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Soros P.,Imaging Research | Bose A.,University of Windsor | Sokoloff L.G.,Communication Disorders Technology, Inc | Sokoloff L.G.,University of Toronto | And 6 more authors.
Neurobiology of Aging | Year: 2011

Alterations of existing neural networks during healthy aging, resulting in behavioral deficits and changes in brain activity, have been described for cognitive, motor, and sensory functions. To investigate age-related changes in the neural circuitry underlying overt non-lexical speech production, functional MRI was performed in 14 healthy younger (21-32 years) and 14 healthy older individuals (62-84 years). The experimental task involved the acoustically cued overt production of the vowel /a/ and the polysyllabic utterance /pataka/. In younger and older individuals, overt speech production was associated with the activation of a widespread articulo-phonological network, including the primary motor cortex, the supplementary motor area, the cingulate motor areas, and the posterior superior temporal cortex, similar in the /a/ and /pataka/ condition. An analysis of variance with the factors age and condition revealed a significant main effect of age. Irrespective of the experimental condition, significantly greater activation was found in the bilateral posterior superior temporal cortex, the posterior temporal plane, and the transverse temporal gyri in younger compared to older individuals. Significantly greater activation was found in the bilateral middle temporal gyri, medial frontal gyri, middle frontal gyri, and inferior frontal gyri in older vs. younger individuals. The analysis of variance did not reveal a significant main effect of condition and no significant interaction of age and condition. These results suggest a complex reorganization of neural networks dedicated to the production of speech during healthy aging. © 2009 Elsevier Inc.


Mansfield A.,Heart and Stroke Foundation of Ontario Center for Stroke Recovery | Mansfield A.,Sunnybrook Health science Center | Mansfield A.,University of Toronto | Danells C.J.,Heart and Stroke Foundation of Ontario Center for Stroke Recovery | And 10 more authors.
Clinical Biomechanics | Year: 2011

Background: During standing, forces and moments exerted at the feet serve to maintain stability in the face of constant centre-of-mass movement. These actions are temporally synchronized in healthy individuals. Stroke is typically a unilateral injury resulting in increased sensori-motor impairment in the contra-lesional compared with the ipsi-lesional lower-limb, which could lead to reduced between-limb synchronization for control of standing balance. The purpose of this study is to investigate between-limb synchronization of standing balance control in individuals with stroke; a potentially important index of control of upright stability. Methods: Twenty healthy controls and 33 individuals with unilateral stroke were assessed. Stability was assessed during a 30-second quiet standing trial by measuring data from two force plates (one per foot). Limb-specific centre of pressure was calculated. Between-limb synchronization was defined as the coefficient of the correlation between the left and right foot for both the antero-posterior and medio-lateral centre of pressure time series. Synchronization, weight-bearing symmetry, and root mean square of the total centre of pressure excursion were compared between controls and stroke participants. Findings: Stroke participants swayed more, were more asymmetric, and had less between-limb synchronization than healthy controls. Among individuals with stroke, reduced between-limb synchronization was related to increased postural sway in the medio-lateral direction and increased weight-bearing asymmetry. Interpretation: Individuals with stroke have reduced temporal synchronization of centre of pressure fluctuations under the feet when controlling quiet standing. The clinical significance of reduced synchronization remains to be determined, although it appears linked to increased medio-lateral sway and weight-bearing asymmetry. © 2010 Elsevier Ltd.


Soros P.,Sunnybrook Health science Center | Macintosh B.J.,Sunnybrook Health science Center | Macintosh B.J.,University of Oxford | Tam F.,Sunnybrook Health science Center | And 5 more authors.
Frontiers in Human Neuroscience | Year: 2010

A functional magnetic resonance imaging (fMRI)-compatible fi ber-optic bend sensor was investigated to assess whether the device could be used effectively to monitor opening and closing of the jaw during an fMRI experiment at 3 T. In contrast to surface electromyography, a bend sensor fi xed to the chin of the participant is fast and easy to use and is not affected by strong electromagnetic fields. Bend sensor recordings are characterized by high validity (compared with concurrent video recordings of mouth opening) and high reliability (comparing two independent measurements). The results of this study indicate that a bend sensor is able to record the opening and closing of the jaw associated with different overt speech conditions (producing the utterances /a/, /pa/, /pataka/) and the opening of the mouth without speech production. Data post-processing such as fi ltering was not necessary. There are several potential applications for bend sensor recordings of speech-related jaw movements. First, bend sensor recordings are a valuable tool to assess behavioral performance, such as response latencies, accuracies, and completion times, which is particularly important in children, seniors, or patients with various neurological or psychiatric conditions. Second, the timing information provided by bend sensor data may improve the predicted hemodynamic response that is used for fMRI analysis based on the general linear model (GLM). Third, bend sensor recordings may be included in GLM analyses not for statistical contrast purposes, but as a covariate of no interest, accounting for part of the data variance to model fMRI artifacts due to motion outside the field of view. © 2010 Sörös, MacIntosh, Tam and Graham. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited. © 2010 Söro7die;s, MacIntosh, Tam and Graham.


Kuo A.Y.-C.,University of Toronto | Chiew M.,University of Toronto | Chiew M.,Rotman Research Institute | Tam F.,Rotman Research Institute | And 6 more authors.
Magnetic Resonance in Medicine | Year: 2011

"Real-time" functional magnetic resonance imaging is starting to be used in neurofeedback applications, enabling individuals to regulate their brain activity for therapeutic purposes. These applications use two-dimensional multislice echo planar or spiral readouts to image the entire brain volume, often with a much smaller region of interest within the brain monitored for feedback purposes. Given that such brain activity should be sampled rapidly, it is worthwhile considering alternative functional magnetic resonance imaging pulse sequences that trade spatial resolution for temporal resolution. We developed a prototype sequence localizing a column of magnetization by outer volume saturation, from which densely sampled transverse relaxation time decays are obtained at coarse voxel locations using an asymmetric gradient echo train. For 5 × 20 × 20 mm3 voxels, 256 echoes are sampled at ∼1 msec and then combined in weighted summation to increase functional magnetic resonance imaging signal contrast. This multiecho coarse voxel pulse sequence is shown experimentally at 1.5 T to provide the same signal contrast to noise ratio as obtained by spiral imaging for a primary motor cortex region of interest, but with potential for enhanced temporal resolution. A neurofeedback experiment also illustrates measurement and calculation of functional magnetic resonance imaging signals within 1 sec, emphasizing the future potential of the approach. Copyright © 2011 Wiley-Liss, Inc.


Rotenberg D.,Rotman Research Institute | Rotenberg D.,University of Toronto | Chiew M.,Rotman Research Institute | Chiew M.,University of Toronto | And 9 more authors.
Magnetic Resonance in Medicine | Year: 2013

Head motion artifacts are a major problem in functional MRI that limit its use in neuroscience research and clinical settings. Real-time scan-plane correction by optical tracking has been shown to correct slice misalignment and nonlinear spin-history artifacts; however, residual artifacts due to dynamic magnetic field nonuniformity may remain in the data. A recently developed correction technique, Phase Labeling for Additional Coordinate Encoding, can correct for absolute geometric distortion using only the complex image data from two echo planar images with slightly shifted k-space trajectories. An approach is presented that integrates Phase Labeling for Additional Coordinate Encoding into a real-time scan-plane update system by optical tracking, applied to a tissue-equivalent phantom undergoing complex motion and an functional MRI finger tapping experiment with overt head motion to induce dynamic field nonuniformity. Experiments suggest that such integrated volume-by-volume corrections are very effective at artifact suppression, with potential to expand functional MRI applications. Copyright © 2012 Wiley Periodicals, Inc.


Schweizer T.A.,St Michaels Hospital | Schweizer T.A.,University of Toronto | Schweizer T.A.,Heart and Stroke Foundation of Ontario Center for Stroke Recovery | Al-Khindi T.,St Michaels Hospital | And 2 more authors.
Journal of the Neurological Sciences | Year: 2012

Objective: Recent studies suggest that the Montreal Cognitive Assessment (MoCA) is more sensitive to stroke-associated cognitive dysfunction than the Mini-Mental State Examination (MMSE), but little is known about how these screening measures relate to neurocognitive test performance or real-world functioning in patients with good recovery after aneurysmal subarachnoid hemorrhage (aSAH). The aim of the present study was to determine how MoCA and MMSE scores relate to neurocognitive impairment and return to work after aSAH. Methods: Thirty-two patients with aSAH who had made a good recovery completed the MoCA, the MMSE, and a battery of neurocognitive tests. Results: 42% and 0% of aSAH patients were impaired on the MoCA and MMSE, respectively. The MoCA had acceptable sensitivity (40-100%) and specificity (54-68%) (Table 3). The MMSE failed to detect impairment in any cognitive domain. The MoCA, but not the MMSE, predicted performance on tests of verbal learning, executive function, working memory, visuospatial function, and motor function. Superior performance on the Animal naming and Abstraction subtests of the MoCA score were associated with return to work following aSAH. Conclusion: Compared to the MMSE, the MoCA is more sensitive to aSAH-associated cognitive impairment. Certain MoCA subtests are also sensitive to functional difficulties after aSAH such as return to work. These findings support the utility of the MoCA as a brief bedside assessment of cognitive and real-world outcome in aSAH survivors. © 2012 Elsevier B.V. All rights reserved.


Tam F.,Rotman Research Institute | Churchill N.W.,Rotman Research Institute | Churchill N.W.,University of Toronto | Strother S.C.,Rotman Research Institute | And 5 more authors.
Human Brain Mapping | Year: 2011

Writing and drawing are understudied with fMRI, partly for lack of a device that approximates these behaviors well while supporting task feedback and quantitative behavioral logging in the confines of the magnet. Consequently, we developed a tablet based on touchscreen technology that is accurate, reliable, relatively inexpensive, and fMRI compatible. After confirming fMRI compatibility, we conducted preliminary fMRI experiments examining the neural correlates of a widely used pen-and-paper neuropsychological assessment, the trail making test. In two subjects, we found left hemisphere frontal lobe activations similar to the major results of a previous group study, and we also noted individual differences mostly in the right hemisphere. These results demonstrate the utility of the new tablet for adaptations of pen-and-paper tests and suggest possible uses of the tablet for longitudinal, within-subjects studies of disease or therapy. We also discuss using the tablet for several other types of tests requiring many, continuous, or two-dimensional responses that were previously very difficult to perform during fMRI. Hum Brain Mapp, 2011. © 2010 Wiley-Liss, Inc. Copyright © 2010 Wiley-Liss, Inc.


Tam F.,Rotman Research Institute | Churchill N.W.,Rotman Research Institute | Churchill N.W.,University of Toronto | Strother S.C.,Rotman Research Institute | And 5 more authors.
Human Brain Mapping | Year: 2012

The article to which this erratum refers was published in ©; 2011 Wiley-Liss, Inc.


Miller D.I.,University of Ottawa | Taler V.,University of Ottawa | Taler V.,Elisabeth Bruyere Research Institute | Davidson P.S.R.,University of Ottawa | And 3 more authors.
Neurobiology of Aging | Year: 2012

Physical exercise and fitness have been proposed as potential factors that promote healthy cognitive aging. Support for this hypothesis has come from cross sectional, longitudinal, and intervention studies. In the present review, we discuss several methodological problems that limit the conclusions of many studies. The lack of consensus on how to retrospectively measure exercise intensity is a major difficulty for all studies that attempt to estimate lifelong impact of exercise on cognitive performance in older adults. Intervention studies have a much better capacity to establish causality, but still suffer from difficulties arising from inadequate control groups and the choice and modality of administration of cognitive measures. We argue that, while the association between exercise and preserved cognition during aging is clearly demonstrated, the specific hypothesis that physical exercise is a cause of healthy cognitive aging has yet to be validated. A number of factors could mediate the exercise-cognition association, including depression, and social or cognitive stimulation. The complex interactions among these 3 factors and the potential impact of exercise on cognition remain to be systematically studied. At this time, the best prescription for lifestyle interventions for healthy cognitive aging would be sustained physical, social, and mental activities. What remains unknown is which type of activity might be most useful, and whether everyone benefits similarly from the same interventions. © 2012 Elsevier Inc.


Young-Bernier M.,University of Ottawa | Young-Bernier M.,Elisabeth Bruyere Research Institute | Davidson P.S.R.,University of Ottawa | Davidson P.S.R.,Elisabeth Bruyere Research Institute | And 3 more authors.
Neurobiology of Aging | Year: 2012

Changes in motor cortical excitability were examined in 2 groups of participants, young (18-30 years of age, n = 25) and senior (65-82 years of age, n = 31), using paired-pulse afferent stimulation with transcranial magnetic stimulation (TMS). Motor evoked potentials (MEPs) elicited by TMS at suprathreshold intensity (120% motor threshold) were first recorded in unconditioned trials (TMS alone) and then in conditioned trials, in which TMS pulses were preceded by median nerve stimulation at 3 different interstimulus intervals (ISI; 20, 50, and 200 ms). Conditioning of MEP responses revealed a similar pattern of modulation in the 2 age groups, with 2 periods of inhibition at 20- and 200-ms ISIs, separated by a period in which MEPs tended to return to baseline at a 50-ms ISI. Afferent-induced inhibition at the short interval (i.e., SAI 20-ms ISI), was selectively reduced in seniors, with half of them showing either low or no MEP suppression. Age-associated changes in SAI level were also good predictors of performance on tests of processing speed and dexterity. The selective decrease in SAI exhibited by many seniors is consistent with reported alterations in intracortical inhibition with age. Our observations also highlight the potential value of SAI, as a putative marker of central cholinergic activity, in predicting declines in motor and cognitive function with age. © 2012 Elsevier Inc.

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