Nancy D. Chiaravalloti

Cognitive impairment in multiple sclerosis.

Multiple sclerosis (MS) is a progressive disease of the CNS that is characterised by widespread lesions in the brain and spinal cord. MS results in motor, cognitive, and neuropsychiatric symptoms, all of which can occur independently of one another. The common cognitive symptoms include deficits in complex attention, efficiency of information processing, executive functioning, processing speed, and long-term memory. These deficits detrimentally affect many aspects of daily life, such as the ability to run a household, participate fully in society, and maintain employment--factors that can all affect the overall quality of life of the patient. The increased use of neuroimaging techniques in patients with MS has advanced our understanding of structural and functional changes in the brain that are characteristic of this disease, although much remains to be learned. Moreover, examination of efforts to treat the cognitive deficits in MS is still in the early stages.

Cerebral activation patterns during working memory performance in multiple sclerosis using FMRI.

Working memory deficits are common in Multiple Sclerosis (MS) and have been identified behaviorally in numerous studies. Despite recent advance in functional magnetic resonance imaging (fMRI), few published studies have examined cerebral activations associated with working memory dysfunction in MS. The present study examines brain activation patterns during performance of a working memory task in individuals with clinically definite MS, compared to healthy controls (HC). fMRI was performed using a 1.5 Tesla GE scanner during a modified Paced Auditory Serial Addition Test (mPASAT). Participants were 6 individuals with MS with working memory impairment as evidenced on neuropsychological testing, 5 individuals with MS without working memory impairment, and 5 HC. Groups were demographically equivalent. Data were analyzed using Statistical Parametric Mapping (SPM99) software, with a stringent significance level (alpha < .005, voxel extent ≥ 8). Both MS groups and the HC group were able to perform the task, with comparable performance in terms of numbers of correct responses. Activation patterns within the HC and MS not-impaired groups were noted in similar brain regions, consistent with published observations in healthy samples. That is, activations were lateralized to the left hemisphere, involving predominantly frontal regions. In contrast, the MS impaired group showed greater right frontal and right parietal lobe activation, when compared with the HC group. Thus, it appears that working memory dysfunction in MS is associated with altered patterns of cerebral activation that are related to the presence of cognitive impairment, and not solely a function of MS. This research was supported by the Henry H. Kessler Foundation, the Hyde and Watson Foundation and the Kirby Foundation. The authors wish to thank Rinki Jajoo for her help with data management, as well as Dr. Scott Millis and Dr. Dane Cook for their statistical advice. Dr. Christopher Christodoulou is now in the Department of Neurology, State University of New York at Stony Brook. Dr. Joseph Ricker is now in the Department of Physical Medicine and Rehabilitation, University of Pittsburgh.

Prefrontal modulation of working memory performance in brain injury and disease.

The inter‐related cognitive constructs of working memory (WM) and processing speed are fundamental components to general intellectual functioning in humans. Importantly, both WM and processing speed are highly susceptible to disruption in cases of brain injury, neurologic illness, and even in normal aging. A goal of this article is to summarize and critique the functional imaging studies of speeded working memory in neurologically impaired populations. This review focuses specifically on the role of the lateral prefrontal cortex in mediating WM performance and integrates the relevant WM literature in healthy adults with the current findings in the clinical literature. One important finding emerging from a summary of this literature is the dissociable contributions made by ventrolateral and dorsolateral prefrontal cortex (VLPFC and DLPFC) in guiding performance on tasks of WM. Throughout this review, it is shown that when cerebral resources are challenged, it is DLPFC, and often right DLPFC specifically, that plays a critical role in modulating WM functioning. In addition, this article will examine the relationship between task performance and brain activation across studies to clarify the role of increased DLPFC activity in clinical samples. Finally, explanations are offered for the observed increased DLPFC activation and the potentially unique role of right DLPFC in mediating WM performance during periods of cerebral challenge. Hum. Brain Mapp, 2006.

Cognitive reserve moderates the negative effect of brain atrophy on cognitive efficiency in multiple sclerosis

According to the cognitive reserve hypothesis, neuropsychological expression of brain disease is attenuated among persons with higher education or premorbid intelligence. The current research examined cognitive reserve in multiple sclerosis (MS) by investigating whether the negative effect of brain atrophy on information processing (IP) efficiency is moderated by premorbid intelligence. Thirty-eight persons with clinically definite MS completed a vocabulary-based estimate of premorbid intelligence (Wechsler Vocabulary) and a composite measure of IP efficiency (Symbol Digit Modalities Test and Paced Auditory Serial Addition Task). Brain atrophy was estimated from measurements of third ventricle width using high-resolution anatomical brain magnetic resonance imaging (magnetization-prepared rapid gradient echo). In a hierarchical regression analysis controlling for age and depressive symptomatology, brain atrophy predicted worse IP efficiency (R2 = .23, p = .003) and cognitive reserve predicted better IP efficiency (R2 = .13, p = .013), but these effects were moderated by an Atrophy x Cognitive Reserve interaction (R2 = .15, p = .004). The negative effect of brain atrophy on IP efficiency was attenuated at higher levels of reserve, such that MS subjects with higher reserve were better able to withstand MS neuropathology without suffering cognitive impairment. Results help explain the incomplete and inconsistent relationship between brain atrophy and IP efficiency in previous research.

An Investigation of Working Memory Rehearsal in Multiple Sclerosis Using fMRI

The present study examined patterns of cerebral activation during a working memory (WM) rehearsal task in individuals diagnosed with multiple sclerosis (MS) and in healthy adults. BOLD functional magnetic resonance imaging (fMRI)was performed using a 1.5TGE scanner to assess activation during aWMtask adapted fromthe Sternberg paradigm (Sternberg, 1969). Participants included 8 individuals diagnosed with MS, and 5 healthy controls (HCs) matched for age and education. Task difficulty was manipulated by increasing the length of time that strings of letters were to be rehearsed. Findings revealed increased right prefrontal cortex activation and increased right temporal lobe activation in individuals diagnosed with MS compared to HCs. The potential explanations for increased right hemisphere activation in persons with MS are discussed.

Vision therapy in adults with convergence insufficiency: clinical and functional magnetic resonance imaging measures.

Purpose. This research quantified clinical measurements and functional neural changes associated with vision therapy in subjects with convergence insufficiency (CI). Methods. Convergence and divergence 4° step responses were compared between 13 control adult subjects with normal binocular vision and four CI adult subjects. All CI subjects participated in 18 h of vision therapy. Clinical parameters quantified throughout the therapy included: nearpoint of convergence, recovery point of convergence, positive fusional vergence at near, near dissociated phoria, and eye movements that were quantified using peak velocity. Neural correlates of the CI subjects were quantified with functional magnetic resonance imaging scans comparing random vs. predictable vergence movements using a block design before and after vision therapy. Images were quantified by measuring the spatial extent of activation and the average correlation within five regions of interests (ROI). The ROIs were the dorsolateral prefrontal cortex, a portion of the frontal lobe, part of the parietal lobe, the cerebellum, and the brain stem. All measurements were repeated 4 months to 1 year post-therapy in three of the CI subjects. Results. Convergence average peak velocities to step stimuli were significantly slower (p = 0.016) in CI subjects compared with controls; however, significant differences in average peak velocities were not observed for divergence step responses (p = 0.30). The investigation of CI subjects participating in vision therapy showed that the nearpoint of convergence, recovery point of convergence, and near dissociated phoria significantly decreased. Furthermore, the positive fusional vergence, average peak velocity from 4° convergence steps, and the amount of functional activity within the frontal areas, cerebellum, and brain stem significantly increased. Several clinical and cortical parameters were significantly correlated. Conclusions. Convergence peak velocity was significantly slower in CI subjects compared with controls, which may result in asthenopic complaints reported by the CI subjects. Vision therapy was associated with and may have evoked clinical and cortical activity changes.

Premorbid cognitive leisure independently contributes to cognitive reserve in multiple sclerosis

Objective: Consistent with the cognitive reserve hypothesis, higher education and vocabulary help persons with Alzheimer disease (AD) and multiple sclerosis (MS) better withstand neuropathology before developing cognitive impairment. Also, premorbid cognitive leisure (e.g., reading, hobbies) is an independent source of cognitive reserve for elders with AD, but there is no research on the contribution of leisure activity to cognition in MS. We investigated whether premorbid cognitive leisure protects patients with MS from cognitive impairment. Methods: Premorbid cognitive leisure was surveyed in 36 patients with MS. Neurologic disease severity was estimated with brain atrophy, measured as third ventricle width on high-resolution MRI. Cognitive status was measured with a composite score of processing speed and memory. Results: Controlling for brain atrophy, premorbid cognitive leisure was positively associated with current cognitive status (rp = 0.49, p < 0.01), even when controlling for vocabulary (rp = 0.39, p < 0.05) and education (rp = 0.47, p < 0.01). Also, premorbid cognitive leisure was unrelated to brain atrophy (r = 0.03, p > 0.5), but a positive partial correlation between leisure and atrophy emerged when controlling for cognitive status (rp = 0.37, p < 0.05), which remained when also controlling for vocabulary (rp = 0.34, p < 0.05) and education (rp = 0.35, p < 0.05). Conclusions: Premorbid cognitive leisure contributes to cognitive status in patients with MS independently of vocabulary and education. Also, patients with MS who engaged in more cognitive leisure were able to withstand more severe brain atrophy at a given cognitive status. Premorbid cognitive leisure is supported as an independent source of cognitive reserve in patients with MS.

Retrieval practice improves memory in multiple sclerosis: clinical application of the testing effect.

The testing effect is a robust cognitive phenomenon by which memory retrieval on a test improves subsequent recall more than restudying. Also known as retrieval practice, the testing effect has been studied almost exclusively in healthy undergraduates. The current study investigated whether retrieval practice during testing leads to better delayed recall than restudy among persons with multiple sclerosis (MS), a neurologic disease associated with memory dysfunction. In a within-subjects design, 32 persons with MS and 16 demographically matched healthy controls (HC) studied 48 verbal paired associates (VPA) divided across 3 learning conditions: massed restudy (MR), spaced restudy (SR), and spaced testing (ST). Delayed VPA cued recall was measured after 45 min. There was a large main effect of learning condition (etap2 = .54, p < .001) such that both MS and HC participants produced better delayed recall for VPAs learned through ST relative to MR and SR; and SR relative to MR. This same pattern was observed for MS participants with objective memory impairment (n = 16), thereby providing the first evidence that retrieval practice improves memory more than restudy among persons with neurologically based memory impairment.

Unemployment in multiple sclerosis (MS): utility of the MS Functional Composite and cognitive testing

Unemployment is a significant concern among individuals with multiple sclerosis (MS). Determinations regarding ability to work are highly dependent on measurement tools used by neurologists and allied professionals. However, little is known of the usefulness of these tools when determining issues pertaining to employment status. The purpose of the present investigation was to examine the utility of the Multiple Sclerosis Functional Composite (MSFC) and a brief cognitive test battery when examining employment status in MS. Seventy-seven individuals with MS completed the MSFC and a brief cognitive test battery. On the MSFC, unemployed individuals demonstrated worse upper extremity functioning. There was no difference on the Paced Auditory Serial Addition Task (PASAT), the sole cognitive measure of the MSFC. On cognitive testing, unemployed individuals performed worse on measures of memory, information processing speed, and executive functioning. Through logistic regression analysis, the Symbol Digit Modalities Test (SDMT) was found to be the sole predictor of employment status among the significant disease, MSFC and cognitive variables. Consistent with previous findings, logistic regression found the SDMT to be a significant predictor of employment status. Given the lack of significant group differences on the PASAT, continued consideration of replacing the PASAT with the SDMT in the MSFC appears warranted.

A functional application of the spacing effect to improve learning and memory in persons with multiple sclerosis

The present study examined the utility of using spaced learning trials (when trials are distributed over time) versus massed learning trials (consecutive learning trials) in the acquisition of everyday functional tasks. In a within-subjects design, 20 participants with multiple sclerosis (MS) and 18 healthy controls (HC) completed two route learning tasks and two paragraph reading tasks. One task in each area was presented in the “spaced” condition, in which the task was presented to the participants three times with 5-minutes break between each trial, and the second task in each area was presented in the “massed” condition, in which the task was presented three consecutive times to the participants. The dependent variables consisted of recall and recognition of the paragraphs and routes both immediately and 30 minutes following initial learning. Results showed that for paragraph learning, the spaced condition significantly enhanced memory performance for this task relative to the massed condition. However, this effect was not demonstrated in the route learning task. Thus, the spacing effect can be beneficial to enhance recall and performance of activities of daily living for individuals with MS; however, this effect was significant for verbal tasks stimuli, but not for visual tasks stimuli. It will be important during future investigations to better characterize the factors that maximize the spacing effect.