An analysis of the specificity and the syndromal correlates of verbal memory impairments in schizophrenia

Chinese version of the auditory verbal learning test: normative study and clinical applications in Chinese-speaking population in Shijiazhuang city

OBJECTIVE

The purposes were to establish standardized values for the Auditory Verbal Learning Test (AVLT) in the communities of Shijiazhuang city (China), with particular focus on the influences of age, education and sex, and to detect the discriminant validity data of the AVLT in patients with acute ischemic stroke (AIS).

METHODS

406 Chinese-speaking subjects (age: 50-84 years old) from Shijiazhuang city, were brought into this study. Using linear regression analyses, standardized values were developed for three variables of interest, including scores on short-term memory (sum of AVLT trials 1-3), delayed recall (AVLT trial 4), and an index representing recognition memory corrected for false-positive identifications (AVLT trial 5). 177 patients with AIS were included to probe the discriminant validity of the AVLT.

RESULTS

The linear regression analysis showed statistically significant effect of age and sex on all trials of the AVLT. Years of education contributed significantly to trial 1-3 and trial 4 but not trial 5. Based on the results obtained, trail 1-3 and trail 4 of AVLT norms were stratified by age (3 strata), education (2 strata), and sex (2 strata). Trail 5 norms were stratified by age (3 strata) and sex (2 strata). Moreover, AIS groups performed significantly worse on most AVLT trials than matched cognitively healthy controls.

CONCLUSIONS

Normative data stratified by age, education and sex for the Chinese-speaking community-residents in Shijiazhuang was presented for use in research and clinical settings. The AVLT measures adequately differentiated between the cognitive performance (especially memory decline) of healthy adults and patients with AIS.

From Memories of Past Experiences to Present Motivation? A Meta-analysis on the Association Between Episodic Memory and Negative Symptoms in People With Psychosis

Based on findings from cognitive science, it has been theorized that the reductions in motivation and goal-directed behavior in people with psychosis could stem from impaired episodic memory. In the current meta-analysis, we investigated this putative functional link between episodic memory deficits and negative symptoms. We hypothesized that episodic memory deficits in psychosis would be related to negative symptoms in general but would be more strongly related to amotivation than to reduced expressivity. We included 103 eligible studies (13,622 participants) in the analyses. Results revealed significant, moderate negative associations of episodic memory with negative symptoms in general (k = 103; r = -.23; z = -13.40; P ≤ .001; 95% CI [-.26; -.20]), with amotivation (k = 16; r = -.18; z = -6.6; P ≤ .001; 95% CI [-.23; -.13]) and with reduced expressivity (k = 15; r = -.18; z = -3.30; P ≤.001; 95% CI[-.29; -.07]). These associations were not moderated by sociodemographic characteristics, positive symptoms, depression, antipsychotic medication or type of negative symptom scale. Although these findings provide sound evidence for the association between episodic memory deficits and amotivation, the rather small magnitude and the unspecific pattern of this relationship also indicate that episodic memory deficits are unlikely to be the only factor relevant to amotivation. This implicates that future research should investigate episodic memory in conjunction with other factors that could account for the association of episodic memory deficits and amotivation in psychosis.

Cognitive impairment in schizophrenia and depression: A comparison of stability and course

Cognitive deficits are clinically relevant features in schizophrenia and depression, yet little comparative data on changes in both disorders is available. This study compares cognitive performance of inpatients with schizophrenia (N = 52) and unipolar major depression (N = 67) during psychiatric treatment, assessing performance twice: after admission to hospital (acute) and prior to discharge (postacute) on average seven weeks later. A group of healthy controls was tested at comparable intervals. Data was analyzed using a multivariate linear model. Patients with schizophrenia and depression showed significantly impaired performance compared to healthy controls. On follow-up both patient groups showed improved performance. Contrary to expectation, patients with schizophrenia showed greater improvement in verbal memory, visual memory, and psychomotor speed than depressive patients. Verbal fluency presented as a possible candidate to differentiate between both disorders. Similar profiles of generalized cognitive deficits were observed in both patient-groups on acute and postacute assessment, which might indicate trait-like deficits with persistent functional implications in both disorders. Findings do not support assumptions of greater cognitive impairment in schizophrenia compared to depression. A distinction of the disorders on the grounds of cognitive functioning seems to be less specific than presumed.

Neurocognitive deficits in schizophrenia. Are we making mountains out of molehills?

BACKGROUND

Most original studies and all meta-analyses conducted to date converge on the conclusion that patients with schizophrenia display rather generalized neurocognitive deficits. For the present study, we reopen this seemingly closed chapter and examine whether important influences, such as lack of motivation and negative attitudes towards cognitive assessment, result in poorer secondary neuropsychological performance.

METHOD

A sample of 50 patients with an established diagnosis of schizophrenia were tested for routine neurocognitive assessment and compared to 60 nonclinical volunteers. Before and after the assessment, subjective momentary influences were examined (e.g. motivation, concerns about assessment, fear about poor outcome) for their impact on performance using a new questionnaire called the Momentary Influences, Attitudes and Motivation Impact (MIAMI) on Cognitive Performance Scale.

RESULTS

As expected, patients performed significantly worse than controls on all neurocognitive domains tested (large effect size, on average). However, patients also displayed more subjective momentary impairment, as well as more fears about the outcome and less motivation than controls. Mediation analyses indicated that these influences contributed to (secondary) poorer neurocognitive performance. Differences in neurocognitive scores shrank to a medium effect size, on average, when MIAMI scores were accounted for.

CONCLUSIONS

The data argue that performance on measures of neurocognition in schizophrenia are to a considerable extent due to secondary factors. Poor motivation, fears and momentary impairments distinguished patients from controls and these variables heavily impacted performance. Before concluding that neurocognitive deficits in psychiatric patients are present, clinicians should take these confounding influences into account. Although patients with schizophrenia achieved, on average, worse test scores than controls, a large subgroup displayed spared performance.

Stress is a bad advisor. Stress primes poor decision making in deluded psychotic patients

Stress is implicated in the onset of psychosis but the complex links between stress and psychotic breakdown are yet poorly understood. For the present study, we examined whether two prominent cognitive biases in psychosis, jumping to conclusions and distorted attribution, in conjunction with neuropsychological deficits play a role in this process. Thirty participants with schizophrenia and acute delusional symptoms were compared with 29 healthy controls across three conditions involving a noise stressor, a social stressor or no stressor. Under each condition participants had to perform parallel versions of cognitive bias tasks and neuropsychological tests including a probabilistic reasoning task (jumping to conclusions), the revised Internal, Personal and Situational Attributions Questionnaire (IPSAQ-R; attributional style), and the Corsi block-tapping task (nonverbal memory). Stress, particularly noise, aggravated performance differences of patients relative to controls on memory. Participants with psychosis demonstrated an escalated jumping to conclusion bias under stress. At a medium effect size, patients made more monocausal attributions, which increased under social stress. The present study is partially in line with prior studies. It suggests that stress negatively affects cognition in psychosis more than in controls, which is presumably insufficiently realized by patients and thus not held in check by greater response hesitance. Raising patients' awareness about these response tendencies and encouraging them to be more cautious in their judgments under conditions of increased stress may prove beneficial for improving positive symptoms.

Behavioral and cognitive effects of the N-methyl-D-aspartate receptor co-agonist D-serine in healthy humans: initial findings

The efficacy of compounds having agonistic activity at the glycine site associated with the N-methyl-D-aspartate receptor (NMDAR) is presently assessed in psychiatric disorders. In contrast to NMDAR antagonists, the neuropsychiatric effects of NMDAR agonists in the healthy human organism are not known. We studied neuropsychiatric and neurochemical effects of the NMDAR-glycine site obligatory co-agonist d-serine (DSR) in healthy subjects using a randomized, controlled crossover challenge design including a baseline assessment day and two DSR/placebo administration days. Thirty-five subjects aged 23-29 years participated in the study and received a 2.1 g orally administered DSR dose. The main outcome measures were the changes in scores of mood-related Visual Analogue Scale (VAS), Continuous Performance Test-Identical Pairs (CPT-IP), and Rey Auditory Verbal Learning Test (RAVLT). DSR acute administration: (1) was well tolerated and resulted at 2 h in ≥ 200 times increase in DSR serum levels; (2) elicited reduced VAS-measured depression and anxiety feelings; (3) improved attention and vigilance as measured by CPT-IP D-prime score; (4) preferentially improved performance in RAVLT list 7 reflecting ability to retain information over interference; (5) had significant but nonspecific effects on Category Fluency and Benton Visual Retention tests; and (6) did not affect glycine and glutamate serum levels. These data indicate that in healthy subjects, DSR reduces subjective feelings of sadness and anxiety and has procognitive effects that are overall opposed to the known effects of NMDAR antagonists. The findings are relevant to translational research of NMDAR function and the development of NMDAR-glycine site treatments for specific psychiatric entities. ClinicalTrials.gov: Behavioral and Cognitive Effects of the N-methyl-D-aspartate Receptor (NMDAR) Co-agonist D-serine in Healthy Humans; http://www.clinicaltrials.gov/ct2/show/NCT02051426?term=NCT02051426&rank=1; NCT02051426.

Neuropsychological Deficits in the Prodromal Phase and Course of an Early-Onset Schizophrenia

Objectives: Although clear advances have been achieved in the study of early-onset schizophrenia (EOS), little is known to date about premorbid and prodromal neuropsychological functioning in EOS. Method: Here, we report on a case of an adolescent male with EOS who underwent neuropsychological testing before and after illness onset. Results: Marked cognitive deficits in the domains of attention, set-shifting, and verbal memory were present both pre-onset and during the course of schizophrenia, though only deficits in verbal memory persisted after illness-onset and antipsychotic treatment. Conclusion: The findings of this case study suggest that impairments in the verbal memory domain are particularly prominent symptoms of cognitive impairment in prodromal EOS and persist in the course of the disorder, which further demonstrates the difficult clinical situation of adequate schooling opportunities for adolescent patients with EOS.

Source memory errors in schizophrenia, hallucinations and negative symptoms: a synthesis of research findings

BACKGROUND

Previous research has shown associations between source memory errors and hallucinations in patients with schizophrenia. We bring together here findings from a broad memory investigation to specify better the type of source memory failure that is associated with auditory and visual hallucinations.

METHOD

Forty-one patients with schizophrenia and 43 healthy participants underwent a memory task involving recall and recognition of lists of words, recognition of pictures, memory for temporal and spatial context of presentation of the stimuli, and remembering whether target items were presented as words or pictures.

RESULTS

False recognition of words and pictures was associated with hallucination scores. The extra-list intrusions in free recall were associated with verbal hallucinations whereas the intra-list intrusions were associated with a global hallucination score. Errors in discriminating the temporal context of word presentation and the spatial context of picture presentation were associated with auditory hallucinations. The tendency to remember verbal labels of items as pictures of these items was associated with visual hallucinations. Several memory errors were also inversely associated with affective flattening and anhedonia.

CONCLUSIONS

Verbal and visual hallucinations are associated with confusion between internal verbal thoughts or internal visual images and perception. In addition, auditory hallucinations are associated with failure to process or remember the context of presentation of the events. Certain negative symptoms have an opposite effect on memory errors.

Reliable biomarkers and predictors of schizophrenia and its treatment

Biomarkers are chemical and physiologic parameters that can provide reliable and predictive information about the course and treatment of a given illness. Biomarkers are being increasingly sought after in other medical conditions, and in some instances (eg, breast cancer therapy) are beginning to be incorporated into clinical decision making. There is a confluence of research investigating potential biomarkers for schizophrenia. This article reviews early progress and strategies for evaluating biomarkers, as well as how this approach can advance the treatment of schizophrenia toward personalized medicine.

Cognitive mechanisms of auditory verbal hallucinations in psychotic and non-psychotic groups

The continuum model of psychosis has been extremely influential. It assumes that psychotic symptoms, such as auditory verbal hallucinations (AVH), are not limited to patients with psychosis but also occur in healthy, non-clinical individuals - suggesting similar mechanisms of origin. Recent debate surrounding this model has highlighted certain differences, as well as similarities, in the phenomenology of AVH in clinical and non-clinical populations. These findings imply that there may, in fact, be only partial overlap of the mechanism(s) involved in generating AVH in these groups. We review evidence of continuity or similarity, and dissimilarity, in cognitive, and related neural processes, underlying AVH in clinical and non-clinical samples. The results reveal some shared (intrusive cognitions, inhibitory deficits) and some distinct (aspects of source memory and cerebral lateralization) mechanisms in these groups. The evidence, therefore, supports both continuous and categorical models of positive psychotic symptoms. The review considers potential risks of uncritical acceptance of the continuum model and highlights some important methodological issues for future research.

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.

Comorbid mood, psychosis, and marijuana abuse disorders: a theoretical review

There is a need to bridge the gap between the fields of addiction psychiatry and general psychiatry to effectively treat co-morbid substance abuse and psychiatric disorders. This alarming epidemic transcends communities and severely impacts healthcare worldwide, yielding poor treatment outcomes and prognoses for afflicted patients. Because substance abuse can exacerbate or trigger psychosis and mood disorders, it is important to keep these issues in the forefront when evaluating patients. To address some of the complications stemming from not enough interactions between various groups of practitioners, this review addresses the neurobehavioral effects of cannabis use and their impact on patients who suffer from psychotic or affective disorders. The hope is that this article will serve as a spring board for further discussions among practitioners who treat these patients. Greater interactions between caretakers are bound to impact the care of our patients in a very positive way.

Correspondences between theory of mind, jumping to conclusions, neuropsychological measures and the symptoms of schizophrenia

Tasks measuring reasoning biases and social cognition were originally applied to the study of schizophrenia in order to shed light on the cognitive underpinnings of positive symptoms. However, the empirical evidence for overlap between these tasks, and their association with positive symptoms, remains preliminary. In the current study we explore these associations using multivariate methodology, with primary interest in two commonly studied paradigms: jumping to conclusions (JTC) and theory of mind (ToM). We also included measures of memory, executive function and fluency performance, in order to relate the cognitive constructs to more traditional neuropsychological constructs. Forty-six schizophrenia inpatients were administered JTC, ToM, verbal fluency, executive functioning, and verbal memory tasks. A principal component analysis resulted in three components interpreted as Memory, Elaboration and Flexibility. ToM loaded with verbal fluency on the Elaboration component, whereas JTC loaded with executive functioning on the Flexibility component. The negative susbscale of the Positive and Negative Syndrome Scale (PANSS) correlated with the Elaboration component, but no other component-subscale correlations reached significance. Implications of these results are that impairments in elaboration may underlie the commonly observed correlation between ToM and negative symptoms, but argue against a common neurocognitive system for JTC, ToM and positive symptoms.

Symptoms as mediators of the relationship between neurocognition and functional outcome in schizophrenia: a meta-analysis

BACKGROUND

Neurocognitive functioning in schizophrenia has received considerable attention because of its robust prediction of functional outcome. Psychiatric symptoms, in particular negative symptoms, have also been shown to predict functional outcome, but have garnered much less attention. The high degree of intercorrelation among all of these variables leaves unclear whether neurocognition has a direct effect on functional outcome or whether that relationship to functional outcome is partially mediated by symptoms.

METHODS

A meta-analysis of 73 published English language studies (total n=6519) was conducted to determine the magnitude of the relationship between neurocognition and symptoms, and between symptoms and functional outcome. A model was tested in which symptoms mediate the relationship between neurocognition and functional outcome. Functional outcome involved measures of social relationships, school and work functioning, and laboratory assessments of social skill.

RESULTS

Although negative symptoms were found to be significantly related to neurocognitive functioning (p<.01) positive symptoms were not (p=.97). The relationship was moderate for negative symptoms (r=-.24, n=4757, 53 studies), but positive symptoms were not at all related to neurocogniton (r=.00, n=1297, 25 studies). Negative symptoms were significantly correlated with functional outcome (r=-.42, p<.01), and again the correlation was higher than for positive symptoms (r=-.03, p=.55). Furthermore, our findings support a model in which negative symptoms significantly mediate the relationship between neurocognition and functional outcome (Sobel test p<.01).

CONCLUSIONS

Although neurocognition and negative symptoms are both predictors of functional outcome, negative symptoms might at least partially mediate the relationship between neurocognition and outcome.

Working memory in schizophrenia: a meta-analysis

BACKGROUND

Memory impairment is being recognized increasingly as an important feature of the neuropsychology of schizophrenia. Dysfunction of working memory, a system for the short-term storage and manipulation of information, may relate to a number of core symptoms of schizophrenia. Many studies have examined working memory function in schizophrenia but a clear understanding of the nature and extent of any deficit has been elusive.

METHOD

A systematic review and meta-analysis of studies comparing working memory function in subjects with schizophrenia and healthy controls was performed. Following a comprehensive literature search, meta-analyses were conducted on 36 measures of phonological, visuospatial and central executive working memory functioning, encompassing 441 separate results from 187 different studies.

RESULTS

Statistically significant effect sizes were found for all working memory measures, indicating deficits in schizophrenia groups. Some of these were robust findings in the absence of evidence of significant heterogeneity or publication bias. Meta-regression analyses showed that the working memory deficit was not simply explained by discrepancies in current IQ between schizophrenia and control groups.

CONCLUSIONS

Large deficits in working memory were demonstrated in schizophrenia groups across all three working memory domains. There were, however, no clear differences across subdomains or between particular working memory tasks. There was substantial heterogeneity across results that could only be partly explained.

Hallucinations and two types of free-recall intrusion in schizophrenia

BACKGROUND

Previous research has demonstrated that various types of verbal source memory error are associated with positive symptoms in patients with schizophrenia. Notably, intrusions in free recall have been associated with hallucinations and delusions. We tested the hypothesis that extra-list intrusions, assumed to arise from poor monitoring of internally generated words, are associated with verbal hallucinations and that intra-list intrusions are associated with global hallucination scores.

METHOD

A sample of 41 patients with schizophrenia was administered four lists of words, followed by free recall. The number of correctly recalled words and the number of extra- and intra-list intrusions were tallied.

RESULTS

The verbal hallucination score was significantly correlated with the number of extra-list intrusions, whereas it was unrelated to the number of correctly recalled words. The number of intra-list intrusions was significantly correlated with the global, but not with the verbal, hallucination score in the subsample of hallucinating patients. It was marginally significantly correlated with the delusion score in delusional patients.

CONCLUSIONS

The data corroborate the view that verbal hallucinations are linked to defective monitoring of internal speech, and that errors in context processing are involved in hallucinations and delusions.

Verbal memory and verbal fluency in adolescents with schizophrenia spectrum disorders

AIM

Although impaired verbal memory and verbal fluency are frequently found in adults with schizophrenia, there has been a paucity of studies investigating adolescents with schizophrenia. Thus, the aim of the present study was to investigate the main subcomponents of verbal memory and verbal fluency in adolescents with schizophrenia spectrum disorders.

METHODS

Verbal learning and memory and verbal fluency was assessed in 21 adolescents with schizophrenia spectrum disorders (mean age, 15.4 years) compared with 28 healthy adolescents (mean age, 15.1 years).

RESULTS

The patient group performed significantly below healthy controls on measures of learning, delayed recall and on a frequency estimation task. No differences between the groups were found for measures of recognition, retention, implicit memory, or susceptibility to interference. Although they had impaired delayed recall the patients remembered most of what they actually learned. The patient group was impaired on phonological and semantic fluency, but there were no differences between the groups with respect to clustering or switching on the fluency tasks, when controlling for total output. There was no disproportionate impairment in semantic, as compared to phonological fluency, in the patient group.

CONCLUSIONS

Adolescents with schizophrenia spectrum disorders exhibit impairments in verbal learning and verbal fluency, which might have an impact on the individual's everyday functioning.

Memory and metamemory in schizophrenia: a liberal acceptance account of psychosis

BACKGROUND

In previous studies we suggested that liberal acceptance (LA) represents a fundamental cognitive bias in schizophrenia and may explain why patients are more willing to accept weak response alternatives and display overconfidence in incorrect responses. The aim of the present study was to test a central assumption of the LA account: false alarms in schizophrenia should be particularly increased when the distractor-target resemblance is weak relative to a control group.

METHOD

Sixty-eight schizophrenia patients were compared to 25 healthy controls on a visual memory task. At encoding, participants studied eight complex displays, each consisting of a unique pairing of four stimulus attributes: symbol, shape, position and colour. At recognition, studied items were presented along with distractors that resembled the targets to varying degrees (i.e. the match between distractors and targets ranged from one to three attributes). Participants were required to make old/new judgements graded for confidence.

RESULTS

The hypotheses were confirmed: false recognition was increased for patients compared to controls for weakly and moderately related distractors only, whereas strong lure items induced similar levels of false recognition for both groups. In accordance with prior research, patients displayed a significantly reduced confidence gap and enhanced knowledge corruption compared to controls. Finally, higher neuroleptic dosage was related to a decreased number of high-confident ratings.

CONCLUSIONS

These data assert that LA is a core mechanism contributing to both enhanced acceptance of weakly supported response alternatives and metamemory deficits, and this may be linked to the emergence of positive symptomatology.

Role of processing speed and depressed mood on encoding, storage, and retrieval memory functions in patients diagnosed with schizophrenia

The role of various types of slowing of processing speed, as well as the role of depressed mood, on each stage of verbal memory functioning in patients diagnosed with schizophrenia was investigated. Mixed lists of high- and low-frequency words were presented, and immediate and delayed free recall and recognition were required. Two levels of encoding were studied by contrasting the relatively automatic encoding of the high-frequency words and the more effortful encoding of the low-frequency words. Storage was studied by contrasting immediate and delayed recall. Retrieval was studied by contrasting free recall and recognition. Three tests of motor and cognitive processing speed were administered as well. Regression analyses involving the three processing speed measures revealed that cognitive speed was the only predictor of the recall and recognition of the low-frequency words. Furthermore, slowing in cognitive speed accounted for the deficit in recall and recognition of the low-frequency words relative to a healthy control group. Depressed mood was significantly associated with recognition of the low-frequency words. Neither processing speed nor depressed mood was associated with storage efficiency. It is concluded that both cognitive speed slowing and depressed mood impact on effortful encoding processes.

Metacognitive control over false memories: a key determinant of delusional thinking

This article reviews the current literature on false memories in schizophrenia. Increasing evidence suggests that neither memory impairment in general nor false memories in particular can reliably differentiate patients with schizophrenia or delusions from psychiatric controls. In contrast, it is proposed that a reduced metacognitive awareness of one's own fallibility, and overconfidence in errors, may predispose a person to fixed, false beliefs (ie, delusions). Congruent with this position, a number of recent investigations suggest that the memory of patients with schizophrenia, as well as healthy subjects scoring high on delusional ideation, is corrupted by an increased number of incorrect memories held with high confidence, possibly relating to a jumping-to-conclusions or liberal acceptance bias in schizophrenia spectrum disorders. A new training approach is described that is intended to sharpen patients' awareness of such errors and reduce confidence in fallible memories. Some empirical gaps and directions for further research are outlined.

Investigation of metamemory dysfunctions in first-episode schizophrenia

A number of recent studies have suggested that schizophrenia patients share metamemory deficits, particularly, a decreased ability to distinguish between errors and correct responses in terms of response confidence (i.e., decreased confidence gap): patients are over-confident in errors while at the same time being under-confident in responses that are in fact correct. This, along with increased error rates, leads to an inflation of inaccurate but confidently held memories, which has been termed knowledge corruption. Previous studies on metamemory in schizophrenia patients predominantly tested chronic patients, leaving open the possibility that metamemory deficits stem partly from increased chronicity and long-term treatment. The primary aim of the current study was to establish whether a decreased confidence gap is also detectable in first-episode schizophrenia. For this purpose, a source memory task was administered to 30 first-episode patients with a diagnosis of schizophrenia or schizophreniform disorder, and 15 healthy control subjects. During encoding, items were read aloud by the experimenter and the participant in alternating order. For the recognition phase, participants were required to state the source of the item, and their confidence in their response. In agreement with previous studies, the patients displayed a decreased confidence gap, and increased knowledge corruption relative to controls. A reduced distinction between correct and incorrect information in metacognition is proposed to be a vulnerability factor for the development of delusions in schizophrenia.

The contribution of metamemory deficits to schizophrenia

A number of recent studies have demonstrated that individuals with schizophrenia display knowledge corruption; that is, they hold false information with strong conviction. This aberration in metamemory is thought to stem from poor memory accuracy in conjunction with impaired discrimination of correct and incorrect judgments in terms of confidence. Thirty-one participants with schizophrenia, along with 61 healthy control participants and 48 control participants with other psychiatric conditions, participated in a computerized source memory task. Whereas no differences in memory accuracy were observed between the group with schizophrenia and the group with other psychiatric diagnoses, knowledge corruption was specifically impaired in those with schizophrenia. Schizophrenia participants showed a significantly decreased confidence gap: They were more confident in errors and less confident in correct responses relative to those in the control groups. Knowledge corruption is theorized to be a potential risk factor for the emergence of delusions.

Investigation of mood-congruent false and true memory recognition in depression

The present study investigated the extent of mood-congruent false and true memory recognition in depression. A group of 25 patients with depression and 28 healthy controls completed a variant of the Deese-Roediger McDermott task. Four lists were read to participants in sequence, followed by a recognition task. The words in each list were associated with a central but unmentioned theme word that was either depression-relevant (i.e., loneliness), delusion-relevant (betrayal), positive (holidays), or neutral (window). Whereas it was expected to replicate the conventional mood-congruent effect in depression (better recognition of depression-relevant items), the available literature did not allow strong predictions to be made on the extent of mood-congruent false recognition in depression. Results showed that depressed patients learned emotionally charged material equally well as healthy participants but forgot significantly more neutral material. A conventional mood-congruent memory bias was not found, but relative to healthy controls, patients with depression committed more false recognition errors for emotionally charged words, particularly for depression-relevant items. The results confirm that depressed patients are biased toward emotional material. Reasons for the absence of the expected mood-congruent memory bias are discussed. It is suggested that researchers as well as clinicians should pay more attention to mood-congruent false recollection, because it may undermine the validity of autobiographic reports in depressive patients and may represent a maintenance factor for the disorder.

Confidence in errors as a possible basis for delusions in schizophrenia

In two previous studies, it was observed that schizophrenic patients display increased confidence in memory errors compared with controls. The patient group displayed an increased proportion of errors in their knowledge system, quantified as the percentage of high-confident responses that are errors. The latter phenomenon has been termed knowledge corruption and is put forward as a risk factor for the emergence of delusions. In the present study, knowledge corruption was analyzed separately for different aspects of memory errors. A source-monitoring task was used, for which participants (30 schizophrenic patients with past or current paranoid ideas and 15 healthy controls) were asked to provide associates for each of 20 prime words. Later, participants were required to recognize studied words among distractor words, judge the original source, and provide a confidence rating for the most recent decision. Schizophrenic patients displayed greater confidence in memory errors compared with controls. Knowledge corruption was observed to be significantly greater in schizophrenic patients relative to controls for false-positive and false-negative judgments. It is proposed that reliance on false knowledge represents a candidate mechanism for the emergence of fixed false beliefs (i.e., delusions).

Secondary verbal memory: a potential endophenotype of schizophrenia

This study aimed at identifying neuropsychological endophenotypes of schizophrenia which met the criteria of stability and sensitivity. Twenty-six non-schizophrenic first-degree relatives together with their affected family members (all simplex-families) underwent assessment with a comprehensive neuropsychological test battery both at baseline and 13 months follow-up. Follow-up patients were in a state of stable remission. Further, 21 unrelated, demographically balanced, non-vulnerable controls were tested one at a time. A principal components analysis of our test battery resulted in four factors: (1) Vigilance, attention, and psychomotor, (2) secondary verbal memory, (3) immediate and working memory, and (3) abstraction and problem solving. At baseline testing our study revealed a pattern of selective cognitive deficits in the relative group that is less pronounced, yet qualitatively similar, to that found in the patient sample. The most severe deficits displayed both the patients and their relatives in the secondary verbal memory domain. The dysfunctions in secondary verbal memory at baseline testing significantly correlated with negative symptoms only. Secondary verbal memory deficits proved to be relatively independent of age at onset of illness, illness duration, and neuroleptic dosage. Longitudinally, dysfunctions in the patients' secondary verbal memory fluctuated over time and with negative symptoms, and persisted in remitted patients at the same level as in their relatives. In conclusion, the secondary verbal memory met the criteria of relative stability and sensitivity in our sample of simplex-families. Thus, the secondary verbal memory seems to be a potential endophenotypic marker of schizophrenia, even for cases with a hypothetically lower genetic loading.

Relationship between psychopathology and cognitive functioning in schizophrenia

The purpose of this study was to delineate the relationship between positive, negative, cognitive, depressive, and excitement symptom dimensions of schizophrenia and cognitive functioning. Fifty-eight patients with schizophrenia (DSM-IV criteria) were assessed using the Positive and Negative Syndrome Scale (PANSS) and a battery of neuropsychological tests (executive function/abstraction, verbal and spatial working memory, verbal and nonverbal memory/learning, attention, visuospatial ability, and psychomotor speed). The cognitive symptom dimension correlated with executive functions, attention, verbal memory, and spatial ability. Severity of the negative symptom dimension was related to impairment in the structure of the semantic knowledge system, verbal memory, and auditory attention. In contrast, severity of the positive symptom dimension correlated only with impairment in the structure of the semantic knowledge system, and psychomotor speed. Finally, severity of the depressive and excitement symptom dimension was not associated with cognition. Correlations between symptom dimensions and cognitive measures were at best modest. Severity of cognitive and negative symptoms was mainly correlated with deficits on executive functions, semantic memory, and verbal memory, while positive symptoms only with semantic memory. These correlations were modest, suggesting that psychopathology and cognitive deficits in schizophrenia are caused, at least partially, by distinct pathophysiological processes.

Material-specific episodic memory associates of the psychomotor poverty syndrome in schizophrenia

INTRODUCTION

Episodic memory deficits consistently correlate with the presence of negative symptoms in schizophrenia, suggesting overlap between the underlying neural systems. Functional neuroimaging and lesion studies suggest that prefrontal hypoactivity may underlie both. The purpose of the present study was to further characterise this association in terms of functional lateralisation. A more pronounced association between psychomotor poverty and verbal memory deficits would suggest more left prefrontal overlap than right, and vice-versa for a more pronounced association with nonverbal memory deficits.

METHODS

A total of 68 inpatients (48 males, 20 females) diagnosed with schizophrenia or schizoaffective disorder participated in this study. We evaluated the correlation between verbal and nonverbal memory performance (assessed using the RAVLT and BVMT, respectively) and psychomotor poverty (assessed using the SSPI).

RESULTS

A trend towards a more pronounced association for nonverbal compared to verbal material was not upheld by conservative statistical testing.

CONCLUSIONS

Bilateral prefrontal overlap between psychomotor poverty and episodic memory is the most conservative interpretation of these data.

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.

Neuropsychological Deficits and Concomitant Clinical Symptoms in Schizophrenia

The most frequently reported neuropsychological deficits in schizophrenia are those of attention, executive function, and verbal memory. Whereas the former appear to be related to negative symptoms of schizophrenia, there is little agreement about which clinical symptoms are related to the verbal memory deficit. The aim of the present study was to delineate further the pattern of neuropsychological deficits in schizophrenia—especially those of verbal memory—and their relationship to clinical symptoms. One hundred patients with chronic schizophrenia and 62 healthy control subjects took part in the study. Assessments of patients took place within the first 3 weeks after admission to hospital. Nine neuropsychological tests, mainly measuring executive and memory function and attention, were administered to all subjects, and clinical symptoms, such as psychotic and negative symptoms and conceptual disorganization, were assessed in patients by means of the Positive and Negative Syndrome Scale (PANSS). Patients showed widespread cognitive deficits with verbal memory impairment best discriminating patients and controls. Conceptual disorganization was partly accounted for by poor verbal memory and a low IQ estimate, and negative symptoms by deficient word fluency; positive symptoms were not significantly related to cognitive deficits. The results indicate that there is a specific relationship between neuropsychological deficits and the more chronic of the clinical symptoms.

Impact of comorbid depressive symptoms on nonverbal memory and visuospatial performance in obsessive-compulsive disorder

INTRODUCTION

Recent research has suggested that some executive dysfunctions in obsessive-compulsive disorder (OCD) represent an epiphenomenon of comorbid depressive symptoms. The present study investigated whether the impact of comorbid depressive symptoms on cognitive dysfunction in OCD extends to nonverbal memory impairment.

METHODS

A total of 32 OCD patients and 20 healthy controls took part in the study. Participants were administered a neurocognitive battery with a focus on nonverbal memory and visuospatial functions.

RESULTS

While evidence was provided that neurocognitive processes necessitating visuospatial transformation and visuoconstruction are deficient in OCD patients regardless of comorbid depressive symptoms, nonverbal memory dysfunctions were only apparent for patients with elevated scores in the Hamilton Depression (HDRS) Rating Scale (total score > or = 8). Correlations with subscores of the HDRS revealed that core depressive symptoms are related to nonverbal memory deficits in OCD. Mental rotation, middle discrimination, and position discrimination were found to be unaffected in OCD. Y-BOCS scores, length of illness, onset of illness, number of hospital admissions, and checking compulsions were not associated with neurocognitive disturbances.

CONCLUSIONS

Nonverbal memory is disturbed in only a subgroup of OCD patients displaying elevated HDRS scores (HDRS > or = 8). It is claimed but awaits further empirical testing that differences in depression profile across OCD studies have contributed to inconsistencies in prior investigations on neurocognitive functioning in OCD. Our results are questioning the hypothesis that nonverbal deficits are a causal factor for the development of checking compulsions.

Reliable change indexes for memory performance in schizophrenia as a means to determine drug-induced cognitive decline

Some psychotropic medications frequently prescribed in schizophrenia, especially agents that contain anticholinergic properties, have adverse effects on learning and memory. Given the impact of memory on both functional and symptomatic outcome in schizophrenia, it is important to determine if patients suffer from medication-related memory impairment. This study provides a statistical methodology for identifying medication-related changes in memory functioning. Reliable change estimates were determined for Rey Auditory Verbal Learning Test performance in 38 inpatients with schizophrenia. When an 80% confidence criterion was applied, improvement or decline of 12 words in the total score (sum score: Trials 1-5) cannot be attributed to measurement error. These findings should help clinicians better understand cognitive side effects and facilitate decision making regarding changes to individual patient's psychopharmacotherapy.

Methodological considerations regarding the association of Stroop and verbal fluency performance with the symptoms of schizophrenia

Previous research on schizophrenia has reported conflicting findings regarding the association between Stroop performance and the disorganization syndrome, as well as performance on verbal fluency tests and the psychomotor poverty syndrome. In the present work, we consider whether these inconsistencies may be increased due to variations in test format and failures to report the appropriate test parameters. In 36 schizophrenic inpatients, we administered list and single-trial versions of the Stroop test, and report the correlation with the disorganization syndrome for both errors and speed. For verbal fluency, we separated the total score into measures of switching and clustering, and observed the relationship with psychomotor poverty. For both versions of the Stroop test, accuracy, but not speed, was correlated with disorganization. For verbal fluency, decreased cluster production relative to total words generated was associated with psychomotor poverty, but the number of switches between clusters was not. It is suggested that assessing and reporting a full range of test parameters can reduce between-study inconsistencies. Cognitive interpretations for the present set of results are discussed.

The MMPI-168(L) and ADD in assessing psychopathology in individuals with mental retardation: between and within instrument associations

An abbreviated version of the Minnesota Multiphasic Personality Inventory, the MMPI-168(L), modified for use with clients who have moderate or mild mental retardation, was administered to 58 clients, most of whom had co-existing dual psychiatric diagnoses. Another recently developed instrument, the Assessment of Dual Diagnosis (ADD), was administered by interviewing a knowledgeable care giver. Correlations were examined among the raw scores on the 13 ADD scales and T scores of the 13 MMPI-168(L) scales. Contrary to expectations few correlations were found between the scales of the two instruments including scales purported to assess similar psychological constructs. The major exception was the Mania scale of the MMPI-168(L), which correlated moderately well with the Schizophrenia and Dementia scales of the ADD. Client age correlated strongly and negatively with scores on the Conduct Disorder and Sexual Disorder scales of the ADD. Finally, intra-instrument scale correlations were surprisingly large and, from a clinical and diagnostic perspective, meaningful. However, the large number of intra-instrument correlations showed that the scales of both instruments possess considerable overlap, which could make differential diagnosis problematic. It is suggested that it might be necessary to administer both instruments, and carefully consider behavioral history, to accurately diagnose psychiatric disturbances or personality characteristics of individuals with mental retardation.

Source monitoring impairments in schizophrenia: characterisation and associations with positive and negative symptomatology

This article describes a consistent pattern of the associations between source monitoring failure and clinical symptomatology in schizophrenia. The associations with positive symptoms in this sample have been reported previously, but not the associations with negative symptoms. Forty patients with schizophrenia were administered several memory tasks including free recall of lists of words, recognition and source memory. Various memory errors assumed to stem from source monitoring failure were derived. They include intrusions and recall of words from previous lists in free recall, false recognitions, and confusion with regard to the source of the stimuli. We studied the associations of these memory errors with positive symptoms and with a broad range of negative symptoms. All the memory errors were positively associated with at least one positive symptom. On the other hand, these errors were inversely associated with certain negative symptoms reflecting lack of emotion or lack of social interactions. Thus positive and negative symptomatology appear to have opposite links to the source monitoring errors observed in patients with schizophrenia. Cognitive mechanisms leading to different types of source monitoring errors and possibly to the formation of positive symptoms are discussed.

Impact of comorbid depressive symptoms on neuropsychological performance in obsessive-compulsive disorder

There is indirect evidence from previous research that several executive disturbances in obsessive-compulsive disorder (OCD) are mediated by comorbid depressive symptoms. For the present study, the authors investigated whether OCD patients with elevated Hamilton Rating Scale for Depression (HRSD) scores would exhibit deficits in tasks sensitive to the medial and dorsolateral frontal cortex as well as other executive tasks. The 36 OCD patients were split along the median according to their HRSD scores and compared with matched control subjects. Patients with high HRSD scores performed significantly worse than control subjects and patients with low HRSD scores on the Wisconsin Card Sorting Test, the Trail-Making Test (TMT, Part B), and the TMT difference score. Moreover, patients with high HRSD scores exhibited deficits on a (creative) verbal fluency task. It is suggested that comorbid depressive symptoms may have artificially inflated some executive deficit scores in previous studies.