Temporal Stability and Moderating Effects of Age and Sex on CNTRaCS Task Performance

Research in schizophrenia has increasingly focused on incorporating measures from cognitive neuroscience, but little is known about their psychometric characteristics. Here, we extend prior research by reporting on temporal stability, as well as age and sex effects, for cognitive neuroscience paradigms optimized as part of the Cognitive Neuroscience Test Reliability and Clinical applications for Schizophrenia consortium. Ninety-nine outpatients with schizophrenia and 131 healthy controls performed 5 tasks assessing 4 constructs at 3 sessions. The constructs were (1) Goal maintenance (Dot Probe Expectancy [DPX] and AX continuous performance tasks [AX-CPT]); (2) Episodic memory (Relational and Item-Specific Encoding and Retrieval task [RiSE]); (3) Visual integration (Jittered Orientation Visual Integration task [JOVI]); and (4) Perceptual gain control (Contrast-Contrast Effect Task [CCE]). Patients performed worse than controls on all but the CCE, and the magnitude of these group differences was stable across sessions, with no sex differences observed. Improvements over sessions were seen for the AX-CPT, the DPX, and the JOVI though practice effects for the AX-CPT and the DPX were primarily present in older participants. For the AX-CPT and the JOVI, practice effects were larger for T1 to T2 than for T2 to T3. Age was associated with poor associative recognition on the RiSE and accuracy on the JOVI. Test-rest reliability ranged from poor for the JOVI threshold score to adequate to good for the DPX, AX-CPT, and JOVI accuracy measures, with RiSE and CCE measures in the moderate range. These results suggest that group differences in DPX, AX-CPT, RiSE, and JOVI are robust and consistent across repeated testing.Key words: psychometrics, schizophrenia, cognitive neuroscience, goal maintenance, episodic memory, visual integration     

Reaction time and sustained attention in schizophrenia and its genetic predisposition

Sustained attention is affected by schizophrenia. The simplest form of Continuous Performance Test (CPT-X) is a purer test of vigilance than more demanding variants but widely thought too insensitive to detect abnormalities in those with genetic predisposition to schizophrenia. We used a 7-minute CPT to compare 61 patients diagnosed with schizophrenia, 45 of their never-psychotic relatives, and 47 control subjects. We found a significant impairment in stimulus discrimination in both patients (p=0.001) and their relatives (p=0.006). There was no difference in stimulus discrimination between relatives of patients with impaired and unimpaired stimulus discrimination. Relatives of patients with unimpaired stimulus discrimination were still inferior to controls (p=0.02). Reactions slowed in all groups equally as the test progressed. Patients showed increased mean reaction time (p<0.0001) and interquartile range (p=0.003). Relatives showed slower reaction times (p=0.01) but normal interquartile range. Groups did not differ in respect of individuals' fastest reaction times. We conclude that genetic predisposition to schizophrenia reduces performance even during a task placing minimal cognitive load on working memory and perceptual processing, suggesting impaired vigilance. Increased reaction time in the disease and its predisposition appear to be due to changes in response distribution rather than by a limitation of maximum speed. Our results raise the possibility of separating the cognitive components of vigilance, working memory and perceptual processing tapped by more demanding variants of the CPT, and draw attention to the need for consideration of dynamic neurocognitive processes in schizophrenia.     

Deficient inhibition of return in chronic but not first-episode patients with schizophrenia

Background

Inhibition of return (IOR) has been tested in patients with schizophrenia with contradictory results. Some studies indicated that patients with schizophrenia have normal levels of IOR; however, other studies reported delayed or blunted IOR. Inconsistency in findings might be due to differences across studies in relevant aspects associated with disease, such as heterogeneity of the disorder, different medications, onset and severity of the illness. The present study was to explore different patterns of IOR in antipsychotic medication free first-episode schizophrenia and chronic schizophrenia.

Methods

Forty two patients with first-episode schizophrenia, 44 patients with chronic schizophrenia, and 38 healthy controls were included in the study. All subjects went through a covert orienting of attention task with seven stimulus onset asynchrony (SOA) intervals (400 ms, 500 ms, 600 ms, 700 ms, 800 ms, 1200 ms and 1500 ms).

Results

Compared with healthy controls, the magnitude and onset of IOR in first-episode patients with schizophrenia were intact. However, in patients with chronic schizophrenia, there was an attenuated cuing effect especially at SOA 700 ms; in addition, there was a robust IOR until at SOAs 800 ms or above. Moreover, the illness duration and the number of psychotic episodes were significantly correlated with the validity effect at SOAs 400 ms and 600 ms.

Conclusion

Our study suggests that deficient IOR presents in chronic but not in first-episode patients with schizophrenia. IOR deficit in schizophrenia may begin during the course of illness and deteriorate over the course of illness. Our findings are consistent with the neurodegenerative model of schizophrenia.     

Neuromagnetic oscillations and hemodynamic correlates of P50 suppression in schizophrenia

Behavioral and electrophysiological data indicate compromised stimulus suppression in schizophrenia. The physiological basis of this effect and its contributions to the etiology of the disease are poorly understood. We examined neural and metabolic measures of P50 suppression in 12 patients with schizophrenia and controls. First, whole-head magnetoencephalography (MEG) assessed amplitudes of left- and right-hemispheric evoked responses and induced oscillations. Secondly, functional magnetic resonance imaging (fMRI) measured the hemodynamic responses to pairs of beeps with a short interval (500ms) as compared with those with a long interval (1500ms). The suppression of alpha power (8-13Hz) time-locked to the stimuli was negatively correlated with the suppression of evoked components and the hemodynamic measures. Remarkably, the suppression of alpha power was reduced in the patients already prior to stimulus onset. Conceivably, alpha oscillations play a central role in stimulus adaptation of neuronal networks and reflect an active mechanism for sensory suppression. The reduced stimulus suppression in schizophrenia seems to be in part due to impaired generation of alpha oscillations in the auditory cortex, resulting in higher metabolic demand as detected by fMRI. Delayed recovery of alpha rhythm may reflect an impaired gating function and contribute to sensory and cognitive deficits in schizophrenia.     

Sustained attention in the context of emotional processing in patients with schizophrenia

Patients with schizophrenia show dysfunction in sustained attention and facial emotion processing. We investigated the interplay between sustained attention and emotion by presenting emotional faces as background during AX-CPT in patients with schizophrenia. Nineteen schizophrenia patients and 21 healthy control subjects participated. We presented AX-CPT number stimuli superimposed on the nose of background facial expressions (happy, neutral or sad) over three experimental blocks for each emotion. Signal detection sensitivity (A') and reaction time were measured. Patients showed a steeper sensitivity decline when happy faces (compared with sad faces) were presented as background stimuli. By contrast, controls' sensitivity was not affected by the background facial emotion stimuli. Across the emotion conditions, the decline of sensitivity over time was evident in patients, but not in controls. To our knowledge, the present study is the first to explore a change in sustained attention accompanied by simultaneous processing of emotional faces in schizophrenia patients. Our findings suggest that mechanisms underlying continuous performance test (CPT) performance decline over time and facial emotion deficit may interact with each other in patients with schizophrenia.     

Semantic and syntactic processes during sentence comprehension in patients with schizophrenia: evidence from event-related potentials

Language and thought disorders are core symptoms in schizophrenia. We therefore studied language comprehension processes in patients with schizophrenia and control subjects during a sentence processing paradigm using event-related potentials (ERPs). In the ERP, assignment of syntactic structure to a string of words is reflected by an early left anterior negativity (ELAN) at about 80 ms after stimulus onset. Integration of syntactic and semantic information into a coherent representation is indexed by a positive potential at 600 ms (P600). Amplitudes of the ELAN and the P600 components are higher for grammatically incorrect sentences. Semantic processes are associated with a negative deflection peaking at 400 ms (N400). N400 amplitude is higher in semantically incongruent sentences. Nineteen patients with DSM IV schizophrenia and 19 healthy controls were presented with correct, semantically incorrect (semantic mismatch) and grammatically incorrect sentences (syntactic mismatch). Syntactic mismatch elicited an ELAN component in both subject groups. However, only controls but not patients with schizophrenia exhibited a P600 syntactic mismatch effect. Semantic mismatch was associated with a larger N400 potential which did not differ between groups. These results suggest that patients with schizophrenia are not impaired in syntactic structure assignment as reflected by the ELAN, but show deficits in semantic-syntactic integration processes underlying the P600.     

Deficits in auditory and visual context-dependent processing in schizophrenia: defining the pattern

BACKGROUND: Brain mechanisms underlying deficits in precision of transient memory storage in schizophrenia were investigated using a combined behavioral and event-related potential approach. Performance was measured simultaneously in 2 tasks: an AX-type visual continuous performance test (AX-CPT), which required subjects to press a button whenever they saw a letter A followed by a letter X, and a mismatch negativity paradigm. The AX-CPT is designed to assess prefrontal function, whereas mismatch negativity assesses functioning of the auditory sensory memory system. METHODS: Subjects were 17 patients with chronic schizophrenia, 13 with recent-onset schizophrenia, and 20 normal comparison subjects. Potentials were recorded from 36 scalp locations in response to cue stimuli in the CPT and to duration- and pitch-deviant stimuli in the mismatch negativity paradigm. Behavioral measures including responses to incorrect cue-target sequences that should have been ignored ("false alarms") were analyzed as a function of cue-target interval. RESULTS: Chronic and recent-onset schizophrenic patients showed significantly decreased mismatch negativity amplitude but normal latency and topography. In the CPT, patients showed significantly higher rates of false alarms following incorrect cues ("BX" errors) and decreased rates of correct detections. Impaired performance correlated with decreased frontocentral event-related potential activation to incorrect cues that was manifest within several hundred milliseconds of cue presentation. All groups performed worse with increasing cue-target intervals. Patients were no more affected by increased cue-target interval than were controls. CONCLUSIONS: Schizophrenic patients are significantly impaired in their ability to form and utilize transient memory traces to guide behavior. These deficits are associated with failures of cortical activation occurring within several hundred milliseconds of stimulus presentation. A similar pattern of deficit is observed across sensory and cognitive systems. Arch Gen Psychiatry. 2000;57:1131-1137.     

Automated classification of fMRI during cognitive control identifies more severely disorganized subjects with schizophrenia

The establishment of a neurobiologically based nosological system is one of the ultimate goals of modern biological psychiatry research. Developments in neuroimaging and statistical/machine learning have provided useful basic tools for these efforts. Recent studies have demonstrated the utility of fMRI as input data for the classification of schizophrenia, but none, to date, has used fMRI of cognitive control for this purpose. In this study, we evaluated the accuracy of an unbiased classification method on fMRI data from a large cohort of subjects with first episode schizophrenia and a cohort of age matched healthy control subjects while they completed the AX version of the Continuous Performance Task (AX-CPT). We compared these results to classifications based on AX-CPT behavioral data. Classification accuracy for DSM-IV defined schizophrenia using fMRI data was modest and comparable to classifications conducted with behavioral data. Interestingly fMRI classifications did however identify a distinct subgroup of patients with greater behavioral disorganization, whereas behavioral data classifications did not. These results suggest that fMRI-based classification could be a useful tool in defining a neurobiologically distinct subgroup within the clinically defined syndrome of schizophrenia, reflecting alterations in discrete neural circuits. Independent validation of classification-based phenotypes using other biological data such as genetics would provide a strong test of this hypothesis.     

Inefficient face detection in schizophrenia

BACKGROUND: Higher levels of facial processing, such as recognition of the individuality and emotional expression of faces, are abnormal in schizophrenia. It is unknown, however, whether the visual detection of a face as face is impaired as well. METHODS: We examined the performance of schizophrenia patients (n=29) and normal controls (n=28) in locating a line-drawn face on the left or the right side of a larger line drawing. To prevent the normal formation of general facial impressions, stimulus presentations were brief (13-104 ms). The face stimuli were either displayed upright or inverted in order to study the face inversion effect, ie, the specific effect of stimulus inversion on face processing. RESULTS: Schizophrenia patients showed a significantly reduced face inversion effect, resulting primarily from significantly lower accuracy in detecting upright faces than normal controls. In tree detection, a comparison task that was also administered, the stimulus inversion effect was similarly small in both groups. CONCLUSION: Given the primitive nature and brief duration of the stimuli, and the simplicity of the task, these results indicate that at the initial visual detection stage, facial processing is inefficient in schizophrenia. By isolating face detection from other aspects of face recognition, this study identifies a face-specific visual deficit in schizophrenia, which may ultimately contribute to impaired face-related cognitive and emotional processing and social interaction.     

Cognitive decision modelling of emotion-based learning impairment in schizophrenia: the role of awareness

Individuals with schizophrenia often lack insight or awareness. Resulting impairment has been observed in various cognitive domains and, recently, linked to problems in emotion-based learning. The Iowa Gambling Task (IGT) has been used to assess emotion-based decision-making in patients with schizophrenia, but results have been inconclusive. The current study further investigates emotion-based decision-making in schizophrenia by elucidating the unique contribution of awareness. Twenty-five patients with schizophrenia and 24 healthy controls were assessed with a modified version of the IGT recording awareness at regular intervals. Symptom assessment, medication and medical history were recorded for the clinical group. Patients with schizophrenia underperformed on the IGT compared to controls. Subjective awareness levels were significantly lower in the schizophrenia group and were associated with hallucination severity. Cognitive decision modelling further indicated that patients with schizophrenia had impaired attention to losses, compared to controls. This parameter was positively correlated with awareness. We also found that positive symptoms altered awareness levels and suggest that this disruption may contribute to sub-optimal decision-making. Overall, a lack of awareness may be an important aspect in understanding impaired social cognitive functioning and emotion-based learning observed in schizophrenia.     

Visuo-spatial cognition in schizophrenia: confirmation of a preference for local information processing

During visuo-spatial cognitive tasks, patients with schizophrenia show a preference for local (detailed) rather than global (holistic) information processing. The efficiency of such information processing is influenced by task difficulty. We tested whether patients' preference for local processing would persist if task demands favored global or local processing. Twenty-four stabilized patients with schizophrenia (SZ) and 25 healthy, matched controls (C) were tested in a mental mirroring task. Task difficulty was manipulated while stimulus surface structures were maintained unchanged. Information processing was assessed by recording eye movements. SZ were slower than C in the easiest condition but they made more errors than C in the more difficult conditions. Further, SZ did not adapt their average fixation duration to task demands resulting in longer fixation duration in the easiest condition and shorter fixation duration in the most difficult condition compared to C. These findings suggest that patients employ local information processing even when it is maladaptive for task demands. That is, patients do not adapt their fixation duration to task demands implicating (i) a preference for scanning local stimuli features and (ii) information processing inflexibility. These features need to be taken into account when evaluating visuo-spatial cognitive performance in schizophrenia.     

Ketamine-induced deficits in auditory and visual context-dependent processing in healthy volunteers: implications for models of cognitive deficits in schizophrenia

BACKGROUND: In patients with schizophrenia, deficient generation of mismatch negativity (MMN)-an event-related potential (ERP) indexing auditory sensory ("echoic") memory-and a selective increase of "context dependent" ("BX") errors in the "A-X" version of the Continuous Performance Test (AX-CPT) indicate an impaired ability to form and use transient memory traces. Animal and human studies implicate deficient N-methyl-D-aspartate receptor (NMDAR) functioning in such abnormalities. In this study, effects of the NMDAR antagonists ketamine on MMN generation and AX-CPT performance were investigated in healthy volunteers to test the hypothesis that NMDARs are critically involved in human MMN generation, and to assess the nature of ketamine-induced deficits in AX-CPT performance. METHODS: In a single-blind placebo-controlled study, 20 healthy volunteers underwent an infusion with subanesthetic doses of ketamine. The MMN-to-pitch and MMN-to-duration deviants were obtained while subjects performed an AX-CPT. RESULTS: Ketamine significantly decreased the peak amplitudes of the MMN-to-pitch and MMN-to-duration deviants by 27% and 21%, respectively. It induced performance deficits in the AX-CPT characterized by decreased hit rates and specific increases of errors (BX errors), reflecting a failure to form and use transient memory traces of task relevant information. CONCLUSIONS: The NMDARs are critically involved in human MMN generation. Deficient MMN in schizophrenia thus suggests deficits in NMDAR-related neurotransmission. N-methyl-D-aspartate receptor dysfunction may also contribute to the impairment of patients with schizophrenia in forming and using transient memory traces in more complex tasks, such as the AX-CPT. Thus, NMDAR-related dysfunction may underlie deficits in transient memory at different levels of information processing in schizophrenia. Arch Gen Psychiatry. 2000;57:1139-1147.     

The effect of oppositional parietal transcranial direct current stimulation on lateralized brain functions

Cognitive functions such as numerical processing and spatial attention show varying degrees of lateralization. Transcranial direct current stimulation (tDCS) can be used to investigate how modulating cortical excitability affects performance of these tasks. This study investigated the effect of bi‐parietal tDCS on numerical processing, spatial and sustained attention. It was hypothesized that tDCS would have distinct effects on these tasks because of varying lateralization (numerical processing left, spatial attention right) and that these effects are partly mediated by modulation of sustained attention. A single‐blinded, crossover, sham‐controlled study was performed. Eighteen healthy right‐handed participants performed cognitive tasks during three sessions of oppositional parietal tDCS stimulation: sham; right anodal with left cathodal (RA/LC); and right cathodal with left anodal (RC/LA). Participants performed a number comparison task, a modified Posner task, a choice reaction task (CRT) and the rapid visual processing task (RVP). RA/LC tDCS impaired number comparison performance compared with sham, with slower responses to numerically close numbers pairs. RA/LC and RC/LA tDCS had distinct effects on CRT performance, specifically affecting vigilance level during the final block of the task. No effect of stimulation on the Posner task or RVP was found. It was demonstrated that oppositional parietal tDCS affected both numerical performance and vigilance level in a polarity‐dependent manner. The effect of tDCS on numerical processing may partly be due to attentional effects. The behavioural effects of tDCS were specifically observed under high task demands, demonstrating the consequences of an interaction between stimulation type and cognitive load.     

Dissociation of emotional decision-making from cognitive decision-making in chronic schizophrenia

Recent studies have examined the decision-making ability of schizophrenic patients using the Iowa Gambling Task (IGT). These studies, however, were restricted to the assessment of emotional decision-making. Decision-making depends on cognitive functions as well as on emotion. The purpose of this study was to examine the performance of schizophrenic patients on the IGT and the Game of Dice Task (GDT), a decision-making task with explicit rules for gains and losses. In addition, it was intended to test whether poor performance on IGT is attributable to impairments in reversal learning within the schizophrenia group using the Simple Reversal Learning Task (SRLT), which is sensitive to measure the deficit of reversal learning following ventromedial prefrontal cortex damage. A group of 23 stable schizophrenic patients and 28 control subjects performed computerized versions of the IGT, GDT, SRLT and Wisconsin Card Sorting Test (WCST). While schizophrenic patients performed poorly on the IGT relative to normal controls, there was no significant difference between the two groups on GDT performance. The performance of the schizophrenia group on the SRLT was poorer than that of controls, but was not related to IGT performance. These data suggest that schizophrenic patients have impaired emotional decision-making but intact cognitive decision-making, suggesting that these two processes of decision-making are different. Furthermore, the impairments in reversal learning did not contribute to poor performance on the IGT in schizophrenia. Therefore, schizophrenic patients have difficulty in making decisions under ambiguous and uncertain situations whereas they make choices easily in clear and unequivocal ones. The emotional decision-making deficits in schizophrenia might be attributable more to another mechanism such as a somatic marker hypothesis than to an impairment in reversal learning.     

Neuropsychological dysfunctions in siblings discordant for schizophrenia

Although cognitive impairments are well recognized in patients with schizophrenia, it is unclear which impairments are due to a genetic predisposition and which are caused by secondary disease effects or phenotype. The aim of this study is to investigate the possible relationship between genetic vulnerability to schizophrenia and cognitive functioning. Three groups of subjects were compared: 14 patients with schizophrenia, 15 healthy siblings and 32 healthy control subjects. All subjects were tested neuropsychologically. The raw test data were rescaled to standard equivalents (z-scores). Subjects' z scores on tests assessing the same cognitive domain were clustered and analyzed. Differences in cognitive functioning were found in the domains of abstraction, attention, executive functioning, spatial memory, and sensory-motor functioning. The schizophrenic probands were impaired on all these five domains whereas the healthy probands showed impairments on executive functioning and partially on sensory-motor functioning. Furthermore, for spatial memory the significant finding could mainly be attributed to impaired functioning in the patients, but not healthy siblings or control subjects, whereas for executive functioning patients and healthy siblings seemed equally impaired as compared to control subjects. The planning time of the Tower of London (TOL) and the initiation time of the Motor Planning Task (MPT) were used for measures of executive functioning, while the 'time to move of the Motor Planning Task' was used as measures of sensory motor functioning. These results suggest that the cognitive abnormalities in schizophrenia that may be related to genotype are represented in the domain of executive functioning and to some extent in the domain of sensory-motor functioning.     

Independent effects of tobacco abstinence and bupropion on cognitive function in schizophrenia

OBJECTIVE: The objective of this study was to examine the effects of tobacco abstinence and bupropion treatment on cognitive functioning in adult smokers with schizophrenia in the setting of a randomized, double-blind, placebo-controlled clinical trial of bupropion for smoking cessation. METHOD: Fifty-three adults with schizophrenia (DSM-IV) took part in a trial of bupropion for smoking cessation. Subjects were enrolled in the study from August 1999 to March 2003. Forty-five subjects remained in the trial at week 4; 41 subjects, 19 taking bupropion and 22 taking placebo, completed the baseline and week 4 cognitive assessments and were included in the analysis of adjusted effects of abstinence and bupropion treatment on cognitive function. RESULTS: Controlling for bupropion treatment and baseline performance, 7 days of tobacco abstinence was associated with slowed motor speed (finger tapping) but was not associated with worsening of performance on tests of attention (AX Continuous Performance Test [AX-CPT]), verbal learning and memory (California Verbal Learning Test [CVLT]), working memory (digit span), or executive function/inhibition (Stroop) and was not associated with worsening of any clinical measures. Controlling for abstinence status, bupropion was associated with reduction (improvement) in reaction time variability on the AX-CPT and with reduction in perseverative errors on the CVLT. CONCLUSION: We conclude that 1 week of tobacco abstinence is associated with slowed motor speed but is not associated with detectable worsening in performance on a range of neuropsychological tests or clinical symptoms in the subset of patients who were able to quit smoking. We also conclude that bupropion treatment may be associated with improvement in variability of attention.     

Iconic Decay in Schizophrenia

Working memory impairment is considered a core deficit in schizophrenia, but the precise nature of this deficit has not been determined. Multiple lines of evidence implicate deficits at the encoding stage. During encoding, information is held in a precategorical sensory store termed iconic memory, a literal image of the stimulus with high capacity but rapid decay. Pathologically increased iconic decay could reduce the number of items that can be transferred into working memory before the information is lost and could thus contribute to the working memory deficit seen in the illness. The current study used a partial report procedure to test the hypothesis that patients with schizophrenia (n = 37) display faster iconic memory decay than matched healthy control participants (n = 28). Six letters, arranged in a circle, were presented for 50 ms. Following a variable delay of 0–1000 ms, a central arrow cue indicated the item to be reported. In both patients and control subjects, recall accuracy decreased with increasing cue delay, reflecting decay of the iconic representation of the stimulus array. Patients displayed impaired memory performance across all cue delays, consistent with an impairment in working memory, but the rate of iconic memory decay did not differ between patients and controls. This provides clear evidence against faster loss of iconic memory representations in schizophrenia, ruling out iconic decay as an underlying source of the working memory impairment in this population. Thus, iconic decay rate can be added to a growing list of unimpaired cognitive building blocks in schizophrenia.     

Interactive effects of background facial emotion stimulus and target salience on sustained attention performance in schizophrenia

Schizophrenia impairs both facial emotion processing and sustained attention. Through separate studies, it is known that the presence of a task-irrelevant facial stimulus disproportionately interferes with performance, whereas increasing the salience of task stimulus improves performance during a sustained attention task in patients with schizophrenia. We wished to investigate a potential interaction effect of background facial emotion expression (black and white happy faces vs. grey oval) and target stimulus salience (bright white vs. grey) using the Continuous Performance Test-Identical Pairs version (CPT-IP) in patients with schizophrenia. Thirty-six patients with schizophrenia and 28 healthy control subjects completed 4 different versions of the CPT-IP. We found that healthy controls exhibited higher signal detection sensitivity (d') when salient target stimuli were presented on the facial background than when the same stimuli were presented on the grey-oval background. By contrast, patients were not affected by background stimuli when target number stimuli were salient. When target number stimuli were not salient, both patients and controls showed higher d' in the grey-oval background condition compared with the facial background condition. This study highlight the significance of stimulus salience during CPT-IP in schizophrenia as background stimuli did not produce a differential effect on performance. Our results suggest that, in the situations where facial emotion stimuli are present, patients' sustained attention can be deteriorated and that the use of salient materials is important in improving performance in schizophrenia.     

Switching between univalent task-sets in schizophrenia: ERP evidence of an anticipatory task-set reconfiguration deficit.

OBJECTIVE: The present study used behavioral and event-related potential (ERP) indices of task-switching to examine whether schizophrenia patients have a specific deficit in anticipatory task-set reconfiguration. METHODS: Participants switched between univalent tasks in an alternating runs paradigms with blocked response-stimulus interval (RSI) manipulation (150, 300, 600, and 1200ms). Nineteen high functioning people with schizophrenia were compared to controls that were matched for age, gender, education and premorbid IQ estimate. RESULTS: Schizophrenia patients had overall increased RT, but no increase in corrected RT switch cost. In the schizophrenia group, ERPs showed reduced activation of the differential positivity in anticipation of switch trial at the optimal 600ms RSI and reduced activation of the frontal post-stimulus switch negativity at both 600 and 1200ms RSI compared to the control group. CONCLUSIONS: Despite no behavioral differences in task switching performance, anticipatory and stimulus-triggered ERP indices of task-switching suggest group differences in processing of switch and repeat trials, especially at longer RSI conditions that for control participants provide opportunity for anticipatory activation of task-set reconfiguration processes. SIGNIFICANCE: These results are compatible with impaired implementation of endogenously driven processes in schizophrenia and greater reliance on external task cues, especially at long preparation intervals.     

全面性发作癫痫患者的情绪词汇加工

目的比较全面性发作癫痫患者不同情绪效价词汇的加工情况,评估其是否存在情感认知功能损害。方法采用事件相关电位技术,研究全面性发作癫痫患者和正常人群3种不同情绪效价词汇刺激诱发情绪反应的差异。结果癫痫组与对照组在汉密尔顿抑郁量表得分、正确率、平均反应时比较差异均有统计学意义(P0.05),癫痫组负性情绪词汇刺激反应时最长。负性、中性、正性三种不同情绪效价刺激反应时组间比较差异有统计学意义(P0.05)。ERP的t检验统计参数映射:2组3种不同情绪效价在刺激后130~160ms双侧后颞区及枕极均可见显著差异。负性情绪刺激400~640ms的注意加工阶段,正性情绪刺激700~970ms进一步加工阶段,癫痫组与对照组比较差异有统计学意义(P0.05);中性刺激后310~950ms额极,前颞部区域,2组差异有统计学意义(P0.05)。结论全面性发作癫痫患者有伴发抑郁情绪障碍高风险,其情绪性词汇刺激行为效能降低,反应时显著延长,反应错误率增加。全面性发作癫痫患者存在明显情绪认知功能损害,其负性情绪认知严重受损,并且其视觉皮层的早期知觉加工也受到损害。