Dual-task information processing in schizotypal personality disorder: Evidence of impaired processing capacity.

Working memory theories heavily rely on the concept of processing resources and the their efficient deployment. Some recent work with schizophrenia-spectrum patients has suggested that many associated cognitive impairments may be reduced to deficits in working memory, possibly related to reductions in information-processing capacity resources. In this study, 38 patients with schizotypal personality disorder (SPD), 22 patients with other personality disorders, and 14 healthy comparison participants performed a dual-task processing assessment that was designed specifically for use in this type of study. Participants recalled lists of digits at their predetermined maximum digit span and performed box-checking tests, first alone and then in a dual-task format. Instructions included equal prioritization of both tasks. SPD patients had significantly shorter digit spans, and they also showed more deterioration on both tasks. Performance operating characteristics curves indicated that SPD patients' reduced performance was not due to abnormal resource allocation strategies leading to strategic failures. The authors discuss the implications of these processing capacity limitations for understanding both the signature of cognitive impairment within the schizophrenia spectrum and general abnormalities in working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Controlled information processing resources and the development of automatic detection responses in schizophrenia.

The relation between resource limitations and the type of processing (automatic vs controlled) on a multiple-frame search task (MFST) was examined in 15 schizophrenic and 15 normal control Ss. After 320 trials of consistently mapped practice, the patients' detection accuracy was normalized, and the effect of processing load (letter array size) on their detection accuracy was eliminated, which suggests automatization. Changes in load effects with practice could not be used as an index of automatization in control Ss, because of their unexpected lack of load effects at the beginning of practice. In a dual-task (MFST during auditory shadowing) condition after MFST practice, patients' MFST accuracy deteriorated nonsignificantly, and patients' shadowing declined significantly. The findings suggest schizophrenics have reduced available processing resources, but research is needed to determine whether this is due to abnormal automatization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pupillary responses index overload of working memory resources in schizophrenia.

The authors examined the hypothesis that schizophrenia patients have reduced availability of working memory resources by using pupillary responses as an index of resource overload. Pupillary responses were recorded during a verbal working memory task (digit recall) in 24 schizophrenia patients and 32 normal controls. Pupil size increased with increased processing load (digit-span length) but changed little or declined when processing demands exceeded available resources (overload). The schizophrenia patients showed impaired digit recall and abnormally small pupillary responses during digit presentation only in the higher processing load conditions, but they showed abnormally small pupillary responses during digit retrieval in all processing load conditions. The results suggest reduced availability of slave store and central executive working memory resources in schizophrenia. This study serves as an example of how pupillography methods can be used to test current hypotheses regarding overload of cognitive capacities in schizophrenia patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Easier tasks can have higher processing loads: Task difficulty and cognitive resource limitations in schizophrenia.

A differential deficit on the more difficult of 2 cognitive tasks has been found in numerous studies of schizophrenia. Resource limitations, rather than impairments in particular cognitive abilities, can explain these findings. Researchers often match tasks for difficulty level (healthy participant performance) to rule out resource limitations. This assumes processing resource load can be estimated from task difficulty, which is not always the case. A direct measure of resource allocation is needed. In this study, pupillary responses were recorded to index resource allocation (greater dilation indicates greater allocation) during performance of the digit span distractibility task in participants with schizophrenia (n = 35) and nonpsychiatric participants (n = 35). Nonpsychiatric participants recalled significantly more digits in the distraction, relative to the neutral, condition but also showed significantly greater pupil dilation in the distraction condition. The psychometrically "easier" condition, therefore, had a higher processing load. Participants with schizophrenia showed greater impairment relative to nonpsychiatric participants in the distraction condition. This finding cannot be attributed to a deficit in distractibility, however, because poorer performance was found in the higher-load condition, so resource limitations cannot be ruled out. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rumination and impaired resource allocation in depression.

Depression is characterized by a range of cognitive deficits that theorists posit are due to the resource capturing properties of rumination. The present study was designed to examine the relation between rumination and resource allocation in depression. Twenty-five depressed and 25 nondepressed participants completed a modified dual-task version of the recency-probes task, which assesses the controlled allocation of cognitive resources by comparing performance across low- and high-interference conditions. In low-interference conditions, participants performed either the recency-probes task or a tracking task, which required participants to track specific stimuli across trials (i.e., no dual-task interference). In the high-interference condition, participants performed both the recency-probes task and the tracking task, which required the controlled allocation of resources to resolve dual-task interference. Depressed participants performed significantly worse than did their nondepressed counterparts in only the high-interference condition; performance of the 2 groups was comparable in the low-interference conditions. Furthermore, the degree to which depressed participants were impaired in the high-interference condition was correlated .74 with rumination. These findings suggest that an association between rumination and impairments in resource allocation underlies the cognitive difficulties experienced by depressed individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotion regulation in schizophrenia: Affective, social, and clinical correlates of suppression and reappraisal.

Individuals can exert considerable control over their experience and expression of emotion by applying different regulatory strategies such as reappraisal and suppression. However, although it has been suggested that blunted affect in schizophrenia, characterized by markedly reduced emotion expressivity alongside apparently normal emotion experience, may reflect overuse of suppression, no study to date has assessed self-reported use of these different emotion regulatory strategies in relation to this disorder. In the present study, 41 individuals with schizophrenia and 38 control participants completed a self-report measure that differentiated between use of suppression and reappraisal. Symptom severity and various aspects of cognitive and psychosocial functioning were also assessed. Relative to controls, individuals with schizophrenia did not differ with regard to their reported use of suppression and reappraisal, and reported use of both strategies was unrelated to clinical ratings of blunted affect. However, whereas (lower) use of reappraisal was associated with greater social function impairment for both groups, only for controls was (greater) use of suppression associated with reduced social functioning. Implications for understanding blunted affect and social dysfunction in schizophrenia are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Everyday action in schizophrenia: Performance patterns and underlying cognitive mechanisms.

Everyday action is impaired among individuals with schizophrenia, yet few studies have characterized the nature of this deficit using performance-based measures. This study examined the performance of 20 individuals with schizophrenia or schizoaffective disorder on the Naturalistic Action Test (M. F. Schwartz, L. J. Buxbaum, M. Ferraro, T. Veramonti, & M. Segal, 2003). Performance was coded to examine overall impairment, task accomplishment, and error patterns and was compared with that of healthy controls (n = 28) and individuals with mild dementia (n = 23). Additionally, 2 competing accounts of everyday action deficits, the resource theory and an executive account, were evaluated. When compared with controls, the participants with schizophrenia demonstrated impaired performance. Relative to dementia patients, participants with schizophrenia obtained higher accomplishment scores but committed comparable rates of errors. Moreover, distributions of error types for the 2 groups differed, with the participants with schizophrenia demonstrating greater proportions of errors associated with executive dysfunction. This is the 1st study to show different Naturalistic Action Test performance patterns between 2 neurologically impaired populations. The distinct performance pattern demonstrated by individuals with schizophrenia reflects specific deficits in executive function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context-processing deficits in schizophrenia: Diagnostic specificity, 4-week course, and relationships to clinical symptoms.

Previous research on schizophrenia suggests that context-processing disturbances are one of the core cognitive deficits present in schizophrenia. However, it is not clear whether such deficits are specific to schizophrenia as compared with other psychotic disorders. To address this question, the authors administered a version of the AX Continuous Performance Test designed to assess context processing in a sample of healthy controls, patients with schizophrenia, and patients with other psychotic disorders. Participants were tested at index (when medication naive and experiencing their first contact with psychiatric services) and 4 weeks later, following medication treatment. At index, patients with schizophrenia and the psychotic comparison group demonstrated similar impairments in context processing. However, context-processing deficits improved in the psychotic comparison group at 4 weeks but did not improve in patients with schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anhedonia, positive and negative affect, and social functioning in schizophrenia

This study examines the relationship between anhedonia and the trait dimensions of positive affect (PA) and negative affect (NA) in schizophrenia. The relationship between poor social functioning in schizophrenia and these individual differences in affectivity is also examined. Schizophrenia outpatients (n = 37) and normal controls (n = 15) were assessed at a baseline evaluation and again approximately 90 days later. Consistent with the hypothesized decrease in hedonic capacity in schizophrenia, patients reported significantly greater physical and social anhedonia and less PA than controls. However, the schizophrenia group also reported significantly greater NA and social anxiety than did controls. In support of the dispositional view of these individual differences in affectivity, trait measures demonstrated test-retest reliability, and group differences between the schizophrenia group and controls were stable over the 90-day followup period. Within the schizophrenia group, physical and social anhedonia were comparably negatively correlated with trait PA; however, social but not physical anhedonia was significantly positively correlated with NA and social anxiety. Poor social functioning in the schizophrenia group was associated with greater physical and social anhedonia and greater NA and social anxiety. Alternatively, greater trait PA was related to better social functioning. These findings indicate that schizophrenia is characterized by both low PA and elevated NA and that these affective characteristics are a stable feature of the illness. The results also suggest important links between affect and social functioning in schizophrenia.     

Emotion responsivity, social cognition, and functional outcome in schizophrenia.

Social functioning deficits have long been a defining feature in schizophrenia, but relatively little research has examined how emotion responsivity influences functional outcome in this disorder. The goal of the current study was to begin to elucidate the relationships between emotion responsivity, social cognition, and functional outcome in schizophrenia. Participants were 40 outpatients diagnosed with schizophrenia or schizoaffective disorder according to the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) and 40 controls. Each participant completed measures of emotion responsivity, social cognition (both emotion and social perception), and functional outcome. Individuals with schizophrenia demonstrated somewhat reduced emotion responsivity for positive and negative stimuli, as well as deficits in both social cognition and functional outcome, in comparison with controls. Additionally, results indicated that both social perception and emotion responsivity were positively correlated with functional outcome. Importantly, the relationship of emotion responsivity to functional outcome was not mediated by social perception and showed a significant relationship to functional outcome independent of social cognition. This finding suggests that emotion responsivity is an important factor in understanding functional outcome in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The time course of visuospatial processing deficits in schizophrenia: An event-related brain potential study.

Event-related brain potentials (ERPs) were recorded during a dot enumeration task so as to investigate electrophysiologic correlates of early visuospatial processing in schizophrenia. Twenty-eight patients having a diagnosis of schizophrenia (n?=?19) or schizoaffective disorder (n?=?9) and 28 controls were tested. Patients showed poorer dot enumeration than did controls and also had markedly reduced early negative ERPs, which began about 150 ms after stimulus onset at the peak of the N1 potential and reached its maximum about 275 ms at the N2 peak. The N1 reduction in patients was greatest over left parietal sites for stimuli in the right visual field. The marked N1 and N2 reductions in patients are supportive of models postulating deficits in early visuospatial attention and allocation of conceptual resources in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Residual performance deficit in clinically remitted schizophrenics: A marker of schizophrenia?

The study of remitted schizophrenic outpatients is proposed as a way of minimizing the effects of the "nuisance variables" that confound the study of hospitalized schizophrenics. 20 hospitalized acutely disturbed schizophrenics (mean age, 37.0 yrs), 20 schizophrenic outpatients in clinical remission (mean age, 42.8 yrs) and 20 normal controls (mean age, 35.1 yrs) were administered a span of apprehension test and the Continuous Performance Test (CPT). All Ss were controlled for sex and WAIS scores and schizophrenics were rated with Phillips Prognostic Rating Scale. On the CPT, both acute and remitted schizophrenics made significantly more errors of omission and commission than did the normal controls. On the span of apprehension, both groups of schizophrenics showed a significantly greater decrement in accuracy of detection of the target stimuli than did normal controls. The same pattern of results has been observed in children at risk for schizophrenia, which suggests that the span of apprehension may be sensitive to core schizophrenic processes that are independent of clinical state. The cross-sectional study of the 3 stages of schizophrenia—the premorbid, acute, and remitted—is proposed as a way of identifying "core" schizophrenic processes and markers of vulnerability to schizophrenia. The adequacy of a general "attentional impairment" interpretation of schizophrenic deficit is questioned. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention deficits in childhood-onset schizophrenia: Reaction time studies.

The hypothesis of continuity between childhood-onset and adult schizophrenia was tested by comparing the performance of 15 patients with childhood-onset schizophrenia and 52 age-matched controls on 2 reaction time paradigms that have been used to study adult schizophrenia. On simple reaction time to tones with regular and irregular preparatory intervals of 2, 4, and 8 s, patients showed greater effects of the length of the preparatory interval in the regular condition and greater effects of the preparatory interval (girls only) and the preceding preparatory interval in the irregular series. On simple reaction time to random lights and tones, patients were faster on sequences than cross-modal sequences compared with controls. Overall, patients were much slower than controls in both paradigms. The results suggest similar attention dysfunction as is found in adult schizophrenia and thus are consistent with the continuity hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

False Memories in Schizophrenia.

In prior studies, it was observed that patients with schizophrenia show abnormally high knowledge corruption (i.e., high-confident errors expressed as a percentage of all high-confident responses were increased for schizophrenic patients relative to controls). The authors examined the conditions under which excessive knowledge corruption occurred using the Deese-Roediger-McDermott paradigm. Whereas knowledge corruption in schizophrenia was significantly greater for false-negative errors relative to controls, no group difference occurred for false-positive errors. The groups showed a comparable high degree of confidence for false-positive recognition of critical lure items. Similar to findings collected in elderly participants, patients, but not controls, showed a strong positive correlation between the number of recognized studied items and false-positive recognition of the critical lure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in perceptual asymmetries with clinical improvement of depression and schizophrenia.

16 depressed patients, 16 schizophrenic patients, and 16 normal controls (20–50 yrs old) were given 2 dichotic listening tests and 2 cognitive tests at intervals ranging from patients' initial hospitalization to recovery. Repeated-measures ANOVA revealed that severely depressed Ss failed to obtain normal ear-superiority in either dichotic test; however, normal superiorities emerged with recovery from depression. Schizophrenic Ss initially failed to show normal right-ear superiority on a dichotic-words test but did obtain the expected left-ear advantage on a dichotic-chords test. Following treatment, schizophrenics shifted from a left-ear to a right-ear advantage in dichotic chords and also increased (although not significantly) their right-ear advantage in dichotic words. Both patient groups showed normal word-fluency but impaired spatial ability, which did not improve with recovery. Results suggest that both depression and schizophrenia are associated with a breakdown in the process of interhemispheric inhibition that mediates perceptual asymmetry. In depression, treatment returned Ss' normal patterns of asymmetry, whereas in schizophrenia, treatment created an abnormal pattern of asymmetry that may have reflected the allocation of both verbal and nonverbal material to the left hemisphere. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autonomic orienting and the allocation of processing resources in schizophrenia patients and putatively at-risk individuals.

The differential allocation of attentional resources to attended and ignored stimuli was examined by measuring skin conductance orienting responses and secondary reaction time in relatively asymptomatic schizophrenia outpatients, demographically matched normal controls, college students putatively at risk for psychosis, and a college student control group. At-risk participants were those with extreme scores on scales for either anhedonia or perceptual aberration-magical ideation (per-mags). Compared to control groups, the patients and per-mags showed secondary reaction time results suggesting a delay in the differential allocation of attentional resources. This deficit was observed particularly in patients and matched controls with few or no skin conductance orienting responses, suggesting that impaired autonomic orienting is related to underlying cognitive-attentional vulnerability factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantitative MRI volume changes in late onset schizophrenia and Alzheimer's disease compared to normal controls

Volumes of medial and lateral temporal lobe structures were assessed using magnetic resonance imaging (MRI) in 11 patients with late-life onset schizophrenia (LOS), 18 normal elderly controls and 12 patients with moderate cognitive impairment due to Alzheimer's disease (AD) who had no non-cognitive symptoms. While both patient groups had smaller volumes of several medial temporal regions (e.g. entorhinal cortex, left hippocampus), schizophrenics had significantly smaller anterior superior temporal gyri (STG) than normal controls, but AD patients did not. We have previously demonstrated anterior STG volume to be reduced in early life onset schizophrenia.     

Neural Gate Keeping: The Role of Interhemispheric Interactions in Resource Allocation and Selective Filtering.

The corpus callosum has been proposed to contribute to attention by modulating resource allocation between the hemispheres and filtering interhemispheric signal transmission (M. T. Banich, 1998). The resource allocation hypothesis predicts that interhemispheric interactions become more advantageous with increasing resource demands. The selective filtering hypothesis predicts that interhemispheric interactions become less advantageous as filtering requirements increase. The authors tested both predictions by comparing within- and across-hemisphere letter matching under dual-task (Experiment 1) and selective attention conditions (Experiment 2). Task-specific resource demands (i.e., letter processing load) alter the bihemispheric advantage, but the general demand imposed by an unrelated secondary task does not. Filtering requirements influenced the advantage from interhemispheric interactions, providing new evidence for the role of the corpus callosum in selective attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Idiom processing in schizophrenia: Literal implausibility saves the day for idiom priming.

Schizophrenia patients have difficulty processing nonliteral forms of discourse such as idiomatic expressions. We hypothesized that schizophrenia patients would show impaired idiom processing for literally plausible idioms (e.g., kick the bucket) but not for literally implausible idioms (e.g., be on cloud nine). Thirty-two patients and 36 controls listened to sentences containing literally plausible and implausible idioms and made lexical decisions about idiom-related or literal-related targets. Schizophrenia patients showed reduced priming for literally plausible idioms but intact priming for literally implausible idioms compared with controls. Both groups showed evidence of literal word priming. These results are consistent with the notion that schizophrenia patients make normal use of context under conditions that minimize the need for controlled processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit learning of visuospatial sequences in schizophenia.

The authors examined whether patients with schizophrenia learned sequential patterns in a probabilistic serial response time task in which pattern trials alternated with random ones. Patients showed faster and more accurate responses to pattern trials than to random trials, but controls showed greater sensitivity to patterns. The highest level of regularity learned in both groups was information about runs of 3 events. Pattern learning occurred largely outside of awareness, as participants could not describe patterns. Controls with higher memory spans learned the sequential pattern better than those with lower memory spans, suggesting that working memory influences implicit pattern learning. Pathology in motor sequencing systems and poor working memory may lead to deficits in learning sequence structure in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)