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Toronto, Canada

Meusel L.A.C.,Rotman Research Institute | Meusel L.A.C.,Center for Stroke Recovery | Hall G.B.C.,Mood Disorders Program | Hall G.B.C.,McMaster University | And 4 more authors.
Psychiatry Research - Neuroimaging | Year: 2013

Little is known about the brain changes that mediate improvement following cognitive remediation. We used neuropsychological tests and functional magnetic resonance imaging to study working memory and recollection memory in patients with mood disorders, before (PRE) and after (POST) 10 weeks of cognitive remediation. Thirty-eight patients completed a recollection memory task at PRE (28 had complete PRE and POST scans) and 35 patients completed an n-back working memory task at PRE (23 had complete PRE and POST scans). We also compared patients at PRE with two groups of healthy controls subjects ( n=18 for the recollection memory task and n=15 for the working memory task). At PRE, compared to controls, patients had (i) poorer backward digit span scores, (ii) lower accuracy scores and weaker frontopolar activation during the 2-back condition, and (iii) poorer recollection scores and altered medial temporal activation on the recollection memory task. Following remediation, patients (i) improved on the backward digit span, (ii) activation increased in lateral and medial prefrontal, superior temporal, and lateral parietal regions in the 2-back condition, and (iii) recollection-related activation increased in the bilateral hippocampus. Improvements in 2-back accuracy correlated with activation increases in lateral and medial prefrontal and lateral parietal regions, and improved recollection scores correlated with activation increases in the left hippocampus. PRE-POST improvements on the backward digit span correlated with PRE-POST improvements in 2-back task accuracy; however, there was no direct association between improvement on the backward digit span following training and change in functional activation. These findings suggest that cognitive remediation may lead to behavioural improvements on tests of working memory. The relation between behavioural change and changes in functional activation following remediation requires further study. © 2013 Elsevier Ireland Ltd. Source


St. Jacques P.L.,Harvard University | Grady C.,Rotman Research Institute | Davidson P.S.R.,University of Ottawa | Davidson P.S.R.,Bruyere Research Institute | And 3 more authors.
Neurocase | Year: 2015

Behavioral variant frontotemporal dementia (bvFTD) affects emotional evaluation, but less is known regarding the patients’ ability to remember emotional stimuli. Here, bvFTD patients and age-matched controls studied positive, negative, and neutral pictures followed by a recognition memory test. Compared to controls, bvFTD patients showed a reduction in emotional evaluation of negative scenes, but not of positive or neutral scenes. Additionally, the patients showed an overall reduction in recognition memory accuracy, due to impaired recollection in the face of relatively preserved familiarity. These results show that bvFTD reduces the emotional evaluation of negative scenes and impairs overall recognition memory accuracy and recollection. © 2014 Taylor & Francis. Source


Atir-Sharon T.,Haifa University | Atir-Sharon T.,Yezreel Valley College | Gilboa A.,Rotman Research Institute | Gilboa A.,Center for Stroke Recovery | And 4 more authors.
Neural Plasticity | Year: 2015

Neocortical structures typically only support slow acquisition of declarative memory; however, learning through fast mapping may facilitate rapid learning-induced cortical plasticity and hippocampal-independent integration of novel associations into existing semantic networks. During fast mapping the meaning of new words and concepts is inferred, and durable novel associations are incidentally formed, a process thought to support early childhood's exuberant learning. The anterior temporal lobe, a cortical semantic memory hub, may critically support such learning. We investigated encoding of semantic associations through fast mapping using fMRI and multivoxel pattern analysis. Subsequent memory performance following fast mapping was more efficiently predicted using anterior temporal lobe than hippocampal voxels, while standard explicit encoding was best predicted by hippocampal activity. Searchlight algorithms revealed additional activity patterns that predicted successful fast mapping semantic learning located in lateral occipitotemporal and parietotemporal neocortex and ventrolateral prefrontal cortex. By contrast, successful explicit encoding could be classified by activity in medial and dorsolateral prefrontal and parahippocampal cortices. We propose that fast mapping promotes incidental rapid integration of new associations into existing neocortical semantic networks by activating related, nonoverlapping conceptual knowledge. In healthy adults, this is better captured by unique anterior and lateral temporallobe activity patterns, while hippocampal involvement is less predictive of this kind of learning. © 2015 Tali Atir-Sharon et al. Source


Chisholm A.E.,Toronto Rehabilitation Institute | Chisholm A.E.,University of Toronto | Perry S.D.,Toronto Rehabilitation Institute | Perry S.D.,University of Toronto | And 6 more authors.
Clinical Biomechanics | Year: 2013

Background The purpose of this paper is to 1) evaluate the relationship between ankle kinematics during gait and standardized measures of ankle impairments among sub-acute stroke survivors, and 2) compare the degree of stroke-related ankle impairment between individuals with and without dropped foot gait deviations. Methods Fifty-five independently ambulating stroke survivors participated in this study. Dropped foot was defined as decreased peak dorsiflexion during the swing phase and reduced ankle joint motion in stance. Standardized outcome measures included the Chedoke-McMaster Stroke Assessment (motor impairment), Modified Ashworth Scale (spasticity), Medical Research Council (muscle strength), passive and active range of motion, and isometric muscle force. Findings Foot impairment was not related to peak dorsiflexion during swing (r = - 0.17, P = 0.247) and joint motion during stance (r = 0.05, P = 0.735). Active (r = 0.45, P < 0.001) and passive (r = 0.48, P < 0.001) range of motion was associated with stance phase joint motion. Peak dorsiflexion during swing was related to isometric dorsiflexor muscle force (r = - 0.32, P = 0.039). Individuals with dropped foot demonstrated greater motor impairment, plantarflexor spasticity and ankle muscle weakness compared to those without dropped foot. Interpretation Our investigation suggests that ankle-foot impairments are related to ankle deviations during gait, as indicated by greater impairment among individuals with dropped foot. These findings contribute to a better understanding of gait-specific ankle deviations, and may lead to the development of a more effective clinical assessment of dropped foot impairment. © 2013 Elsevier Ltd. Source


Marzolini S.,University of Toronto | Marzolini S.,Toronto Rehabilitation Institute | Oh P.,Toronto Rehabilitation Institute | Oh P.,Center for Stroke Recovery | And 7 more authors.
Stroke | Year: 2012

Background and Purpose-Despite the importance of exercise training in mitigating cardiovascular risk, the development of exercise programs for people poststroke has been limited by lack of feasibility data concerning cardiopulmonary exercise testing (CPET) to inform the exercise prescription. Therefore, we examined the feasibility of CPETs for developing an exercise prescription in people ≥3 months poststroke. Methods-CPET results from 98 consecutively enrolled patients poststroke with motor impairments and 98 age-and sex-matched patients with coronary artery disease were examined at baseline and after 6 months of exercise training. Results-The proportion of patients with stroke and coronary artery disease attaining an intensity sufficient for prescribing exercise at baseline was 68.4% versus 82.7%, respectively (P=0.02) and 84.7% versus 83.8% (P=0.9) at 6 months. Women were less likely than men poststroke to achieve a sufficient intensity at baseline (40% versus 80.9%, P<0.001) but not at 6 months (78.3% versus 87.1, P=0.3). A clinically relevant abnormality occurred in 11.2% of stroke and 12.2% of patients with coronary artery disease on baseline CPETs (P=0.8) and 10.6% of stroke and 5.9% of patients with coronary artery disease on the 6-month CPET (P=0.4). No serious cardiovascular events occurred during 349 CPETs. Conclusions-Most patients after stroke achieved a level of exertion during the CPET sufficient to inform an exercise prescription. At least 1 of 10 patients poststroke developed a clinically relevant abnormality on baseline and postprogram CPETs with no serious cardiovascular events. These data support the feasibility and safety of CPETs for prescribing exercise poststroke. Strategies to improve use of baseline CPETs for women poststroke require further investigation. © 2012 2012 American Heart Association, Inc. Source

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