A longitudinal analysis of memory in patients with schizophrenia

Memory deficits are widely reported in patients with schizophrenia, but uncertainties remain about the extent and the longitudinal course of these deficits. Twenty-eight patients with a DSM-IV diagnosis of schizophrenia were tested on multiple aspects of memory at baseline, 9- and 18-month follow-up. Measures included: digit span, the Rivermead Behavioural Memory test (RBMT) battery, the Graded Naming Test (GNT) and several computerized memory tests from the Cambridge Automated Neuropsychological Testing Battery (CANTAB). A group of healthy controls (N=17) was tested on the CANTAB battery at baseline and 9-month follow up. The patients performed significantly poorer than controls on all CANTAB measures; however, there was no difference in change between groups over a 9-month period. Within-group patient comparisons revealed that symptoms reduced significantly over the study period, but had no association with memory. Significant improvements were observed for patients on two verbal memory tasks: the GNT and digit span, but not on any other measure. Interestingly, these were the only two tests on which patients were within normal limits at baseline. This study shows that patients with schizophrenia have deficits in multiple aspects of memory which remain stable over long periods of time. In addition, patients showed a tendency to improve on memory tasks which contained a verbal component.     

Verbal working memory impairment in schizophrenia patients and their first-degree relatives: evidence from the digit span task

OBJECTIVE: The evidence for verbal working memory deficits in schizophrenia has been inconsistent. Few studies have evaluated verbal working memory in the first-degree relatives of schizophrenia patients, who likely share the genetic diathesis for schizophrenia but not the potential confounds associated with chronic mental illness. METHOD: The Wechsler Digit Span Task was used to investigate verbal working memory in 52 schizophrenia patients, 56 of their first-degree relatives, and 73 nonpsychiatric comparison subjects. RESULTS: The nonpsychotic relatives showed no impairment on the forward digit span task, a measure of general attention, but did show impairment on the backward digit span task, a measure of verbal working memory. Schizophrenia patients showed impairment on both the forward and backward digit span tasks. CONCLUSIONS: These results indicate that the forward and backward digit span tasks tap different cognitive abilities that are differentially associated with the diathesis for schizophrenia. Working memory deficits associated with schizophrenia appear to be generalized and not limited to the spatial modality.     

Short-term memory treatment: patterns of learning and generalisation to sentence comprehension in a person with aphasia

Auditory-verbal short-term memory deficits (STM) are prevalent in aphasia and can contribute to sentence comprehension deficits. This study investigated the effectiveness of a novel STM treatment in improving STM (measured with span tasks) and sentence comprehension (measured with the Token Test and the Test for the Reception of Grammar, TROG) in a person with severe aphasia (transcortical motor). In particular, the research questions were: (1) Would STM training improve STM? (2) Would improvements from the STM training generalise to improvements in comprehension of sentences? STM was trained using listening span tasks of serial word recognition. No other language or sentence comprehension skills were trained. Following treatment, STM abilities improved (listening span, forward digit span). There was also evidence of generalisation to untreated sentence comprehension (only on the TROG). Backward digit span, phonological processing and single word comprehension did not improve. Improvements in sentence comprehension may have resulted from resilience to rapid decay of linguistic representations within sentences (words and phrases). This in turn facilitated comprehension.     

认知矫正治疗慢性精神分裂症患者认知功能缺陷的随机对照研究

目的 探讨认知矫正治疗(CRT)和计算机认知矫正治疗(CCRT)对精神分裂症患者认知缺陷的疗效.方法 180例慢性期病情稳定的精神分裂症患者随机分成3组,CCRT组、CRT组和工娱治疗(WAT)组.CCRT组108例,治疗以自主开发的计算机认知矫正治疗系统为工具,每周4次,每次45 min,持续3个月;CRT组36例,以Ann Delahunty和Rodney Morice等制定的神经认知矫正手册(汉化)为治疗工具,在治疗师的指导下进行认知矫正治疗;WAT组36例,接受相同时间的工娱治疗.3组在治疗频度和治疗持续时间上完全一致.治疗前后及治疗结束后第3个月分别进行临床症状和认知功能评定,内容包括阳性和阴性症状量表(PANSS)、精神分裂症认知功能成套测验(MCCB)、威斯康星卡片分类测验(WCST).结果 治疗结束后及随访第3个月时,CCRT组和CRT组在改善WCST完成分类数、连线测验、空间广度方面显著优于WAT组(P均＜0.05);CCRT组在空间广度方面明显优于CRT组(P＜0.05),CRT组在符号编码方面则优于CCRT组(P＜0.05);3组的临床症状在治疗结束及随访阶段无明显变化.结论 CCRT和CRT均能显著改善慢性精神分裂症患者的认知功能,主要表现在记忆、执行功能、精神运动速度方面;CCRT在空间记忆方面较CRT有优势,CRT在精神运动方面较CCRT有优势,CCRT和CRT在执行功能、记忆、精神运动速度等方面的疗效能持续3个月.     

Cognitive training of verbal memory using a dichotic listening paradigm: impact on symptoms and cognition

OBJECTIVE: The objective was to investigate the impact of a verbal memory training task on psychiatric symptoms and cognition in schizophrenia. METHOD: As part of a larger, 6-month cognitive remediation program, 57 patients with schizophrenia were randomly assigned to receive performance-based, hierarchical training on a verbal memory task based on a dichotic listening (DL) with distracter paradigm. These patients were compared with 68 patients who had been randomly assigned to a control condition. RESULTS: Training on the DL task was not associated with changes in general psychopathology or auditory hallucinations (AH) specifically. Training was associated with improvements in verbal memory, but not attention. CONCLUSION: The current investigation adds to the growing literature on the effectiveness of cognitive remediation training and indicates that training on the DL task enhances verbal episodic memory. The results do not support the use of DL training as a method for reducing AH.     

Computerized cognitive remediation improves verbal learning and processing speed in schizophrenia

Computerized cognitive remediation has resulted in improved executive function in schizophrenia, whereas results with regard to verbal memory were inconsistent. In the present study, 42 inpatients with schizophrenia were randomly assigned to a computerized cognitive remediation group or to a treatment-as-usual (TAU) control group. The remediation group received 15 sessions of computerized cognitive training (Cogpack) over a 3-week period. Neurocognitive functions were assessed at the beginning and end of this period. Compared to the control condition, remediation training resulted in improvements in verbal learning, processing speed and executive function (verbal fluency). The results indicate that cognitive remediation may lead to improvements beyond those of executive function.     

The gains of a 4‐week cognitive training are not modulated by novelty

Cognitive training should not only improve performance of the trained task, but also untrained abilities. Exposure to novelty can improve subsequent memory performance, suggesting that novelty exposure might be a critical factor to promote the effects of cognitive training. Therefore, we combined a 4‐week working memory training with novelty exposure. Neuropsychological tests and MRI data were acquired before and after training to analyze behavior and changes in gray matter volume, myelination, and iron levels. In total, 83 healthy older humans participated in one of three groups: Two groups completed a 4‐week computerized cognitive training of a two‐back working memory task, either in combination with novel or with familiarized nature movies. A third group did not receive any training. As expected, both training groups showed improvements in task specific working memory performance and reaction times. However, there were no transfer or novelty effects on fluid intelligence, verbal memory, digit‐span, and executive functions. At the neural level, no significant micro‐ or macrostructural changes emerged in either group. Our findings suggest that working memory training in healthy older adults is associated with task‐specific improvements, but these gains do not transfer to other cognitive domains, and it does not lead to structural brain changes.     

A Multisite,Randomized Controlled Clinical Trial of Computerized Cognitive Remediation Therapy for Schizophrenia

The effectiveness of cognitive remediation therapy (CRT) for the neuropsychological deficits seen in schizophrenia is supported by meta-analysis. However, a recent methodologically rigorous trial had negative findings. In this study, 130 chronic schizophrenic patients were randomly assigned to computerized CRT, an active computerized control condition (CC) or treatment as usual (TAU). Primary outcome measures were 2 ecologically valid batteries of executive function and memory, rated under blind conditions; other executive and memory tests and a measure of overall cognitive function were also employed. Carer ratings of executive and memory failures in daily life were obtained before and after treatment. Computerized CRT was found to produce improvement on the training tasks, but this did not transfer to gains on the primary outcome measures and most other neuropsychological tests in comparison to either CC or TAU conditions. Nor did the intervention result in benefits on carer ratings of daily life cognitive failures. According to this study, computerized CRT is not effective in schizophrenia. The use of both active and passive CCs suggests that nature of the control group is not an important factor influencing results.Key words: schizophrenia, cognition, neuropsychology, cognitive remediation     

Arithmetic fact retrieval and working memory in schizophrenia.

Despite its importance in every-day life and vocational rehabilitation, arithmetic ability has rarely been investigated in schizophrenic patients. Those few studies reporting arithmetic deficits in schizophrenia, however, administered complex calculation tasks which drew not only on arithmetic abilities, but also on working memory resources known to be impaired in schizophrenia. In the present study, arithmetic abilities and working memory functions were investigated in schizophrenic patients (n=24) and healthy control subjects (n=24). Arithmetic fact retrieval was assessed in single-digit multiplication and corresponding division problems using a result verification task which minimized working memory demands. Problem size and the disparity of the proposed result were manipulated. The storage component of working memory was tested with a digit span forward task and the executive control component with a digit span backward as well as with verbal fluency tasks. Schizophrenic patients performed worse than controls only in the executive tasks. Digit span forward was preserved. In the arithmetic tasks, groups did not differ from each other, and a similar pattern of task manipulations was obtained. Hence, despite the executive control deficit retrieval of arithmetic facts is preserved in schizophrenia. Moreover, the same underlying cognitive processes as in control subjects are involved.     

Measures of short-term memory: a historical review

Following Ebbinghaus (1885/1964), a number of procedures have been devised to measure short-term memory using immediate serial recall: digit span, Knox's (1913) cube imitation test and Corsi's (1972) blocks task. Understanding the cognitive processes involved in these tasks was obstructed initially by the lack of a coherent concept of short-term memory and later by the mistaken assumption that short-term and long-term memory reflected distinct processes as well as different kinds of experimental task. Despite its apparent conceptual simplicity, a variety of cognitive mechanisms are responsible for short-term memory, and contemporary theories of working memory have helped to clarify these. Contrary to the earliest writings on the subject, measures of short-term memory do not provide a simple measure of mental capacity, but they do provide a way of understanding some of the key mechanisms underlying human cognition.     

A central executive deficit in patients with Parkinson''s disease.

Eight patients with Parkinson's disease and eight matched controls were tested for concurrent task performance to examine whether Parkinson's disease produces deficits in the coordinating and integrating function of the central executive component of Baddeley's working memory model. Consistent with this prediction, the patients showed a significant decline in performance on a random pursuit tracking task while recalling digit span forward sequences, whereas the controls showed no such change. Performance on the component pursuit and digit span tasks, which did not differ between groups, was equated across subjects by varying the size of a target square and by using individual subjects' digit spans. The patient group also produced poorer word fluency scores and reported higher levels of depression, but there was no significant impairment on the Wisconsin card sort test. There was no association between dual task performance and any psychometric measure, target size, or disease related variables. Baddeley's working memory model is advantageous in providing a rich conceptual basis to explore and characterise cognitive abilities in patients with Parkinson's disease.     

Prefrontal cognitive deficits in patients with schizophrenia treated with atypical or conventional antipsychotics.

Forty-three patients with schizophrenia were investigated with a short neurocognitive screening battery focussing on working memory and executive functions. As compared to healthy controls, patients showed impairments in the modified card sorting test, in verbal fluency and all span tasks with exception of digit span forward. Patients who were treated with atypicals showed better performance in the digit ordering test (manipulation task) when compared to a group of patients who received conventional antipsychotics; this difference was not due to disease severity, age or education. Manipulation tasks might be useful for neurocognitive follow-up and intervention studies.     

The effects of neurocognitive remediation on executive processing in patients with schizophrenia.

Approaches to cognitive remediation have differed across studies. Most of the larger studies have concentrated on group treatments designed without the benefit of recent laboratory-based studies. The current study describes a randomized trial of an intensive cognitive remediation program involving individual daily sessions of 1 hour for up to 3 months. It targets executive functioning deficits (cognitive flexibility, working memory, and planning) that are known to be problematic in people with schizophrenia. Procedural learning, as well as the principles of errorless learning, targeted reinforcement, and massed practice, was the basis of the intervention. The program was compared with an alternative therapy (intensive occupational therapy) to control for some of the effects of therapeutic contact. Some improvements in cognition followed both therapies. A differential effect in favor of cognitive remediation therapy was found for tests in the cognitive flexibility and the memory subgroups. There was a trend for those receiving atypical antipsychotic medication to benefit more from cognitive remediation for tests of cognitive flexibility. Although there were no consistent changes in symptoms or social functioning between groups, if improvement in cognitive flexibility tasks reached a threshold then there is some evidence that social functioning improved, even over the short duration of the trial. In addition, cognitive remediation differentially improved self-esteem. This study supports the view that cognitive remediation can reduce cognitive deficits and that this reduction may affect social outcome, at least in the short term.     

Impact of intellectual status on response to cognitive task training in patients with schizophrenia

Cognitive remediation is a promising rehabilitation procedure for people with schizophrenia, but very little is known about who can benefit. In the current analyses, we examined the role of pre-morbid and morbid intellectual function in predicting response to cognitive remediation in a sample of 152 patients diagnosed with schizophrenia or schizoaffective disorder. They were participants in a trial of work therapy and cognitive remediation and had been randomized to receive either Neurocognitive Enhancement Therapy with Work Therapy (NET+WT) or Work Therapy only (WT only). For the current analyses, patients were divided into three intellectual subgroups based on their pattern of premorbid and morbid deficits (preserved intelligence, compromised intelligence, and deteriorated intelligence), and their cognitive remediation outcomes were examined. Cognitive remediation response was measured in two ways: normalization of performance on a computerized training task, and pre-post neuropsychological test performance. Subjects in NET+WT showed greater improvement in cognition than those in WT only, but response differed by intellectual group. For patients in the compromised group, those in NET+WT showed a significantly higher proportion of task normalization than those in the WT only condition, but no such differences were found with the preserved and deteriorated intellectual groups. For patients in the preserved and deteriorated intellectual groups, those in the NET+WT condition showed significantly greater improvement in the analysis of pre-post neuropsychological test performance, but this difference was not found in the compromised intellectual group. These findings suggest that the compromised intellectual group, which had the lowest frequency of normal performers at intake, benefited from NET by achieving dramatic increases in normalization, but that they had difficulty in generalizing these gains to untrained tasks. Those in the preserved and deteriorated intellectual groups were more successful in generalizing their training.     

Cognition in dysthymia

Depression is named as one of the most prevalent Mental Health problem, affecting almost 10 % of the population. According to Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) different subtypes are included. Dysthymic Disorder is characterized by a depressed mood for most of the day, for more days than not, as indicated either by subjective account or observation by others, for at least 2 years. The aim of this study was to investigate the neuropsychological profile of dysthymic disorder. Ninety three patients fulfilling criteria for dysthymia were examined on a variety of cognitive tasks, neurological exam and a semi-structured psychiatric interview. Forty one non-depressed individuals served as controls. Significant differences between groups were found in digit span; immediate and delayed recall of a story; and semantic and phonologic fluency. Logic memory was worse than serial learning task, and has a correlation with attention deficit and depressive features. Conclusions: This results indicate that the neuropsychological performance of patients with dysthymic disorder exhibit impairments in attention and memory. Attentional deficits appear to be the key of cognitive deficits in dysthymia.     

Performance of Individuals with Left-Hemisphere Stroke and Aphasia and Individuals with Right Brain Damage on Forward and Backward Digit Span Tasks

BACKGROUND: Working memory (WM) limitations have been suggested as a significant source of the linguistic processing deficits observed in individuals with aphasia (IWA). Digits forward (DF) and digits backward (DB) span tasks are frequently used to study WM in both healthy and clinical populations. Unfortunately, only a handful of studies have explored digit span in IWA. AIMS: The purpose of the current study is to measure the DF and DB spans of IWA and compare their digit spans to a group with right brain damage, but no aphasia (RBD). Additionally, DF and DB span is compared within each group to determine if there is indeed a performance differential that may support the idea that DB is a more difficult WM task in these populations. METHODS AND PROCEDURES: Seventeen IWA and 14 individuals with RBD participated in a DF and DB span task. Modifications to the span tasks were implemented to accommodate language deficits. A series of two digits were orally presented to each participant continuing to a maximum of eight digits. There were seven trials per digit series. Participants were asked to point to the correct order of digits on a written 1-9 digit list provided on individual note cards or verbally repeat the numbers if the participant was able to do so. OUTCOMES AND RESULTS: IWA demonstrated shorter digit spans than the RBD group. Both groups performed worse on the DB span tasks than the DF span tasks. CONCLUSIONS: The results are consistent with previous studies suggesting that DB span is shorter than DF span in other populations and that there are differences in performance on digit span tasks between the two groups. The differences between RBD group and IWA may be explained by decreased attentional capacity or inefficient resource allocation in IWA, or alternatively, a deficient phonological loop. Future studies should explore these possibilities.     

Cognitive remediation of working memory deficits: durability of training effects in severely impaired and less severely impaired schizophrenia

OBJECTIVE: To determine whether augmenting work therapy (WT) with neurocognitive enhancement therapy (NET) yields greater improvement in working memory performance than WT alone and whether there is an interaction with severity of impairment. METHOD: A total of 102 participants with schizophrenia or schizoaffective disorder were categorized as severely or less severely cognitively impaired and randomly assigned to receive NET + WT or WT alone. NET consisted of cognitive training exercises in attention, memory, executive function, and social information processing, and WT was a 6-month work program. RESULTS: Comparison on Digits Backwards from intake to follow-up revealed significantly greater improvement for participants receiving NET + WT, but there was no interaction with severity group. Follow-up 6 months after training showed that training effects endured. CONCLUSION: NET + WT improved working memory for most participants regardless of impairment severity. Intensity and duration of training may have contributed to duration of effects. Findings support continued exploration of cognitive remediation.     

Schizophrenics show spatial working memory deficits.

The present study demonstrates that schizophrenics are impaired on spatial delayed-response tasks, analogous to those that have been used to assess the working memory function of the dorsolateral prefrontal cortex in rhesus monkeys. Schizophrenic patients and two control groups, normal subjects and bipolar psychiatric patients, were tested on the oculomotor version of the memory task, a haptic version of the same task, and two control tasks: a sensory task that did not require working memory and a digit span test. The schizophrenic patients showed marked deficits relative to the two control groups in both the oculomotor and haptic delayed-response tasks. They were not, however, impaired on the digit span test, which taps verbal working memory as well as voluntary attention, and on the sensory control task, in which their responses were guided by external cues rather than by spatial working memory. These findings provide direct evidence that schizophrenics suffer a loss in representational processing and that this deficit is modality independent. These data on spatial working memory add to the growing evidence for involvement of the dorsolateral prefrontal cortex in schizophrenic disease.     

Expectancy-Value Theory in Persistence of Learning Effects in Schizophrenia: Role of Task Value and Perceived Competency

Expectancy-value theory, a widely accepted model of motivation, posits that expectations of success on a learning task and the individual value placed on the task are central determinants of motivation to learn. This is supported by research in healthy controls suggesting that beliefs of self-and-content mastery can be so influential they can predict the degree of improvement on challenging cognitive tasks even more so than general cognitive ability. We examined components of expectancy-value theory (perceived competency and task value), along with baseline arithmetic performance and neuropsychological performance, as possible predictors of learning outcome in a sample of 70 outpatients with schizophrenia randomized to 1 of 2 different arithmetic learning conditions and followed up after 3 months. Results indicated that as with nonpsychiatric samples, perceived self-competency for the learning task was significantly related to perceptions of task value attributed to the learning task. Baseline expectations of success predicted persistence of learning on the task at 3-month follow-up, even after accounting for variance attributable to different arithmetic instruction, baseline arithmetic ability, attention, and self-reports of task interest and task value. We also found that expectation of success is a malleable construct, with posttraining improvements persisting at follow-up. These findings support the notion that expectancy-value theory is operative in schizophrenia. Thus, similar to the nonpsychiatric population, treatment benefits may be enhanced and better maintained if remediation programs also focus on perceptions of self-competency for the training tasks. Treatment issues related to instilling self-efficacy in cognitive recovery programs are discussed.     

Spatial working memory deficits and clinical symptoms in schizophrenia: a 4-month follow-up study.

BACKGROUND: Our goal was to examine spatial working memory function in relation to clinical symptoms of schizophrenia over a period of 4 months. METHODS: We assessed spatial working memory, spatial detection and clinical symptoms in 34 acutely psychotic schizophrenia patients within the first 2 weeks of hospitalization, and 4 months later. Spatial working memory was assessed by a delayed response task. A spatial control task was included to rule out simple sensorimotor deficits. Positive and negative symptoms were assessed by the Positive and Negative Syndrome Scale (PANSS). Thirty-nine matched normal control subjects were also examined on the same tasks over the same period. RESULTS: Patients showed deficits in working memory, but they performed well on the spatial control task. Both positive and negative symptoms improved at the 4-month follow up. Spatial working memory also improved over time but there was still a significant deficit at the follow-up session. CONCLUSIONS: These results indicate that both symptoms and spatial working memory improved 4 months after the initial hospitalization but spatial working memory, hypothesized to be mediated by the dorsolateral prefrontal system, did not normalize. Thus, spatial working memory deficit may be a stable marker for schizophrenia.