Heterogeneity of auditory verbal working memory in schizophrenia.

The heterogeneity of schizophrenia remains an obstacle for understanding its pathophysiology. Studies using a tone discrimination screening test to classify patients have found evidence for 2 subgroups having either a specific deficit in verbal working memory (WM) or deficits in both verbal and nonverbal memory. This study aimed to (a) replicate in larger samples differences between these subgroups in auditory verbal WM; (b) evaluate their performance on tests of explicit memory and sustained attention; (c) determine the relation of verbal WM deficits to auditory hallucinations and other symptoms; and (d) examine medication effects. The verbal WM and tone discrimination performance did not differ between medicated (n = 45) and unmedicated (n = 38) patients. Patients with schizophrenia who passed the tone screening test (discriminators; n = 60) were compared with those who did not (nondiscriminators; n = 23) and healthy controls (n = 47). The discriminator subgroup showed poorer verbal WM than did controls and a deficit in verbal but not visual memory on the Wechsler Memory Scale–Revised (Wechsler, 1987), whereas the nondiscriminator subgroup showed overall poorer performance on both verbal and nonverbal tests and a marked deficit in sustained attention. Verbal WM deficits in discriminators were correlated with auditory hallucinations but not with negative symptoms. The results are consistent with a verbal memory deficit in a subgroup of schizophrenia having intact auditory perception, which may stem from dysfunction of language-related cortical regions, and a more generalized cognitive deficit in a subgroup having auditory perceptual and attentional dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory for visual features and conjunctions in schizophrenia.

The visual working memory (WM) storage capacity of patients with schizophrenia was investigated using a change detection paradigm. Participants were presented with 2, 3, 4, or 6 colored bars with testing of both single feature (color, orientation) and feature conjunction conditions. Patients performed significantly worse than controls at all set sizes but demonstrated normal feature binding. Unlike controls, patient WM capacity declined at set size 6 relative to set size 4. Impairments with subcapacity arrays suggest a deficit in task set maintenance: Greater impairment for supercapacity set sizes suggests a deficit in the ability to selectively encode information for WM storage. Thus, the WM impairment in schizophrenia appears to be a consequence of attentional deficits rather than a reduction in storage capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance of schizophrenia and bipolar patients on verbal and figural working memory tasks.

Working memory (WM) was studied in 82 healthy volunteers, 43 schizophrenia patients, and 81 bipolar patients. Schizophrenia patients were impaired on verbal and figural WM tasks that possessed similar test discriminating power. Bipolar patients performed similarly to healthy volunteers. A mathematical model of WM performance revealed a primary role for reduced WM span in accounting for the impaired verbal WM of schizophrenia patients and a primary role for diminished attention in accounting for impaired figural WM. Although WM impairment in schizophrenia is due neither to the general effects of severe mental illness nor to the specific type of material studied, the microarchitecture of abnormal WM in schizophrenia may depend on the stimulus material presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional neuroimaging of working memory in schizophrenia: Task performance as a moderating variable.

Functional neuroimaging studies in schizophrenia have demonstrated abnormal activation of dorsolateral prefrontal cortex (DLPFC) during working memory (WM) performance. However, findings of increased and decreased activity have been reported. The authors used meta-analysis to investigate whether diverging results arise as a function of differential WM task performance between patients and control participants. Results indicate that the magnitude of the group difference in WM performance is a moderator of DLPFC activation differences, and concepts such as hypo- or hyperfrontality do not universally characterize WM findings in schizophrenia. Thus, the variability in the WM activation findings between participants with schizophrenia and control participants reflects the specific conditions under which WM functions are evaluated, not just the WM construct per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working Memory Consolidation Is Abnormally Slow in Schizophrenia.

This study reports evidence that patients with schizophrenia demonstrate a slowing of working memory (WM) consolidation, which is the process of transforming transient perceptual representations into durable WM representations. Sixteen schizophrenia patients and 16 healthy control participants performed a task measuring the visual WM consolidation rate in a change-detection paradigm. A target display containing 3 colored squares was followed by a variable delay of 17-483 ms, a pattern mask, and then a test stimulus. This pattern mask does not interfere with perception but disrupts WM consolidation. Control participants reached no-mask performance by 250 ms, indicating completed WM consolidation, whereas patients failed to reach no-mask performance by 483 ms. Slowed consolidation may play an important and largely unrecognized role in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional modulation of the P50 suppression deficit in recent-onset and chronic schizophrenia.

Schizophrenia is associated with deficits in P50 suppression to the second stimulus in a pair, a process often conceptualized as a preattentive index of sensory gating. This study assessed the malleability of the deficit by determining whether early attentional control can influence P50 gating across different phases of schizophrenia. Participants included 28 patients in the recent-onset (n = 16) or chronic (n = 12) phase of illness and 28 healthy comparison subjects. During the standard paradigm, chronic schizophrenia patients exhibited impaired P50 suppression relative to healthy subjects, whereas recent-onset schizophrenia patients were intermediate. Directing voluntary attention toward the initial stimulus yielded substantial improvements in the P50 ratio; recent-onset schizophrenia patients achieved ratio scores comparable to those of healthy participants, whereas chronic patients also improved and could no longer be distinguished clearly from the healthy comparison sample. Directing attention toward the second stimulus enhanced P50 amplitude to the second stimulus across groups, possibly because activation of the inhibitory mechanism was overridden or circumvented by task demands. Thus, P50 suppression may be primarily preattentive under standard conditions, but manipulation of early attention can exert a modulatory influence on P50, indicating that the suppression deficit is malleable in schizophrenia without pharmacological agents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired visual working memory consolidation in schizophrenia.

This study investigated working memory (WM) consolidation, that is, the time required to create durable WM representations, at different levels of WM load in schizophrenia. Twenty-three schizophrenia spectrum patients and 16 control subjects participated in a change-detection task in which a sample array of 1-3 squares appeared followed by a delay and a test array. An array of pattern masks was inserted into the delay interval--covering the locations of the sample-array squares--100-800 ms after the offset of the sample array. If a durable WM representation is formed prior to mask onset, the mask should not impair performance. The degree of masking at an interval reflects the degree of WM consolidation at that time. Neither group showed masking at set size 1. Unlike controls, patients demonstrated robust masking effects at set size 2. Both groups showed masking at set size 3, but masking effects were larger and longer lasting in patients. These data demonstrate abnormally prolonged WM consolidation in schizophrenia. This impairment may slow the formation of stable representations of the visual environment, impacting everyday visually guided behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus configuration and context effects in perceptual organization in schizophrenia.

Two studies assessed perceptual organization in schizophrenia to determine (a) whether inpatient and outpatient groups with poor premorbid schizophrenia have comparable levels of perceptual organization deficit; and (b) whether the deficit could be eliminated by task manipulations. In Study 1, inpatients demonstrated clear evidence of a perceptual organization deficit, whereas outpatients performed similarly to the control groups. In Study 2, a performance pattern that operationally defined a perceptual organization deficit was eliminated by a task manipulation thought to aid in context processing. The perceptual organization deficit is most pronounced in actively symptomatic patients with poor premorbid schizophrenia, and the deficit reflects, in part, deficient top-down influences to basic perceptual processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional asymmetry in schizophrenia: Disengagement and inhibition of return deficits.

This research examined 2 components of visual orienting in medicated schizophrenia patients: the validity effect and the inhibition of return (IOR). In the 1st experiment, patients showed the expected asymmetry in orienting attention, that is, larger validity effect in the right visual field than in the left. However, this asymmetry was due to a deficit in facilitatory processes rather than a disengagement deficit. In addition, patients showed a deficit in IOR. In the 2nd experiment, a 2nd central cue for summoning attention, explicitly, back to the center was used. In this experiment, normal IOR in schizophrenia patients was found. Because it was shown that schizophrenia patients do not have a disengagement deficit, IOR possibly could not be observed because of the increased facilitation in that location. It was proposed that the abnormality in visual attention in schizophrenia is due to a deficit in inhibitory processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurocognition in first-episode schizophrenia: A meta-analytic review.

Compromised neurocognition is a core feature of schizophrenia. Following Heinrichs and Zakzanis’s (1998) seminal meta-analysis of middle-aged and predominantly chronic schizophrenia samples, the aim of this study is to provide a meta-analysis of neurocognitive findings from 47 studies of first-episode (FE) schizophrenia published through October 2007. The meta-analysis uses 43 separate samples of 2,204 FE patients with a mean age of 25.5 and 2,775 largely age- and gender-matched control participants. FE samples demonstrated medium-to-large impairments across 10 neurocognitive domains (mean effect sizes from ?0.64 to ?1.20). Findings indicate that impairments are reliably and broadly present by the FE, approach or match the degree of deficit shown in well-established illness, and are maximal in immediate verbal memory and processing speed. Larger IQ impairments in the FE compared to the premorbid period, but comparable to later phases of illness suggests deterioration between premorbid and FE phases followed by deficit stability at the group level. Considerable heterogeneity of effect sizes across studies, however, underscores variability in manifestations of the illness and a need for improved reporting of sample characteristics to support moderator variable analyses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

P50 suppression in recent-onset schizophrenia: Clinical correlates and risperidone effects.

Chronic schizophrenic patients often do not suppress the auditory P50 component of the event-related potential to the second of 2 clicks, presented 500 ms apart, suggesting a loss of normal inhibition. This study attempted to replicate the P50 suppression deficit in patients with recent-onset schizophrenia and to examine whether P50 is related to clinical symptoms or is affected by an atypical antipsychotic medication. Data from 22 recent-onset schizophrenia patients and 11 normal controls revealed that disruption in P50 suppression is present during the early stages of illness. In addition, impaired P50 suppression covaried with clinical ratings of anxiety, depression, and anergia; results also suggested that the P50 inhibitory deficit may be related to the degree of patients' attentional impairment. Finally, risperidone, compared with a typical antipsychotic medication, improved inhibition of P50 to the second click. These results support P50 suppression as a measure of disordered neurocognition in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context-processing deficits in schizophrenia: Converging evidence from three theoretically motivated cognitive tasks.

To test the hypothesis that the ability to actively represent and maintain context information is a central function of working memory and that a disturbance in this function contributes to cognitive deficits in schizophrenia, the authors modified 3 tasks—the AX version of the Continuous Performance Test Stroop, and a lexical disambiguation task—and administered them to patients with schizophrenia as well as to depressed and healthy controls. The results suggest an accentuation of deficits in patients with schizophrenia in context-sensitive conditions and cross-task correlations of performance in these conditions. However, the results do not definitively eliminate the possibility of a generalized deficit. The significance of these findings is discussed with regard to the specificity of deficits in schizophrenia and the hypothesis concerning the neural and cognitive mechanisms that underlie these deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial frequency processing in schizophrenia: Trait or state marker?

B. F. O'Donnell et al. (see record 2002-06065-009) found impaired discrimination performances at low and medium spatial frequencies in patients with schizophrenia. In this study, the authors replicated this finding in a group of remitted, unmedicated, and highly functioning outpatients with spared IQ and attentional functions. However, the deficit was restricted to low spatial frequencies (0.5 cycles/degree), which suggests that this deficit is a trait marker of schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning and forgetting in schizophrenia.

Recent studies of patients with schizophrenia have consistently demonstrated marked deficits on measures of initial learning. However, contradictory results have been reported concerning retention and forgetting. The present study examined the level of initial and delayed recall of stories and visual figures in a group of 76 patients with schizophrenia and 51 normal controls. Schizophrenia patients demonstrated marked impairments in initial and delayed recall as well as significantly worse percentage retention scores. However, schizophrenia patients and healthy controls individually matched on level of initial recall had nearly identical delayed recall performance. The results suggest a primary deficit in the initial acquisition of information rather than an accelerated rate of forgetting in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Stroop task and attention deficits in schizophrenia: A critical evaluation of card and single-trial Stroop methodologies.

The Stroop task, considered by many to be a paradigmatic measure of selective attention, has often been employed to investigate attention deficits in schizophrenia. Card and single-trial versions of this task have yielded different results. In this study both card and single-trial versions were administered to healthy controls (n?=?24) and patients with schizophrenia (n?=?55). No differences in reaction time (RT) interference were found on either version. On the single-trial version, patients showed greater RT facilitation and error rate interference, evidence for a deficit in selective attention. Methodologic and analytic issues that account for the mixed results from earlier card Stroop studies are addressed. It is concluded that single-trial versions provide greater sensitivity to selective attention pathology in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impairment in abstract responses of schizophrenics, neurotics, and brain-damaged patients

Attempted to identify a deficit in information input that may be specific to schizophrenia. The Ss were 60 male 19–58 yr old veterans representing 5 groups of 12 each: normals, neurotics, paranoid schizophrenics, nonparanoid schizophrenics, and brain-damaged patients. In the present and previous studies scores on single- and multiple-proverbs tests were analyzed to show effects of stimulus enrichment and practice gain in identifying this deficit. Previous studies differentiate normals and schizophrenics, demonstrate the deficit over a range of schizophrenic severity, and show that the deficit is independent of general loss of competence. Results of the present study indicate that the deficit is present over the paranoid–nonparanoid continuum; that it is absent in normals, neurotics, and brain-damaged patients; and that it is not a function of such intellectual factors as education and vocabulary. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric and attentional contributions to perceptual organization deficits on the global-local task in schizophrenia.

Right and left hemisphere hypotheses have been proposed to account for cognitive deficits in schizophrenia. To examine these hypotheses, perception of global-local patterns was studied in 22 patients with schizophrenia and 28 normal comparison participants. The patients with schizophrenia showed an abnormally exaggerated global processing advantage when attention was divided between global and local levels but not when participants were instructed to attend to either the local or global level. This finding suggested a local processing (left hemisphere) deficit, which was overcome through strategic attentional allocation (instructional set). When the stimulus visual angle was reduced from 9° to 3°, the normal participants showed a shift from a local to a global processing advantage, but the patients did not. This finding suggested a more subtle deficit in strategic attentional processes that develop through exposure to stimulus context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vernier Threshold in Patients With Schizophrenia and in Their Unaffected Siblings.

The aim of this study was to investigate magnocellular (M) and parvocellular (P) visual functions in nonmedicated patients with schizophrenia and in their unaffected siblings. Possible abnormalities in cortical integration of retinal receptive fields also were addressed. Twenty-two nonmedicated patients with schizophrenia, their unaffected siblings, and 20 age- and IQ-matched healthy control subjects received 4 vernier acuity tasks (blue-on-yellow, frequency-doubling, achromatic low and high contrast conditions) in which they were asked to detect the spatial alignment of dots and gratings. Results revealed that the patients with schizophrenia and their unaffected siblings showed selective dysfunctions in the frequency-doubling and achromatic low contrast conditions, which were devoted to investigate M pathways. In the isoluminant blue-on-yellow and high contrast achromatic conditions, there were no significant differences between the experimental groups. These results suggest that the deficit of M pathway is an endophenotype of schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maintenance of grip-induced muscle tension: A behavioral marker of schizophrenia.

A grip-induced muscle tension maintenance task distinguished between schizophrenic patients, regardless of medication or hospitalization status, and both normals and controls with affective (unipolar and bipolar) disorders. Unaffected 1st-degree relatives of schizophrenic patients also showed a grip deficit. Coupling the grip task with a visual discrimination task that divided attention through instruction or reinforcement contingency increased grip error times for all groups. No group differences appeared on the discrimination task, regardless of difficulty level, and the tone used to provide corrective feedback was not implicated in the grip deficit. The results suggest that the grip task is tapping, in a systematic and reliable manner, a motor-control abnormality that may be useful as a behavioral marker of schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact attentional control of working memory encoding in schizophrenia.

This study reports evidence that individuals with schizophrenia (SC) demonstrate intact attentional selection for visual working memory (WM) storage. A group of 62 participants with SC and 55 control participants without SC were studied in a series of 5 experiments that examined the ability to use top-down and bottom-up cues to guide WM encoding, as well as the ability to spontaneously select a subset of representations for storage. Participants with SC exhibited a consistent and robust ability to use selective attention in the control of WM in all 5 experiments, demonstrating a remarkable island of preserved functioning given the broad spectrum of impairments of attention and WM that have been widely reported in those with SC. These findings indicate that attention is not globally impaired in SC and make it possible to delineate more precisely the nature of the specific impairment of attention in this disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)