Donald T Stuss

University of Toronto, Toronto, Ontario, Canada

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Publications (261)992.21 Total impact

  • R.S. Rosenbaum · D Kwan · D Floden · B Levine · D.T. Stuss · C.F. Craver
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    ABSTRACT: Does advantageous decision-making require one to explicitly remember the outcome of a series of past decisions or to imagine future personal consequences of one's choices? Findings that amnesic people with hippocampal damage cannot form a clear preference for advantageous decks over many learning trials on the Iowa Gambling Task (IGT) have been taken to suggest that complex decision-making on the IGT depends on declarative (episodic) memory and hippocampal integrity. Alternatively, impaired IGT performance in amnesic individuals could be secondary to risk-taking and/or impulsive behaviour resulting from impaired episodic future thinking (i.e., prospection) known to accompany amnesia. We tested this possibility in the amnesic individual K.C. using the IGT and the Toronto Gambling Task (TGT), a novel task that dissociates impulsivity from risk-taking without placing demands on declarative memory. K.C. did not develop a preference for advantageous over disadvantageous decks on the IGT and, instead, showed a slight preference for short-term gains and an inability to acquire a more adaptive appreciation of longer-term losses. He also did not display impulsive or risk-taking behaviour on the TGT, despite a profound inability to imagine personal future experiences. These findings suggest that impaired decision-making on the IGT in amnesia is unlikely to reflect a predilection to act in the moment or failure to take future consequences into account. Instead, some forms of future-regarding decision-making may be dissociable, with performance on tasks relying on declarative learning or on episodic-constructive processes more likely to be impaired.
    No preview · Article · Oct 2015 · Quarterly journal of experimental psychology (2006)
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    ABSTRACT: Background and Purpose—Poststroke cognitive impairment is typified by prominent deficits in processing speed and executive function. However, the underlying neuroanatomical substrates of executive deficits are not well understood, and further elucidation is needed. There may be utility in fractionating executive functions to delineate neural substrates. Methods—One test amenable to fine delineation is the Trail Making Test (TMT), which emphasizes processing speed (TMT-A) and set shifting (TMT-B-A difference, proportion, quotient scores, and TMT-B set-shifting errors). The TMT was administered to 2 overt ischemic stroke cohorts from a multinational study: (1) a chronic stroke cohort (N=61) and (2) an acute–subacute stroke cohort (N=45). Volumetric quantification of ischemic stroke and white matter hyperintensities was done on magnetic resonance imaging, along with ratings of involvement of cholinergic projections, using the previously published cholinergic hyperintensities projections scale. Damage to the superior longitudinal fasciculus, which colocalizes with some cholinergic projections, was also documented. Results—Multiple linear regression analyses were completed. Although larger infarcts (β=0.37, P<0.0001) were associated with slower processing speed, cholinergic hyperintensities projections scale severity (β=0.39, P<0.0001) was associated with all metrics of set shifting. Left superior longitudinal fasciculus damage, however, was only associated with the difference score (β=0.17, P=0.03). These findings were replicated in both cohorts. Patients with ≥2 TMT-B set-shifting errors also had greater cholinergic hyperintensities projections scale severity. Conclusions—In this multinational stroke cohort study, damage to lateral cholinergic pathways and the superior longitudinal fasciculus emerged as significant neuroanatomical correlates for executive deficits in set shifting.
    No preview · Article · Sep 2015 · Stroke

  • No preview · Article · Sep 2015 · International Journal of Stroke
  • Donald T Stuss
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    ABSTRACT: The Ontario Brain Institute manages a network of partnerships among researchers, clinicians, industry representatives and patients to maximize their collective impact on developing better treatment and care for those living with brain disorders.
    No preview · Article · Apr 2015 · Nature Reviews Drug Discovery
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    ABSTRACT: We explored the effects of age and time of day (TOD) on verbal fluency ability with respect to performance level and intraindividual variability (IIV). Verbal fluency, which involves complex cognitive operations, was examined in 20 older (mean age = 72.8 years) and 20 younger (mean age = 24.2 years) adults with test start time alternating between morning and evening across four days. Older adults generated more words in the morning and younger adults more in the evening, corresponding with self-report peak TOD. Age by TOD interactions were also observed across fluency tasks on the number of switches among subcategory exemplars during word generation and on the IIV observed in switching behavior. Older adults exhibited greater variability in switching in the evening than in the morning, whereas younger adults showed the opposite pattern. These findings demonstrate that processes involving energization (initiating and sustaining) and attentional control may be particularly sensitive to age differences in TOD influences on cognition.
    No preview · Article · Apr 2015 · Aging Neuropsychology and Cognition
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    Donald T Stuss
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    ABSTRACT: The Province of Ontario recognized the pressing need to improve the understanding, diagnosis, and treatment of brain disorders. It also recognized that maximizing the existing strengths through a province-wide integrated approach was a pivotal mechanism. To achieve this, the Province established the Ontario Brain Institute. The goal of this article is to introduce the elements of the Ontario Brain Institute to the neuroscience community: the motivation for establishing it, the philosophy behind its creation, the principles guiding its development, the rapid evolution of its functional structure, the tools available to achieve its vision, and the management structure to ensure success. The singular goal of the Province and the Ontario Brain Institute is a comprehensive system that assures that basic research is embedded in the clinical system and is facilitating product development to accelerate benefits to both health and the economy of health: science with impact.
    Preview · Article · Nov 2014 · The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques
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    ABSTRACT: Introduction: Despite widespread use of second-generation cholinesterase inhibitors for the symptomatic treatment of Alzheimer's disease (AD), little is known about the long term effects of cholinergic treatment on global cognitive function and potential specific effects in different cognitive domains. The objectives of this study were to determine the association between cholinergic treatment and global cognitive function over one and two years in a cohort of patients with mild or moderate AD and identify potential differences in domain-specific cognitive outcomes within this cohort. Methods: A cohort of patients meeting the revised National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria for mild or moderate AD, including patients both on treatment with a cholinesterase inhibitor and untreated controls (treated = 65, untreated = 65), were recruited from the Cognitive Neurology Clinic at Sunnybrook Health Sciences Centre, as part of the Sunnybrook Dementia Study. Patients were followed for one to two years and underwent standardized neuropsychological assessments to evaluate global and domain-specific cognitive function. Associations between cholinesterase inhibitor use and global and domain-specific cognitive outcome measures at one and two years of follow-up were estimated using mixed model linear regression, adjusting for age, education, and baseline mini mental state examination (MMSE). Results: At one year, treated patients showed significantly less decline in global cognitive function, and treatment and time effects across tests of executive and visuospatial function. At two years, there was a significant trend towards less decline in global cognition for treated patients. Moreover, treated patients showed significant treatment and time effects across tests of executive functioning, memory, and visuospatial function. Conclusions: The present study offers two important contributions to knowledge of the effectiveness of cholinesterase inhibitor treatment in patients with mild-moderate AD: 1) that second-generation cholinesterase inhibitors demonstrate long-term effectiveness for reducing global cognitive decline over one to two years of follow-up, and 2) that decline in function for cognitive domains, including executive function, memory, and visuospatial skill that are primarily mediated by frontal networks and by the cholinergic system, rather than memory, may be slowed by treatment targeting the cholinergic system.
    Full-text · Article · Aug 2014 · Alzheimer's Research and Therapy
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    ABSTRACT: Background: Subcortical hyperintensities within the cholinergic fiber projections (chSH) on MRI are believed to reflect cerebral small vessel disease (SVD) which may adversely impact cognition. Additionally, hippocampal atrophy represents a commonly used biomarker to support the diagnosis of Alzheimer's disease (AD). Objective: To examine potential differences in neuropsychological test performance between AD patients (n = 234) with high and low chSH volumes and whether these differences corresponded to hippocampal atrophy. Methods: A modified version of Lesion Explorer was used to volumetrically quantify chSH severity. The Sunnybrook Hippocampal Volumetry Tool was applied to obtain hippocampal volumes. Composite z-scores to assess executive, memory, and visuospatial functioning were generated from standardized neuropsychological test performance scores. Results: Inter-method technique validation demonstrated a high degree of correspondence with the Cholinergic Pathways Hyperintensities Scale (n = 40, ρ = 0.84, p < 0.001). After adjusting for brain atrophy, disease severity, global SH volumes, and demographic variables, multivariate analyses revealed a significant group difference, with the high chSH group demonstrating poorer memory function compared to the low chSH group (p = 0.03). A significant difference was found between low and high chSH groups in total (p < 0.05) and left (p < 0.01) hippocampal volume. Conclusion: These results suggest degradation of the cholinergic projections due to strategic SVD may independently contribute to memory dysfunction and hippocampal atrophy. Future studies examining subcortical vasculopathy in the cholinergic pathways may have implications on the development of therapeutic strategies for dementia and SVD.
    Full-text · Article · Aug 2014 · Journal of Alzheimer's disease: JAD
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    ABSTRACT: Subcortical hyperintensities (SHs) are radiological entities commonly observed on magnetic resonance imaging (MRI) of patients with Alzheimer's disease (AD) and normal elderly controls. Although the presence of SH is believed to indicate some form of subcortical vasculopathy, pathological heterogeneity, methodological differences, and the contribution of brain atrophy associated with AD pathology have yielded inconsistent results in the literature. Using the Lesion Explorer (LE) MRI processing pipeline for SH quantification and brain atrophy, this study examined SH volumes of interest and cognitive function in a sample of patients with AD (n = 265) and normal elderly controls (n = 100) from the Sunnybrook Dementia Study. Compared with healthy controls, patients with AD were found to have less gray matter, less white matter, and more sulcal and ventricular cerebrospinal fluid (all significant, P <0.0001). Additionally, patients with AD had greater volumes of whole-brain SH (P <0.01), periventricular SH (pvSH) (P <0.01), deep white SH (dwSH) (P <0.05), and lacunar lesions (P <0.0001). In patients with AD, regression analyses revealed a significant association between global atrophy and pvSH (P = 0.02) and ventricular atrophy with whole-brain SH (P <0.0001). Regional volumes of interest revealed significant correlations with medial middle frontal SH volume and executive function (P <0.001) in normal controls but not in patients with AD, global pvSH volume and mental processing speed (P <0.01) in patients with AD, and left temporal SH volume and memory (P <0.01) in patients with AD. These brain-behavior relationships and correlations with brain atrophy suggest that subtle, yet measurable, signs of small vessel disease may have potential clinical relevance as targets for treatment in Alzheimer's dementia.
    Full-text · Article · Aug 2014 · Alzheimer's Research and Therapy
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    Full-text · Article · Jul 2014
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    ABSTRACT: We report a single-case study of a female patient (VL) who exhibited frequent episodes of erroneous recollections triggered by everyday events. Based on neuropsychological testing, VL was classified as suffering from mild to moderate dementia (MMSE=18) and was given a diagnosis of probable Alzheimer’s disease. Her memory functions were uniformly impaired but her verbal abilities were generally well preserved. A structural MRI scan showed extensive areas of gray matter atrophy particularly in frontal and medial-temporal (MTL) areas. Results of experimental recognition tests showed that VL had very high false alarm rates on tests using pictures, faces and auditory stimuli, but lower false alarm rates on verbal tests. We provide a speculative account of her erroneous recollections in terms of her MTL and frontal pathology. In outline, we suggest that owing to binding failures in MTL regions, VL’s recognition processes were forced to rely on earlier than normal stages of analysis. Environmental features on a given recognition trial may have combined with fragments persisting from previous trials resulting in erroneous feelings of familiarity and of recollection that were not discounted or edited out, due to her impaired frontal processes.
    Full-text · Article · Apr 2014 · Neuropsychologia
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    ABSTRACT: Functional contributions of cognitive impairment may vary by domain and severity. (1) To characterize frequency of cognitive impairment by domain after stroke by severity (mild: -1.5 ≤ z-score < -2; severe: Z ≤ -2) and time (sub-acute: < 90d; chronic: 90d-2yrs); and (2) To assess the association of cognitive impairment with function in chronic stroke. Cognitive function was characterized among 215 people with sub-acute or chronic stroke (66.8 years, 43.3% female). Z-scores by cognitive domain were determined from normative data. Function was defined as the number of IADLs minimally independent. 76.3% of sub-acute and 67.3% of chronic stroke participants had cognitive impairment in ≥ 1 domain (p-for-difference = 0.09). Severe impairment was most common in psychomotor speed (sub-acute: 53.5%; chronic: 33.7%). Impairment in executive function was common (sub-acute: 39.5%; chronic: 30.7%) but was usually mild. Severe impairment in psychomotor speed, visuospatial function, and language and any impairment in executive function and memory was associated with IADL impairment (p < 0.03). Mild cognitive impairment is common after stroke but is not associated with functional disability. Impairment in psychomotor speed, executive function, and visuospatial function is common and associated with functional impairment so should be a focus of screening and rehabilitation post-stroke.
    No preview · Article · Jan 2014 · Neurorehabilitation
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    ABSTRACT: To compare the validity of the Montreal Cognitive Assessment (MoCA) with the criterion standard of standardized neuropsychological testing and to compare the convergent validity of the MoCA with that of existing screening tools and global measures of cognition. Cross-sectional observational study. Tertiary care hospital-based cognitive neurology subspecialty clinic. A convenience sample of 107 individuals with mild Alzheimer's disease (AD, n = 75) or mild cognitive impairment (MCI, n = 32) from the Sunnybrook Dementia Study. In addition to the MoCA, all participants completed the Mini-Mental State Examination (MMSE), the Mattis Dementia Rating Scale (DRS), and detailed neuropsychological testing. Convergent validity was supported, with MoCA scores correlating well with the MMSE (correlation coefficient (r) = 0.66, P < .001) and the DRS (r = 0.77, P < .001) and the MoCA better associated with the DRS than did the MMSE. Criterion validity was supported, with MoCA subscores according to cognitive domain correlating well with analogous neuropsychological tests and, in the case of memory (area under the receiver operating characteristic curve (AUC) = 0.86), executive (AUC = 0.79), and visuospatial function (AUC = 0.79), being reasonably sensitive to impairment in those domains. The MoCA is a valid assessment of cognition that shows good agreement with existing screening tools and global measures (convergent validity) and was superior to the MMSE in this regard. The MoCA domain-specific subscores align with performance on more-detailed neuropsychological tests, suggesting not only good criterion validity for the MoCA, but also that it may be useful in guiding further neuropsychological testing.
    No preview · Article · Dec 2013 · Journal of the American Geriatrics Society

  • No preview · Conference Paper · Dec 2013

  • No preview · Conference Paper · Dec 2013
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    Katherine M Krpan · Nicole D Anderson · Donald T Stuss
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    ABSTRACT: Coping has been suggested as the final common pathway related to outcome after traumatic brain injury (TBI). Different types of coping have been related to either positive or negative psychosocial outcomes. As a result, a small set of studies have attempted to remediate coping through intervention, but the effectiveness of these studies has been modest. We propose that three primary factors are limiting our ability to effectively remediate coping following TBI through intervention TBI: 1) limited understanding of inter-patient variability following TBI; 2) limited understanding of the mechanisms underlying coping following TBI; and 3) reliance on self-report measures of coping. We discuss these obstacles in the context of a model of frontal lobe function, and in light of recent behavioural work on coping.
    Full-text · Article · Jul 2013 · Neurorehabilitation
  • David P Salmon · Donald T Stuss
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    ABSTRACT: Frontotemporal degeneration is the overarching label used to describe a spectrum of neurodegenerative disorders characterized by relatively circumscribed frontal and temporal lobar atrophy that leads to profound changes in personality, behavior, or language. The dementia syndrome associated with frontotemporal degeneration is usually divided into 2 broad categories: a language-based variant referred to as primary progressive aphasia(1) and a behavioral variant frontotemporal dementia (bvFTD) in which changes in social cognition, behavior, and personality are the earliest and most prominent features.(2) Although not as common as Alzheimer disease (AD), FTD is not rare and accounts for about 9% of all cases of dementia, and is particularly prevalent when the age at onset of dementia is younger than 65 years.(3.)
    No preview · Article · May 2013 · Neurology
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    ABSTRACT: Schizophrenia (SCZ)-related verbal memory impairment is hypothesized to be mediated, in part, by frontal lobe (FTL) dysfunction. However, little research has contrasted the performance of SCZ patients with that of patients exhibiting circumscribed frontal lesions. The current study compared verbal episodic memory in patients with SCZ and focal FTL lesions (left frontal, LF; right frontal, RF; and bi-frontal, BF) on a four-trial list learning task consisting of three lists of varying semantic organizational structure. Each dependent variable was examined at two levels: scores collapsed across all four trials and learning scores (i.e., trial 4-trial 1). Performance deficits were observed in each patient group across most dependent measures at both levels. Regarding patient group differences, SCZ patients outperformed LF/BF patients (i.e., either learning scores or scores collapsed across trial) on free recall, primacy, primary memory, secondary memory, and subjective organization, whereas they only outperformed RF patients on the semantically blocked list on recency and primary memory. Collectively, these results indicate that the pattern of memory performance is largely similar between patients with SCZ and those with RF lesions. These data support tentative arguments that verbal episodic memory deficits in SCZ may be mediated by frontal dysfunction in the right hemisphere.
    Full-text · Article · May 2013 · The Clinical Neuropsychologist
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    ABSTRACT: We studied behavioral variant frontotemporal dementia (bvFTD) using object alternation (OA) as a novel probe of cognition. This task was adopted from animal models and is sensitive to ventrolateral-orbitofrontal and medial frontal function in humans. OA was administered to bvFTD patients, normal controls, and a dementia control group with Alzheimer disease (AD). Two other frontal lobe measures adopted from animal models were administered: delayed response (DR) and delayed alternation (DA). Brain volumes were measured using the semiautomatic brain region extraction method. Compared with the normal controls, bvFTD patients were significantly impaired on OA and DR. For OA and DR, sensitivities and specificities were 100% and 51.5% (cutoff=22.5 errors) and 9.5% and 98% (cutoff=1.5 errors), respectively. Negative predictive value (NPV) for OA was 100% at all prevalence rates. Comparing AD with bvFTD, there were no significant differences on OA, DR, or DA. Nevertheless, positive predictive value (PPV) and NPV were good at all prevalence rates for OA (cutoff=36.5 errors) and DA (cutoff=6 errors); PPV was good for DR (cutoff=9 errors). Error scores above cutoffs favored diagnosis of AD. Performance on OA was significantly related to medial frontal gray matter atrophy. OA, together with DR and DA, may facilitate assessment of bvFTD as a novel probe of medial frontal function.
    No preview · Article · Apr 2013 · Alzheimer disease and associated disorders
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    Full-text · Dataset · Mar 2013

Publication Stats

20k Citations
992.21 Total Impact Points

Institutions

  • 1989-2015
    • University of Toronto
      • • Department of Psychology
      • • Division of Neurology
      • • Rotman Research Institute
      Toronto, Ontario, Canada
  • 2014
    • Brain Canada
      Montréal, Quebec, Canada
  • 2013
    • Sunnybrook Health Sciences Centre
      Toronto, Ontario, Canada
    • The University of Calgary
      Calgary, Alberta, Canada
  • 2002-2012
    • Baycrest
      • Rotman Research Institute
      Toronto, Ontario, Canada
  • 2008
    • Cambridge Eco
      Cambridge, England, United Kingdom
  • 2007
    • York University
      • Department of Psychology
      Toronto, Ontario, Canada
  • 2001
    • Beth Israel Deaconess Medical Center
      Boston, Massachusetts, United States
  • 1978-1992
    • University of Ottawa
      • • Division of Medical Oncology
      • • Department of Medicine
      Ottawa, Ontario, Canada
  • 1990
    • Ottawa University
      Kansas, United States
  • 1981-1986
    • The Ottawa Hospital
      • Department of Medicine
      Ottawa, Ontario, Canada
  • 1983
    • Boston University
      Boston, Massachusetts, United States