Awareness of remembering achieved through automatic and conscious processes in multiple sclerosis

Naturalistic Assessment using a Simulated Environment: Cognitive Correlates and Relationship to Functional Status in Individuals with Neurologic Conditions

Objective

Research has shown that neurologic conditions, such as traumatic brain injury and multiple sclerosis, result in a number of cognitive and functional deficits. However, little is known about the relationship between various cognitive domains and ability to perform everyday activities. The Community Shopping Task (CST), a naturalistic assessment task conducted in a simulated environment, was used to examine functional abilities and cognitive correlates of everyday functioning in individuals with neurologic conditions.

Method

Thirty-four participants with neurologic conditions and 34 healthy controls completed the CST as well as traditional paper-pencil measures of cognition. In addition, all participants completed a questionnaire assessing instrumental activities of daily living (IADLs).

Results

The results indicated that participants with neurologic conditions required significantly more cues and time to complete the CST compared to control participants and that immediate memory and executive functioning were important predictors of CST performance. Furthermore, time to complete the CST accounted for a significant amount of variance in IADL performance, over and beyond the traditional measures of cognition.

Conclusions

These results provide evidence that a naturalistic task completed in an everyday environment can enhance our understanding of how daily functioning is impacted in individuals with neurologic conditions and subsequently inform rehabilitation strategies.

A Comparison of Implicit and Explicit Motor Sequence Learning in Patients with Relapsing-Remitting Multiple Sclerosis

This study tends to assess implicit and explicit types of motor learning in patients with Multiple Sclerosis (MS) and normal peers by means of a serial reaction time. Sample size was 15 for each group and Samples included 30 patients with MS and 30 normal peers and were assigned to implicit and explicit learning groups. A repeated measures ANOVA was used for measuring reaction time and response error, and a paired samples t-test was used to compare regular and irregular sequence data in each group. Comparison of these two types of learning in speed (response time) and accuracy (number of errors) showed the number of errors (P = 0.012) and response time (P = 0.012) in the implicit motor learning group of MS patients and the number of errors (P = 0.096) and response time (P = 0.954) in the explicit motor learning group of MS patients. Moreover, comparison showed the number of errors (P = 0.008) and response time (P = 0.05) in the implicit group of normal peers and the number of errors (P = 0.011) and response time (P = 0.442) in the explicit group of normal peers. The results showed that explaining and describing the task is less effective at training the motor sequence of MS patients and that these patients benefit more from implicit learning.

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.

Preservation of gray matter volume in multiple sclerosis patients with the Met allele of the rs6265 (Val66Met) SNP of brain-derived neurotrophic factor

To investigate the association of the rs6265 (Val66Met) single nucleotide polymorphism (SNP) of brain-derived neurotrophic factor (BDNF) with brain morphometry and functional status as measured by quantitative magnetic resonance imaging (MRI) and neurocognitive testing in multiple sclerosis (MS) patients. BDNF is released by neurons and by immune cells in MS brain. The rs6265 SNP variation of BDNF causes substitution of valine (Val) for methionine (Met) and interferes with activity-dependent BDNF secretion. A total of 209 treated MS patients (161 females; 48 males) underwent clinical brain MRI and were genotyped for the BDNF rs6265 Val66Met SNP. A subset of 108 patients had neurocognitive testing for processing speed, memory and executive function. The MRI measurements included T2 and T1-lesion volume (LV); normalized brain volume measures of whole brain (WB) volume, white and gray matter volume (NWMV and NGMV) and the diffusion-weighted imaging measure of WB mean parenchyma diffusivity (MPD). The Met66 allele status was positively associated with NGMV (P = 0.015, standardized beta = 0.15) and negatively associated with T2-LV (P = 0.041, standardized beta = -0.14). There were no significant associations between Met66 allele status and T1-LV, NWMV or MPD. On the Paced Serial Addition Test (PASAT), a trend (P = 0.057) favoring the Met66 allele group was observed. There were no significant associations between Met66 allele status and other neurocognitive measures. The BDNF Met66 allele is associated with lower damage as evidenced by measurement of NGMV and T2-LV in MS patients.

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.

Validity of the minimal assessment of cognitive function in multiple sclerosis (MACFIMS)

Cognitive impairment occurs in roughly 50% of patients with multiple sclerosis (MS). It is well known that processing speed and episodic memory deficits are the most common neuropsychological (NP) sequelae in this illness. Consensus has emerged about the specific tests that prove most helpful for routine monitoring of MS associated cognitive impairment. The purpose of this study was to examine the validity of the Minimal Assessment of Cognitive Function in MS (MACFIMS), a recommended battery based on the findings of an international conference held in 2001. We tested 291 MS patients and 56 healthy controls. Frequencies of impairment paralleled those reported in previous work for both individual cognitive domains and general impairment. All tests were impaired in the MS group, and distinguished relapsing-remitting (RR) from secondary progressive (SP) course. Principle components analysis showed a distinct episodic memory component. Most of the MACFIMS tests discriminated disabled from employed patients. However, in regression models accounting for all NP tests, those emphasizing verbal memory and executive function were most predictive of vocational status. We conclude that the MACFIMS is a valid approach to routine NP assessment of MS patients. Future work is planned to determine its psychometric properties in a longitudinal study.

Ordinal Process Dissociation and the Measurement of Automatic and Controlled Processes

The process-dissociation equations (L. Jacoby, 1991) have been applied to results from inclusion and exclusion tasks to derive quantitative estimates of the influence of controlled and automatic processes on memory. This research has provoked controversies (e.g., T. Curran & D. Hintzman, 1995) regarding the validity of specific assumptions underlying the process-dissociation equations. In this article, the author explores the conclusions one can draw about the ordinal relations between automatic and controlled processes across experimental conditions from results in the inclusion and exclusion tasks. Given relatively neutral assumptions, this article presents and proves 6 theorems that allow investigators to draw conclusions about the ordinal relations between automatic and/or controlled processes across experimental conditions. An illustrative example is presented, and the current approach is compared with the original process-dissociation framework.

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.

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.

Verbal learning strategies in patients with multiple sclerosis

Word list learning was studied in patients with a definite diagnosis of Multiple Sclerosis and in Normal Control subjects by means of the selective reminding procedure of Buschke and Fuld in two learning conditions: (1) using unrelated items and (2) paired-associate items. The Multiple Sclerosis patients displayed poor learning in both conditions. To identify the functional locus of their deficit, stochastic Markov chain analyses were performed, which allowed individual measurements of encoding, automatic and intentional retrieval abilities. On both tasks, encoding on the first trial and automatic retrieval on the subsequent trials were impaired in Multiple Sclerosis patients, whereas intentional retrieval, both with and without reminding by the examiner, appeared to be preserved. As all of the impaired abilities require a normal speed of information processing, the salient learning deficit of the Multiple Sclerosis patients could be tentatively traced back to the slowing down of their mental activity.

APOE and risk of cognitive impairment in multiple sclerosis

OBJECTIVES

The APOE gene polymorphism and the -491 A/T polymorphism in its regulatory region have been associated with an increased risk for developing Alzheimer's disease. We examined these polymorphisms in multiple sclerosis (MS) patients, to determine if a genetic predisposition may explain the risk for developing cognitive decline in MS.

MATERIAL AND METHODS

Eighty-nine relapsing-remitting and secondary progressive MS patients underwent to a full neuropsychological battery as well as to determination of APOE and -491 A/T polymorphisms. Genetic analysis was also performed in 107 population controls.

RESULTS

The APOE polymorphism was not associated with the risk of cognitive impairment in MS patients. The AA genotype of the -491 A/T polymorphism in the APOE regulatory region was more frequent in cognitively impaired than in cognitively preserved MS subjects.

CONCLUSION

The AA homozygous state of the -491 A/T polymorphism of the APOE regulatory region is associated with cognitive impairment in patients with MS.

Memory dissociation and metamemory in multiple sclerosis

A previous study by Scarrabelotti and Carroll [60] was the first to use Jacoby's process dissociation procedure [31] with an MS group to investigate memory function, and the first to obtain metamemory judgments about recall under inclusion and exclusion instructions. Twelve months later using different words, 49 MS and 39 matched controls were readministered a word stem completion task, and made metamemory judgments about their performance. The California Verbal Learning Test (CVLT) [18], Stroop [64], and Reitan's Word Finding Test (WFT) [57], tests considered to particularly rely on conscious processing, were also readministered. At year one testing no group differences were identified in word stem completion under indirect, inclusion, or exclusion instructions, nor in conscious and automatic estimates. By contrast in year two, MS subjects remembered significantly fewer words under inclusion, and employed significantly less conscious processing than the control group to achieve remembering. However, estimates of automatic memory processing were the same for both groups. MS subjects equalled controls in the prospective and retrospective monitoring of words they consciously recalled under inclusion instructions, in both years. By contrast, each group was poor at monitoring words completed automatically under exclusion instructions; and by year two, MS subjects were even less able to monitor such material than controls. Finally by the second year, reduced conscious processing was also related to reduced performance on the Stroop, WFT, and CVLT recall and use of semantic clustering. Taken together, these findings indicate that automatic memory processing is intact in MS, but impairment in memory, metamemory, and other cognitive tasks becomes evident over time when they rely on conscious processes.