Search PubMed⌕ Search

Biomedical subjects

Stephen M Rao

Publications and source records attributed to Stephen M Rao.

23 records · Page 2Linked to original sources
PubMed2003

Cognitive dysfunction in multiple sclerosis: a review of recent developments.

PURPOSE OF REVIEW: Nearly half of all patients diagnosed with multiple sclerosis will develop cognitive dysfunction, a symptom associated with significant decline in activities of daily living. The purpose of this review is to discuss recent literature investigating issues related to cognitive dysfunction in multiple sclerosis. RECENT FINDINGS: Recent studies, examined in this review, have provided increased understanding regarding specific cognitive processes affected in multiple sclerosis, as well as a characterization of its natural history. Studies have also continued to emphasize the extent to which cognitive deficits in the condition are associated with decline in daily living skills. Recent concerns regarding driving performance have been documented among cognitively impaired individuals. Studies have also examined correlates of cognitive dysfunction, with particular emphasis on neuroimaging techniques reflecting disease activity or lesion burden. With increased understanding of neurobiological correlates of cognitive deficits, investigators have begun to examine potential treatments for managing cognitive dysfunction. SUMMARY: This area of research has suggested that disease modifying medications can have an impact on magnetic resonance imaging disease activity by altering the cerebral demyelinating process resulting in a slower decline in cognitive functions over time and improved activities of daily living for patients with multiple sclerosis.

Activities of Daily Living↗
PubMed2002

Neural basis of the Stroop interference task: response competition or selective attention?

Previous neuroimaging studies of the Stroop task have postulated that the anterior cingulate cortex (ACC) plays a critical role in resolution of the Stroop interference condition. However, activation of the ACC is not invariably seen and appears to depend on a variety of methodological factors, including the degree of response conflict and response expectancies. The present functional MRI study was designed to identify those brain areas critically involved in the interference condition. Healthy subjects underwent a blocked-trial design fMRI experiment while responding to 1 of 3 stimulus conditions: (1) incongruent color words, (2) congruent color words, and (3) color-neutral words. Subjects responded to the printed color of the word via a manual response. Compared to the congruent and neutral conditions, the incongruent condition produced significant activation within the left inferior precentral sulcus (IpreCS) located on the border between the inferior frontal gyrus, pars opercularis (BA 44) and the ventral premotor region (BA 6). Significant deactivations in the rostral component of the ACC and the posterior cingulate gyrus were also observed. Selective activation of the left IpreCS is compatible with findings from previous neuroimaging, lesion, electrophysiological, and behavioral studies and is presumably related to the mediation of competing articulatory demands during the interference condition.

Adolescent↗
PubMed2002

Minimal neuropsychological assessment of MS patients: a consensus approach.

Cognitive impairment is common in multiple sclerosis (MS), yet patients seen in MS clinics and neurologic practices are not routinely assessed neuropsychologically. In part, poor utilization of NP services may be attributed to a lack of consensus among neuropsychologists regarding the optimal approach for evaluating MS patients. An expert panel composed of neuropsychologists and psychologists from the United States, Canada, United Kingdom, and Australia was convened by the Consortium of MS Centers (CMSC) in April, 2001. Our objectives were to: (a) propose a minimal neuropsychological (NP) examination for clinical monitoring of MS patients and research, and (b) identify strategies for improving NP assessment of MS patients in the future. The panel reviewed pertinent literature on MS-related cognitive dysfunction, considered psychometric factors relevant to NP assessment, defined the purpose and optimal characteristics of a minimal NP examination in MS, and rated the psychometric and practical properties of 36 candidate NP measures based on available literature. A 90-minute NP battery, the Minimal Assessment of Cognitive Function in MS (MACFIMS), emerged from this discussion. The MACFIMS is composed of seven neuropsychological tests, covering five cognitive domains commonly impaired in MS (processing speed/working memory, learning and memory, executive function, visual-spatial processing, and word retrieval). It is supplemented by a measure of estimated premorbid cognitive ability. Recommendations for assessing other factors that may potentially confound interpretation of NP data (e.g., visual/sensory/motor impairment, fatigue, and depression) are offered, as well as strategies for improving NP assessment of MS patients in the future.

Cognition Disorders↗
PubMedDate not supplied

fMRI biomarker of early neuronal dysfunction in presymptomatic Huntington's Disease.

BACKGROUND AND PURPOSE: Functional MR imaging (fMRI) has been used to probe basal ganglia function in people with presymptomatic Huntington's disease (pre-HD). A previous fMRI study in healthy individuals demonstrated activation of the basal ganglia during a time-discrimination task. The current study was designed to examine the relative sensitivity of fMRI compared with that of behavioral testing and morphometric measurements in detecting early neurodegenerative changes related to Huntington's disease (HD). METHODS: Pre-HD participants were assigned to two groups based on estimated years to diagnosis of manifest disease: close <12 years and far >or=12 years. Age at disease onset was estimated using a regression equation based on the number of trinucleotide CAG repeats. The time-discrimination task required participants to determine whether a specified interval was shorter or longer than a standard interval of 1200 milliseconds. RESULTS: Participants in the close group performed more poorly on the time-task discrimination than did control subjects; however, no differences were observed between far participants and control subjects. Similarly, close participants had reduced bilateral caudate volume relative to that of control subjects, whereas far participants did not. On functional imaging, close participants had significantly less activation in subcortical regions (caudate, thalamus) than control subjects; far participants had an intermediate degree of activation. In contrast, far participants had hyperactivation in medial hemispheric structures (anterior cingulate, pre-supplementary motor area) relative to close and control subjects. CONCLUSION: Hyperactivation of medial prefrontal regions compensated for reduced subcortical participation during time discrimination in pre-HD. This pattern of brain activation may represent an early neurobiologic marker of neuronal dysfunction.

Adult↗