomic studies. Favorable construct validity in younger schizophrenia patients has been reported, but not in older patients. New variables afforded by computerized assessments were used to clarify age-associated cognitive impairment across the lifespan.

METHODS

624 patients with schizophrenia and 624 healthy comparison (HC) subjects age 16-75 completed a 1-2-hour computerized neurocognitive battery (CNB) that assessed abstraction and mental flexibility, attention, working memory, recognition memory (verbal, facial, spatial), language, visuospatial, and emotion processing. Linear mixed effects models tested for group differences in accuracy, response time, and efficiency scores. Contrasts were stratified by age.

RESULTS

91% of older (45+) and 94% of younger (< 45) groups provided "good" data quality. After controlling for parental education and project, there were significant three-way interactions for diagnosis x domain x age group on all three outcome variables. Patients performed worse than HC across all neurocognitive domains, except in the oldest group of 60+ patients. Age-stratified analyses did not show differences between younger (16-45) and older patients (45-60, 60+), except for the attention domain. Older patients' reduced working memory efficiency was due to worse speed, not accuracy. Older patients were quicker than younger patients in processing emotions.

CONCLUSIONS

Computerized assessments are feasible in large cohorts of schizophrenia patients. There is stable and generalized neurocognitive dysfunction across the lifespan in schizophrenia, albeit with fewer differences in some domains between older patients and HC after age 60. Speed-accuracy tradeoff strategies suggest deceleration of some frontal networks and improvements in speed of emotional processing.

Is prematurity associated with adult cognitive outcome and brain structure?

Previous studies have indicated that preterm birth and low birth weight are associated with structural brain abnormalities and neurocognitive deficits in childhood and adolescence, although very few studies have included follow-up in adulthood. Here we assessed the effect of preterm delivery (524 subjects; mean 34.6 weeks, S.D. = 1.7) or low birth weight (366 subjects; mean 2159 g, S.D. = 303) on educational and occupational outcomes at age 31 years in the Northern Finland 1966 Birth Cohort, along with 10,132 term, normal birth weight control subjects. Cognitive tests and brain morphology using magnetic resonance imaging were assessed at age 33-35 years in a subset of the cohort (9 subjects; 95 controls). The preterm or low birth weight subjects had slightly lower school ratings and lower educational levels in adulthood, and they performed worse in verbal learning. The low birth weight subjects were less likely to be employed. There were no mean differences in the magnetic resonance imaging tissue segmentation analysis of the brain. In conclusion, although there were no overall changes in brain morphology in the preterm or low birth weight group, there was evidence for slightly poorer educational and occupational careers and cognitive capacity, which may reflect functional disruption not evident in structure.

Cognitive control deficits in schizophrenia: mechanisms and meaning

Although schizophrenia is an illness that has been historically characterized by the presence of positive symptomatology, decades of research highlight the importance of cognitive deficits in this disorder. This review proposes that the theoretical model of cognitive control, which is based on contemporary cognitive neuroscience, provides a unifying theory for the cognitive and neural abnormalities underlying higher cognitive dysfunction in schizophrenia. To support this model, we outline converging evidence from multiple modalities (eg, structural and functional neuroimaging, pharmacological data, and animal models) and samples (eg, clinical high risk, genetic high risk, first episode, and chronic subjects) to emphasize how dysfunction in cognitive control mechanisms supported by the prefrontal cortex contribute to the pathophysiology of higher cognitive deficits in schizophrenia. Our model provides a theoretical link between cellular abnormalities (eg, reductions in dentritic spines, interneuronal dysfunction), functional disturbances in local circuit function (eg, gamma abnormalities), altered inter-regional cortical connectivity, a range of higher cognitive deficits, and symptom presentation (eg, disorganization) in the disorder. Finally, we discuss recent advances in the neuropharmacology of cognition and how they can inform a targeted approach to the development of effective therapies for this disabling aspect of schizophrenia.

Neurocognitive markers of psychosis in bipolar disorder: a meta-analytic study

BACKGROUND

It has been suggested that patients with psychotic bipolar disorder (BDP+) might have more severe cognitive deficits than non-psychotic bipolar disorder patients (BDP-). However, only a handful of studies have compared cognition between BDP+ and BDP-. Our aim was to examine cognitive deficits associated with psychosis in BD using meta-analytic methods.

METHODS

After a systematic literature review, we conducted a meta-analysis on studies that compared cognition in bipolar disorder (BD) patients with and without a history of psychosis. In addition the effects of clinical and demographic confounder factors were examined with meta-regression analyses.

RESULTS

There were no significant differences for gender and duration of illness between groups. Compared with BDP-, BDP+ patients had more inpatient admissions, a younger onset of illness and used antipsychotics more commonly. BDP+ patients also performed significantly worse in 4 of 6 cognitive domains (planning and reasoning, working memory, verbal memory and processing speed). There were also differences for some individual tasks (List Learning, Delayed Recall, Trail Making B, Wisconsin Card Sorting Test, Digits Backwards, Stroop Interference, Semantic Fluency) with BDP+ patients showing moderately greater impairment on these tasks (d=0.30-0.55).

CONCLUSIONS

A history of psychosis is associated with greater severity of cognitive deficits in BD. However, this effect is modest, and these findings do not suggest a complete categorical distinction between BDP+ and BDP-. Psychosis in BD might reflect partly distinct neurobiological processes.

Disorganization and reality distortion in schizophrenia: a meta-analysis of the relationship between positive symptoms and neurocognitive deficits

BACKGROUND

Factor analytic studies have shown that in schizophrenia patients, disorganization (e.g., conceptual disorganization and bizarre behavior) is a separate dimension from other types of positive symptoms such as reality distortion (delusions and hallucinations). Although some studies have found that disorganization is more strongly linked to neurocognitive deficits and poor functional outcomes than reality distortion, the findings are not always consistent.

METHODS

A meta-analysis of 104 studies (combined n=8015) was conducted to determine the magnitude of the relationship between neurocognition and disorganization as compared to reality distortion. Additional analyses were conducted to determine whether the strength of these relationships differed depending on the neurocognitive domain under investigation.

RESULTS

The relationship between reality distortion and neurocognition was weak (r=-.04; p=.03) as compared to the moderate association between disorganization and neurocognition (r=-.23; p<.01). In each of the six neurocognitive domains that were examined, disorganization was more strongly related to neurocognition (r's range from -.20 to -.26) than to reality distortion (r's range from .01 to -.12).

CONCLUSIONS

The effect size of the relationship between neurocognition and disorganization was significantly larger than the effect size of the relationship between neurocognition and reality distortion. These results hold across several neurocognitive domains. These findings support a dimensional view of positive symptoms distinguishing disorganization from reality distortion.

Asocial beliefs as predictors of asocial behavior in schizophrenia

Poor social and vocational outcomes have long been observed in schizophrenia, and therapeutic outcomes have been modest. Most studies have identified neurocognition and emotion perception as important contributors to social functioning. Recent research has suggested that personal beliefs, attitudes, and expectancies contribute to negative symptoms. However, the impact of specific beliefs and expectancies on social withdrawal in schizophrenia has not been examined. The present study explored: 1. whether asocial beliefs made a significant contribution to social functioning after accounting for neurocognitive performance and emotion perception; and, 2. whether asocial beliefs predicted asocial behavior in a longitudinal design. 123 outpatients diagnosed with schizophrenia or schizoaffective disorder completed tests of neurocognitive performance, emotion perception, asocial beliefs, symptomatology, and functional outcome. A subset of 13 outpatients was retested one year after the initial assessment. Hierarchical regression indicated that asocial beliefs accounted for 18% of the variability in social functioning. Depression and negative symptoms explained another 9% of the dispersion. Contrary to expectations, neurocognition and emotion perception accounted for less than 1% of the variance. In the longitudinal study, baseline asocial beliefs predicted asocial behavior one year later. Asocial beliefs predict poor social functioning in schizophrenia, and may be modifiable by psychological interventions.

Project among African-Americans to explore risks for schizophrenia (PAARTNERS): evidence for impairment and heritability of neurocognitive functioning in families of schizophrenia patients

OBJECTIVE

Neurocognitive impairments in schizophrenia are well replicated and widely regarded as candidate endophenotypes that may facilitate understanding of schizophrenia genetics and pathophysiology. The Project Among African-Americans to Explore Risks for Schizophrenia (PAARTNERS) aims to identify genes underlying liability to schizophrenia. The unprecedented size of its study group (N=1,872), made possible through use of a computerized neurocognitive battery, can help further investigation of the genetics of neurocognition. The current analysis evaluated two characteristics not fully addressed in prior research: 1) heritability of neurocognition in African American families and 2) relationship between neurocognition and psychopathology in families of African American probands with schizophrenia or schizoaffective disorder.

METHOD

Across eight data collection sites, patients with schizophrenia or schizoaffective disorder (N=610), their biological relatives (N=928), and community comparison subjects (N=334) completed a standardized diagnostic evaluation and the computerized neurocognitive battery. Performance accuracy and response time (speed) were measured separately for 10 neurocognitive domains.

RESULTS

The patients with schizophrenia or schizoaffective disorder exhibited less accuracy and speed in most neurocognitive domains than their relatives both with and without other psychiatric disorders, who in turn were more impaired than comparison subjects in most domains. Estimated trait heritability after inclusion of the mean effect of diagnostic status, age, and sex revealed significant heritabilities for most neurocognitive domains, with the highest for accuracy of abstraction/flexibility, verbal memory, face memory, spatial processing, and emotion processing and for speed of attention.

CONCLUSION

Neurocognitive functions in African American families are heritable and associated with schizophrenia. They show potential for gene-mapping studies.

Exploring predictors of outcome in the psychosis prodrome: implications for early identification and intervention

Functional disability is a key component of many psychiatric illnesses, particularly schizophrenia. Impairments in social and role functioning are linked to cognitive deficits, a core feature of psychosis. Retrospective analyses demonstrate that substantial functional decline precedes the onset of psychosis. Recent investigations reveal that individuals at clinical-high-risk (CHR) for psychosis show impairments in social relationships, work/school functioning and daily living skills. CHR youth also demonstrate a pattern of impairment across a range of cognitive domains, including social cognition, which is qualitatively similar to that of individuals with schizophrenia. While many studies have sought to elucidate predictors of clinical deterioration, specifically the development of schizophrenia, in such CHR samples, few have investigated factors relevant to psychosocial outcome. This review integrates recent findings regarding cognitive and social-cognitive predictors of outcome in CHR individuals, and proposes potential directions for future research that will contribute to targeted interventions and improved outcome for at-risk youth.