Frontal and non-frontal lobe neuropsychological test performance and clinical symptomatology in schizophrenia

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.

Rethinking the Neural Basis of Prosody and Non-literal Language: Spared Pragmatics and Cognitive Compensation in a Bilingual With Extensive Right-Hemisphere Damage

Above and beyond the critical contributions of left perisylvian regions to language, the neural networks supporting pragmatic aspects of verbal communication in native and non-native languages (L1s and L2, respectively) have often been ascribed to the right hemisphere (RH). However, several reports have shown that left-hemisphere activity associated with pragmatic domains (e.g., prosody, indirect speech, figurative language) is comparable to or even greater than that observed in the RH, challenging the proposed putative role of the latter for relevant domains. Against this background, we report on an adult bilingual patient showing preservation of pragmatic verbal skills in both languages (L1: Spanish, L2: English) despite bilateral damage mainly focused on the RH. After two strokes, the patient sustained lesions in several regions previously implicated in pragmatic functions (vast portions of the right fronto-insulo-temporal cortices, the bilateral amygdalae and insular cortices, and the left putamen). Yet, comparison of linguistic and pragmatic skills with matched controls revealed spared performance on multiple relevant tasks in both her L1 and L2. Despite mild difficulties in some aspects of L2 prosody, she showed no deficits in comprehending metaphors and idioms, or understanding indirect speech acts in either language. Basic verbal skills were also preserved in both languages, including verbal auditory discrimination, repetition of words and pseudo-words, cognate processing, grammaticality judgments, equivalent recognition, and word and sentence translation. Taken together, the evidence shows that multiple functions of verbal communication can be widely spared despite extensive damage to the RH, and that claims for a putative relation between pragmatics and the RH may have been overemphasized in the monolingual and bilingual literature. We further discuss the case in light of previous reports of pragmatic and linguistic deficits following brain lesions and address its relation to cognitive compensation in bilingual patients.

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.

Association between learning capabilities and practice-related activation changes in schizophrenia

The present functional magnetic resonance imaging study investigated the neural correlates of practice-associated activation changes in patients with schizophrenia and their association with symptom severity. A group of patients (n = 24) were divided into more successful and less successful learners and were asked to perform a verbal overlearning task in the scanner. We found that both patient groups profited from practice, showing significant decreases in mean response times as well as significant learning-related decreases in cerebral activation. Direct comparison between groups yielded a relative hyperactivation in the group of the less successful learners at the beginning of practice, which showed a reduction with increasing practice. This was reflected by relatively stronger signal decreases in a predominantly fronto-parieto-cerebellar network. In the group of less successful learners, there was a negative correlation between general symptom scores and learning-related signal decreases in a task-relevant network involving cerebellar, inferior and middle frontal (BA 45/47, 46), superior parietal (BA 31), and superior temporal (BA 39) regions. Present data indicate that hyperactivity under high task demands might serve to identify those patients with less potential to profit from practice. However, at least in the context of moderate- to low-working memory demands, this activation abnormality seems to constitute a state rather than a trait characteristic, which patients manage to reduce by successful short-term learning. The findings also suggest that successful learners can better compensate potentially interfering effects exerted by disorder-related psychopathology.

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.

Neuropsychological impairment in deficit vs. non-deficit schizophrenia

This study aimed to assess the severity and specificity of cognitive impairments that affect individuals with deficit versus non-deficit schizophrenia. We compared 26 patients with the deficit subtype of schizophrenia (SZ-D) and 79 with non-deficit schizophrenia (SZ-ND) to 316 healthy adults (NC). All study participants completed a battery with 19 individual cognitive measures. After adjusting their test performance for age, sex, race, education and estimated premorbid IQ, we derived regression-based T-scores for each measure and the six derived cognitive domains including attention, psychomotor speed, executive function, verbal fluency, visual memory, and verbal memory. Multivariate analyses of variance revealed significant group effects for every individual measure and domain of cognitive functioning (all ps<0.001). Post hoc comparisons revealed that patients with SZ-D performed significantly worse than NCs in every cognitive domain. They also produced lower scores than the SZ-ND group in every domain, but only the difference for verbal fluency reached statistical significance. The correlations of the effect sizes shown by the SZ-D and SZ-ND patients were of intermediate magnitude for the individual tests (r=0.56, p<0.01) and higher, but not statistically significant for the cognitive domains (r=0.79, p=0.06). Patients with SZ-D demonstrate cognitive deficits that are both common and distinct from those shown by patients with SZ-ND. Their impairment of verbal fluency is consistent with the observation that poverty of speech is a clinically significant feature of patients with SZ-D.

Specific executive dysfunction in patients with first-episode medication-naïve schizophrenia

Many studies have shown that schizophrenia is associated with a wide range of cognitive impairments. Empirical findings suggest that patients with schizophrenia suffer from a "dysexecutive syndrome". However, the extent to which a general decline in neuropsychological function accounts for symptoms of executive dysfunction in schizophrenia is not clear. In this study, we examined further the nature and pattern of executive function in a sample of medication-naïve patients experiencing a first-episode of schizophrenia with a set of tests capturing the specific components of executive function. We also compared the performance of this clinical group with healthy controls. A total of 78 medication-naïve patients with first episode schizophrenia were recruited from the Early Assessment Service for Young People with Psychosis (EASY). Another 60 healthy controls were recruited for comparison. All subjects participated in a comprehensive set of executive function tests assessing initiation, sustained attention, online updating, switching, attention allocation, inhibition, and non-executive function. The executive function of patients with first-episode schizophrenia was found to be compromised relative to healthy controls. However, unlike patients with established schizophrenia, first episode patients exhibited only a limited deficit in sustained attention. Moreover, the majority of executive function deficits did not correlate with intellectual functioning and memory impairment in a sub-group of first episode patients without intellectual impairment. These findings suggest that first-episode patients exhibit a specific pattern of executive dysfunction compared to healthy controls and patients with an established illness. This differential breakdown of executive function components is unlikely to be an artefact of general intellectual decline or memory impairment in schizophrenia.

The components of executive functioning in a cohort of patients with chronic schizophrenia: a multiple single-case study design

We examined the fractionation of executive functioning performance in ninety patients with schizophrenia, who were tested for initiation, sustained attention, switching/flexibility, attention allocation and impulsivity/disinhibition. The participants were also given tests of general intelligence and memory. We analysed the executive functioning performance of individual patients against normative data from our laboratory, and summary scores for all of the executive functioning components were computed. For each component, participants were classified as having impairment with a test performance of 1.5 standard deviations or more from the norm of the corresponding test. Of all of the participants, 27.8% (n=25) demonstrated poor performance in all of the components, and 5.6 % (n=5) exhibited intact or fair performance in all of the components. Furthermore, 18.9% (n=17) showed intact or fair performance in one component, 16.7% (n=15) in two components, 21.1% (n=19) in three components and 10% (n=9) in four components. The groups did not differ in education, gender or duration of illness, but the group that showed impaired performance in all of the components demonstrated the most severe psychotic symptoms after controlling for background intelligence, age and medication. The differential breakdown for the executive functioning performance across the participants suggests that the fractionation of central executive functioning occurs in schizophrenia.

Does negative symptom change relate to neurocognitive change in schizophrenia? Implications for targeted treatments

Negative symptoms and cognitive dysfunction are among the most challenging obstacles in the treatment of schizophrenia. It is unknown to what extent they are overlapping or independent disease processes. In the search for targeted treatments of negative symptoms and cognitive impairments, it is imperative to determine their longitudinal relationship. 267 stable outpatients with schizophrenia in a work and cognitive rehabilitation program were evaluated using symptom measures and a comprehensive neuropsychological test battery at baseline and at the conclusion of rehabilitation, 6 months later. Baseline negative symptom, neuropsychological variables and change scores from intake to follow-up on these variables were correlated. These analyses were repeated with a subsample (n = 161) who had clinically significant negative symptoms at baseline. ANCOVA's were performed to compare patients whose negative symptoms improved by 5 points or more (n = 69) with those whose negative symptoms got worse by 5 points or more (n = 26) on their neurocognitive performance at follow-up. Intake negative symptoms were significantly associated with theory of mind and visuomotor processing. Results failed to support a lawful relationship between change in negative symptoms and neurocognition. These findings suggest that negative symptoms and neurocognition should be viewed as relatively independent targets for intervention.

A 4.0-T fMRI study of brain connectivity during word fluency in first-episode schizophrenia

OBJECTIVE

To use functional magnetic resonance imaging (fMRI) to investigate functional connectivity, and hence, underlying neural networks, in never-treated, first-episode patients with schizophrenia using a word fluency paradigm known to activate prefrontal, anterior cingulate, and thalamic regions. Abnormal connectivity between the prefrontal cortex (PFC) and other brain regions has been demonstrated in chronic, medicated patients in previous positron emission tomography (PET) studies, but has not to our knowledge, previously been demonstrated using both first-episode, drug-naïve patients and fMRI technology.

METHODS

A 4.0-Tesla (T) fMRI was used to examine activation and functional connectivity [psychophysiological interactions (PPIs)] during a word fluency task compared to silent reading in 10 never-treated, first-episode patients with schizophrenia and 10 healthy volunteers of comparable age, sex, handedness, and parental education.

RESULTS

Compared to healthy volunteers, the schizophrenia patient group exhibited less activation during the word fluency task, mostly in the right anterior cingulate and prefrontal regions. Psychophysiological interactions between right anterior cingulate and other parts of the brain revealed a localized interaction with the left temporal lobe in healthy volunteers during the task and a widespread unfocussed interaction in patients.

CONCLUSION

These findings suggest anterior cingulate involvement in the neuronal circuitry underlying schizophrenia.

Neurological soft signs in schizophrenic patients with obsessive-compulsive disorder

The purpose of this study was to examine neurological soft signs (NSS) in schizophrenic patients with obsessive-compulsive disorder (OCD). Neurological soft signs were assessed in 15 schizophrenic patients with OCD (OCD-schizophrenia), 38 schizophrenia patients without OCD (non-OCD-schizophrenia), and 24 healthy controls (HC) by means of the Neurological Evaluation Scale (NES). The OCD-schizophrenia group had significantly higher scores on total and subscales of 'sensory integration' and 'others' of NES than the HC group. Subscale scores of 'sequencing of motor acts' in-non-OCD-schizophrenia patients were significantly higher compared to OCD-schizophrenia patients. Total NES scores of both groups were significantly correlated with Scale for the Assessment of Negative Symptoms (SANS) scores. Only the subscale of 'sequencing of motor acts' was significantly correlated with SANS within the OCD-schizophrenia group. These results suggest that NSS do not significantly differ between schizophrenia patients with and without OCD, contrary to expectations. The NES scores in OCD-schizophrenic patients do not appear to be related to a more severe form of schizophrenia. Neurological signs and negative symptoms in schizophrenia patients with and without OCD may be considered as neurodevelopmental predisposing factors. Further research is required in schizophrenia patients with OCD to investigate the relationships between NSS and several neuroimaging or neuropsychological findings, constituting a subgroup within the schizophrenia spectrum.

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.

Verbal declarative memory dysfunction in schizophrenia: from clinical assessment to genetics and brain mechanisms

The recent literature on the neuropsychology of schizophrenia has emphasized memory deficits as a key area of impairment. Abnormalities in the medial temporal lobe, a brain region crucial for long-term memory formation, have also consistently been reported. We conducted a comprehensive review of verbal declarative memory (VDM) in schizophrenia with the aim of systematically addressing the nature of this impairment. We conclude that verbal declarative memory is significantly impaired in schizophrenia and is largely accounted for by deficits in the encoding stage. Subtle impairments in increased rates of forgetting are present, but are mild compared with those in amnestic disorders. Impairment in other cognitive domains studied thus far (e.g., attention), medication effects, or fluctuations in symptoms do not completely account for the deficit. VDM is among the most impaired neurocognitive domains in schizophrenia (along with attention and executive functions). Milder encoding deficits are present in high-risk subjects and non-psychotic relatives of individuals with schizophrenia suggesting that components of the deficit are associated with a genetic vulnerability to the illness, and are independent of the frank psychotic illness. Furthermore, VDM is observed in individuals experiencing their first-psychotic episode and it remains fairly consistent over time. Preliminary imaging studies and other work suggest abnormalities in prefrontal-hippocampal processing networks. Future work should emphasize delineating specific information processing components contributing to the deficit. This would allow imaging studies to determine which brain regions contribute to specific information processing deficits in schizophrenia.

Perseveration and over-switching in schizophrenia

Perseveration and switching in positive and negative schizophrenic patients are usually seen as manifestations of attention disorders. They may be closely related to each other, but have not been investigated in an integrated fashion. Such integrated investigation could contribute to the neurophysiological understanding of the relationship between the regional and the pharmacological deficit in schizophrenia. This study has developed a new tool-the Combined Attention Test (CAT)-for the simultaneous measuring of perseveration and switching. Forty-one unmedicated schizophrenic patients were tested. Using the Positive and Negative Sorting Scale (PANSS), subjects were classified into the two experimental groups: positive and negative schizophrenics. The control group consisted of 24 healthy subjects. Schizophrenic patients with positive symptoms tended to switch more than schizophrenic patients with negative symptoms and normal subjects; schizophrenic patients with negative symptoms tended to perseverate more than schizophrenic patients with positive symptoms and normal subjects. Over-switching is discussed as a specific symptom related to positive schizophrenia.

Impaired Trail-Making Test-B performance in patients with acute schizophrenia is related to inefficient sequencing of planning and acting

In order to investigate the functional basis of the frequently described deficits of schizophrenia patients in Trail Making Test B (TMT-B) performance, the performance process was analyzed based on the interaction of eye and hand movements. In a longitudinal design, 23 acute schizophrenia patients, 17 acute depressive inpatients, and 21 healthy controls were assessed twice within 4 weeks. Computer versions of both TMT-A and TMT-B were used, which require to connect different targets with a cursor, with concurrent infrared oculography. In both TMT-versions, schizophrenia patients demonstrated poorer performance and longer "planning periods"--as defined by fixations outside the cursor area--containing more fixations, which were stable over time. However, these "planning fixations" were only also longer in duration during TMT-B and differed in time and context of their occurrence compared with healthy controls. Schizophrenia patients demonstrated more fixations while the cursor rested between targets. Significant correlations with performance time gave evidence that it is important for short planning periods to be performed parallel to ongoing connection of targets, to obtain a satisfactory result. No relationship between "planning variables" with psychopathology and medication could be found. Accordingly, poorer TMT-B performance in schizophrenia patients was found to be related to insufficient sequencing of planning and acting, which appears to be a trait-like characteristic. Though depressive patients also performed poorer in TMT-B, they did not differ from either of the other groups in the main process variables, which may hint to different underlying causes of the performance deficits in both groups of patients.

WCST performance and schizotypal features in the first-degree relatives of patients with schizophrenia

Since the findings concerning the Wisconsin Card Sorting Test (WCST) performance of healthy first-degree relatives of patients with schizophrenia are equivocal, it still remains unclear whether the WCST may serve as a neuropsychological indicator of vulnerability to schizophrenia. The aim of this study was to evaluate whether the first-degree relatives' schizotypal features could account for these discrepancies. The subjects were 24 schizophrenic probands, 49 of their first-degree relatives and 41 normal controls. The computerized version of the WCST was used and schizotypy features were assessed using four of Chapman's scales. The patient group performed worse on the WCST and had higher scores of schizotypy than the control group. The relatives group did not significantly differ from the control, neither on the WCST performance nor on the scores of schizotypy. However, the subgroup of relatives and the subgroup of patients with high scores on the negative dimension of schizotypy showed a worse performance on the WCST than the subgroups with low scores. There were no differences on the WCST performance between the subgroups with high vs. low scores on the positive dimension of schizotypy. Thus, discrepancies across studies could be explained by a confounding factor represented by the negative dimension of schizotypy.

Functional neuroanatomy of auditory working memory in schizophrenia: relation to positive and negative symptoms

Functional brain imaging studies of working memory (WM) in schizophrenia have yielded inconsistent results regarding deficits in the dorsolateral prefrontal (DLPFC) and parietal cortices. In spite of its potential importance in schizophrenia, there have been few investigations of WM deficits using auditory stimuli and no functional imaging studies have attempted to relate brain activation during auditory WM to positive and negative symptoms of schizophrenia. We used a two-back auditory WM paradigm in a functional MRI study of men with schizophrenia (N = 11) and controls (N = 13). Region of interest analysis was used to investigate group differences in activation as well as correlations with symptom scores from the Brief Psychiatric Rating Scale. Patients with schizophrenia performed significantly worse and were slower than control subjects in the WM task. Patients also showed decreased lateralization of activation and significant WM related activation deficits in the left and right DLPFC, frontal operculum, inferior parietal, and superior parietal cortex but not in the anterior cingulate or superior temporal gyrus. These results indicate that in addition to the prefrontal cortex, parietal cortex function is also disrupted during WM in schizophrenia. Withdrawal-retardation symptom scores were inversely correlated with frontal operculum activation. Thinking disturbance symptom scores were inversely correlated with right DLPFC activation. Our findings suggest an association between thinking disturbance symptoms, particularly unusual thought content, and disrupted WM processing in schizophrenia.

Executive/attentional performance and measures of schizotypy in patients with schizophrenia and in their nonpsychotic first-degree relatives

Previous studies of executive/attentional functions have found impairments in nonpsychotic first-degree relatives of patients with schizophrenia. The aims of this study were: (1) to replicate these findings by three laboratory measures of attention/information processing - a continuous performance test (DS-CPT), a forced-choice span of apprehension task (SPAN), and a digit symbol substitution test (DSST), and by a series of neuropsychological tests sensitive to prefrontal cortical damage - Trail Making A and B, verbal fluency (VFT), Stroop Color and Word Test (Stroop), and Wisconsin Card Sorting Test (WCST); (2) to investigate whether such executive/attentional deficits are associated with schizotypal traits assessed using the social anhedonia, physical anhedonia, perceptual aberration and magical ideation scales (Chapman, L.J., Chapman, J.P., Raulin, M.L. 1976. Scales for physical and social anhedonia. J. Abnorm. Psychol. 85, 374-382; Chapman, L.J., Chapman, J.P., Raulin, M.L., 1978. Body-image aberration in schizophrenia. J. Abnorm. Psychol. 87, 399-407; Eckblad, M., Chapman, L.J., 1983. Magical ideation as an indicator of schizotypy. J. Consult. Clin. Psychol. 51, 215-225). In both patient and relative groups, performance was significantly poorer on the DSST, VFT and Trail B, and the reaction time on the SPAN was significantly longer. These neuropsychological impairments were present as much in siblings as in parents of schizophrenic patients; age did not appear to cancel differences between the relative and control groups. In the relative group, the four scores of schizotypy were at an intermediate level between those of patient and control groups, and the social anhedonia and perceptual aberration scores tended to be significantly different between the relative and the control groups. Only two significant correlations were found between the neuropsychological performance and the measures of schizotypy.

Hypofrontality in unmedicated schizophrenia patients studied with PET during performance of a serial verbal learning task

Previous research indicates that verbal learning and memory deficits are among the most severe cognitive deficits observed in schizophrenia. However, the concomitant patterns of regional brain function associated with these deficits in schizophrenia are not well understood. The present study examined verbal-memory performance and simultaneous relative glucose metabolic rates (rGMR) with FDG PET in 20 unmedicated schizophrenia patients who met stringent memory-performance criteria and 32 age- and sex-matched normal volunteers. On a modified version of the California Verbal Learning Test, patients recalled fewer correct words using a semantic-clustering strategy and exhibited more intrusions compared with normal subjects. However, patients had higher serial-ordering strategy scores, indicating their use of a less efficient organizational strategy. Among patients, greater use of the serial-ordering strategy was associated with decreased rGMR in frontal cortex and increased rGMR in temporal cortex. Patients had lower rGMR primarily in frontal and temporal cortex, but not parietal and occipital lobe regions. Patients also exhibited hypofrontality (lower ratio of frontal to occipital rGMR) compared with normal subjects. Among the patients, more severe hypofrontality was associated with increased perseveration errors.

Executive functions in adolescents with schizotypal personality disorder

Adolescents meeting diagnostic criteria for schizotypal personality disorder (SPD) are presumed to be at risk for developing schizophrenia in adulthood, making them an important group for exploring the developmental trajectory of the disease. Deficits in executive functioning have been documented in schizophrenia patients and adults with SPD. The present study examined executive functions in adolescents with SPD. It was predicted that the SPD group would score below comparison groups (normals and adolescents with other disorders) on measures of executive function, and that those with greater 'negative' signs of SPD would show more pronounced performance deficits. Analyses revealed that the performance of the SPD subjects was impaired relative to the other groups on the modified Wisconsin Card Sorting Test (MCST), but not on the Tower of London or the Controlled Oral Word Association Test. Consistent with prediction, regression analyses indicated that MCST deficits were associated with greater negative signs of SPD, but not positive signs.

Cognitive deficits in schizophrenia on the WAIS-R NI Sentence Arrangement Subtest. Wechsler Adult Intelligence Scale-Revised Neuropsychological Inventory

Performance of participants diagnosed with schizophrenia on the Sentence Arrangement subtest of the WAIS-R NI and several tests sensitive to frontal lobe dysfunction was significantly poorer than that of manic depressive or control participants. Several measures of performance of patients diagnosed with schizophrenia on the WAIS-R NI Sentence Arrangement subtest appeared to support recent interpretations of the cognitive deficit seen in schizophrenia. These data represent the first demonstration of deficit performance by patients with schizophrenia on the Sentence Arrangement subtest. This is also supportive of the prediction that one of the areas whose activity may influence scores on this subtest is the prefrontal cortex. In addition, neither positive nor negative symptoms systematically correlated with the cognitive deficits reported despite specific predictions from the current literature.

A meta-analytic review of Wisconsin Card Sort studies in schizophrenia: general intellectual deficit in disguise?

A majority of studies show that schizophrenics perform poorly on so-called tests of executive or frontal lobe function--the paradigmatic case being the Wisconsin Card Sort Test (WCST). Nevertheless, the specific character of this deficit in schizophrenia remains underspecified. In particular, it seems premature to assume that schizophrenia is characterised by an executive dysfunction and/or a disorder of frontal lobe function before determining whether any deficit is: selective; disproportionate to the general level of intellectual functioning; or qualitatively comparable with that of frontal lobe patients. A meta-analysis was conducted on 29 studies comparing the performance of schizophrenics and normal controls on the WCST. This showed that the mean weighted effect size was large for categories achieved (d = 0.91), medium for absolute level of perseveration (d = 0.53), but only small for the proportion of perseverative errors (d = 0.18). By contrast, the effect size for Wechsler Adult Intelligence Scale Intelligence Quotient (WAIS IQ) in a subset of these studies (d = 1.23) was significantly larger than for any WCST measures. This pattern of findings challenges notions that schizophrenia is characterised by an executive dysfunction that is: selective; disproportionate to IQ level; and analogous to that found in frontal lobe patients. Rather, the poor WCST performance of schizophrenics appears to reflect a generalised intellectual deficit.

Executive-frontal lobe cognitive dysfunction in schizophrenia: a symptom subtype analysis

Impairment of executive-frontal lobe functioning, affecting the planning, initiation and regulation of goal-directed behavior, is a common cognitive deficit in schizophrenia. However, it is unclear if deficits in these frontal-lobe-mediated abilities are differentially expressed across clinical subgroups. We analyzed executive-frontal abilities in relation to symptom expression in 53 hospitalized schizophrenic patients. Patients were assigned to one of three subgroups based on rank order analysis of Brief Psychiatric Rating Scale factors: Withdrawal-Retardation, Reality Distortion and Conceptual Disorganization. Executive-frontal tests included Visual Search, Verbal Fluency, Verbal Series Attention, Trail Making - Part B, Symbol Digit, Hopkins Verbal Learning, Digit Span, Wisconsin Card Sorting, Stroop Color-Word and Attentional Capacity. The schizophrenia group showed significant deficits relative to healthy control subjects (n = 20) on all tests. Exploratory factor analysis of test scores revealed three factors: (i) Verbal Processing/Memory; (ii) Cognitive Flexibility/Attention; and (iii) Psychomotor Speed/Visual Scanning. The three symptom subgroups were differentially impaired on executive-frontal abilities: Withdrawal-Retardation on psychomotor speed, verbal fluency, working memory, visual search and cognitive flexibility; Conceptual Disorganization on attention; Reality Distortion on verbal memory. The results have implications for syndrome definition, pharmacological intervention and prediction of outcome in schizophrenia.

Neuropsychological correlates of negative, disorganized and psychotic symptoms in schizophrenia

Recent studies suggest that three dimensions (negative, disorganized and psychotic) categorize schizophrenic symptoms. A developing literature indicates distinct cerebral correlates of each symptom cluster, but few investigations have determined their neuropsychological correlates. In the present study, the Schedules of Negative and Positive Symptoms measured symptom severity in 62 schizophrenics, and a subsequent principal components analysis revealed three symptom dimensions. Factor scores, age and parental socio-economic status were simultaneously entered into regression equations to explain variance across a broad neuropsychological test battery. Negative symptoms were associated with deficits involving intelligence, executive function, memory, sustained-attention and sensory-motor function, whereas disorganized symptoms correlated with decreased intelligence, attention-span and sensory-motor function. Psychotic symptoms were unrelated to deficits. These data are consistent with hypotheses that these three symptom dimensions have distinct neurobehavioral correlates.

Relationships between changes in symptom ratings, neurophysiological test performance and quality of life in schizophrenic patients treated with clozapine

This study examined the correlations between reduction in symptoms, changes in neuropsychological test performance and improved quality of life in 19 schizophrenic outpatients treated with clozapine. Reduction in both negative symptoms and general psychopathology was associated with a better quality of life. Some improvement in neuropsychological test performance was found, with a variable pattern of association with change in psychopathology. Improved verbal fluency was associated with reduction in negative symptoms, while improved verbal concept formation was associated with reduction in positive symptoms.

Non-selective impairment of Wisconsin Card Sorting Test performance in patients with schizophrenia

Sixty-two schizophrenic patients and 26 healthy volunteers were administered the Wisconsin Card Sorting Test (WCST) a task putatively specific for frontal functions and the Wechsler Adult Intelligence Scale (WAIS). The purpose of this study was to evaluate the presence of specific frontal lobe deficits in the course of schizophrenia and the capacity of these tasks to discriminate between patients and controls. Schizophrenic patients showed a poorer performance than control subjects in both tests. No evidence emerged to support a higher discriminant power for the WCST in identifying schizophrenic subjects from healthy controls compared with the WAIS. Our data suggest that the deficit in WCST performance is not selective, but rather part of a more generalized neuropsychological impairment in schizophrenic patients.

Neuropsychological evidence supporting a neurodevelopmental model of schizophrenia: a longitudinal study

The stability of neuropsychological performance in schizophrenia and its relationship to clinical change was contrasted between 60 patients with schizophrenia (30 first-episode, 30 previously treated) and 38 healthy controls using a comprehensive neuropsychological battery and clinical scales administered at intake and at a 19-month follow-up. Consistent with the neurodevelopmental model of schizophrenia, patients demonstrated deficits in cognitive performance at initial testing and did not show decline at follow-up. There were no differences in neuropsychological performance over time between first-episode and previously treated patients, nor between male and female patients or controls. As expected, patients improved clinically with treatment with respect to both positive and negative symptoms. First-episode patients improved more on the positive symptoms of hallucination and delusion; male and female patients showed equivalent clinical improvement. Clinical improvement correlated positively with neuropsychological change, with improved negative symptomatology accounting for most of the significant correlations.

Construct validity of negative symptoms: an empirical and conceptual review

The construct validity of negative symptoms is reviewed, and findings on deficit negative symptoms are also incorporated. A valid negative symptom construct should: (a) have replicable relationships with observable phenomena and other constructs; (b) have good reliability, temporal stability, and homogeneity; and (c) predict prognosis and response to treatment, possess convergent and discriminant validity, and be useful to clinicians. Although a number of well-replicated findings provide support for the validity of the construct, modification is warranted. Specifically, the data suggest that there is a highly correlated set of negative symptoms, which includes flat affect, alogia, anhedonia, and avolition. Primary and enduring symptoms from this set have good predictive and discriminant validity and can be studied in the context of the deficit syndrome, as well as with current negative symptom rating scales. Future studies should examine whether deficit negative symptoms are better conceptualized as a dimension or a category, elucidate the relationship between deficit symptoms and additional clinical and behavioral variables (e.g., response to newer neuroleptic medications and diminished emotional responding), and explore differences between the pattern of correlates of deficit symptoms and those of the positive and thought disorder symptoms.

Reconsidering the gospel according to group studies: a neuropsychological case study approach to schizophrenia

Individual patterns of performance on tests of: visual perception, language, executive function, memory, and face-processing, were examined in 10 schizophrenic patients who were preselected for having current WAIS IQ and premorbid NART IQ scores in the normal range. Although the patients showed some heterogeneity in the type, pervasiveness, and degree of cognitive impairment, a majority had severely impaired verbal recall and familiar face-naming. This contrasted with the low incidence and severity of impairment on tests of executive function, visual recall, recognition memory, naming, and unfamiliar faceprocessing. Contrasts between individual patients indicated that verbal recall and executive performance are independent in some patients and that memory appears to be the core deficit. The profile of impaired and preserved cognitive function revealed some important dissimilarities from the pattern that has emerged from group studies. Finally, face-naming correlated highly with the learning of unrelated paired associates, confirming a similarity with neurological patients who have person name anomia. It is suggested that both deficits might reflect a problem with learning ''meaninglessness'' associations; this interpretation is discussed with reference to a deficit at the level of the Supervisory Attentional System (Shallice, 1988).

Performance on the Wisconsin Card Sorting Test in schizophrenia: perseveration in clinical subtypes

Results are reported from a neuropsychological investigation of a large group of schizophrenic patients (n = 141) and normal control subjects (n = 59) who performed the Wisconsin Card Sorting Test (WCST). The schizophrenic patients were divided into two DSM-III-R diagnostic subgroups: paranoid and nonparanoid schizophrenia. The performance of the WCST by schizophrenic patients was poor compared with that by normal control subjects; furthermore, paranoid patients made a higher number of perseverative errors than did nonparanoid patients. The deficit in WCST performance, which has been widely reported to characterize patients with schizophrenia, appears to be related to the clinical profile and neuropathological differences that contribute to the heterogeneity of the disorder.

Memory impairment in schizophrenia: its' relationship to executive function

The presence of memory impairment in schizophrenia has frequently been documented but much less attention has been given to the qualitative aspects of this impairment and its association to executive function. Using a cognitive-process approach, we examined memory and executive function in 25 patients who met DSM-III-R criteria for schizophrenia. Patients were matched with 25 healthy volunteers. The schizophrenic group was found to have a significant impairment in immediate memory, with relatively spared long-delay memory. Performance on verbal learning and recognition memory was similar to that of controls. Memory deficits were present irrespective of the encoding strategies used and were unrelated to chronicity. In addition, the schizophrenics performed worse than controls on tests of executive function, but the degree of impairment was greater on tests of response initiation and suppression. This pattern of performance resembled that found in patients with subcortical or frontal lesions which was supported by some significant correlations between aspects of memory and executive function. Our results suggest that in schizophrenia, specific executive functions may make a selective contribution to the pattern of memory performance in schizophrenia which is subserved by frontal and to a lesser extent hippocampal/diencephalic systems.

Semantic memory is impaired in schizophrenia

Memory is emerging as a key area of neuropsychological deficit in schizophrenia, with evidence suggesting that the impairment is restricted to long-term memory. Semantic memory, the component of long-term memory containing stored representations of the meanings of words and knowledge about the world, was examined in 46 schizophrenic patients and 40 normal controls using a recently devised battery of tests. Evidence of semantic memory impairment was found which was wide ranging and substantial; in some cases it approached the levels seen in a group of 22 patients with mild-to-moderate Alzheimer's disease. Both group analysis and a more detailed examination of two single cases suggested that semantic memory impairment represents a disproportionate and possibly specific neuropsychological deficit in schizophrenia.

Assessing declarative memory in schizophrenia using Wisconsin Card Sorting Test stimuli: the Paired Associate Recognition Test

The Paired Associate Recognition Test (PART) was developed to measure declarative memory using Wisconsin Card Sorting Test (WCST) stimuli, so that both tasks could be administered during functional neuroimaging to differentiate memory and executive function, and associated frontal and temporal lobe activation in schizophrenia. The current study was designed to compare PART and WCST performance in schizophrenic patients and to examine effects of medication and symptomatology. The PART, WCST, and standard declarative memory tasks were administered to 30 chronic schizophrenic patients and 30 matched healthy control subjects. Supporting task validity was the finding that patients were equally impaired on the PART and the WCST. Neuroleptics did not appear to affect performance. The effect of anticholinergic medication correlated negatively with WCST performance in a small subsample. Severity of schizophrenia-specific symptoms measured at intake on the Brief Psychiatric Rating Scale correlated negatively with performance on the WCST. These results support the application of the PART and WCST in future functional neuroimaging studies.

Negative symptoms, neurological signs and neuropsychological impairments in 204 Hong Kong Chinese patients with schizophrenia

BACKGROUND

Studies of the relationship between negative symptoms, neuropsychological impairments and neurological signs in schizophrenia have yielded inconsistent results. In addition, little attention has been directed to address the extent of cultural modulation of negative symptoms.

METHOD

We carried out cross-cultural validation of the High Royds Evaluation of Negativity Scale (HEN) in 50 Hong Kong Chinese patients with schizophrenia. We then investigated the relationship between negative symptoms, neurological signs and neuropsychological impairment in 204 patients.

RESULTS

Good interrater reliability, internal reliability, convergent and discriminant validity were found with the HEN. The HEN contained four factors corresponding to 'behaviour', 'functioning', 'thought' and 'appearance'. Negative symptoms were correlated with semantic fluency but not with Wisconsin Card Sorting Test performance or sustained attention. Negative symptoms were also correlated with tardive dyskinesia and catatonia but not with soft neurological signs.

CONCLUSIONS

Cross-cultural robustness of the negative symptoms construct is supported. Association of negative symptoms with a specific profile of neurocognitive impairment suggests diversity within deficit domains in schizophrenia.

Verbal fluency in schizophrenia: relationship with executive function, semantic memory and clinical alogia

To examine whether poor verbal fluency in schizophrenia represents a degraded semantic store or inefficient access to a normal semantic store, 25 normal volunteers and 50 DSM-III-R schizophrenic patients, matched for age, sex and IQ, were recruited. Although schizophrenic patients were impaired on both letter and category fluency, they showed a normal pattern of output in that category was superior to letter fluency, and an improvement in category fluency when a cueing technique was employed (Randolph et al. 1993). These results resemble those found in disorders of frontostriatal systems (Parkinson's and Huntington's disease) and suggest that poor verbal fluency in schizophrenia is because of inefficient access to semantic store. A measure of improvement with cueing was directly related to performance on the Stroop executive task. Of all symptom measures derived from SANS and Manchester Scales, only alogia was related to verbal fluency in that superior improvement correlated inversely with the degree of alogia. It is suggested that both alogia and poor verbal fluency are mediated by the same underlying cognitive abnormality that reflects frontostriatal dysfunction.

Schizophrenic syndrome and Wisconsin Card Sorting Test dimensions

A principal component analysis of Wisconsin Card Sorting Test (WCST) scores has recently shown three factors. Only the Perseveration factor may measure the activity of the dorsolateral prefrontal cortex in schizophrenic patients. Liddle has hypothesized that a dysfunction in this area is specifically related to the negative syndrome and not to other schizophrenic syndromes (positive and disorganization). The factor analysis of the WCST was replicated with similar results in 38 schizophrenic or schizoaffective patients. In the total group, the correlation between the negative syndrome and the Perseveration factor did not reach significant levels. In the patients with a DSM-III-R diagnosis of schizophrenia (n = 30), the correlations did reach significant levels.

Neuropsychological deficit in newly diagnosed patients with schizophrenia or schizophreniform disorder

Forty-six patients with schizophrenia or schizophreniform disorder admitted to hospital for the first time were compared with 21 healthy volunteers on neuropsychological tests reflecting prefrontal and left respectively right hemisphere function. The patients with schizophrenia or schizophreniform disorder had a poorer performance on neuropsychological tests (such as Wisconsin Card Sorting) compared with healthy volunteers. Both left and right hemisphere seemed to be involved. Especially poor performance was found on somewhat complicated tests requiring ability of analysis, abstraction and memory, thus indicating dysfunction of prefrontal and temporohippocampal regions. Signs of sulcal enlargement and size of lateral ventricles on computed tomographic scan correlated with poor test performance on some tests both in patients and in healthy volunteers. No correlations were found between performance on neuropsychological test and negative symptoms.

Cognitive features of psychotic states arising in late life (late paraphrenia)

The cognitive performance of 47 elderly psychotic patients with onset of symptoms in late life (late paraphrenia) was compared to that of 33 controls matched for age, sex, ethnic origin, number of years of education, and pre-morbid IQ as measured by the NART. Neuropsychological indices of general cognitive functioning (MMSE, CAMCOG, WAIS-R verbal and performance scores) showed that patients were performing the tasks at a significantly lower level than controls. Patients also showed a trend to have a lower span capacity than controls, particularly at the spatial span subtest. There was no obvious impairment of learning as measured by the digit and spatial recurring span tasks nor of simultaneous matching-to-sample ability. However, patients' performance on a delayed-matching-to-sample procedure was significantly worse than that of controls. In addition, patients performed worse than controls on the Recognition Memory Test for Faces, but not for Words. Finally, the performance of patients on tests assessing executive functioning (Verbal Fluency Test, Computerized Extra and Intra-Dimensional Shift Task, Computerized Spatial Working Memory Task, and Computerized Tower of London Task) was consistently worse than that of controls. These results suggest that psychotic states arising in late life are predominantly associated with a decline on measures of general cognitive ability and executive functioning. The neuropsychological meaning of these findings is discussed in the light of cognitive models of psychotic symptoms, as well as of schizophrenia and dementia research. We concluded that the lack of a clear pattern of impairment among these patients may be the result of their clinical and cognitive diversity.

The neuropsychology of schizophrenia: relations with clinical and neurobiological dimensions

It is now beyond question that the symptoms observed in schizophrenia include a range of cognitive neuropsychological deficits that may be more enduring than psychotic symptoms (Cassens et al. 1990; Goldberg et al. 1993) Goldberg et al. (1993) found that a group of patients treated with clozapine whose psychotic symptoms improved significantly over a 15 month study period showed no improvement in cognitive impairments. He argued that the enduring cognitive deficits are responsible for failure of patients to rehabilitate socially even when psychotic symptoms are in remission. Clearly an understanding of neuropsychological deficits is Important from a clinical as well as a theoretical viewpoint. There is, however, still much debate about the nature of these deficits and how they related to the psychotic symptoms of schizophrenia and also to the neurobiological substrate of this disorder.

Dysfluency in Huntington's disease, Parkinson's disease and schizophrenia

Verbal fluency was compared in Huntington's disease (n=12), Parkinson's disease (n=25) and schizophrenia (n=18) with a series of fluency tasks evaluating the effects on productivity of cuing with subordinate categories and alternation between fluency probes. Findings indicated reduced output in the patient groups across all tasks consistent with a difficulty in intrinsic generation. A significant group interaction was observed with cue provision, but not with alternation. The facilitation of performance with cuing in all groups suggests a common mechanism of disruption in these disorders, most likely reflecting interruption of the prefrontal modulation of retrieval processes. To explain the observed pattern, we propose that the semantic retrieval anomaly in these disorders reflects a difficulty in intrinsic extra-dimensional shift. Verbal productivity was significantly associated with negative dimensions of schizophrenia, such as poverty of speech and flattened affect, a finding that is discussed in terms of the neurocognitive heterogeneity of schizophrenia and theories of cognitive dysfunction in subtypes of this disorder.

Memory function in schizophrenia

Memory impairment in schizophrenia has been reported in several studies during the last decades. Issues related to the interpretation of such deficits are discussed. Research strongly suggests specific memory dysfunction in schizophrenia that may be neither drug induced nor secondary consequences of attentional disorders. Our own longitudinal data indicate that these deficits deviate from normal function in a relatively stable way. Although medial temporal lobe structures seems to be of special importance, memory function may be vulnerable to a variety of neurobiological abnormalities.

Symptom dimensions and cognitive and social functioning in recent-onset schizophrenia

The relationships among symptoms, cognitive functioning and social functioning were investigated in 60 patients with recent-onset schizophrenia. Positive symptoms were unrelated to cognitive measures. Disorganization and depressive symptoms were correlated significantly with Card Sorting performance. Furthermore, only negative symptoms were correlated significantly with social functioning. These results replicate earlier studies with chronic and mixed samples, and support the validity of disorganization as a separate symptom dimension. In contrast to most previous studies, no significant correlations were found between negative symptoms and cognitive measures. However, some evidence was found for a non-linear association between negative symptoms had several cognitive measures. The variation explained by a curvilinear model was not high, but for some cognitive measures this model was clearly superior to a linear model. If replicated, this finding supports the position that cross-sectionally measured negative symptoms cannot be viewed as a unitary concept.

Cognitive functioning and anhedonia in subjects at risk for schizophrenia

This study investigated the performance of individuals with familiar loading of schizophrenia (healthy siblings of schizophrenic inpatients) on three neuropsychological tasks assumed to require frontal lobe functions: Trail Making Test (TMT), verbal fluency and Wisconsin Card Sorting Test (WCST). Healthy siblings of schizophrenics differed in performance from healthy controls not only on the WCST, but also on the Trail Making Test and the verbal fluency task. Furthermore, scores of physical anhedonia, assessed in a self-report rating scale (Chapman et al., 1976) were also significantly higher in the high risk group than in the control sample. However, healthy siblings of schizophrenics did not differ from controls with regard to experiences of perceptual aberrations, measured by the same method (Chapman et al., 1978). Neuropsychological performance and elevated anhedonia scores in the high risk group were interpreted under the conceptual framework of vulnerability markers: they were supposed to represent a trait shared by family members of schizophrenic probands. Amongst the neuropsychological tests, there were significant correlations between the physical anhedonia score and WCST and Trail Making test performance in the group of healthy siblings of schizophrenics, but not in the control group.