The role of speed versus working memory in predicting learning new information in multiple sclerosis

Influence of cognition on the correlation between objective and subjective upper limb measures in people with multiple sclerosis

BACKGROUND

A comprehensive assessment of upper limb (UL) function is mandatory in people with multiple sclerosis (PwMS), and the use of multiple objective and subjective measures is advisable. Findings on the role of cognitive impairment on the assessment of UL function are scant and inconclusive. The present study investigated the influence of cognitive function on the distribution of objective and subjective UL measures and on their association.

METHODS

In the cross-sectional study, subjects with a diagnosis of MS, age ≥ 18 years, right-hand dominance, no presence of orthopedic UL impairment, or other neurological diseases were recruited. The assessment protocol included the Nine-Hole Peg Test (9-HPT), Box and Block Test (BBT), and hand grip strength (HGS), a validated PROM (MAM-36), and the Symbol Digit Modalities Test (SDMT).

RESULTS

Two hundred forty-six PwMS were recruited (158 females, mean age = 51.65 ± 13.45 years; mean EDSS = 5.10 ± 1.88) Subject with mild-to-moderate cognitive impairment (SDMT ≤  - 2 SD of normative values) scored lower on the 9-HPT and higher on the BBT and MAM-36 when compared with subject with no cognitive impairment. Cognitive impairment showed a small but significant effect on the association between 9-HPT scores and the MAM-36.

DISCUSSION

Findings suggest that cognitive impairment is associated with subjects' performance on 9-HPT, BBT, and MAM-36 (but not HGS), resulting in scores indicating a poorer UL function. Interestingly, cognitive impairment slightly affected the congruence between subjective and objective UL measures, although only minor differences in the correlation pattern across groups reporting different cognitive performances emerged.

Association Between Disease-Modifying Therapy and Information Processing Speed in Multiple Sclerosis

BACKGROUND

Cognitive impairment (CI) is common in multiple sclerosis (MS). Processing speed (PS) is often affected, making it an ideal target for monitoring CI. This study aims to evaluate the association between disease-modifying therapy (DMT) use and intensity and longitudinal changes in Processing Speed Test (PST) scores for individuals with MS.

METHODS

A retrospective analysis of individual PST scores at a single MS center was conducted. Individuals with 2 or more PST assessments were included. Scores on the PST were compared longitudinally between those who had been on a DMT for 2 or more years and those who had been off a DMT for 2 or more years and between those on high-efficacy DMTs and those on low-/moderate-efficacy DMTs. A linear regression model was approximated to evaluate the rate of cognitive change over time. A propensity score adjustment was conducted using a multivariable logistic regression.

RESULTS

The cohort was 642 individuals, 539 on DMT and 103 off DMT. Median age and disease duration was 49.7 (IQR 42.4-57.9) and 16.6 years (IQR 9.3-23.0) in the DMT group, and 58.9 (IQR 52.2-65.3) and 20.0 years (IQR 14.1-31.4) in the non-DMT group. Both cohorts were predominantly female (75% DMT, 79.6% non-DMT), with a mean of 4 assessments (IQR 3-5), and an average monitoring duration of 1.9 years (1.2-2.4) in the DMT group, and 1.8 years (1.4-2.4) in the non-DMT group. After adjusting for multiple factors, DMT status and intensity were not found to be significant predictors of longitudinal PST change.

CONCLUSIONS

Neither DMT status nor intensity was a significant predictor of cognitive processing speed over a period of approximately 2 years. Future prospective studies are needed to further support these findings.

Predictors of multiple sclerosis progression: A systematic review of conventional magnetic resonance imaging studies

INTRODUCTION

Multiple Sclerosis (MS) is a chronic neurodegenerative disorder that affects the central nervous system (CNS) and results in progressive clinical disability and cognitive decline. Currently, there are no specific imaging parameters available for the prediction of longitudinal disability in MS patients. Magnetic resonance imaging (MRI) has linked imaging anomalies to clinical and cognitive deficits in MS. In this study, we aimed to evaluate the effectiveness of MRI in predicting disability, clinical progression, and cognitive decline in MS.

METHODS

In this study, according to PRISMA guidelines, we comprehensively searched the Web of Science, PubMed, and Embase databases to identify pertinent articles that employed conventional MRI in the context of Relapsing-Remitting and progressive forms of MS. Following a rigorous screening process, studies that met the predefined inclusion criteria were selected for data extraction and evaluated for potential sources of bias.

RESULTS

A total of 3028 records were retrieved from database searching. After a rigorous screening, 53 records met the criteria and were included in this study. Lesions and alterations in CNS structures like white matter, gray matter, corpus callosum, thalamus, and spinal cord, may be used to anticipate disability progression. Several prognostic factors associated with the progression of MS, including presence of cortical lesions, changes in gray matter volume, whole brain atrophy, the corpus callosum index, alterations in thalamic volume, and lesions or alterations in cross-sectional area of the spinal cord. For cognitive impairment in MS patients, reliable predictors include cortical gray matter volume, brain atrophy, lesion characteristics (T2-lesion load, temporal, frontal, and cerebellar lesions), white matter lesion volume, thalamic volume, and corpus callosum density.

CONCLUSION

This study indicates that MRI can be used to predict the cognitive decline, disability progression, and disease progression in MS patients over time.

The nature of memory impairment in multiple sclerosis: understanding different patterns over the course of the disease

Introduction

Memory deficit is one of the most common and severe cognitive impairments in patients with multiple sclerosis and can greatly affect their quality of life. However, there is currently no agreement as to the nature of memory deficit in multiple sclerosis.

Methods

This cross-sectional study, carried out at the Dr. Josep Trueta and Santa Caterina hospitals in Girona (Spain), was designed to determine the semiology of verbal memory deficit in the different stages of the disease. To this end, a modification of Rey's verbal auditory test was created by introducing two recognition trials between the five learning trials, thus monitoring what happens in terms of acquisition versus the retrieval of information during the learning phase. Linear regression models were used to evaluate verbal episodic memory performance between-groups adjusting results by age, sex, educational level, and the presence of anxiety and/or depressive symptoms.

Results

133 patients with multiple sclerosis, clinically isolated syndrome, and radiologically isolated syndrome and 55 healthy controls aged 18-65 years were assessed. It was observed that the memory processes of multiple sclerosis patients worsen with the progression of the disease. In this respect, patients in pre-diagnostic phases (radiologically isolated syndrome and clinically isolated syndrome) show no differences in verbal episodic memory compared to the healthy controls. Patients in the inflammatory stage (relapsing-remitting multiple sclerosis) show a previously learned information retrieval deficit, while patients in progressive stages (secondary progressive multiple sclerosis and primary progressive multiple sclerosis) do not even correctly acquire information.

Discussion

These results provide significant information to assist in understanding the nature of memory deficits in multiple sclerosis over the course of the disease. These results are discussed in terms of possible cognitive rehabilitation strategies depending on the evolutive stage and are related to neuropathological mechanisms involved in the progression of the disease.

Effect of deep gray matter atrophy on information processing speed in early relapsing-remitting multiple sclerosis

BACKGROUND

Cognitive dysfunction, including reduced Information processing speed (IPS), is relatively common in multiple sclerosis(MS). IPS deficits have profound effects on several aspects of patients' life. Previous studies showed that deep gray matter atrophy is highly correlated with overall cognitive impairment in MS. However, the effect of deep gray matter atrophy on IPS deficits is not well understood. In this study, we evaluated the effects of deep gray matter volume changes on IPS in people with early relapse-remitting MS (RRMS) compared to healthy control.

METHODS

In this case-control study, we enrolled 63 case with RRMS and 36 healthy controls. All patients were diagnosed within 6 years. IPS was evaluated using the Integrated Cognitive Assessment (ICA) test. We also performed a 1.5T MRI to evaluate deep gray matter structures.

RESULTS

People with RRMS had lower accuracy in the ICA test (p = .01). However, the reaction time did not significantly differ between RRMS and control groups (p = .6). Thalamus volume was significantly lower in the RRMS group with impaired IPS compared to the RRMS with normal IPS and control groups (p < 10-4). Other deep gray matter structures were not significantly different between the RRMS with impaired IPS group and the RRMS with normal IPS group.

CONCLUSION

Some people with MS are impaired in IPS even in the early stages of the disease. Thalamic atrophy affected IPS in these patients, however atrophy in other deep gray matter structures, including caudate, putamen, globus pallidus, hippocampus, amygdala, accumbens, and cerebellum, were not significantly correlated with IPS impairment in early RRMS.

The Efficacy of the Speed of Processing Training Program in Improving Functional Outcome: From Restoration to Generalization

OBJECTIVE

To examine the efficacy of Speed of Processing Training (SOPT) in improving everyday functional outcomes in persons with multiple sclerosis (MS).

DESIGN

Randomized controlled trial.

SETTING

A nonprofit rehabilitation research institution and the community.

PARTICIPANTS

In total, 60 participants with MS with impaired processing speed were randomly assigned to SOPT (n=33) or an active control group (n=27).

INTERVENTION

SOPT, a restorative computerized cognitive intervention involving 10 treatment sessions consisting of visual tasks designed to improve speed and accuracy of information processing MAIN OUTCOME MEASURES: Outcomes included performance on the Timed Instrumental Activities of Daily Living (TIADL) and self-report of functional behavior, quality of life, and affect.

RESULTS

The treatment group showed improvement in the total TIADL score and 2 subtests compared with the active control group. Participants in the treatment group who demonstrated improved cognitive performance after the intervention also showed improved performance on one TIADL subtest. Quality of life, affective symptomatology, and self-reported functional status were not changed after the intervention.

CONCLUSIONS

Improvement in underlying cognitive or perceptual deficits is thought to promote recovery and everyday performance as per the restorative approach to cognitive rehabilitation. However, this study showed only selected improvements in everyday functional outcomes for persons with MS.

The relationship between processing speed and verbal and non-verbal new learning and memory in progressive multiple sclerosis

Objective:

Processing speed (PS) deficits are the most common cognitive deficits in multiple sclerosis (MS), followed by learning and memory deficits, and are often an early cognitive problem. It has been argued that impaired PS is a primary consequence of MS, which in turn decreases learning. The current analysis examined the association between PS and learning in a large cohort of individuals with progressive MS.

Methods:

Baseline data from a randomized clinical trial on rehabilitation taking place at 11 centers across North America and Europe were analyzed. Participants included 275 individuals with clinically definite progressive MS (primary, secondary) consented into the trial.

Results:

Symbol Digit Modalities Test (SDMT) significantly correlated with California Verbal Learning Test-II (CVLT-II) ( r = 0.21, p = 0.0003) and Brief Visuospatial Memory Test–Revised (BVMT-R) ( r = 0.516, p < 0.0001). Receiver operating characteristic (ROC) analysis of the SDMT z score to distinguish between impaired and non-impaired CVLT-II performance demonstrated an area under the curve (AUC) of 0.61 (95% confidence interval (CI): 0.55–0.68) and a threshold of −1.62. ROC analysis between SDMT and BVMT-R resulted in an AUC of 0.77 (95% CI: 0.71–0.83) and threshold of −1.75 for the SDMT z score to predict impaired BVMT-R.

Conclusion:

Results indicate little ability beyond chance to predict CVLT-II from SDMT (61%), albeit statistically significant. In contrast, there was a 77% chance that the model could distinguish between impaired and non-impaired BVMT-R. Several potential explanations are discussed.

The degree of cortical plasticity correlates with cognitive performance in patients with Multiple Sclerosis

BACKGROUND

Cortical reorganization and plasticity may compensate for structural damage in Multiple Sclerosis (MS). It is important to establish sensitive methods to measure these compensatory mechanisms, as they may be of prognostic value.

OBJECTIVE

To investigate the association between the degree of cortical plasticity and cognitive performance and to compare plasticity between MS patients and healthy controls (HCs).

METHODS

The amplitudes of the motor evoked potential (MEP) pre and post quadripulse stimulation (QPS) applied over the contralateral motor cortex served as measure of the degree of cortical plasticity in 63 patients with relapsing-remitting MS (RRMS) and 55 matched HCs. The main outcomes were the correlation coefficients between the difference of MEP amplitudes post and pre QPS and the Symbol Digit Modalities Test (SDMT) and Brief Visuospatial Memory Test-Revised (BVMT-R), and the QPS^xgroup interaction in a mixed model predicting the MEP amplitude.

RESULTS

SDMT and BVMT-R correlated significantly with QPS-induced cortical plasticity in RRMS patients. Plasticity was significantly reduced in patients with cognitive impairment compared to patients with preserved cognitive function and the degree of plasticity differentiated between both patient groups. Interestingly, the overall RRMS patient cohort did not show reduced plasticity compared to HCs.

CONCLUSIONS

We provide first evidence that QPS-induced plasticity may inform about the global synaptic plasticity in RRMS which correlates with cognitive performance as well as clinical disability. Larger longitudinal studies on patients with MS are needed to investigate the relevance and prognostic value of this measure for disease progression and recovery.

The efficacy of speed of processing training for improving processing speed in individuals with multiple sclerosis: a randomized clinical trial

OBJECTIVE

The current study examines the efficacy of speed of processing training (SOPT) to improve processing speed (PS) in individuals with multiple sclerosis (MS). Outcomes included changes in the useful field of view (UFOV) and neuropsychological evaluation (NPE).

METHODS

This double-blind, placebo-controlled randomized clinical trial included 84 participants with clinically definite MS and impaired PS, 43 in the treatment group and 41 in the placebo control group. Participants completed a baseline NPE and a repeat NPE post-treatment. The treatment group was randomized to booster sessions or no contact. Long-term follow-up assessments were completed 6 months after treatment.

RESULTS

A significant effect of SOPT was observed on both the UFOV (large effect) and pattern comparison with a similar pattern of results noted on letter comparison, albeit at a trend level. The treatment effect was maintained 6 months later. The impact of booster sessions was not significant. Correlations between degree of improvement on the UFOV and the number of levels completed within each training task were significant for both speed and divided attention indicating that completion of more levels of training correlated with greater benefit.

CONCLUSION

SOPT is effective for treating PS deficits in MS with benefit documented on both the UFOV and a neuropsychological measure of PS. Less benefit was observed as the outcome measures became more distinct in cognitive demands from the treatment. Long-term maintenance was observed. The number of training levels completed within the 10-sessions exerted a significant impact on treatment benefit, with more levels completed resulting in greater benefit.

Diffusion imaging of fornix and interconnected limbic deep grey matter is linked to cognitive impairment in multiple sclerosis

Diffusion tensor imaging (DTI) and volumetric magnetic resonance imaging (MRI) have shown white matter (WM) and deep grey matter (GM) abnormalities in the limbic system of multiple sclerosis (MS) participants. Structures like the fornix have been associated with cognitive impairment (CI) in MS, but the diffusion metrics are often biased by partial volume effects from cerebrospinal fluid (CSF) due to its small bundle size and intraventricular location. These errors in DTI parameter estimation worsen with atrophy in MS. The goal here was to evaluate DTI parameters and volumes of the fornix, as well as associated deep GM structures like the thalamus and hippocampus, with high-resolution fluid-attenuated inversion recovery (FLAIR)-DTI at 3T in 43 MS patients, with and without CI, versus 43 controls. The fornix, thalamus and hippocampus displayed atrophy and/or abnormal diffusion metrics, with the fornix showing the most extensive changes within the structures studied here, mainly in CI MS. The affected fornix volumes and diffusion metrics were associated with thalamic atrophy and atypical diffusion metrics in interconnected limbic GM, larger total lesion volume and global brain atrophy. Lower fractional anisotropy (FA) and higher mean and radial diffusivity in the fornix, lower hippocampus FA and lower thalamus volume were strongly correlated with CI in MS. Hippocampus FA and thalamus atrophy were negatively correlated with fatigue and longer time since MS symptoms onset, respectively. FLAIR-DTI and volumetric analyses provided methodologically superior evidence for microstructural abnormalities and extensive atrophy of the fornix and interconnected deep GM in MS that were associated with cognitive deficits.

Application of neuropsychology and imaging to brain injury and use of the integrative cognitive rehabilitation psychotherapy model

BACKGROUND

An early approach to cognitive rehabilitation therapy (CRT) was developed based on A. R. Luria's theory of brain function. Expanding upon this approach, the Integrative Cognitive Rehabilitation Psychotherapy model (ICRP) was advanced.

OBJECTIVE

To describe the ICRP approach to treatment of clients post brain injury and provide a comprehensive list of evaluation tools to determine the client's abilities and needs. Finally, to provide a link between CRT and functional imaging studies designed to improve rehabilitation efforts.

METHODS

History of cognitive rehabilitation and neuropsychological testing is reviewed and description of cognitive, academic, psychiatric, and substance abuse tools are provided. Cognitive and emotional treatment techniques are fully described. Additionally, a method of determining the client's stage of recovery and pertinent functional imaging studies is detailed.

RESULTS

Authors have been able to provide a set of tools and techniques to use in comprehensive treatment of clients with brain injury.

CONCLUSIONS

Inclusive treatment which is outlined in the ICRP model is optimal for the client's recovery and return to a full and satisfying life post brain injury. The model provides a framework for neuropsychologists to integrate issues that tend to co-occur in clients living with brain injury into a unified treatment plan.

Staging and stratifying cognitive dysfunction in multiple sclerosis

BACKGROUND

The sequence in which cognitive domains become impaired in multiple sclerosis (MS) is yet to be formally demonstrated. It is unclear whether processing speed dysfunction temporally precedes other cognitive impairments, such as memory and executive function.

OBJECTIVE

Determine the order in which different cognitive domains become impaired in MS and validate these findings using clinical and vocational outcomes.

METHODS

In a longitudinal sample of 1073 MS patients and 306 healthy controls, we measured performance on multiple, consensus-standard, neurocognitive tests. We used an event-based staging approach to model the sequence in which cognitive domains become impaired. Linear and logistic mixed-effects models were used to explore associations between stages of impairment, neurological disability, and employment status.

RESULTS

Our model suggested that the order of impairments was as follows: processing speed, visual learning, verbal learning, working memory/attention, and executive function. Stage of cognitive impairment predicted greater neurological disability, β = 0.16, SE = 0.02, p < 0.001, and probability of unemployment, β = 1.14, SE = 0.001, p < 0.001.

CONCLUSION

This is the first study to introduce a cognitive staging and stratification system for MS. Findings underscore the importance of using the Symbol Digit Modalities Test in routine screening for cognitive impairment and memory testing to assess patients later in disease evolution.

Early neuropsychological markers of cognitive involvement in multiple sclerosis

BACKGROUND

Cognitive impairment due to multiple sclerosis (MS) is common and often limits occupational functioning, contributes to disability, and reduces quality of life. Early detection of cognitive involvement in MS is critical for treatment planning and intervention, and frequent, regular cognitive monitoring may provide insight into subtle changes in disease progression.

OBJECTIVE

To compare the sensitivity and specificity of clinical, computer-based and experimental measures to early cognitive involvement in MS.

METHODS

Cognitive functioning was compared in MS participants early in the disease course to matched healthy controls using conventional, computer-based and functional assessments: the Brief International Cognitive Assessment in MS (BICAMS); the computer-based Cogstate Brief Battery (CBB); the Attention Network Test-Interaction (ANT-I), including intra-individual variability; and the Test of Everyday Cognitive Ability (TECA), a functional measure of instrumental activities of daily living.

RESULTS

MS participants (n = 25, mean disease duration= 5.82 ± 3.65 years) and demographically matched healthy controls (n = 29) completed the cognitive assessments. The Cogstate measure of choice reaction time (AUC = 0.73, p = .004), intra-individual variability on the ANT-I (AUC = 0.79, p = .001), and TECA (AUC = 0.78, p = .001) scores were the most sensitive and specific markers of cognitive involvement in MS.

CONCLUSIONS

Brief, repeatable, computer-based measures of reaction time and variability detect early MS associated cognitive involvement.

An Interview-Based Assessment of the Experience of Cognitive Impairment in Multiple Sclerosis: The Cognitive Assessment Interview (CAI)

Background: Cognitive impairment is a common feature of multiple sclerosis (MS). A semi-structured interview, including informant input, can characterize the experience of individuals living with MS and cognitive involvement.

Objective: We administered the Cognitive Assessment Interview (CAI), a patient- and informant-based semi-structured interview, to characterize the experience of cognitive impairments in those living with MS.

Methods: Trained raters administered the CAI to a sample of MS participants and their informants enrolled for a trial of cognitive remediation. Cognitive impairments on the CAI were characterized and compared to those captured by neuropsychological and self-report measures.

Results: A total of n = 109 MS participants (mean age = 50.3 ± 12.2) and their available informants (n = 71) were interviewed. Participants reported experiencing processing speed (90/106, 85%), working memory (87/109, 80%), and learning and memory (79/109, 72%) problems most commonly. CAI-based ratings were moderately correlated with a self-report measure (Multiple Sclerosis Neuropsychological Screening Questionnaire, r_s = 0.52, p < 0.001) and only mildly correlated with objective neuropsychological measures specific to executive functions (r_s = 0.21, p = 0.029). For those with informant interviews, ratings were overall consistent, suggesting that the CAI is valid even in cases in which an informant is unavailable and the interview is conducted with the patient alone (as is often the case in clinical and research settings).

Conclusions: The CAI provides a semi-structured interview to characterize the experience of cognitive impairment in MS, with findings representing real-world functioning, adding valuable information to both self-report measures and neuropsychological assessment.

Cognitive impairment in multiple sclerosis: lessons from cerebrospinal fluid biomarkers

Cognitive impairment is a common clinical manifestation of multiple sclerosis, but its pathophysiology is not completely understood. White and grey matter injury together with synaptic dysfunction do play a role. The measurement of biomarkers in the cerebrospinal fluid and the study of their association with cognitive impairment may provide interesting in vivo evidence of the biological mechanisms underlying multiple sclerosis-related cognitive impairment. So far, only a few studies on this topic have been published, giving interesting results that deserve further investigation. Cerebrospinal fluid biomarkers of different pathophysiological mechanisms seem to reflect different neuropsychological patterns of cognitive deficits in multiple sclerosis. The aim of this review is to discuss the studies that have correlated cerebrospinal fluid markers of immune, glial and neuronal pathology with cognitive impairment in multiple sclerosis. Although preliminary, these findings suggest that cerebrospinal fluid biomarkers show some correlation with cognitive performance in multiple sclerosis, thus providing interesting insights into the mechanisms underlying the involvement of specific cognitive domains.

Brain activity pattern changes after adaptive working memory training in multiple sclerosis

Cognitive impairment and related abnormal brain activity are common in people with multiple sclerosis (PwMS). Adaptive training based on working memory (WM) has been shown to ameliorate cognitive symptoms, although the effects at a neural level are unclear. The aim of this study was to expand the existing research on the effects of an adaptive WM rehabilitative intervention on brain functional activity in PwMS. A sample of eighteen PwMS performed an 8-week home-based cognitive rehabilitation treatment based on adaptive WM training. PwMS were assessed before and after treatment using a validated neuropsychological battery and undergoing an fMRI session while carrying out a cognitive task (i.e., Paced Visual Serial Addition Test - PVSAT). fMRI activations were compared to the activation pattern elicited by eighteen matched healthy subjects performing the same task. At baseline, we found abnormal brain activity during PVSAT in PwMS when compared to healthy subjects, with a pattern including several bilateral activation clusters. Following rehabilitation, PwMS improved cognitive performance, as evaluated by the neuropsychological battery, and showed a different activation map with clusters mainly located in the right cerebellum and in the left hemisphere. The only significant cluster in the right hemisphere was located in the inferior parietal lobule, and the BOLD signal extracted in this area significantly correlated with cognitive performance both before and after the treatment. We suggest that WM training can improve the cognitive performance and reduce the abnormal activation of PwMS by partially maintaining or even restoring brain cognitive function.

Non-classical behavior of the default mode network regions during an information processing task

The default mode network (DMN) efficient deactivation and suppressed functional connectivity (FC) during goal-directed tasks, which require attentional resources, have been considered essential to healthy brain cognition. However, recent studies have shown that DMN regions do not always show the expected behavior. Then, we aimed to investigate the functional activation and connectivity of DMN nodes in young, healthy controls during a goal-directed task. We used an adaptation of the symbol digit modalities test (SDMT) to evaluate the information processing speed (IPS). Twenty-four subjects (10 women, age: 29 ± 7 years) underwent two functional Magnetic Resonance Imaging experiments: one during resting-state and one during a block-designed SDMT paradigm. We superimposed the templates of the DMN on the group activation map and observed the reorganization of the network. For the posterior cingulate cortex (PCC) node of the DMN, which is spatially extensive, comprising the precuneus (dorsal portion) and the posterior cingulate gyrus (PCG, ventral portion), the extent of each region was different between conditions, suggesting different functional roles for them. Therefore, for the functional connectivity (FC) analysis, we split the DMN-PCC region into two regions: left precuneus (BA 7) and PCG. The left precuneus (BA 7) was positively correlated with the left lingual gyrus (BA 17), a task-positive region, and negatively associated with the DMN nodes when comparing task performance with the resting-state condition. The other DMN regions presented the classical antagonistic role during the attentional task. In conclusion, we found that the activation and functional connectivity of the DMN is, in general, suppressed during the information processing. However, the left precuneus BA 7 presented a context-dependent modulatory behavior, working as a transient in-between hub connecting the DMN to task-positive areas. Such findings support studies that show increased activation and excitatory functional connectivity of DMN portions during goal-directed tasks. Moreover, our results may contribute to defining more precise functional correlates of IPS deficits in a wide range of clinical and neurological diseases.

Evaluating the relationship between working memory and information processing speed in multiple sclerosis

The aim of the present study was to evaluate the effect of information processing speed on the functioning of specific working memory components, i.e. phonological loop, visuospatial sketchpad, central executive and episodic buffer. Cognitive tasks that assess working memory ("word lists recall" for the phonological loop, "block recall" for the spatial component of visuospatial sketchpad, "listening recall" for the central executive and "immediate story recall" for the episodic buffer) and information processing speed (symbol digit modalities test- oral form) were administered to 38 patients with multiple sclerosis. Results showed that the central executive and episodic buffer components were significantly related to information processing speed. However, when age was included in the regression model, information processing speed significantly predicted only the episodic buffer scores. Further research on the relationship between the episodic buffer and information processing speed is recommended.

Cognitive processing speed in multiple sclerosis clinical practice: association with patient-reported outcomes, employment and magnetic resonance imaging metrics

BACKGROUND AND PURPOSE

To analyze the relationship between cognitive processing speed, patient-reported outcome measures (PROMs), employment and magnetic resonance imaging (MRI) metrics in a large multiple sclerosis cohort.

METHODS

Cross-sectional clinical data, PROMs, employment and MRI studies within 90 days of completion of the Processing Speed Test (PST), a technology-enabled adaptation of the Symbol Digit Modalities Test, were collected. MRI was analyzed using semi-automated methods. Correlations of PST score with PROMs and MRI metrics were examined using Spearman's rho. Wilcoxon rank sum testing compared MRI metrics across PST score quartiles and linear regression models identified predictors of PST performance. Effects of employment and depression were also investigated.

RESULTS

In 721 patients (mean age 47.6 ± 11.4 years), PST scores were significantly correlated with all MRI metrics, including cord atrophy and deep gray matter volumes. Linear regression demonstrated self-reported physical disability, cognitive function, fatigue and social domains (adjusted R²  = 0.44, P < 0.001) as the strongest clinical predictors of PST score, whereas that of MRI variables included T2 lesion volume, whole-brain fraction and cord atrophy (adjusted R²  = 0.42, P < 0.001). An inclusive model identified T2 lesion volume, whole-brain fraction, self-reported upper extremity function, cognition and social participation as the strongest predictors of PST score (adjusted R²  = 0.51, P < 0.001). There was significant effect modification by depression on the relationship between self-reported cognition and PST performance. Employment status was associated with PST scores independent of age and physical disability.

CONCLUSION

The PST score correlates with PROMs, MRI measures of focal and diffuse brain injury, and employment. The PST score is a feasible and meaningful measure for routine multiple sclerosis care.

The neurovascular basis of processing speed differences in humans: A model-systems approach using multiple sclerosis

Behavioral studies investigating fundamental cognitive abilities provide evidence that processing speed accounts for large proportions of performance variability between individuals. Processing speed decline is a hallmark feature of the cognitive disruption observed in healthy aging and in demyelinating diseases such as multiple sclerosis (MS), neuromyelitis optica, and Wilson's disease. Despite the wealth of evidence suggesting a central role for processing speed in cognitive decline, the neural mechanisms of this fundamental ability remain unknown. Intact neurovascular coupling, acute localized blood flow increases following neural activity, is essential for optimal neural function. We hypothesized that efficient coupling forms the neural basis of processing speed. Because MS features neural-glial-vascular system disruption, we used it as a model to test this hypothesis. To assess the integrity of the coupling system, we measured blood-oxygen-level-dependent (BOLD) signal in healthy controls (HCs) and MS patients using a 3T MRI scanner while they viewed radial checkerboards that flickered periodically at 8 ​Hz. To assess processing speed and cognitive function, we administered a battery of neuropsychological tests. While MS patients exhibited reduced ΔBOLD with reductions in processing speed, no such relationships were observed in HCs. To further investigate the mechanisms that underlie ΔBOLD-processing speed relationships, we assessed the physiologic components that constitute ΔBOLD signal (i.e., cerebral blood flow, ΔCBF; cerebral metabolic rate of oxygen, ΔCMRO₂; neurovascular coupling ratio) in speed-preserved and -impaired MS patients. While ΔCBF and ΔCMRO₂ showed no group-differences, the neurovascular coupling ratio was significantly reduced in speed-impaired MS patients compared to speed-preserved MS patients. Together, these results suggest that neurovascular uncoupling might underlie cognitive slowing in MS and might be the central pathogenic mechanism governing processing speed decline.

If Invalid PVT Scores Are Obtained, Can Valid Neuropsychological Profiles Be Believed?

Background

Performance Validity Testing (PVT) decision-making rules may be indeterminate in patients with neurological disease in which PVT characteristics have not been adequately studied. We report a patient with multiple sclerosis (MS) who failed computerized PVT testing but had normal memory scores with a neuropsychological profile consistent with expected MS disease-related weaknesses.

Method

Neuropsychological testing was conducted on two occasions in a middle-aged woman with an established MS diagnosis to address concerns of possible memory decline. Testing was discontinued after PVT scores below recommended cut-points were obtained during the first evaluation. During the second assessment, subthreshold PVT scores on a different computerized PVT were obtained, but unlike the first assessment, the entire neuropsychological protocol was administered.

Results

Despite subthreshold computerized PVT scores, normal learning and memory performance was obtained providing objective data to answer the referral question. Other neuropsychological findings included decreased processing speed, poor working memory, and poor executive function consistent with her MS diagnosis. Embedded PVT scores were normal.

Conclusions

We speculate that poor computerized PVT scores resulted from the disease-related features of MS, although we also discuss approaches to reconcile apparently contradictory PVT versus neuropsychological results if the contributions of disease-related variables on PVTs scores are discounted. This case demonstrates the value of completing the assessment protocol despite obtaining PVT scores below publisher recommended cutoffs in clinical evaluations. If subthreshold PVT scores are considered evidence of performance invalidity, it is still necessary to have an approach for interpreting seemingly credible neuropsychological test results rather than simply dismissing them as invalid.

Repeated Working Memory Training Improves Task Performance and Neural Efficiency in Multiple Sclerosis Patients and Healthy Controls

BACKGROUND/OBJECTIVE

To explore the effectiveness of a specific working memory (WM) training program in MS patients and healthy controls (HC).

METHOD

29 MS patients and 29 matched HC were enrolled in the study. MS and HC were randomly split into two groups: nontraining groups (15HC/14 MS) and training groups (14 HC/15 MS). Training groups underwent adaptive n-back training (60 min/day; 4 days). Functional magnetic resonance imaging (fMRI) was used to monitor brain activity during n-back performance (conditions: 0-back, 2-back, and 3-back) at 3 time points: (1) baseline, (2) post-training (+7days), and (3) follow-up (+35days).

RESULTS

In post-training and follow-up fMRI sessions, trained groups (HC and MS patients) exhibited significant reaction time (RT) reductions and increases in Correct Responses (CRs) during 2-back and 3-back performance. This improvement of task performance was accompanied by a decrease in brain activation in the WM frontoparietal network. The two effects were significantly correlated.

CONCLUSIONS

After WM training, both cognitively preserved MS patients and HC participants showed task performance improvement made possible by neuroplastic processes that enhanced neural efficiency.

The efficacy of the modified Story Memory Technique in progressive MS

Background:

Impairments in new learning and memory are common in individuals with multiple sclerosis (MS), negatively impacting everyday life, including occupational and social functioning.

Objective:

This study examined the efficacy of the modified Story Memory Technique (mSMT) in a progressive multiple sclerosis (PMS) sample through a double-blind, placebo-controlled, randomized clinical trial (RCT).

Methods:

Thirty (30) individuals with PMS, naïve to the mSMT, were randomized to the treatment or placebo control group. The Treatment Group completed mSMT training twice per week for 5 weeks while the Placebo Group met with the therapist at the same frequency, engaging in non-training-oriented tasks to control for professional contact and disease alterations.

Results:

The treatment group showed significant improvements in learning compared with the placebo control group, evident on both objective evaluation of new learning and self-report of functioning in daily life. Increased awareness of cognitive deficits was also noted post-treatment.

Conclusion:

These data provide Class I evidence supporting the efficacy of the mSMT in PMS. A behavioral intervention, targeted to specifically strengthen new learning, can significantly improve memory performance in PMS, and this improvement in memory performance is maintained 3 months later.

Mapping face encoding using functional MRI in multiple sclerosis across disease phenotypes

Using fMRI during a face encoding (FE) task, we investigated the behavioral and fMRI correlates of FE in patients with relapse-onset multiple sclerosis (MS) at different stages of the disease and their relation with attentive-executive performance and structural MRI measures of disease-related damage. A fMRI FE task was administered to 75 MS patients (11 clinically isolated syndromes - CIS, 40 relapsing-remitting - RRMS - and 24 secondary progressive - SPMS) and 22 healthy controls (HC). fMRI activity during the face encoding condition was correlated with behavioral, clinical, neuropsychological and structural MRI variables. All study subjects activated brain regions belonging to face perception and encoding network, and deactivated areas of the default-mode network. Compared to HC, MS patients had the concomitant presence of areas of increased and decreased activations as well as increased and decreased deactivations. Compared to HC or RRMS, CIS patients experienced an increased recruitment of posterior-visual areas. Thalami, para-hippocampal gyri and right anterior cingulum were more activated in RRMS vs CIS or SPMS patients, while an increased recruitment of frontal areas was observed in SPMS vs RRMS. Areas of abnormal activations were significantly correlated with clinical, cognitive-behavioral and structural MRI measures. Abnormalities of FE network occur in MS and vary across disease clinical phenotypes. Early in the disease, an increased recruitment of areas typically devoted to face perception and encoding occurs. In SPMS patients, abnormal functional recruitment of frontal lobe areas might contribute to the severity of clinical manifestations.

Brain connectivity and cognitive processing speed in multiple sclerosis: A systematic review

BACKGROUND

Processing speed (PS) decline is the most commonly observed cognitive deficit in people with multiple sclerosis (MS) resulting in a significant impact on quality of life. Despite its importance, knowledge of the underlying neural substrates is lacking.

OBJECTIVE

As MS is increasingly recognised as a disconnection syndrome, our aim was to carry out a systematic literature review to clarify the relationship between PS performance and MRI measures of structural and functional brain connectivity in people with MS.

SEARCH METHODS

A literature search was carried out on PubMed and Web of Science that included publications predating September 2017. Additional articles were added after inspection of the reference lists of all selected papers.

DATA EXTRACTION

All selected papers were categorised in three sections according to the MRI measures investigated, independently or both. Quality assessment was carried out using a customised set of criteria.

RESULTS

Thirty-two articles met the inclusion criteria and were included in the review. Microstructural integrity of the anterior corpus callosum and functional connectivity of frontal areas were more consistently found to correlate with PS performance, though high variability of findings was observed across studies. Several methodological flaws emerged from the reviewed literature.

CONCLUSIONS

Despite the observed trends, no definite conclusions can be drawn on the relationship between brain connectivity and PS decline in MS given the limitations of the current literature. Future investigations may benefit from theoretical and methodological advances to clarify how MS-related brain damage affects patients' cognition.

Symbol Digit Modalities Test adaptation for Magnetic Resonance Imaging environment: A systematic review and meta-analysis

BACKGROUND

The Symbol Digit Modalities Test (SDMT) is widely used for cognitive evaluation of information processing speed (IPS), required in many cognitive operations. Despite being unspecific for different neurological disorders, it is sensitive to assess impaired performance related to stroke, Parkinson's disease, traumatic brain injury, and multiple sclerosis. However, in addition to evaluate the presence and severity of IPS impairment, it is of interest to determine the localization and integration of brain regions responsible for the functions assessed by the SDMT.

OBJECTIVE

To review the studies that adapted the SDMT to the magnetic resonance environment and obtain the brain areas associated with the performance of the task in healthy subjects with a meta-analysis.

METHODOLOGY

A systematic review was performed using ten studies published between 1990 and 2017, and selected from four databases. All studies included participants of both genders and age between 18 and 50 years, used Functional Magnetic Resonance Imaging (fMRI) and SDMT adaptation and reported brain regions associated with the task. Six of them also reported the region coordinates in a standard space, so they were included in a meta-analysis. Activation Likelihood Estimation algorithm, with significance for p < 0.05 corrected for multiple comparisons, was used to identify areas that are robustly related to the performance of the SDMT.

RESULTS

The areas predominantly reported in the studies of our meta-analysis were regions of the frontoparietal attentional network and occipital cortex, as well as cuneus, precuneus, and cerebellum. Individually all regions that survived the statistical threshold are consistent with what is expected after reviewing prospective studies.

CONCLUSIONS

The present study allowed the identification of brain areas activated during the performance of the SDMT in healthy subjects, and therefore it will help understanding the differences in brain activation by this task in clinical populations. Moreover, it may guide future studies of therapeutic strategies and interventions in those populations.

Limbic system damage in MS: MRI assessment and correlations with clinical testing

Volume loss in some limbic region structures has been observed in multiple sclerosis (MS) patients. However, in vivo evaluation of existing tissue cellular microstructure integrity has received less attention. The goal of studies reported here was to quantitatively assess loss of limbic system volumes and tissue integrity, and to evaluate associations of these measures with cognitive and physical dysfunction in MS patients. Thirty-one healthy controls (HC) and 80 MS patients, including 32 relapsing remitting (RRMS), 32 secondary progressive (SPMS) and 16 primary progressive (PPMS), participated in this study. Tissue cellular integrity was evaluated by means of recently introduced tissue-specific parameter R2t* that was calculated from multi-gradient-echo MRI signals using a recently developed method that separates R2t* from BOLD (blood oxygen level dependent) contributions to GRE signal decay rate constant (R2*), and accounting for physiological fluctuations and artifacts from background gradients. Volumes in limbic system regions, normalized to skull size (NV), were measured from standard MPRAGE images. MS patients had lower R2t* and smaller normalized volumes in the hippocampus, amygdala, and several other limbic system regions, compared to HC. Alterations in R2t* of several limbic system regions correlated with clinical and neurocognitive test scores in MS patients. In contrast, smaller normalized volumes in MS were only correlated with neurocognitive test scores in the hippocampus and amygdala. This study reports the novel finding that R2t*, a measure that estimates tissue integrity, is more sensitive to tissue damage in limbic system structures than is atrophy. R2t* measurements can serve as a biomarker that is distinct from and complementary to volume measurements.

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.

Validity of the Symbol Digit Modalities Test as a cognition performance outcome measure for multiple sclerosis

Cognitive and motor performance measures are commonly employed in multiple sclerosis (MS) research, particularly when the purpose is to determine the efficacy of treatment. The increasing focus of new therapies on slowing progression or reversing neurological disability makes the utilization of sensitive, reproducible, and valid measures essential. Processing speed is a basic elemental cognitive function that likely influences downstream processes such as memory. The Multiple Sclerosis Outcome Assessments Consortium (MSOAC) includes representatives from advocacy organizations, Food and Drug Administration (FDA), European Medicines Agency (EMA), National Institute of Neurological Disorders and Stroke (NINDS), academic institutions, and industry partners along with persons living with MS. Among the MSOAC goals is acceptance and qualification by regulators of performance outcomes that are highly reliable and valid, practical, cost-effective, and meaningful to persons with MS. A critical step for these neuroperformance metrics is elucidation of clinically relevant benchmarks, well-defined degrees of disability, and gradients of change that are deemed clinically meaningful. This topical review provides an overview of research on one particular cognitive measure, the Symbol Digit Modalities Test (SDMT), recognized as being particularly sensitive to slowed processing of information that is commonly seen in MS. The research in MS clearly supports the reliability and validity of this test and recently has supported a responder definition of SDMT change approximating 4 points or 10% in magnitude.

Information processing speed in multiple sclerosis: Past, present, and future

BACKGROUND

Information processing speed (IPS) is a prevalent cognitive impairment in multiple sclerosis (MS).

OBJECTIVES

This review aims to summarize the methods applied to assess IPS in MS and its theoretical conceptualization. A PubMed search was performed to select articles published between 1 January 2004 and 31 December 2013, resulting in 157 articles included.

RESULTS

The majority (54%) of studies assessed IPS with heterogeneous samples (several disease courses). Studies often report controlling for presence of other neurological disorders (60.5%), age (58.6%), education (51.6%), alcohol history (47.8%), or use of steroids (39.5%). Potential confounding variables, such as recent relapses (50.3%), history of developmental disorders (19.1%), and visual problems (29.9%), were often neglected. Assessments used to study IPS were heterogeneous (ranging from simple to complex tasks) among the studies under review, with 62 different tasks used. Only 9.6% of articles defined the construct of IPS and 22.3% discussed IPS in relation to a theoretical model.

FUTURE DIRECTIONS

The challenges for the upcoming decade include clarification of the definition of IPS as well as its theoretical conceptualization and a consensus on assessment. Based on the results obtained, we propose a new theoretical model, the tri-factor model of IPS.

The mediating role of processing speed in the relationship between depressive symptoms and cognitive function in multiple sclerosis

INTRODUCTION

Although disorders of mood and cognition are frequently observed in multiple sclerosis, their relationship remains unclear. We aimed to investigate whether this mood-cognition relationship is mediated by inefficient processing speed, a deficit typically associated with mood symptomatology in the psychiatric literature and a common deficit observed in multiple sclerosis patients.

METHOD

In this study, comprehensive cognitive data and self-reported mood data were retrospectively analyzed from 349 patients with relapsing remitting multiple sclerosis. We performed a bootstrapping analysis to examine whether processing speed provided an indirect means by which depressive symptoms influenced cognitive functioning, specifically memory and executive function.

RESULTS

We observed that processing speed mediated the relationship between depressive symptoms and measures of memory and executive function. Interestingly, exploratory analyses revealed that this mediational role of processing speed was specific to MS patients who were younger, had a lower disability level, and had fewer years since MS diagnosis.

CONCLUSIONS

Together, these findings have implications for mood and cognitive intervention with multiple sclerosis patients.

Slowing of information processing speed without motor slowing in multiple sclerosis observed during two crossing-off tasks

INTRODUCTION

Slowing of information processing speed (IPS) is often considered one of the primary deficits seen in multiple sclerosis (MS). IPS is usually measured by tasks that involve many cognitive functions. The aim of this study was to determine whether similar IPS slowing can also be observed during two simple, timed, psychomotor crossing-off tasks.

METHOD

The Crossing-Off Test (COT), a simple psychomotor task, was performed under two conditions (COT1 corresponded to writing habits, COT2 used horizontal sweeping) in 25 relapsing-remitting MS patients (EDSS 0-1) and 25 healthy controls.

RESULTS

The MS group compared with the control group was impaired on COT1 (P=0.0043) and not on COT2 (P=0.4), and the COT1 performance of MS patients with EDSS 1 was more impaired than those of patients with EDSS 0 (P=0.008).

DISCUSSION/CONCLUSION

These results indicate that only some of the IPS cognitive subcomponents linked with COT1 tasks are initially involved in the slowing of IPS during MS, suggesting that different mechanisms are involved in each tested version of the COT.

Altered Effective Connectivity during a Processing Speed Task in Individuals with Multiple Sclerosis

OBJECTIVES

Processing speed impairment is the most prevalent cognitive deficit in individuals with multiple sclerosis (MS). However, the neural mechanisms associated with processing speed remain under debate. The current investigation provides a dynamic representation of the functioning of the brain network involved in processing speed by examining effective connectivity pattern during a processing speed task in healthy adults and in MS individuals with and without processing speed impairment.

METHODS

Group assignment (processing speed impaired vs. intact) was based on participants' performance on the Symbol Digit Modalities test (Parmenter, Testa, Schretlen, Weinstock-Guttman, & Benedict, 2010). First, brain regions involved in the processing speed task were determined in healthy participants. Time series from these functional regions of interest of each group of participants were then subjected to the effective connectivity analysis (Independent Multiple-Sample Greedy Equivalence Search and Linear, Non-Gaussian Orientation, Fixed Structure algorithms) that showed causal influences of one region on another during task performance.

RESULTS

The connectivity pattern of the processing speed impaired group was significantly different from the connectivity pattern of the processing speed intact group and of the healthy control group. Differences in the strength of common connections were also observed.

CONCLUSIONS

Effective connectivity results reveal that MS individuals with processing speed impairment not only have connections that differ from healthy participants and MS individuals without processing speed impairment, but also have increased strengths of connections.

The influence of cognitive dysfunction on benefit from learning and memory rehabilitation in MS: A sub-analysis of the MEMREHAB trial

BACKGROUND

This study examined the influence of processing speed (PS) on benefit from treatment with the modified Story Memory Technique(©) (mSMT), a behavioral intervention shown to improve new learning and memory in multiple sclerosis (MS).

METHODS

This double-blind, placebo-controlled, randomized clinical trial included 85 participants with clinically definite MS, 45 assigned to the treatment group and 40 to the placebo-control group. Participants completed baseline and follow-up neuropsychological assessment. The present study represents a post-hoc analysis to examine the role of PS on treatment efficacy.

FINDINGS

The treatment group showed a significantly improved CVLT learning slope relative to the placebo group post-treatment, after co-varying PS performance. SDMT performance was a significant predictor of benefit from mSMT treatment, beyond group assignment. Post-hoc analysis indicated a significant correlation between the SDMT and overall cognition, indicating that the SDMT may be serving as a proxy for overall cognitive impairment.

INTERPRETATION

Performance on measures of cognitive dysfunction aside from learning and memory impact the benefit of mSMT treatment. While the current study focused on PS as a critical factor, PS may be serving as a marker for generalized cognitive dysfunction. Implications for cognitive rehabilitation in MS are discussed.