Biomedical subjects

Gail A Eskes

Publications and source records attributed to Gail A Eskes.

11 recordsLinked to original sources

PubMed2007

Temporal processing deficits in letter-by-letter reading.

Theories of the cognitive impairment underlying letter-by-letter reading vary widely, including prelexical and lexical level deficits. One prominent prelexical account proposes that the disorder results from difficulty in processing multiple letters simultaneously. We investigated whether this deficit extends to letters presented in rapid temporal succession. A letter-by-letter reader, G.M., was administered a rapid serial visual presentation task that has been used widely to study the temporal processing characteristics of the normal visual system. Comparisons were made to a control group of 6 brain-damaged individuals without reading deficits. Two target letters were embedded at varying temporal positions in a stream of rapidly presented single digits. After each stream, the identities of the two letters were reported. G.M. required an extended period of time after he had processed one letter before he was able to reliably identify a second letter, relative to the controls. In addition, G.M.'s report of the second letter was most impaired when it immediately followed the first letter, a pattern not seen in the controls, indicating that G.M. had difficulty processing the two items together. These data suggest that a letter-by-letter reading strategy may be adopted to help compensate for a deficit in the temporal processing of letters.

Adult↗

PubMed2006

Parametric exploration of the Simon effect across visual space.

The Simon effect refers to the performance advantage for responding to the nonspatial identity of the target when the target's irrelevant location corresponds with the relative location of the response. The present study is a parametric examination of the magnitude of the Simon effect across visual space. Response keys were arranged along vertical, horizontal, and two diagonal axes, and stimuli were arranged in two concentric circles (near and far from fixation) along the same axes. The results show that the Simon effect is of similar magnitude regardless of stimulus-response axis. In contrast to findings from stimulus-response compatibility paradigms, there was no evidence in this study for the presence of an orthogonal compatibility effect or left-right prevalence effect, suggesting that these effects only arise when response location is relevant. The results demonstrate the robust generalizability of the Simon effect under different spatial conditions and thus broaden the relevance of the Simon effect to a variety of applications.

Adolescent↗

PubMed2006

Using limb movements to improve spatial neglect: the role of functional electrical stimulation.

PURPOSE: Spatial neglect is common after right-hemisphere stroke and has proven resilient to a number of therapeutic interventions. Both active and experimenter-induced passive movements of the left limb in left hemispace have been shown to ameliorate neglect in subsets of patients by improving performance on tasks requiring attention to the left side of space. However, the high incidence of contralesional hemiparesis and poor motor recovery in neglect makes active limb movement therapies applicable to only a small subset of patients. The purpose of our studies was to investigate the effects of passive movements of the left hand by functional electrical stimulation (FES), a common and portable motor rehabilitation technique, on performance in a visual scanning task. METHODS: The effect of FES-induced passive movement on target detection in a visual scanning task was compared to no movement and active movement conditions and also investigated in scanning tasks in both near and far space. RESULTS: Passive limb movement effects in neglect were variable across and within studies, reference spaces, and individuals, with a subset of positive responders differing from non-responders in regard to constructional deficits and lesion location. CONCLUSIONS: The potential viability of FES as a therapy for neglect deserves further investigation and directions for future research in this area are discussed.

Electric Stimulation Therapy↗

PubMed2005

Wheelchair-skill performance: controlled comparison between people with hemiplegia and able-bodied people simulating hemiplegia.

OBJECTIVE: To test the hypothesis that able-bodied people simulating hemiplegia (using the hemiplegic-propulsion pattern [1 arm and 1 leg]) have as much difficulty performing wheelchair skills as people with hemiplegia. DESIGN: Single-blind, controlled comparison of 2 groups. SETTING: Kinesiologic laboratory in a rehabilitation center. PARTICIPANTS: Twenty wheelchair users with hemiplegia (HP group) (median age, 68y; 80% men) and 20 able-bodied participants (AB group) (median age, 67y; 75% men). INTERVENTIONS: The participants in the AB group simulated hemiplegia and received a brief period of wheelchair skills training. Participants in both groups were asked to attempt the 50 skills of the Wheelchair Skills Test, version 2.4 (WST 2.4). MAIN OUTCOME MEASURES: Total and subtotal percentage scores on the WST 2.4 and success rates for the 50 individual skills. RESULTS: The mean percentage WST scores for the AB group were significantly greater than those for the HP group for the total WST scores ( P <.001), the indoor skill level ( P <.001), and the community skill level ( P <.001), but the advanced skill level scores were 0% for both groups. On the individual skills, the AB group had success rates at least 25% higher than the HP group for 13 (26%) of the skills. Both groups were generally successful (>/=75% success rate) on 21 skills (42%). Both groups experienced difficulties (</=50% success rate) on 13 skills (26%), notably those in which there was high rolling resistance (eg, incline ascent) or high balance demands (the wheelie skills). CONCLUSIONS: Both people with hemiplegia and able-bodied people who are simulating hemiplegia experience similar difficulties when performing some wheelchair skills. This suggests that there are difficulties inherent in these tasks, a finding that holds promise for solutions based on new techniques and technologies.

Aged↗

PubMed2005

Assessment of working memory abilities using an event-related brain potential (ERP)-compatible digit span backward task.

OBJECTIVE: This study investigated the effectiveness of an ERP-compatible Digit Span Backward (ERP-DB) task to determine working memory abilities in healthy participants. METHODS: Participants were administered both the standard digit span backward and ERP-DB tasks. The ERP-DB task was divided into two sections, consisting of 2, 4, 6 and 8 (Group 1) and 3, 5, and 7 (Group 2) set sizes. A set of digits was aurally presented, followed by a second set that either corresponded to the reverse order of the first set (correct condition) or had one digit in the sequence replaced by an incorrect digit (incorrect condition). RESULTS: Two posterior positive components were found to distinguish the two conditions; an earlier positive component (P200/P300) was elicited in the correct condition, whereas a comparatively robust and prolonged positive slow wave (PSW) was elicited in the incorrect condition. Furthermore, the PSW and the difference in PSW amplitude between incorrect and correct conditions (dPSW) dissipated as working memory load increased and were related to working memory capacity. CONCLUSIONS: The PSW, dPSW and P200/P300 components were found to be associated with working memory abilities and may have the potential to act as neurophysiological markers for the assessment of working memory capacity. SIGNIFICANCE: This research lends support for the utility of the ERP-DB task as a means of assessing working memory abilities, which may have implications for testing patients with expressive communication impairments.

Adult↗

PubMed2004

Gradients of detection in neglect: comparison of peripersonal and extrapersonal space.

Previous studies of target-cancellation performance in visuospatial neglect patients have reported lateral (left-right) and radial (near-far) gradients of attentional ability. The purpose of the present study was to replicate the reported attentional gradients in peripersonal space (within arms reach) and to examine whether lateral gradients of detection also appear in extrapersonal space (beyond arms reach), using equivalent tasks with no manual requirement. The relationship between radial gradients in peripersonal space and neglect severity (degree of lateral gradient) in extrapersonal space was also of interest. Right-hemisphere stroke subjects, with and without neglect, and healthy control subjects named visual targets on scanning sheets placed in peripersonal and extrapersonal space. The neglect group showed lateral gradients of increasing target detection from left to right in both peripersonal and extrapersonal space, which were not evident in the performance of either of the control groups. Double dissociations of neglect severity in peripersonal and extrapersonal space were also found in analyses of individual performance. Lesion analyses showed that peripersonal neglect was related to dorsal stream damage and extrapersonal neglect was related to ventral stream damage. Group analyses showed no significant radial gradients in peripersonal space in the three groups. In addition, while analyses of some individuals found significant near-far and far-near radial gradients, there was no correlation between radial gradients in peripersonal space and neglect severity in extrapersonal space. These results are discussed in terms of theorised hemispheric mechanisms of spatial attention and the relationship of neglect in the two co-ordinate spaces to the extent and location of damaged neurons in the right hemisphere.

Adult↗

PubMed2003

Electrophysiological assessment of language function following stroke.

OBJECTIVE: Event-related brain potentials (ERPs) were used to assess language function after stroke and demonstrate that it is possible to adapt neuropsychological tests to evaluate neurocognitive function using ERPs. Prior ERP assessment work has focused on language in both healthy individuals and case studies of aphasic neurotrauma patients. The objective of the current study was to evaluate left-hemisphere stroke patients who had varying degrees of receptive language impairment. It was hypothesized that ERPs would assess receptive language function accurately and correlate highly with the neuropsychological data. METHODS: Data were collected from 10 left-hemisphere stroke patients; all were undergoing rehabilitation at the time of testing. Each patient received a battery of neuropsychological tests including the Peabody Picture Vocabulary Test-Revised (PPVT-R; Minnesota: American Guidance Service, 1981). ERPs were recorded during a computerized PPVT-R, in which pictures are presented followed by digitized spoken words that are either congruent or incongruent with the pictures. RESULTS AND CONCLUSION: Incongruent spoken words within an individual's vocabulary level elicited well-known ERP components. One of the components (the N400) could be utilized as a marker of intact semantic processing. The ERP results were subsequently quantified and N400 derivative scores correlated highly with the neuropsychological findings. The results provided a clear demonstration of the efficacy of ERP-based assessment in a neurological patient group. SIGNIFICANCE: Language function in stroke patients can be evaluated, independent of behavior, using electrophysiological measures that correlate highly with traditional neuropsychological test scores.

Acoustic Stimulation↗

PubMed2003

Limb activation effects in hemispatial neglect.

OBJECTIVE: To assess the efficacy of passive and active limb movement to improve visual scanning in patients with hemispatial neglect. DESIGN: Before-after trial: behavioral analyses of a case series. SETTING: Stroke rehabilitation unit in a tertiary care hospital. PARTICIPANTS: Nine individuals with right-hemisphere stroke (mean time poststroke, 19.5 mo) and left-sided neglect, as assessed by the Sunnybrook Bedside Neglect Battery. INTERVENTION: Active left limb movement (button push; n=3) or passive left limb movement (n=8) with functional electric stimulation (FES) administered during visual scanning testing. MAIN OUTCOME MEASURES: Performance on visual scanning tests involving naming of letters and numbers. RESULTS: Both active and passive movement significantly improved target detection on the left side, but not on the right side, on the visual scanning task. Positive results were seen in 2 of 3 active movement patients and 6 of 8 passive movement patients. CONCLUSIONS: Both active and FES-stimulated passive movements are potential techniques for the treatment of hemispatial neglect.

Acoustic Stimulation↗

PubMed2003

Fatigue associated with stroke and other neurologic conditions: Implications for stroke rehabilitation.

OBJECTIVES: To examine the general phenomenon of fatigue in stroke and other neurologic disorders and to review what is currently known about its occurrence, including its frequency, duration, severity, and associated factors, to develop a strategy for treatment. DATA SOURCES: Computerized databases (eg, PubMed, PsycInfo, Science Citation Index, Ovid EMBASE, Ovid MEDLINE) searched from inception to May 2002. Additional references were identified from bibliographies of pertinent articles and books. STUDY SELECTION: Over 1000 articles were identified as relevant to fatigue experienced by patients with neurologic or nonneurologic disorders. Articles on fatigue in stroke and neurologic disorders, mechanisms, and/or treatment were selected for inclusion. DATA EXTRACTION: Authors reviewed the articles and assessed the purpose, study design, and conclusions for validity and relevance to the topic of fatigue in stroke. DATA SYNTHESIS: Fatigue is a common complaint among patients with neurologic disorders including stroke. Few studies have documented the high frequency of fatigue in poststroke patients and its negative impact on daily functioning and quality of life. Little is known about associated factors or about therapeutic strategies that may be used to alleviate it. Examination of fatigue in other neurologic populations suggests common characteristics and associated factors that may be useful in the development of potential therapeutic strategies. Pharmacologic and nonpharmacologic therapeutic interventions, such as stimulants, amantadine, or sleep and stress-management education, have been used with some success in neurologic and other patient populations (eg, multiple sclerosis, human immunodeficiency virus, acquired immune deficiency syndrome, cancer), but evidence of effectiveness based on randomized clinical trials is rare. CONCLUSIONS: Poststroke fatigue is common. Therapeutic strategies have been used to treat fatigue in other patient populations, but it is unclear whether these will be beneficial to poststroke patients. Frequency, severity, duration, impact, predisposing factors, and causes of poststroke fatigue, as well as the development of effective treatment, require further research. Criteria for assessment of fatigue and potential therapeutic interventions are outlined as a first step for stimulating further research.

Activities of Daily Living↗

PubMed2002

Description and evaluation of an acute stroke unit.

Clinical trials have demonstrated the superiority of coordinated interdisciplinary stroke unit care over conventional treatment of stroke patients on general medical wards. The evidence is so strong that several national bodies have recommended that stroke unit care be widely implemented. Translation of these research findings and care guidelines into clinical practice, however, represents a challenge for health care systems unaccustomed to managing stroke in a coordinated manner. This report describes the organization, operation and outcomes of the Acute Stroke Unit at the Queen Elizabeth II Health Sciences Centre in Halifax. By replicating and adapting the core characteristics identified in the randomized trials, we have been able to demonstrate the effectiveness of stroke unit care in a routine clinical setting. Our experience may help facilitate the development of organized stroke care in Canada.

Aged↗

PubMedDate not supplied

Role of the frontal lobes in implicit and explicit retrieval tasks.

While the role of the frontal lobes in explicit retrieval tasks is well supported, the findings for implicit tasks are less conclusive. We investigated the role of the frontal lobes in perceptual and conceptual implicit priming. Three memory paradigms were given under both implicit and explicit retrieval instructions, using word fragment completion, picture fragment completion and category exemplar generation. Three groups of individuals with frontal lesions were compared to normal controls: Left dorsolateral lesions (n = 5), right dorsolateral lesions (n = 4), and medial lesions (n = 9). Word fragment completion priming was impaired by left dorsolateral lesions, with other priming tests unaffected by any lesion. Explicit performance showed a different pattern, with category exemplar cued recall impaired by left dorsolateral and medial lesions. These findings support the role of the frontal lobes in both implicit and explicit retrieval mechanisms under certain conditions requiring strategy application or lexical retrieval.

Adult↗