Lisa Tabor Connor

Resting interhemispheric functional magnetic resonance imaging connectivity predicts performance after stroke

Focal brain lesions can have important remote effects on the function of distant brain regions. The resulting network dysfunction may contribute significantly to behavioral deficits observed after stroke. This study investigates the behavioral significance of changes in the coherence of spontaneous activity in distributed networks after stroke by measuring resting state functional connectivity (FC) using functional magnetic resonance imaging.

Age-Related Differences in Absolute but Not Relative Metamemory Accuracy

In 3 experiments, the effects of age on different kinds of metacognitive prediction accuracy were assessed. participants made global memory predictions and item-by-item memory predictions in a single experimental task. Metacognitive accuracy was evaluated with correlational and more traditional difference-score measures. Difference-score measures were found, in some cases, to be sensitive to level of recall performance. Correlational techniques revealed that older adults monitored learning effectively. Relative to younger adults, they showed equally accurate immediate judgments of learning (JOLs), produced an equivalent delayed-JOL effect, and showed equivalent upgrading in the accuracy of their global prediction from before to after study of test materials.

Age differences in the allocation of study time account for age differences in memory performance

How aging affects the utilization of monitoring in the allocation of study time was investigated by having adults learn paired associates during multiple study-test trials. During each trial, a subject paced the presentation of individual items and later judged the likelihood of recalling each item on the upcoming test; after all items had been studied and judged, recall occurred. For both age groups in Study 1, (1) people’s judgments were highly accurate at predicting recall and (2) intraindividual correlations between judgments (or recall) on one trial, and study times on the next trial were negative, which suggests that subjects utilized monitoring to allocate study time. However, the magnitude of these correlations was less for older than for younger adults. Study 2 revealed that these differences were not due to age differences in forgetting. Results from both studies suggest that older adults do not utilize on-line monitoring to allocate study to the same degree as younger adults do, and that these differences in allocation contribute to age deficits in recall.

Semantic Degradation and Lexical Access in Age-Related Naming Failures

This study investigated the impaired lexical access and semantic degradation hypotheses as two potential explanations of naming failures in normal aging. Naming responses on the Boston Naming Test (BNT) and Action Naming Test (ANT) were analyzed across three test sessions for 39 adults from three age groups (50s, 60s, and 70s). Failures to name before and after cues were classified as either impaired access if failures occurred at an earlier test session followed by successful naming at a later test session or semantic degradation if naming was successful at an earlier test session followed by failures at a later test session. The results indicated that on both the BNT and ANT all age groups produced more naming failures attributed to impaired access than to semantic degradation. However, for object naming, the failures showed significantly more semantic degradation for people in their 70s compared to the younger age groups. By contrast, for action naming, semantic degradation was negligible, possibly masked by a ceiling effect, and the only age-difference result that approached significance indicated that adults in their 70s produced more naming failures attributed to impaired access than adults in their 50s.

Age differences in inhibition: Possible causes and consequences

Abstract The relations among age, inhibition, perceptual speed, susceptibility to interference, and working memory were examined in a sample of 301 adults age 20 to 90. Younger adults were found to have more efficient inhibitory mechanisms than were older adults. Significant inhibition, however, was found in all age groups, including the older age group. Older adults were also found to be more susceptible to interference from irrelevant information. There was a small negative relation between interference and inhibition, suggesting that participants with the most efficient inhibitory functioning may be the least susceptible to interference. Perceptual speed, an index of processing efficiency, was found to mediate nearly all of the age-related variance in inhibition and interference. Interference, but not inhibition, was found to mediate some of the age-related variance in working memory.

Noun and verb retrieval in healthy aging

This study tests the hypothesis that retrieval of object and action names declines at different rates with age. Uncued and cued performance on the Boston Naming Test (BNT) and the Action Naming Test (ANT) were examined for 171 individuals from 50 to 88 years old. To control for differences in item difficulty, a subset of items from each of the two tests was selected for which uncued performance was equivalent in individuals in their 50s. With this matched set of items, differences in action and object naming were tested in the 60s and 70+ age groups. Although age-related decline in name retrieval was observed for both the BNT and the ANT subsets, no differences between object and action retrieval were found. Our results, thus, do not confirm previous studies reporting that object names and action names are differentially retrieved with aging. We discuss these new findings in relation to evidence of dissociations in object and action naming in brain-damaged individuals.

Validation of a Dysphagia Screening Tool in Acute Stroke Patients

BACKGROUND Although many dysphagia screening tools exist, none has high sensitivity and reliability or can be administered quickly with minimal training. OBJECTIVE To design and validate a swallowing screening tool to be used by health care professionals who are not speech language pathologists to identify dysphagia and aspiration risk in acute stroke patients. METHODS In a prospective study of 300 patients admitted to the stroke service at an urban tertiary care hospital, interrater and test-retest reliabilities of a new tool (the Acute Stroke Dysphagia Screen) were established. The tool was administered by nursing staff when patients were admitted to the stroke unit. A speech language pathologist blinded to the results with the new tool administered the Mann Assessment of Swallowing Ability, a clinical bedside evaluation, with dysphagia operationally defined by a score less than 178. RESULTS The mean time from admission to screening with the new tool was 8 hours. The mean time between administration of the new tool and the clinical bedside evaluation was 32 hours. For the new tool, interrater reliability was 93.6% and test-retest reliability was 92.5%. The new tool had a sensitivity of 91% and a specificity of 74% for detecting dysphagia and a sensitivity of 95% and a specificity of 68% for detecting aspiration risk. CONCLUSIONS The Acute Stroke Dysphagia Screen is an easily administered and reliable tool that has sufficient sensitivity to detect both dysphagia and aspiration risk in acute stroke patients.

Inhibition and auditory comprehension in Wernicke's aphasia

Background: While research findings support the presence of inefficiencies in allocation of attention in individuals with aphasia, the cognitive mechanisms behind these inefficiencies remain unclear. One mechanism that would affect resource allocation for selective processing is an impaired inhibitory mechanism which, when normally functioning, would actively suppress distracting information. Aims: The purpose of this study was to investigate the cognitive process of inhibition, at the lexical‐semantic level of language processing, and its relation to auditory comprehension in Wernickes aphasia. Methods & Procedures: The classic Stroop Colour‐Word Test was adapted to be applicable for use with an aphasic population. We administered this computerised manual‐response, numerical version of the Stroop test to five individuals with Wernickes aphasia and twelve age‐ and education‐matched non‐brain‐injured controls. Correlations with Stroop interference examined associations with auditory comprehension as measured by the Token Test and the Complex Ideational Material subtest of the Boston Diagnostic Aphasia Examination. Outcomes & Results: Analysis of the Stroop reaction time and error percentage data indicated that the interference effect was significantly larger for the participants with Wernickes aphasia than for the controls, without an accompanying increase in facilitation, reflecting an impairment of inhibition in Wernickes aphasia. In addition, the magnitude of Stroop interference was significantly positively correlated with the clinical‐behavioural symptom of severity of auditory comprehension deficits as measured by the Token Test. Conclusions: Findings support an impairment in inhibition at the lexical‐semantic level of language processing in Wernickes aphasia, reflecting the inability to effectively ignore the automatically evoked, distracting stimulus. The significant correlation between the Stroop interference effect and the severity of auditory comprehension deficits suggests that at least part of the attentional difficulties contributing to the striking reductions in auditory comprehension in this population can be attributed to impaired inhibition. Our findings expand upon our understanding of resource allocation in aphasia and reinforce our need to clinically assess and treat reductions in attention for maximised rehabilitation outcome.

Rehabilitation After Stroke: Current State of the Science

Stroke rehabilitation is evolving into a clinical field based on the neuroscience of recovery and restoration. There has been substantial growth in the number and quality of clinical trials performed. Much effort now is directed toward motor restoration and is being led by trials of constraint-induced movement therapy. Although the results do not necessarily support that constraint-induced movement therapy is superior to other training methods, this treatment has become an important vehicle for developing clinical trial methods and studying the physiology underlying activity-based rehabilitation strategies. Other promising interventions include robotic therapy delivery, magnetic and electrical cortical stimulation, visualization, and constraint-driven aphasia therapies. Amphetamine has not been demonstrated to be effective, and studies of other pharmacologic agents are still preliminary. Future studies will incorporate refinements in clinical trial methods and improved activity- and technology-based interventions.

Interrelations of Age, Self-Reported Health, Speed, and Memory

Contributions of self-reported health to adult age differences in perceptual speed and memory were assessed for 301 adults ages 20-90. Participants were asked 4 health status questions, given 3 perceptual speed tests, 2 working memory tests, and 2 memory tests. Self-reported health was found to predict speed better than it predicted memory. Covariance structural equation modeling was used to assess the relations among age, self-reported health, perceptual speed, working memory, and memory. The results support the hypothesis that any effects of self-reported health on age differences in memory are mediated by perceptual speed.