Memory Performance In Schizophrenia Research Articles

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, O 15–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.

Prefrontal cortex dysfunction during working memory performance in schizophrenia: reconciling discrepant findings

Working memory (WM) deficits are a persistent, disabling and relatively treatment-resistant feature of schizophrenia that may underlie many cognitive deficits and symptoms. They are associated with prefrontal cortex dysfunction. While most neuroimaging studies of WM demonstrate “task-related hypofrontality” in schizophrenic relative to healthy subjects, several recent studies have reported equal or increased prefrontal activity. These findings challenge central assumptions regarding cognitive deficits and prefrontal cortex dysfunction in schizophrenia. The goal of this review is to reconcile these seemingly discrepant findings. Methodological factors addressed include the use of intersubject averaging, WM task parameters and the reliability of the measures. Factors intrinsic to schizophrenia and their relevance to the selection of experimental methods and the interpretation of group data are also discussed. Both hypo- and hyperfrontality are hypothesized to be valid and informative reflections of prefrontal cortex dysfunction in schizophrenia. Due to the heterogeneity and variability of both performance and regional recruitment in schizophrenia, whether individual data is considered, the level and type of WM demands and the composition of the sample with regard to performance deficits all influence study outcome and contribute to discrepancies. Although the prefrontal cortex is consistently implicated in WM deficits, the basis of its dysfunction and its exact contribution remain unclear. Future work might focus on delineating the exact WM processes, domains and components that are deficient. In addition, variability in behavior and activation might best be regarded as intrinsic to schizophrenia and having a neural basis that requires explanation. In combination with other techniques, neuroimaging can identify the neural circuitry responsible for WM deficits and elucidate the contribution of each anatomical component.

Verbal memory in schizophrenia: sex differences over repeated assessments

There is conflicting evidence regarding the presence and direction of gender differences in verbal memory capacity in schizophrenia. We examined gender differences in verbal memory performance in schizophrenia and their interactions with repeated assessments and psychiatric symptoms. California Verbal Learning Test (CVLT) data were collected from 28 outpatients diagnosed with schizophrenia. The CVLT was administered on five occasions, 3 months apart. CVLT data were examined using repeated measures analyses, using maximum likelihood estimates, with Brief Psychiatric Rating Scale (BPRS) scores at assessments 1–5 as a time-varying covariate. There were significant main effects of time and gender, with scores improving over time, and women performing better than men. There was also a significant time by gender interaction. The BPRS covariate effect was not significant. Results are discussed in terms of implications for gender-informed approaches to rehabilitation treatments.

Working memory and schizophrenia: evidence for slowed encoding

Previous studies have found impairments in working memory in individuals with schizophrenia, but have not identified the underlying information processing deficit. Because schizophrenia is associated with slowed cognitive processing, deficits on working memory tests may be due to decreased speed of encoding rather than an inability to maintain information over time. This hypothesis was examined using a Delayed Match to Sample (DMTS) Test. Task difficulty under 0-delay conditions was equated by individually establishing the stimulus presentation time needed to reach approximately 80% accuracy. Schizophrenia participants required longer presentation durations, but there were no group differences under delay conditions when performance was equated in the 0-delay condition. These results suggest that poor working memory performance in schizophrenia results from slowed encoding processes.

A comparison of memory for verbal and non-verbal material in schizophrenia

Verbal memory impairment has been well explored in schizophrenia, but it is unclear whether findings relate to the type of material to be learned or the component process required by the memory task. Also, sparse data on non-verbal memory also open the question of how well schizophrenia patients encode this material. We tested whether episodic memory performance in schizophrenia varies as a function of stimulus material (verbal/non-verbal) and determined the integrity of various component memory processes. Memory tests that differ in stimulus material (words, California Verbal Learning Test, CVLT; designs, Biber Figure Learning Test-Extended, BFLT-E) yet produce similar memory component measures were used. Subjects were 28 neuroleptic-medicated inpatients with a diagnosis of chronic schizophrenia. Results showed that both verbal and non-verbal memory performance was impaired relative to age-matched controls. Learning and recall measures were most severely impaired, with memory storage problems and impairment in recognition memory evident. On the verbal task, the relative sparing of recognition memory suggested retrieval processes, in addition to encoding processes, were disrupted. On the non-verbal task, the deficits appeared more limited to encoding. Therefore, while the operational integrity of components such as encoding were compromised regardless of material, retrieval processes showed material-specific effects. To the degree verbal and non-verbal memory functions can be lateralized in the brain, these data support the possibility of deficits in both right and left hemisphere declarative memory systems in schizophrenia.

Incentive improves recall but not recognition memory performance in schizophrenia

Incentive improves recall but not recognition memory performance in schizophrenia

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.

Relationship of attentional and organizational capacity to recent memory performance in schizophrenia and other psychotic disorders

Relationship of attentional and organizational capacity to recent memory performance in schizophrenia and other psychotic disorders

Abnormal activation of temporal lobe during memory performance in schizophrenia: A pet CBF study with 150 labeled water

A previous study reported abnormally large cavum septi pellucidi (CSP) in posttraumatic stress disorder (PTSD). We utilized magnetic resonance imaging to examine the frequency of large CSP, as defined by Nopoulos et al. (1997), in cancer survivors with and without intrusive recollections in a sample identical to that of our previous study. The frequency of large CSP did not differ between the two groups. The results suggest that alteration in midline structures during the course of neurodevelopment may lead to severe PTSD, while subthreshold PTSD, such as intrusive recollections, appear not to be associated with such alterations.