Memory dissociation and metamemory in multiple sclerosis

Language impairments in people with autoimmune neurological diseases: A scoping review

INTRODUCTION

Autoimmune neurological diseases (ANDs) are a specific type of autoimmune disease that affect cells within the central and peripheral nervous system. ANDs trigger various physical/neuropsychiatric symptoms. However, language impairments in people with ANDs are not well characterized. Here we aimed to determine the kinds of language impairment that most commonly emerge in 10 ANDs, the characteristics of the patients (demographic, neurological damage), and the assessment methods used.

METHODS

We followed the PRISMA Extension for Scoping Reviews (PRISMA-ScR). PubMed and Google Scholar were searched. We used a list of search terms containing 10 types of ANDs (e.g., multiple sclerosis, acute disseminated encephalomyelitis) in combination with the terms aphasia, dysphasia, fluency, language, listening, morphology, phonology, pragmatics, reading, semantics, speaking, syntax, writing. The reference lists and citations of the relevant papers were also investigated. The type of AND, patient characteristics, neurological damage and examination technique, language tests administered, and main findings were noted for each study meeting the inclusion criteria.

RESULTS

We found 171 studies meeting our inclusion criteria. These comprised group studies and case studies. Language impairments differed largely among types of ANDs. Neurological findings were mentioned in most of the papers, but specific language tests were rarely used.

CONCLUSIONS

Language symptoms in people with ANDs are commonly reported. These are often not full descriptions or only focus on specific time points in the course of the disease. Future research needs to assess specific language functions in people with ANDs and relate their language impairments to brain damage at different stages of disease evolution.

Semantic clustering on common list-learning tasks: a systematic review of the state of the literature and recommendations for future directions

INTRODUCTION

On some list-learning tasks, such as the California Verbal Learning Test (CVLT) or Hopkins Verbal Learning Test (HVLT), examinees have the opportunity to group words based on semantically related categories (i.e., semantic clustering). Semantic clustering (SC) is often considered the most efficient organizational strategy and adopting SC is presumed to improve learning and memory. In addition, SC is conceptualized as reflecting higher-order executive functioning skills. Although SC measures have intuitive appeal, to date, there are no comprehensive reviews of the SC literature base that summarize its psychometric utility. In this systematic review, we synthesize the literature to judge the validity of SC scores.

METHOD

We conducted a systematic literature search for empirical articles reporting SC from the CVLT and HVLT. We qualitatively described the relationship of SC with other list-learning and cognitive test scores and clinical diagnoses, contrasting SC with serial clustering and total learning scores when possible.

RESULTS

SC was inversely correlated with serial clustering. Higher SC was strongly associated with better learning and memory performances. When compared with cognitive tests, SC tended to have the strongest relationships with other memory measures and modest relationships with tests of executive functioning. SC had negligible to small relationships with most other cognitive domains. Traditional memory scores yielded stronger relationships to cognitive test performances than did SC. SC across clinical groups varied widely, but clinical groups tended to use SC less often than healthy comparison groups.

CONCLUSION

Our comprehensive review of the literature revealed that SC is strongly related to measures of learning and memory on the CVLT and HVLT and is correlated with a wide range of cognitive functions. SC has been understudied in relevant populations and additional research is needed to test the degree to which it adds incremental validity beyond traditional measures of learning and memory.

The Stroop Task Sex Difference: Evolved Inhibition or Color Naming?

Previous research shows that women outperform men in the classic Stroop task, but it is not known why this difference occurs. There are currently two main hypotheses: (1) women have enhanced verbal abilities, and (2) women show greater inhibition. In two Stroop experiments, we examined the Inhibition hypothesis by adopting a procedure, often used in visual cognition paradigms, that induces a particular inhibitory component. So-called Negative Priming occurs when a distracting non-target stimulus on one trial becomes the target on the following trial. Results from our experiments showed that the degree to which this type of inhibition occurs within the Stroop effect is no different for men and women. This was the case irrespective of whether participants made a vocal response (Experiment 1; n = 64, 32 men and 32 women) or a manual response (Experiment 2; n = 64, 32 men and 32 women). These results do not therefore support the Inhibition hypothesis. We additionally review findings from a range of paradigms that can be seen as indexing the different components required for the Stroop task (e.g., distractor suppression). This review suggests that the sex effect is due to superior color naming ability in women.

Metacognition and self-awareness in Multiple Sclerosis

Although a large range of literature on awareness and metacognition focuses on different neurological populations, little attention has been paid to Multiple Sclerosis (MS). This paper gathers literatures related to studies of anosognosia and the theoretical construct of metacognition which both offer a means to operationalize and measure awareness in MS. We focused on both a clinical concern, regarding the relationship between subjective and objective evolution of cognitive performance, and the theoretical issue of metacognitive processes implicated in disease awareness. We identified 26 papers with findings related to awareness of cognitive impairment in MS using questionnaire-based or performance-based methods. We found support for the idea that the relationship between subjective evaluation and neuropsychological evaluation depends on disease duration and is strongly modulated by other variables, such as mood state. We propose that the metacognitive deficit for memory tasks in this population arises from memory impairment. Finally, we discuss methodological issues, variability in MS patients, and the domain specificity of metacognitive impairment.

Fatigue is associated with poor sleep in people with multiple sclerosis and cognitive impairment

Background. Fatigue is the most common symptom in people with multiple sclerosis (MS). Poor sleep also occurs in this population. Objective. The objective of this study was to determine the relationship between fatigue and sleep quality in people with MS and cognitive impairment. Method. This cross-sectional study assessed relationships among fatigue, assessed with the Modified Fatigue Impact Scale (MFIS) and the Fatigue Severity Scale (FSS), sleep quality assessed with the Pittsburg Sleep Quality Index (PSQI), and demographics in 121 people with MS and cognitive impairment. Results. Fatigue was significantly correlated with poor sleep quality (MFIS: F = 15.60, P < 0.01; FSS: F = 12.09, P < 0.01). FSS scores were also significantly correlated with the PSQI subscore for daytime dysfunction and MFIS scores were significantly correlated with disability, age, and the PSQI subscores for sleep quality, sleep duration, and daytime dysfunction. Conclusions. This study demonstrates a relationship between fatigue and sleep quality in individuals with MS and cognitive impairment.

The nature of verbal memory impairment in multiple sclerosis: a list-learning and meta-analytic study

The primary purpose of this study was to test the hypothesis that multiple sclerosis (MS) patients have impaired acquisition rather than a retrieval deficit. Verbal memory impairment in MS was examined in 53 relapsing-remitting MS patients and 31 healthy controls (HC), and in a meta-analysis of studies that examined memory functioning in MS with list-learning tasks. The MS group demonstrated significantly lower acquisition and delayed recall performance than the HC group, and the meta-analysis revealed that the largest effect sizes were obtained for acquisition measures relative to delayed recall and recognition. Our data argue against a retrieval deficit as the sole explanation for verbal memory impairment in MS, and make a consistent case for the position that deficient acquisition contributes to the memory dysfunction of MS patients. Deficient acquisition may result from demyelination in relevant white matter tracts that reduces encoding efficiency as a result of impaired speed of information processing.

Quality of life in multiple sclerosis: effects of current treatment options

Multiple sclerosis is the most common non-traumatic neurodegenerative disease in adults. Most of the patients present with both physical and mental deficits which reflect the dissemination of the lesions in the central nervous system, produced by the inflammatory process. The incomplete recovery after relapses, the accumulation of new deficits and the progressive nature of the condition interfere with daily activities of individuals and have a negative impact on their well-being. Indeed, studies show that quality of life measurements are constantly lower in patients with multiple sclerosis. Estimation of health-related quality of life is being increasingly recognized as necessary when analysing the effectiveness of treatment modalities and for the follow up of patients with chronic diseases such as multiple sclerosis. Current immunomodulatory interventions that are shown to reduce the frequency of relapses and delay disease progression might also have a positive effect on quality of life measurements. Additive pharmacological agents that target cognitive impairments and common symptoms such as depression, fatigue and pain, along with life-style modifications and rehabilitation programmes are also important for the appropriate management that aims to improve quality of life.

The impact of multiple sclerosis on patients' performance on the Stroop Test: processing speed versus interference

Deficits in multiple sclerosis (MS) patients' performance on the Stroop Test have been attributed to problems with processing speed and selective attention. Data for 248 MS patients and 178 controls on all three trials of the Stroop were combined using various scoring formulas proposed for assessing processing speed, color difficulty, and interference. The greatest differences between patients and controls involved processing speed. Formulas purporting to measure interference yielded highly inconsistent results: Significant differences between groups were found on two of the most common measures but were in opposite directions. This contradiction stems from the failure of both measures to effectively control for processing speed when assessing interference. Three alternative measures, using relative, ratio, and residualized scores, offer much better indices of interference. When assessed with these alternative measures, interference increased with age, but no differences between patients and controls were found. Difficulties that MS patients have with the Stroop Test are confined to processing speed.

Examining the link between information processing speed and executive functioning in multiple sclerosis

Slowed information processing speed (IPS) is frequently reported in those with multiple sclerosis (MS), and at least 20% are compromised on some aspect of executive functioning also. However, any relationship between these two processes has not been examined. The Sternberg Memory Scanning Test, Processing Speed Index (WAIS-III), Delis Kaplan Executive Function System (D.KEFS), and Working Memory Index (WMS-III) were administered to 90 participants with MS. Their performance on the PSI was significantly below the normative scores but no deficits in memory scanning speed were evident. The initial response speed of the Sternberg and the PSI were more closely related to D.KEFS performance, particularly in timed tasks with a high cognitive demand (switching tasks). In contrast, memory scanning speed was related to working memory. This study reinforces the link between IPS and working memory in MS, and supports the suggestion that IPS is not a unitary construct.

Rapid serial processing in patients with multiple sclerosis: the role of peripheral deficits

This study compared speed of information processing in patients with relapsing-remitting or secondary progressive multiple sclerosis (MS) and healthy controls using the Stroop Test and a Picture Naming Test (PNT). While both tests evaluated processing speed within a format calling for rapid serial processing of stimulus information, the PNT included trials designed to impose greater verbal-motor and ocular-motor challenges by using novel rather than repeated pictures and by presenting the pictures in distributed locations rather than always centered on the screen. The results confirmed that a decrease in the speed of information processing is a key feature of the cognitive impairment occurring in conjunction with MS. When this feature is evaluated with tests requiring rapid serial processing of stimulus information, the contribution of peripheral motor deficits appears to be modest.

Automatic and Controlled Uses of Memory in Alzheimer's Disease

This study used the process-dissociation procedure (Jacoby, 1991) to examine the contribution of automatic and controlled uses of memory to a stem completion task in 16 patients with Alzheimer's disease (AD) and a matched group of healthy elderly subjects (EC). In an inclusion task subjects attempted to use a studied word to complete three-letter word stems, in an exclusion task they were instructed to complete stems with unstudied words. Relative to patients with AD, EC subjects produced more target word completions under inclusion conditions, and less target word completions under exclusion conditions. The probability of the AD group using studied words to complete stems was invariant across inclusion and exclusion conditions. Estimates derived from the process-dissociation calculations, showed that the performance of the AD patients was mediated entirely by automatic uses of memory, whereas for EC subjects controlled and automatic processes codetermined task performance. Both estimates of controlled and to a lesser extent automatic uses of memory were greater for the EC than the AD subjects, indicating that the stem completion impairment in AD may not be entirely attributable to a deficiency in controlled memory processes but also due to reduced automatic processing.

Metamemory experiments in neurological populations: a review

Metamemory refers to knowledge about one's memory capabilities and strategies that can aid memory, as well as the processes involved in memory self-monitoring. Although metamemory has been studied in cognitive psychology for several decades, there have been fewer studies investigating the neuropsychology of metamemory. In recent years, a growing number of studies of neurological patient groups have been conducted in order to investigate the neural correlates of metamemory. In this review, we examine the neuropsychological evidence that the frontal lobes are critically involved in monitoring and control processes, which are the central components of metamemory. The following conclusions are drawn from this literature: (1) There is a strong correlation between indices of frontal lobe function or structural integrity and metamemory accuracy (2) The combination of frontal lobe dysfunction and poor memory severely impairs metamemorial processes (3) Metamemory tasks vary in subject performance levels, and quite likely, in the underlying processes these different tasks measure, and (4) Metamemory, as measured by experimental tasks, may dissociate from basic memory retrieval processes and from global judgments of memory.

Cognitive impairment in relapsing and primary progressive multiple sclerosis: mostly a matter of speed

Based on the assumption that cognitive impairment in MS is consistent with subcortical dementia, a battery of neuropsychological tests was assembled that included measures of executive function (Tower of London and Wisconsin Card Sorting Test), verbal learning and memory (a paired associates learning test), and speeded information processing (Stroop Color Word Interference Test). The battery was administered to patients with relapsing and primary progressive MS and to healthy controls. Differences between patients and controls occurred on several of the measures. However, when differences with respect to fatigue and depression were statistically controlled, the only differences that remained significant involved measures relating to the speed of information processing. Patients performed more slowly than controls, with the disparity being greater for relapsing patients than for those with primary progressive disease. The slowing was evident on measures of automatic as well as controlled processing and regardless of whether speed was an explicit feature of successful performance or recorded unobstrusively while the patient concentrated on planning a correct solution to a problem. Parallels were noted between cognitive slowing associated with MS and that of normal aging.

Dissociating perceptual and conceptual implicit memory in multiple sclerosis patients

Previous studies indicate that Multiple Sclerosis (MS) patients exhibit deficits in tests of explicit memory such as free recall, but show normal priming on implicit tests of memory such as word stem completion. However, the memory performance of patients with different MS disease subtypes has not been fully examined. In the current study, memory was assessed in Primary Progressive (PPMS), Relapsing Remitting (RRMS), and Secondary Progressive (SPMS) MS subgroups. Explicit memory as well as perceptual and conceptual implicit memory were examined using free recall, word fragment completion, and exemplar generation tests, respectively. All three groups of MS patients exhibited free recall deficits and normal priming on the exemplar generation test. However, the PPMS group exhibited a deficit in word fragment completion priming, whereas the RRMS and SPMS groups exhibited normal levels of priming on this task. Lesion load was assessed using magnetic resonance imaging and was negatively correlated with explicit memory performance, but it did not account for the observed deficits in perceptual implicit memory. The results indicate that PPMS patients exhibit a pattern of memory impairment that is distinct from that of the RRMS and SPMS groups. Moreover, the results indicate that perceptual implicit memory can be neurologically dissociated from conceptual implicit memory.

Cognitive findings in spinocerebellar ataxia type 2: relationship to genetic and clinical variables

Several authors have recently reported a broad cognitive impairment in autosomal dominant cerebellar ataxias (ADCAs) patients. However, only a few studies on neuropsychological features in spinocerebellar ataxia type 2 (SCA2) patients are present in the current literature. The aim of this study is to evaluate the cognitive impairment in a wide sample of SCA2 patients and to verify the role of different disease-related factors (age of onset, disease duration, and clinical severity) on intellectual abilities. We administered a battery of neuropsychological tests assessing handedness, attention, short- and long-term verbal and visuo-spatial memory, executive functions, constructive abilities, general intellectual abilities and depression to 18 SCA2 patients belonging to eight families who came to our observation. Evidence of impaired verbal memory, executive functions and attention was found. The cognitive status was partially related to clinical severity rather than to disease duration or age at onset of symptoms. We partially confirmed data on cognitive defects already reported by others but we also found defective attention skills as well as significant lower performances in a nonverbal intelligence task.

Stroop interference and negative priming in patients with multiple sclerosis

The experiment reported represents a preliminary assessment of the ability of multiple sclerosis (MS) patients to inhibit distracting stimuli in a selective attention task. Twenty MS and 20 matched control participants were given a card version of the Stroop colour-word interference task. Four conditions were included; neutral (strings of coloured Xs), congruent (colour and word matched), Stroop interference (colour and word conflicted) and ignored repeated (again, conflicting colour and words, but colour on trial n matched the word on trial n-1). Response times (RTs) to 30 trials in each condition were measured to the nearest second. Increased Stroop interference scores were evident for the MS patients relative to the control group. However, a negative priming effect was evident for both MS and control groups; RTs were longer for the ignored repeated condition relative to the Stroop interference condition. This suggests that both groups were able to inhibit distractors on trial n-1, and that increased Stroop interference scores, for MS patients were not due to a complete breakdown of inhibitory processing. Although negative priming effects did not differ across the groups, the possibility of a partial breakdown in inhibitory processes could not be ruled out. Other explanations for increased Stroop interference in MS patients are also briefly considered.

Conscious and unconscious uses of memory in multiple sclerosis

Conscious and unconscious uses of memory and priming were studied in 30 patients with multiple sclerosis (MS) and 15 normal control (NC) subjects. MS patients were classified into two subgroups according to their cognitive status; 15 of them were cognitively deteriorated (the MS-D group) and 15 cognitively preserved (the MS-P group). A process dissociation procedure [J. Mem. Lang. 30 (1991) 513] was used to separate conscious and unconscious memory performance in a word stem completion task. The results showed that the MS-D group had deficient conscious memory performance, but had intact unconscious memory as well as priming. The MS-P group showed normal conscious and unconscious uses of memory and priming. Thus, in MS-related cognitive decline, conscious memory seems to be vulnerable, whereas unconscious memory remains intact. The results provide neuropsychological support for the distinction between conscious and unconscious memory processes. Moreover, the results show the importance of studying cognitively homogenous MS groups as opposed to heterogenous ones, in order to find the underlying mechanisms of memory deficits in MS. Interestingly, the neural systems needed for the unconscious use of memory do not seem to deteriorate even in MS patients with deficient overall cognitive capacity. This finding encourages the development of future rehabilitation programs, suggesting that unconscious remembering might help MS patients with deficient conscious memory to cope with their daily activities.