Assessment of memory deficits in psychiatric disorders: A systematic literature review

Memory deficits are observed across psychiatric disorders ranging from the prodrome of psychosis to common mental disorders such as anxiety, depression, and dissociative disorders. Memory deficits among patients recovering from psychiatric disorders could be directly related to the primary illness or secondary to the adverse effect of a treatment such as Electroconvulsive Therapy (ECT). The trouble in the meaningful integration of working-memory and episodic memory is the most commonly affected domain that requires routine assessments. An update on the recent trends of methods of assessment of memory deficits is the first step towards understanding and correcting these deficits to target optimum recovery. A systematic literature search was conducted from October 2018 to October 2022 to review the recent methods of assessment of memory deficits in psychiatric disorders. The definition of 'Memory deficit' was operationalized as 'selective processes of memory, commonly required for activities of daily living, and affected among psychiatric disorders resulting in subjective distress and dysfunction'. We included 110 studies, most of them being conducted in western countries on patients with schizophrenia. Other disorders included dementia and mild cognitive impairment. Brief Assessment of Cognition in Schizophrenia, Cambridge Automated Neuropsychological Test Battery, California Verbal Learning Test, Trail Making Test Part A and B, Rey Auditory Verbal Learning Test, Wechsler Memory Scale, Wechsler Adults Intelligence Scale-IV were the most common neuropsychological assessments used. Mini-Mental State Examination and Montreal Cognitive Assessment were the most common bedside assessment tools used while Squire Subjective Memory Questionnaire was commonly used to measure ECT-related memory deficits. The review highlights the recent developments in the field of assessment of memory deficits in psychiatric disorders. Findings recommend and emphasize routine assessment of memory deficits among psychiatric disorders in developing countries especially severe mental illnesses. It remains interesting to see the role of standardized assessments in diagnostic systems given more than a decade of research on memory deficits in psychiatric disorders.

Intermittent working memory training during adulthood protects against age-related long-term spatial reference memory decline in rats

Engagement in cognitive activity in adulthood is one of the factors that enable successful cognitive aging, both in humans and rodents. However, some studies emphasize that the beneficial effect on cognition of such an activity may reflect carry over from one test situation to another, including memory for procedural aspects of the behavioral tasks, and thus question whether this effect can be limited to the trained cognitive domain or whether it can be transferred to an untrained ones. In the current study, we assessed whether adulthood intermittent working memory training has beneficial effect on long-term memory of aged rats using two very different test situations. To this aim, rats trained in a delayed non-matching to position task in operant box at 3 and 15 months of age were tested in a place learning task in water maze when they were 24 months. The two tasks differ with regard to the cognitive domain but also in their spatial ability requirement and the nature of the reinforcer used. During the memory tests, accuracy of the platform search indicated age-related impairment only in the aged-untrained group. Thus, intermittent training during adult life in a task involving working memory protects aged animals from the deleterious effects of aging on spatial reference memory. This result highlights the long-term beneficial effects of training on a working memory task on an untrained cognitive domain.

Remote fear memory is sensitive to reconditioning

Exposure of some individuals to recurring traumatic events from the same perpetrator or situation, such as during child abuse or domestic violence, is quite prevalent. Studies have shown that the number of traumatic events experienced is positively related to the severity of post-traumatic stress disorder and other mental disorders. Using a contextual fear conditioning (Cond1) and reconditioning (Cond2) paradigm, which were separated by either 1 or 35 days, we examined fear responses to immediate extinction and retrieval-extinction procedures after repeated fear conditioning stress. Based on the time interval between Cond1 and Cond2, the animals were divided into recent and remote fear memory groups. We observed that when Cond2 was performed in the original conditioning context in which Cond1 was performed, the reconditioned remote fear memory was resistant to the disruptive effect of immediate extinction and retrieval-extinction paradigms. Furthermore, the resistance to disruptive effects could be induced by very low shock intensities, which cannot even induce any fear response in naive animals. When Cond2 was performed in a novel context, animals with remote fear memory acquired a significantly higher fear response to the novel context. Our findings suggest that remote fear memory may be more sensitive to reconditioning and resistant to post-reconditioning disruption.

Unilateral hippocampal inactivation or lesion selectively impairs remote contextual fear memory

RATIONALE

Contextual fear memory depends on the hippocampus, but the role of unilateral hippocampus in this type of memory remains unclear.

OBJECTIVES

Herein, pharmacological inactivation or excitotoxic lesions were used to study the role of unilateral hippocampus in the stages of contextual fear memory.

RESULTS

The pharmacological experiments revealed that compared with the control groups, unilateral hippocampal blockade did not impair 1-day recent memory following learning, whereas bilateral hippocampal blockade significantly impaired this memory. The lesion experiments showed that compared with the control groups, the formed contextual fear memory was retained for 7 days and that 30-day remote memory was markedly reduced in unilateral hippocampal lesion groups.

CONCLUSIONS

These results indicate that an intact bilateral hippocampus is required for the formation of remote memory and that unilateral hippocampus is sufficient for recent contextual fear memory.

AMPA receptor trafficking in recent vs. remote memory

It is now established that iteration of memory circuits takes place from hippocampus to cortical regions. The recall of recent event is largely dependent on the hippocampus networks, however, with passage of time, the cortical regions become largely involved in the recall of remote events. Molecular events, specifically, the AMPA receptor regulation underlying this iteration remains largely elusive.

METHOD

Separate groups of mice were fear conditioned using contextual fear conditioning paradigm. Memory retrieval test was performed 1 day post-training, for the recent memory group, together with respective controls. Where as, in case of remote group retrieval was performed 30 days post training. One hour post retrieval session, hippocampus and anterior cingulate regions were harvested after decapitation from all the groups, which were processed for synaptic membrane isolation and quantitative western blotting.

RESULTS

We observed endocytosis of GluA1 and 2 exclusively in the anterior cingulate regions in the remote memory group, one hour post retrieval session, whereas in recent group, endocytosis of AMPA receptor units was only observed in the hippocampal regions. The endocytosis of GluA1-2 containing AMPARs upon retrieval, showed the weakened state of synapse. At this time point modification in content and strength of memory is possible for treatment of traumatic memories.

Different characteristics of cognitive impairment in elderly schizophrenia and Alzheimer's disease in the mild cognitive impairment stage

We compared indices of the revised version of the Wechsler Memory Scale (WMS-R) and scaled scores of the five subtests of the revised version of the Wechsler Adult Intelligence Scale (WAIS-R) in 30 elderly schizophrenia (ES) patients and 25 Alzheimer's disease (AD) patients in the amnestic mild cognitive impairment (aMCI) stage (AD-aMCI). In the WMS-R, attention/concentration was rated lower and delayed recall was rated higher in ES than in AD-aMCI, although general memory was comparable in the two groups. In WAIS-R, digit symbol substitution, similarity, picture completion, and block design scores were significantly lower in ES than in AD-aMCI, but the information scores were comparable between the two groups. Delayed recall and forgetfulness were less impaired, and attention, working memory and executive function were more impaired in ES than in AD-aMCI. These results should help clinicians to distinguish ES combined with AD-aMCI from ES alone.