Memory and organizational strategies in chronic and acute schizophrenic patients

Eye-tracking training improves the learning and memory of children with learning difficulty

Children who experience difficulty in learning at mainstream schools usually are provided with remediation classes after school to facilitate their learning. The present study aims to evaluate an innovative eye-tracking training as possible alternative remediation. Our previous findings showed that children who received eye-tracking training demonstrated improved attention and inhibitory control, and the present randomized controlled study aims to evaluate if eye-tracking training can also enhance the learning and memory of children. Fifty-three primary school students with learning difficulty (including autism spectrum disorder, attention-deficit/hyperactivity disorder, specific learning disorder, specific language impairment and borderline intellectual functioning) were recruited and randomly assigned to either the Eye-tracking Training group or the after-school remediation class. They were assessed on their learning and memory using the Hong Kong List Learning Test before and after 8-month training. Twenty weekly parallel sessions of training, 50 min per session, were provided to each group. Children who received the eye-tracking training, not those in the control group, showed a significant improvement in memory as measured by the delayed recall. In addition, the Eye-Tracking Training group showed significantly faster learning than the control group. Also, the two groups showed a significant improvement in their reading abilities. In sum, eye-tracking training may be effective training for enhancing the learning and memory of children with learning difficulties.

The neural and molecular basis of working memory function in psychosis: a multimodal PET-fMRI study

Working memory (WM) deficits predict clinical and functional outcomes in schizophrenia but are poorly understood and unaddressed by existing treatments. WM encoding and WM retrieval have not been investigated in schizophrenia without the confounds of illness chronicity or the use of antipsychotics and illicit substances. Moreover, it is unclear if WM deficits may be linked to cannabinoid 1 receptor dysfunction in schizophrenia. Sixty-six volunteers (35 controls, 31 drug-free patients with diagnoses of schizophrenia or schizoaffective disorder) completed the Sternberg Item-Recognition paradigm during an fMRI scan. Neural activation during WM encoding and WM retrieval was indexed using the blood-oxygen-level-dependent hemodynamic response. A subset of volunteers (20 controls, 20 drug-free patients) underwent a dynamic PET scan to measure [11C] MePPEP distribution volume (ml/cm3) to index CB1R availability. In a whole-brain analysis, there was a significant main effect of group on task-related BOLD responses in the superior parietal lobule during WM encoding, and the bilateral hippocampus during WM retrieval. Region of interest analyses in volunteers who had PET/fMRI indicated that there was a significant main effect of group on task-related BOLD responses in the right hippocampus, left DLPFC, left ACC during encoding; and in the bilateral hippocampus, striatum, ACC and right DLPFC during retrieval. Striatal CB1R availability was positively associated with mean striatal activation during WM retrieval in male patients (R = 0.5, p = 0.02) but not male controls (R = -0.20, p = 0.53), and this was significantly different between groups, Z = -2.20, p = 0.02. Striatal CB1R may contribute to the pathophysiology of WM deficits in male patients and have implications for drug development in schizophrenia.

Evaluation of a computer-assisted cognitive remediation program for young people with psychosis: A pilot study

Background

People with psychosis have a range of neuropsychological impairments that impact their functional abilities and rehabilitation outcomes. We designed a Computer-Assisted Cognitive Remediation (CACR) program to help young people with psychosis to restore their cognitive function. The program combines the drill-and-practice approach and the strategic approach to remediation, with sixteen sessions of computerized cognitive training, two sessions of psychoeducation, and four session of coaching on applying cognitive skills to daily life.

Method

This was a randomized, single-blind, controlled study in which the outcomes of the CACR program were compared with outcomes of a treatment-as-usual (TAU) control group. Pre-intervention and post-intervention measures were compared.

Results

When compared with the control group, the intervention group had significant increases in their MCCB neurocognitive composite scores, and specifically in the areas of verbal learning and speed of processing at posttest. They also had significant increases in their secondary outcome measures of mental well-being and perceived occupational competence. There were no significant differences in functional status between the two groups at post-test.

Conclusions

The CACR program was effective in improving overall cognitive function and in the specific domains of verbal learning, speed of processing, and effect sizes were small. Participants also experienced positive changes in mental well-being and perceived competence.

Medial Temporal Lobe Atrophy is Related to Learning Strategy Changes in Amnestic Mild Cognitive Impairment

OBJECTIVE

Deficits in the semantic learning strategy were observed in subjects with amnestic mild cognitive impairment (aMCI) in our previous study. In the present study, we explored the contributions of executive function and brain structure changes to the decline in the semantic learning strategy in aMCI.

METHODS

A neuropsychological battery was used to test memory and executive function in 96 aMCI subjects and 90 age- and gender-matched healthy controls (HCs). The semantic clustering ratio on the verbal learning test was calculated to evaluate learning strategy. Medial temporal lobe atrophy (MTA) and white matter hyperintensities (WMH) were measured on MRI with the MTA and Fazekas visual rating scales, respectively.

RESULTS

Compared to HCs, aMCI subjects had poorer performance in terms of memory, executive function, and the semantic clustering ratio (P < .001). In aMCI subjects, no significant correlation between learning strategy and executive function was observed. aMCI subjects with obvious MTA demonstrated a lower semantic clustering ratio than those without MTA (P < .001). There was no significant difference in the learning strategies between subjects with high-grade WMH and subjects with low-grade WMH.

CONCLUSION

aMCI subjects showed obvious impairment in the semantic learning strategy, which was attributable to MTA but independent of executive dysfunction and subcortical WMH. These findings need to be further validated in large cohorts with biomarkers identified using volumetric brain measurements. (JINS, 2019, 25, 706-717).

The neuropsychology of emerging psychosis and the role of working memory in episodic memory encoding

Background

Episodic memory encoding and working memory (WM) deficits are among the first cognitive signs and symptoms in the course of schizophrenia spectrum disorders. However, it is not clear whether the deficit pattern is generalized or specific in nature. We hypothesized that encoding deficits at an early stage of the disease might be due to the more fundamental WM deficits.

Methods

We examined episodic memory encoding and WM by administering the California Verbal Learning Test, a 2-back task, and the Wisconsin Card Sorting Test in 90 first-episode psychosis (FE) patients and 116 individuals with an at-risk mental state for psychosis (ARMS) compared to 57 healthy subjects.

Results

Learning progress, but not span of apprehension, was diminished to a similar extent in both the ARMS and the FE. We showed that this was due to WM impairment by applying a structural equation approach.

Conclusion

Thus, we conclude that verbal memory encoding deficits are secondary to primary WM impairment in emerging psychosis.

Strategy for Semantic Association Memory (SESAME) training: Effects on brain functioning in schizophrenia

Self-initiation of semantic encoding strategies is impoverished in schizophrenia and contributes to memory impairments. Recently, we observed that following a brief training, schizophrenia patients had the potential to increase the self-initiation of these strategies. In this study, we investigated the neural correlates underlying such memory improvements. Fifteen schizophrenia patients with deficits in self-initiation of semantic encoding strategies were enrolled in a Strategy for Semantic Association Memory (SESAME) training. Patients underwent a memory task in an fMRI scanner. Memory performance and brain activity during the task were measured pre- and post- training, and changes following training were assessed. We also investigated if structural preservation measured by the cortical thickness of the left dorsolateral prefrontal cortex (DLPFC) predicted memory improvement post-training. Memory training led to significant improvements in memory performance that were associated with increased activity in the left DLPFC, during a task in which patients needed to self-initiate semantic encoding strategies. Furthermore, patients with more cortical reserve in their left DLPFC showed greater memory improvement. Our findings provide evidence of neural malleability in the left DLPFC in schizophrenia using cognitive strategies training. Moreover, the brain-behavioural changes observed in schizophrenia provide hope that memory performance can be improved with a brief intervention.

Prefrontal activity and impaired memory encoding strategies in schizophrenia

Schizophrenia patients have significant memory difficulties that have far-reaching implications in their daily life. These impairments are partly attributed to an inability to self-initiate effective memory encoding strategies, but its core neurobiological correlates remain unknown. The current study addresses this critical gap in our knowledge of episodic memory impairments in schizophrenia. Schizophrenia patients (n = 35) and healthy controls (n = 23) underwent a Semantic Encoding Memory Task (SEMT) during an fMRI scan. Brain activity was examined for conditions where participants were a) prompted to use semantic encoding strategies, or b) not prompted but required to self-initiate such strategies. When prompted to use semantic encoding strategies, schizophrenia patients exhibited similar recognition performance and brain activity as healthy controls. However, when required to self-initiate these strategies, patients had significant reduced recognition performance and brain activity in the left dorsolateral prefrontal cortex, as well as in the left temporal gyrus, left superior parietal lobule, and cerebellum. When patients were divided based on performance on the SEMT, the subgroup with more severe deficits in self-initiation also showed greater reduction in left dorsolateral prefrontal activity. These results suggest that impaired self-initiation of elaborative encoding strategies is a driving feature of memory deficits in schizophrenia. We also identified the neural correlates of impaired self-initiation of semantic encoding strategies, in which a failure to activate the left dorsolateral prefrontal cortex plays a key role. These findings provide important new targets in the development of novel treatments aiming to improve memory and ultimately patients' outcome.

A Chinese Chan-based Mind-Body Intervention Improves Memory of Older Adults

There is growing interest in the adoption of lifestyle interventions to remediate age-related declines in memory functioning and physical and psychological health among older adults. This study aimed to investigate whether a Chinese Chan-based lifestyle intervention, the Dejian Mind-Body Intervention (DMBI), leads to positive benefits for memory functioning in older adults. Fifty-six adults aged 60 years or older with subjective memory complaints (SMC) were randomly assigned to receive the DMBI or a control intervention (i.e., a conventional memory intervention; MI) once a week for 10 weeks; 48 of the adults completed the intervention. Participants’ verbal and visual memory functioning before and after the intervention were compared. In addition, changes in the participants’ subjective feelings about their memory performance and physical and psychological health after the intervention were examined. The results showed that both the DMBI and MI resulted in significant improvements in both verbal and visual memory functioning and that the extent of the improvements was correlated with participants’ level of performance at baseline. In addition, compared to the MI group, the DMBI group had significantly greater improvements in subjective physical and psychological health after the intervention. In summary, the present findings support the potential of the DMBI as an alternative lifestyle intervention for improving memory functioning, subjective physical and psychological health of older adults with SMC.

Assessment of a six-week computer-based remediation program for social cognition in chronic schizophrenia

Background

Programs to remediate cognitive deficits have shown promising results in schizophrenia, but remediation of social cognition deficits is less well understood. Social cognitive deficits may cause more disability than the widely recognized neurocognitive deficits, suggesting that this is an area worthy of further investigation.

Aim

Implement and evaluate a brief computerized cognitive remediation program designed to improve memory, attention, and facial affect recognition (FAR) in outpatients with chronic schizophrenia.

Methods

Baseline assessments of FAR and of clinical, cognitive, and psychosocial functioning were completed on 20 males with schizophrenia enrolled in an outpatient rehabilitation program at the Shanghai Mental Health Center (the intervention group) and on 20 males with schizophrenia recruited from among regular outpatients at the Center (the control group). Both groups received treatment as usual, but the intervention group also completed an average of 12.7 sessions of a computer-based remediation program for neurocognitive, social, and FAR functioning over a 6-week period. The baseline measures were repeated in both groups at the end of the 6-week trial.

Results

There were no statistically significant differences in the changes in clinical symptoms (assessed by the Positive and Negative Syndrome Scale, PANSS) or cognitive measures (assessed using the Hong Kong List Learning Test and the Letter-Number Sequencing Task) between the intervention and control groups over the 6-week trial, but there were modest improvements on the PANSS for the intervention group between baseline and after the intervention. There was a significantly greater improvement in the social functioning measure (the Personal and Social Performance scale, PSP) in the intervention group than in the control group. The pre-post change in the total facial recognition score in the intervention group was statistically significant (paired t-test=-2.60, p=0.018), and there was a statistical trend of a greater improvement in facial recognition in the intervention group than in the control group (F_(1,37)=2.93; p=0.092).

Conclusion

Integration of FAR training with a short, computer-administrated cognitive remediation program may improve recognition of facial emotions by individuals with schizophrenia, and, thus, improve their social functioning. But more work on developing the FAR training modules and on testing them in larger, more diverse samples will be needed before this can be recommended as a standard part of cognitive remediation programs.

Effects of integrated supported employment plus cognitive remediation training for people with schizophrenia and schizoaffective disorders

OBJECTIVES

The present study aims to investigate the synergistic effects of cognitive remediation training (CRT) on Integrated Supported Employment (ISE). ISE blends individual placement support service with work-related social skills training for Chinese people suffering from schizophrenia or schizoaffective disorder.

METHOD

Ninety participants with schizophrenia or schizoaffective disorders were recruited from two psychiatric outpatient services in Hong Kong. They were randomly assigned into the ISE+CRT (n=45) and ISE (n=45) conditions. Blinded assessments on vocational, clinical, psychological, and neurocognitive outcomes were conducted by independent assessors. The two groups were followed up at 7 and 11months.

RESULTS

Both groups yielded similar improvements across several outcome domains assessed immediately after the interventions and at 7 and 11month follow-ups, but no significant group differences were found. Significant positive trends over time in vocational, clinical and cognitive outcomes consistently favored the ISE+CRT condition.

CONCLUSION

While both the ISE+CRT and ISE groups demonstrated improvement in vocational, clinical, psychological, and neurocognitive outcomes, there was no evidence to show that cognitive remediation facilitated further improvement in these domains beyond gains associated with ISE alone. Further investigation is needed to fully exploit the synergistic potential of ISE combined with CRT, and to better understand which individuals experience a maximal benefit from the specific rehabilitation program components.

The development of co-speech gesture and its semantic integration with speech in 6- to 12-year-old children with autism spectrum disorders

Previous work leaves open the question of whether children with autism spectrum disorders aged 6-12 years have delay in producing gestures compared to their typically developing peers. This study examined gestural production among school-aged children in a naturalistic context and how their gestures are semantically related to the accompanying speech. Delay in gestural production was found in children with autism spectrum disorders through their middle to late childhood. Compared to their typically developing counterparts, children with autism spectrum disorders gestured less often and used fewer types of gestures, in particular markers, which carry culture-specific meaning. Typically developing children's gestural production was related to language and cognitive skills, but among children with autism spectrum disorders, gestural production was more strongly related to the severity of socio-communicative impairment. Gesture impairment also included the failure to integrate speech with gesture: in particular, supplementary gestures are absent in children with autism spectrum disorders. The findings extend our understanding of gestural production in school-aged children with autism spectrum disorders during spontaneous interaction. The results can help guide new therapies for gestural production for children with autism spectrum disorders in middle and late childhood.

Does practice make perfect? Results from a Chinese feasibility study of cognitive remediation in schizophrenia

Patients with schizophrenia often receive little by way of non-pharmacological interventions. Despite this, promising outcomes in programmes targeting cognitive deficits have been reported, suggesting that this is an area worthy of further investigation. The aim of the study was to implement and evaluate a brief computerised cognitive remediation programme designed to improve memory and attention in a male Chinese sample with chronic schizophrenia. Pre-testing was completed on a number of clinical and cognitive measures for intervention (n = 14) and treatment as usual (n = 17) participants. The intervention group then completed six weeks ( x no. of sessions = 12.78) of the computer-based cognitive remediation programme. Post-test measures for both groups were then collected again. Following the six week intervention, we found, contrary to our expectations, the intervention group improved on several of the clinical variables. The intervention group also performed better than the control group on the post-test measure of attention, but not verbal memory. These findings suggest that it is feasible to improve some aspects of cognitive abilities with a simple computerised training programme for people with serious mental illness.

CE verbal episodic memory impairment in schizophrenia: a comparison with frontal lobe lesion patients

Schizophrenia (SCZ)-related verbal memory impairment is hypothesized to be mediated, in part, by frontal lobe (FTL) dysfunction. However, little research has contrasted the performance of SCZ patients with that of patients exhibiting circumscribed frontal lesions. The current study compared verbal episodic memory in patients with SCZ and focal FTL lesions (left frontal, LF; right frontal, RF; and bi-frontal, BF) on a four-trial list learning task consisting of three lists of varying semantic organizational structure. Each dependent variable was examined at two levels: scores collapsed across all four trials and learning scores (i.e., trial 4-trial 1). Performance deficits were observed in each patient group across most dependent measures at both levels. Regarding patient group differences, SCZ patients outperformed LF/BF patients (i.e., either learning scores or scores collapsed across trial) on free recall, primacy, primary memory, secondary memory, and subjective organization, whereas they only outperformed RF patients on the semantically blocked list on recency and primary memory. Collectively, these results indicate that the pattern of memory performance is largely similar between patients with SCZ and those with RF lesions. These data support tentative arguments that verbal episodic memory deficits in SCZ may be mediated by frontal dysfunction in the right hemisphere.

Distinct episodic verbal memory profiles in schizophrenia

According to some authors, episodic memory impairment may be a feature shared by all schizophrenic patients, whereas others argue in favor of the mnesic heterogeneity. Our aims were to determine whether patients can be grouped based on according to their mnesic performances. The California Verbal Learning Test (CVLT), an episodic verbal learning test, was compared in 61 schizophrenic patients and 61 matched healthy subjects. The 32 indices were calculated using CVLT Scoring Software. This process allowed us to describe patients' episodic processes in detail (encoding, storage, retrieval). We isolated one group with normative data, another showed impairment of both encoding and retrieval processes, and in the last one, only encoding process was impaired. As schizophrenia is heterogeneous with regard to episodic memory, impairments should not be considered as a common core to the various forms of the illness and it would be fruitful to systematically assess episodic processes in detail to take into account individual abilities and challenges.

Symptom severity is more closely associated with social functioning status in inpatients with schizophrenia than cognitive deficits

Background

Prior research has determined that impairment in neurocognition and psychiatric symptoms contribute to reduced occupational and social functioning in schizophrenia.

Objective

Evaluate the relationships of neurocognition, psychiatric symptoms, and psychosocial functioning in male inpatients with schizophrenia in China.

Methods

Fifty-one male patients currently hospitalised at the Shanghai Mental Health Center with a diagnosis of schizophrenia were recruited and 40 of them were included in the final analysis. Participants were assessed with Chinese versions of the Personal and Social Performance Scale (PSP), Clinical Global Impression-Severity (CGI-S) scale, Positive and Negative Symptom Scale (PANSS), Letter-Number Sequencing Task, and Hong Kong List Learning Test.

Results

Robust negative correlations were found between three clinical subscale scores derived from the PANSS and the global measures of social function (the total PSP score and the CGI-S score). Performance on the neurocognitive tasks was not associated with either symptoms or social functioning status.

Conclusions

Among inpatients in the acute phase of schizophrenia, the severity of the clinical symptoms—not the degree of the neurocognitive impairment—is closely associated with the level of social functioning.

Strategic manipulations for associative memory and the role of verbal processing abilities in schizophrenia

Individuals with schizophrenia demonstrate episodic memory (EM) deficits and abnormal EM-related brain activity. Experimental encoding manipulations significantly benefit memory performance in schizophrenia, suggesting that a strategic processing deficit may contribute to memory impairment. However, few studies have investigated the combined effects of encoding and retrieval strategies on EM in schizophrenia. The current study examined the impact of encoding and retrieval strategies on associative memory and brain activity in schizophrenia. We also assessed the role of verbal processing ability in response to strategic memory interventions in schizophrenia. Behavioral and functional neuroimaging data were collected from 23 participants with schizophrenia and 24 comparison subjects while performing associative memory encoding and recall tasks. Behaviorally, both schizophrenia participants and controls benefited from memory strategies and showed significant associations between verbal processing ability and recall. Additionally, among schizophrenia participants, encoding strategy use was associated with enhanced brain activity in multiple brain areas. Schizophrenia participants also demonstrated significant associations between verbal processing ability and encoding-related brain activity in prefrontal cortex. Findings suggest that memory performance and brain activity in schizophrenia can be enhanced via strategic manipulations, and individual differences in cognitive abilities in schizophrenia can affect behavioral and neurobiological responses to strategic memory interventions.

Verbal learning strategy following mild traumatic brain injury

That learning and memory deficits persist many years following mild traumatic brain injury (mTBI) is controversial due to inconsistent objective evidence supporting subjective complaints. Our prior work demonstrated significant reductions in performance on the initial trial of a verbal learning task and overall slower rate of learning in well-motivated mTBI participants relative to demographically matched controls. In our previous work, we speculated that differences in strategy use could explain the differences in rate of learning. The current study serves to test this hypothesis by examining strategy use on the California Verbal Learning Test-Second Edition. Our present findings support the primary hypothesis that mTBI participants under-utilize semantic clustering strategies during list-learning relative to control participants. Despite achieving comparable total learning scores, we posit that the persisting learning and memory difficulties reported by some mTBI patients may be related to reduced usage of efficient internally driven strategies that facilitate learning. Given that strategy training has demonstrated improvements in learning and memory in educational and occupational settings, we offer that these findings have translational value in offering an additional approach in remediation of learning and memory complaints reported by some following mTBI.

The role of encoding strategies in the verbal memory performance in patients with schizophrenia

BACKGROUND. Verbal learning and memory is often compromised in patients with schizophrenia who prefer encoding words in order of their presentation (serial clustering) rather than using semantic categories (semantic clustering). METHOD. One hundred and four in-patients with schizophrenia were assessed twice with the California Verbal Learning Test. RESULTS. Patients showed significantly less semantic than serial clustering at both assessment times. Usage of encoding strategies were not stable over time. An increase in semantic clustering improved recall and recognition performance. CONCLUSIONS. Patients with schizophrenia should be taught to use the more effective encoding strategy of semantic clustering in order to improve their memory performance.

Verbal learning differences in chronic mild traumatic brain injury

Following mild traumatic brain injury (TBI), a percentage of individuals report chronic memory and attention difficulties. Traditional neuropsychological assessments often fail to find evidence for such complaints. We hypothesized that mild TBI patients may, in fact, experience subtle cognitive deficits that reflect diminished initial acquisition that can be explained by changes in cerebral white matter microstructure. In the data presented here, a sample of nonlitigating and gainfully employed mild TBI patients demonstrated statistically significant differences from age and education matched control participants in performance on the first trial of a verbal learning task. Performance on this trial was associated with reduced fractional anisotropy in the uncinate fasciculus and the superior longitudinal fasciculus providing an anatomical correlate for the cognitive findings. Mild TBI patients were not impaired relative to control participants on total learning or memory composite variables. Performance on the first learning trial was not related to any psychological variables including mood. We concluded that patients with mild TBI demonstrate diminished verbal learning that is not often interpreted in standard neuropsychological assessment.

Is semantic memory impaired in schizophrenia? A systematic review and meta-analysis of 91 studies

INTRODUCTION

Semantic memory impairments in schizophrenia have been reported across a wide range of neuropsychological tests. Set against a backdrop of fairly widespread cognitive impairments, it is difficult to know whether there is a primary, or secondary, impairment of semantic memory in schizophrenia. Also, whether there is a profile of differential impairment across the range of neuropsychological tests.

METHODS

Employing a systematic search strategy, 91 papers were identified which have assessed participants with schizophrenia on a measure of semantic memory. A series of meta-analyses were then conducted which provided combined weighted means for performance on tasks of naming, word-picture matching, verbal fluency, priming, and categorisation.

RESULTS

An uneven profile of impairment is reported with large effect sizes for tests of naming and verbal fluency, medium effect sizes for word-picture matching and association and small effect sizes for categorisation and priming tests.

CONCLUSIONS

This uneven profile supports the claim that a degradation of semantic knowledge may not be adequate in explaining the semantic memory impairment in schizophrenia. This conclusion is supported by the data which report a relationship between an executive dysfunction and poor priming and fluency performance particularly. The data support a link between Formal Thought Disorder and semantic memory impairments on tests of naming and verbal fluency but on other tests evidence is equivocal.

Individual Differences in Episodic Memory: The Role of Self-initiated Encoding Strategies

Individuals' abilities to form and retrieve episodic memories vary widely. Consistent with this, there are substantial individual differences in brain activity during encoding and retrieval that are associated with individual differences in memory performance. Growing evidence suggests that individual differences in self-initiated encoding strategy use play an important role in individual differences in episodic memory and brain activity during intentional encoding. This review examines the role of individual differences in self-initiated encoding strategy use in individual differences in episodic memory, and outlines the major findings of brain lesion and functional neuroimaging studies that characterize the neural correlates of individual differences in self-initiated encoding strategy use. The relevance of individual differences in self-initiated encoding strategy use to understanding episodic memory impairments and alterations in brain activity in clinical populations such as individuals with schizophrenia is also discussed.

The relationship between prefrontal brain volume and characteristics of memory strategy in schizophrenia spectrum disorders

The present study investigated the relationship between memory strategy use and prefrontal gray/white matter volumes of healthy control subjects, patients with schizophrenia or schizotypal disorder. Gray/white matter volumes were measured for the superior, middle, inferior, ventral medial and orbital prefrontal regions, using high-resolution magnetic resonance (MR) images that were acquired from 35 patients with schizophrenia, 25 patients with schizotypal disorder and 19 healthy subjects. Participants were also administered the Japanese Verbal Learning Test (JVLT). In control subjects, larger left inferior frontal and straight gyrus's gray matter volumes were associated with higher semantic clustering rates on the JVLT, and smaller left inferior frontal gray matter volumes were associated with higher serial clustering ratio. In schizophrenic patients, smaller left orbitofrontal gray matter volumes were associated with lower semantic clustering rates on the JVLT. In schizotypal patients, smaller left inferior frontal white matter volume was associated with smaller serial clustering rates and larger semantic clustering rate. These findings suggest that semantic organization in schizophrenic patients might depend on mobilization of a memory strategy that is mediated by orbitofrontal cortex functioning. Failure to use a semantic organization strategy might be related to reduced volume in the inferior frontal gyrus. The findings for schizotypal patients suggest a compensation mechanism to remember the words using a serial processing strategy is at work when the inferior frontal gyrus cannot mediate semantic processing.

Functional mechanisms of episodic memory impairment in schizophrenia

OBJECTIVE

To achieve a better understanding of the functional mechanisms underlying episodic memory dysfunction in schizophrenia, which is a prerequisite for unravelling schizophrenia's neural correlates in neuroimaging studies and, more generally, for developing an integrated approach to the pathophysiology of schizophrenia. It is also crucial for developing cognitive remediation.

METHOD

This paper reviews empirical evidence of episodic memory dysfunction in schizophrenia obtained with reference to various theoretical models of episodic memory.

RESULTS

All the studies converge to show a significant impairment of the critical feature of episodic memory: conscious recollection. Schizophrenia is also associated with a defect of autobiographical memory. The episodic memory dysfunction results from a predominant failure of strategic processing at encoding, although an impairment of strategic processing at retrieval cannot be ruled out. The possibility that it is not the execution of the encoding strategies that is defective but, rather, their self-initiation by the patients is plausible.

CONCLUSIONS

These findings may explain some behavioural abnormalities associated with schizophrenia, notably, inadequate functional outcomes in everyday life. They may also have implications for cognitive remediation and better social and work functioning of patients with schizophrenia.

Schizophrenia, ketamine and cannabis: evidence of overlapping memory deficits

Drug models of mental illness are considered useful if they provoke its characteristic symptoms. In this respect, ketamine and tetrahydrocannabinol (cannabis) are coming under increasing scrutiny as models for schizophrenia. However, although both undoubtedly produce psychotic symptoms characteristic of the disorder, we argue here that, because schizophrenia is also accompanied by cognitive deficits, a full understanding of the impact of these drugs on cognition will be crucial in taking these models further. Memory deficits are pronounced in schizophrenia and we focus upon patterns of working and episodic memory impairment produced by ketamine and cannabis, identifying overlaps between drug and illness. We suggest that close attention to these deficits can offer insights into core pathophysiology of schizophrenia.

Verbal memory deficit in patients with schizophrenia: an important future target for treatment

Despite more than two-thirds of patients with schizophrenia showing reductions in delusions and hallucinations following optimum available treatment, many are left with crippling cognitive impairments. Neurocognitive deficit is a core feature of schizophrenia, but the question arises as to whether efforts should be geared towards ameliorating and normalizing these deficits. Verbal memory dysfunction is one of the most consistently reported cognitive deficits and among the best predictors of functional outcome in schizophrenia. Therefore, a better understanding of the nature of this deficit could lead to treatments that not only improve the specific systems mediating the impairment, but could also have wider implications for clinical and social outcome.

Pharmacological treatment to augment hole board habituation in prenatal Vitamin D-deficient rats

Neurocognitive impairment has consistently been considered a central and stable feature of schizophrenia. There is much controversy about the effects of neuroleptics on neurocognitive deficits. Thus, further investigations are needed to clarify the pathological substrate of cognitive deficits in schizophrenia as well as to identify pharmacological tools for treatment. Transient prenatal Vitamin D deficiency is considered a developmental model in schizophrenia research. Recently, it was reported that prenatal Vitamin D-depleted rats showed a habituation deficit in the hole board. Here, we tested the effect on hole board habituation of haloperidol (Hal, 0.075 mg/kg, i.p.), risperidone (Ris, 0.2 mg/kg, i.p.) and the mGluR5 agonist CHPG (0.1 mg, i.c.v.) after subchronic treatment. Hal was found to impair habituation in control animals, Ris restored hole board habituation, whereas Hal and CHPG normalised hole board habituation in the deplete animals completely. The results of the study demonstrate that (i) the Vitamin D model might be a valuable tool in the study of neurodevelopmental aspects of schizophrenia, (ii) the model is sensitive in detecting the effect of antipsychotic drugs and (iii) the model appears to be sensitive in differentiating between typical and atypical antipsychotic drug.

Impairment of specific episodic memory processes by sub-psychotic doses of ketamine: the effects of levels of processing at encoding and of the subsequent retrieval task

RATIONALE

The precise nature of the impact of the N-methyl-D-aspartate antagonist, ketamine, upon human episodic memory, has yet to be elucidated fully.

OBJECTIVES

This study sought to assess the effects of ketamine on the sub-processes facilitating memory encoding and retrieval.

METHODS

We evaluated the effects of the drug on a series of memory performance measures depending upon whether it was administered at the encoding or retrieval stage and on the nature of the encoding task used. Twelve healthy volunteers participated in a double-blind, placebo-controlled, randomized, within-subjects study. Intravenous infusions of placebo, 50 ng/ml ketamine or 100 ng/ml ketamine were administered. We investigated the effects of ketamine on three key aspects of episodic memory: encoding vs retrieval processes, source memory, and depth of processing. Data were analysed using both multinomial modelling and standard measures of item discrimination and response bias.

RESULTS

Deleterious effects of ketamine on episodic memory were primarily attributable to its effects on encoding, rather than retrieval processes. Recognition memory was impaired for items encoded at an intermediate level of processing, but preserved for shallowly and deeply encoded items. Increased source guessing bias was also observed when encoding took place under ketamine.

CONCLUSIONS

The effects of ketamine upon episodic memory seem, therefore, to predominate at encoding. Furthermore, our results are also consistent with a specific impairment of encoding processes that result in subsequent recollective, as opposed to familiarity-based, retrieval. The observed effects are compatible with memory deficits seen in schizophrenia and thus provide some support for the ketamine model of the disease.

The influence of encoding strategy on episodic memory and cortical activity in schizophrenia

BACKGROUND

Recent work suggests that episodic memory deficits in schizophrenia may be related to disturbances of encoding or retrieval. Schizophrenia patients appear to benefit from instruction in episodic memory strategies. We tested the hypothesis that providing effective encoding strategies to schizophrenia patients enhances encoding-related brain activity and recognition performance.

METHODS

Seventeen schizophrenia patients and 26 healthy comparison subjects underwent functional magnetic resonance imaging scans while performing incidental encoding tasks of words and faces. Subjects were required to make either deep (abstract/concrete) or shallow (alphabetization) judgments for words and deep (gender) judgments for faces, followed by subsequent recognition tests.

RESULTS

Schizophrenia and comparison subjects recognized significantly more words encoded deeply than shallowly, activated regions in inferior frontal cortex (Brodmann area 45/47) typically associated with deep and successful encoding of words, and showed greater left frontal activation for the processing of words compared with faces. However, during deep encoding and material-specific processing (words vs. faces), participants with schizophrenia activated regions not activated by control subjects, including several in prefrontal cortex.

CONCLUSIONS

Our findings suggest that a deficit in use of effective strategies influences episodic memory performance in schizophrenia and that abnormalities in functional brain activation persist even when such strategies are applied.

Cognitive and clinical moderators of recognition memory in schizophrenia: a meta-analysis

Recognition memory performance in schizophrenia has been shown to vary greatly across studies. To identify the conditions under which recognition memory is significantly impaired, we used a meta-analytic strategy to quantify the moderating effects of several cognitive and clinical variables. Eighty-four studies (from 1965 to July 2003) provided recognition memory data for both a schizophrenia and control group. The overall group comparison for recognition memory yielded a significant mean weighted effect size of d=0.76. Material specificity was the most significant cognitive variable found, with patients exhibiting greater impairment for figural than verbal recognition. A yes-no recognition format and auditory encoding also led to significantly greater effect sizes for recognition memory relative to forced-choice recognition tests and visual encoding, respectively. Furthermore, the effect size for recognition memory as measured by false alarm was smaller than the effect size as measured by hit rate or by d-prime and its related measures. Among clinical variables that were associated with higher effect sizes, chronicity was the most significant, but different trends linking poor performance to negative symptoms and general symptomatology were also observed. Thus, a recognition memory deficit moderated by both cognitive and clinical variables is clearly present in schizophrenia.

Word frequency effects on free recall and recognition in patients with schizophrenia

BACKGROUND

Word frequency paradigms have been used repeatedly in healthy populations to help understand the functioning of verbal memory. We investigated the word frequency effects in a sample of patients with schizophrenia, assuming these data may shed light on certain encoding processes.

METHODS

Two mixed lists of high- and low-frequency words were presented to 46 patients with schizophrenia and 43 healthy control subjects. List learning was followed by free recall and recognition in immediate and delayed conditions.

RESULTS

Overall the high-frequency words were better recalled, whereas the low-frequency words were better recognised. The lack of interaction with diagnosis indicates that these effects were equivalent in both groups. In immediate recognition, the discrimination deficit for the high-frequency words in patients tended to be increased relative to that for the low-frequency words, suggesting greater impairment in the encoding of those words.

CONCLUSION

It is argued that the encoding of the distinct low-frequency words is less efficient in patients, but qualitatively unimpaired. By contrast, the familiar words might be more difficult for patients to encode, as they are more easily confused with other common words stored in long-term memory.

Semantic Organization and Verbal Memory Efficiency in Patients With Schizophrenia

The role of semantic organization in verbal memory efficiency in schizophrenia was investigated. Patients and healthy controls were administered a free-recall task involving 1 nonsemantically organizable list, 1 list organizable in semantic categories with typical instances, and 1 list organizable in semantic categories with atypical instances. Reduced semantic organization was observed in patients. Regression analyses showed that the semantic clustering score in the atypical organizable list made a significant contribution to recall performance in patients. When semantic clustering was controlled, the effect of diagnosis on free recall was significant. These results suggest that depth of semantic organization is a crucial factor of verbal memory performance in schizophrenia. However, semantic organizational deficit does not account for the whole recall impairment.

Levels-of-processing effect on word recognition in schizophrenia

BACKGROUND

Individuals with schizophrenia have difficulty organizing words semantically to facilitate encoding. This is commonly attributed to organizational rather than semantic processing limitations. By requiring participants to classify and encode words on either a shallow (e.g., uppercase/lowercase) or deep level (e.g., concrete/abstract), the levels-of-processing paradigm eliminates the need to generate organizational strategies.

METHODS

This paradigm was administered to 30 patients with schizophrenia and 30 healthy comparison subjects to test whether providing a strategy would improve patient performance.

RESULTS

Word classification during shallow and deep encoding was slower and less accurate in patients. Patients also responded slowly during recognition testing and maintained a more conservative response bias following deep encoding; however, both groups showed a robust levels-of-processing effect on recognition accuracy, with unimpaired patient performance following both shallow and deep encoding.

CONCLUSIONS

This normal levels-of-processing effect in the patient sample suggests that semantic processing is sufficiently intact for patients to benefit from organizational cues. Memory remediation efforts may therefore be most successful if they focus on teaching patients to form organizational strategies during initial encoding.

Neuropsychological differentiation of late-onset schizophrenia and dementia of the Alzheimer's type

Late-onset schizophrenia and dementia of the Alzheimer's type (DAT) often present with some pathological and behavioral commonalities. Specifically, both illnesses may involve varying degrees of delusional manifestation, apathy, lateral/third-ventricular enlargement, reduced frontal lobe activity, and hippocampal atrophy. Moreover, patients with either disease have shown comparable cognitive impairment on standardized neuropsychological tests. As such, a differential diagnosis of the 2 disorders on the basis of such testing can prove to be difficult. This study evaluated the neuropsychological test results of 32 patients with late-onset schizophrenia and 32 patients with DAT to distinguish the tests that best differentiate the 2 disorders. Results indicate that the Wechsler Adult Intelligence Scale-Revised Similarities subtest and the California Verbal Learning Test (both short- and long-delay free recall) correspond to sensitive diagnostic neuropsychological measures. This investigation was preliminary in nature, and should aid in the development of a definitive differential profile.

Music training improves verbal but not visual memory: cross-sectional and longitudinal explorations in children

The hypothesis that music training can improve verbal memory was tested in children. The results showed that children with music training demonstrated better verbal but not visual memory than did their counterparts without such training. When these children were followed up after a year, those who had begun or continued music training demonstrated significant verbal memory improvement. Students who discontinued the training did not show any improvement. Contrary to the differences in verbal memory between the groups, their changes in visual memory were not significantly different. Consistent with previous findings for adults (A. S. Chan, Y. Ho, & M. Cheung, 1998), the results suggest that music training systematically affects memory processing in accordance with possible neuroanatomical modifications in the left temporal lobe.

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.

Recent Development of Cognitive and Neuropsychological Assessment in Asian Countries

There is a growing trend of research in neuropsychological assessment in Asia: The mean number of published studies increased from 1.8 in the 1980s to 16.0 in 2 recent years. About 40% of the studies reviewed concerned test development or adaptation, with the latter greatly outnumbering the former. To facilitate the test selection for clinical use, 36 clinical measures were evaluated based on some statistical criteria. The results showed that only 8 neuropsychological tests (5 Chinese, 2 Korean, and 1 Japanese) met the criteria. Given that Asian and Western populations differ on certain cognitive processes, future development of neuropsychological assessment measures in Asia should move from the adaptation of Western tests toward the construction of original tests with better ecological validity.

Impaired hippocampal recruitment during normal modulation of memory performance in schizophrenia

BACKGROUND

Patients with schizophrenia demonstrate poor verbal memory, ascribed to impaired prefrontal and hippocampal function. Healthy adults can increase recall accuracy following encoding interventions, such as item repetition and the formation of semantic associations. We examined the effects of these interventions on both memory performance and retrieval-related hippocampal activity in healthy adults and patients with schizophrenia.

METHODS

Twelve patients with schizophrenia and twelve healthy control subjects participated. During study, subjects counted either the number of meanings or T-junctions in words seen only once or repeated four times. At test, O15-positron emission tomography scans were acquired while subjects completed word-stems with previously studied items.

RESULTS

Control subjects recalled more words overall, but both groups demonstrated similar performance benefits following deeper encoding. Both item repetition and the use of a semantic encoding task were associated with memory retrieval-related hippocampal recruitment in control but not schizophrenic participants. Patients with schizophrenia demonstrated greater activation of prefrontal cortical areas during word retrieval.

CONCLUSIONS

Despite a lack of hippocampal recruitment, patients with schizophrenia showed intact modulation of memory performance following both encoding interventions. Impaired hippocampal recruitment, in concert with greater prefrontal activation, may reflect a specific deficit in conscious recollection in schizophrenia.

Neuropsychological profiles delineate distinct profiles of schizophrenia, an interaction between memory and executive function, and uneven distribution of clinical subtypes

Neuropsychological performance in 151 patients with schizophrenia was examined using cluster analysis to identify neurocognitive subtypes. Hierarchical and iterative partitioning methods identified four clusters using an extended neuropsychological battery. Consistent with previous findings two extreme clusters were characterized by near normative performance and profound global dysfunction, respectively. The two remaining neurocognitive clusters displayed moderate-severe dysfunction and were differentiated by unique patterns of abstraction and flexibility, attention, spatial memory, and sensory-perception. Analysis of variance revealed an interaction between global memory and executive function for clusters III and IV. Although limited cluster differences were found relative to clinical and historical data, the distribution of previously defined clinical subtypes was uneven among neurocognitive clusters. Paranoid patients were significantly more likely to be classified into cluster II and disproportionately absent from clusters I and IV. Patients with negative and disorganized clinical subtypes comprised a disproportionate component of clusters I and IV but were less likely to be classified in cluster II. This suggests greater correspondence than previously postulated between systems responsible for clinical symptomatology and those moderating neurocognitive dysfunction.

Memory impairment in schizophrenia: a study using event-related potentials in implicit and explicit tasks

Although memory impairment is recognized as a major fact of schizophrenia, only a few studies have investigated memory impairments with specifically designed event-related potential (ERP) protocols. In this study, ERPs were recorded from 15 schizophrenia patients and 15 matched control subjects during implicit and explicit memory tasks for unfamiliar faces. The results showed that patients have a reduced modulation of an N400-like component in both the implicit and explicit tasks that suggests a deficient integration of incoming information with personal knowledge. Patients also displayed an enhanced frontally distributed activity in the explicit task that may represent an impairment in the integration of intrinsic contextual information, a disturbance in the ability to inhibit proactive interference or a combination of both processes. Finally, the modulation of the late positive component did not differ from that in control subjects in both implicit and explicit tasks, suggesting that the impairment in mnemonic binding processes suggested in schizophrenia is more qualitative, i.e. incomplete or inappropriate, due to the anomalies in antecedent processes. The correlations observed between impairments of ERP modulation and symptoms further support these interpretations.