Baycrest Center

Toronto, Canada

Baycrest Center

Toronto, Canada
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Described here are systems and methods for estimating a quantitative measure of cerebrovascular reactivity (CVR) from data acquired using resting-state functional magnetic resonance imaging (fMRI).


Hirshhorn M.,University of Toronto | Hirshhorn M.,Rotman Research Institute | Grady C.,University of Toronto | Grady C.,Rotman Research Institute | And 8 more authors.
Neuropsychologia | Year: 2012

Functional magnetic resonance imaging (fMRI) was used to compare brain activity during the retrieval of coarse- and fine-grained spatial details and episodic details associated with a familiar environment. Long-time Toronto residents compared pairs of landmarks based on their absolute geographic locations (requiring either coarse or fine discriminations) or based on previous visits to those landmarks (requiring episodic details). An ROI analysis of the hippocampus showed that all three conditions activated the hippocampus bilaterally. Fine-grained spatial judgments recruited an additional region of the right posterior hippocampus, while episodic judgments recruited an additional region of the right anterior hippocampus, and a more extensive region along the length of the left hippocampus. To examine whole-brain patterns of activity, Partial Least Squares (PLS) analysis was used to identify sets of brain regions whose activity covaried with the three conditions. All three comparison judgments recruited the default mode network including the posterior cingulate/retrosplenial cortex, middle frontal gyrus, hippocampus, and precuneus. Fine-grained spatial judgments also recruited additional regions of the precuneus, parahippocampal cortex and the supramarginal gyrus. Episodic judgments recruited the posterior cingulate and medial frontal lobes as well as the angular gyrus. These results are discussed in terms of their implications for theories of hippocampal function and spatial and episodic memory. © 2012 Elsevier Ltd.


Winocur G.,Rotman Research Institute | Winocur G.,Trent University | Winocur G.,University of Toronto | Moscovitch M.,Rotman Research Institute | And 3 more authors.
Neuropsychologia | Year: 2010

Historically, the hippocampus has been viewed as a temporary memory structure. Consistent with the central premise of standard consolidation theory (SCT), a memory is initially hippocampus-dependent but, over time, it undergoes a consolidation process and eventually becoming represented in a distributed cortical network independent of the hippocampus. In this paper, we review evidence that is incompatible with each of the following essential features of SCT that are derived from its central premise: (1) Hippocampal damage reliably produces temporally graded retrograde amnesia, (2) all declarative explicit memories are equivalent with respect to consolidation, (3) consolidation entails a process of duplication in which a particular cortically based memory is identical to the hippocampus-dependent memory from which it derived, (4) consolidated memories are permanent and immutable. We propose an alternative hypothesis that assumes a transformation process and changes in the memory over time. Building on multiple trace theory (Nadel & Moscovitch, 1997), the transformation hypothesis contains three key elements that differentiate it from SCT: (1) An initially formed memory, which is assumed to be episodic and context-bound, remains dependent on the hippocampus for as long as it is available, (2) with time and experience, a hippocampal memory supports the development, in neocortex, of a less integrated, schematic version, which retains the gist of the original memory, but few of its contextual details, (3) there is a dynamic interplay between the two types of memory such that one or another may be dominant, depending on the circumstances at retrieval. Evidence is provided in support of the transformation hypothesis, which is advanced as a framework for unifying the seemingly disparate results of studies of anterograde and retrograde memory in the animal and human literatures. © 2010 Elsevier Ltd.


Winocur G.,Rotman Research Institute | Winocur G.,Trent University | Winocur G.,University of Toronto | Sekeres M.J.,Rotman Research Institute | And 7 more authors.
Hippocampus | Year: 2013

Rats were administered contextual fear conditioning and trained on a water-maze, spatial memory task 28 days or 24 h before undergoing hippocampal lesion or control surgery. When tested postoperatively on both tasks, rats with hippocampal lesions exhibited retrograde amnesia for spatial memory at both delays but temporally graded retrograde amnesia for the contextual fear response. In demonstrating both types of retrograde amnesia in the same animals, the results parallel similar observations in human amnesics with hippocampal damage and provide compelling evidence that the nature of the task and the type of information being accessed are crucial factors in determining the pattern of retrograde memory loss associated with hippocampal damage. The results are interpreted as consistent with our transformation hypothesis (Winocur et al. (2010a) Neuropsychologia 48:2339-2356; Winocur and Moscovitch (2011) J Int Neuropsychol Soc 17:766-780) and at variance with standard consolidation theory and other theoretical models of memory. © 2013 Wiley Periodicals, Inc.


Diaconescu A.O.,Baycrest Center | Diaconescu A.O.,University of Toronto | Alain C.,Baycrest Center | Alain C.,University of Toronto | And 2 more authors.
Journal of Cognitive Neuroscience | Year: 2011

The present study examined the modality specificity and spatio-temporal dynamics of "what" and "where" preparatory processes in anticipation of auditory and visual targets using ERPs and a cue-target paradigm. Participants were presented with an auditory (Experiment 1) or a visual (Experiment 2) cue that signaled them to attend to the identity or location of an upcoming auditory or visual target. In both experiments, participants responded faster to the location compared to the identity conditions. Multivariate spatio-temporal partial least square (ST-PLS) analysis of the scalp-recorded data revealed supramodal "where" preparatory processes between 300-600 msec and 600-1200 msec at central and posterior parietal electrode sites in anticipation of both auditory and visual targets. Furthermore, preparation for pitch processing was captured at modality-specific temporal regions between 300 and 700 msec, and preparation for shape processing was detected at occipital electrode sites between 700 and 1150 msec. The spatio-temporal patterns noted above were replicated when a visual cue signaled the upcoming response (Experiment 2). Pitch or shape preparation exhibited modality-dependent spatiotemporal patterns, whereas preparation for target localization was associated with larger amplitude deflections at multimodal, centroparietal sites preceding both auditory and visual targets. Using a novel paradigm, the study supports the notion of a division of labor in the auditory and visual pathways following both auditory and visual cues that signal identity or location response preparation to upcoming auditory or visual targets. © 2011 Massachusetts Institute of Technology.


Mariani M.,Sudbury Regional Hospital | Shammi P.,Baycrest Center
Clinical Neuropsychologist | Year: 2010

We present a case study of an individual diagnosed with isolated neurosarcoidosis, a rare granulomatous condition of unknown aetiology. Although the extant medical literature on this disease is adequate, no study has focused on the neuropsychological sequelae involved with such an inflammatory disorder. The case described herein is of a 57-year-old woman who participated in a neuropsychological evaluation following complaints of recurring cognitive difficulties. Results of the assessment revealed moderate difficulties in effortful word retrieval and recall of unstructured verbal information, as well as some mild mental rigidity, slowing, and subtle difficulties with attention. Her neuropsychological profile is discussed in terms of neuroanatomic lesion localization and clinical diagnostic implications.


Seitz D.,Baycrest Center | Seitz D.,Kunin Lunenfeld Applied Research Unit | Seitz D.,Womens College Research Institute | Purandare N.,Manchester Academic Health Science Center | Conn D.,Baycrest Center
International Psychogeriatrics | Year: 2010

Background: The population of older adults in long-term care (LTC) is expected to increase considerably in the near future. An understanding of the prevalence of psychiatric disorders in LTC will help in planning mental health services for this population. This study reviews the prevalence of common psychiatric disorders in LTC populations. Methods: We searched electronic databases for studies on the prevalence of major psychiatric disorders in LTC using medical subject headings and key words. We only included studies using validated measures for diagnosing psychiatric disorders or psychiatric symptoms. Our review focused on the following psychiatric disorders: dementia, behavioral and psychological symptoms of dementia (BPSD), major depression, depressive symptoms, bipolar disorder, anxiety disorders, schizophrenia, and alcohol use disorders. We also determined the prevalence of psychiatric disorders in the U.S. LTC population using data from the 2004 National Nursing Home Survey (NNHS). Results: A total of 74 studies examining the prevalence of psychiatric disorders and psychological symptoms in LTC populations were identified including 30 studies on the prevalence of dementia, 9 studies on behavioral symptoms in dementia, and 26 studies on depression. Most studies involved few LTC facilities and were conducted in developed countries. Dementia had a median prevalence (58%) in studies while the prevalence of BPSD was 78% among individuals with dementia. The median prevalence of major depressive disorder was 10% while the median prevalence of depressive symptoms was 29% among LTC residents. There were few studies on other psychiatric disorders. Results from the 2004 NNHS were consistent with those in the published literature. Conclusions: Dementia, depression and anxiety disorders are the most common psychiatric disorders among older adults in LTC. Many psychiatric disorders appear to be more prevalent in LTC settings when compared to those observed in community-dwelling older adults. Policy-makers and clinicians should be aware of the common psychiatric disorders in LTC and further research into effective prevention and treatments are required for this growing population. © 2010 International Psychogeriatric Association.


Clements-Cortes A.,Baycrest Center
Journal of Music, Technology and Education | Year: 2014

This study investigated the utilization of an original sing-a-long DVD and activity package titled ‘Sing-A-Long of the 1930s’ to engage older adults’ participation in singing and therapeutic recreation activities. Participants (n=693) included a combination of persons residing and/or working at 25 long-term care facilities, retirement homes and adult day care centres across Canada engaging in a DVD sing-a-long and activity programme for five weeks. Following this experience, participants were individually interviewed or took part in one of 25 focus groups. The results focused on participant, caregiver and DVD facilitator’s perceived benefits and indicate the DVD was successful in engaging older adults with cognitive impairment in singing, social interaction and discussion, participation in meaningful activity, reminiscence, sensory stimulation, and quality of life in aging. © 2014 Intellect Ltd Article.


Winocur G.,Rotman Research Institute | Winocur G.,University of Toronto | Winocur G.,Trent University | Moscovitch M.,Rotman Research Institute | And 2 more authors.
Journal of the International Neuropsychological Society | Year: 2011

With time and experience, memories undergo a process of reorganization that involves different neuronal networks, known as systems consolidation. The traditional view, as articulated in standard consolidation theory (SCT), is that (episodic and semantic) memories initially depend on the hippocampus, but eventually become consolidated in their original forms in other brain regions. In this study, we review the main principles of SCT and report evidence from the neuropsychological literature that would not be predicted by this theory. By comparison, the evidence supports an alternative account, the transformation hypothesis, whose central premise is that changes in neural representation in systems consolidation are accompanied by corresponding changes in the nature of the memory. According to this view, hippocampally dependent, episodic, or context-specific memories transform into semantic or gist-like versions that are represented in extra-hippocampal structures. To the extent that episodic memories are retained, they will continue to require the hippocampus, but the hippocampus is not needed for the retrieval of semantic memories. The transformation hypothesis emphasizes the dynamic nature of memory, as well as the underlying functional and neural interactions that must be taken into account in a comprehensive theory of memory. © 2011 The International Neuropsychological Society.


Seitz D.P.,Baycrest Center | Gill S.S.,Queen's University | Conn D.K.,Baycrest Center
International Journal of Geriatric Psychiatry | Year: 2010

Objective: To determine the efficacy and tolerability of citalopram when compared to other antidepressants for late-life depression (LLD). Methods We searched electronic databases and trial registries to identify randomized controlled trials comparing citalopram to other antidepressants for LLD. Study quality was assessed using the Cochrane collaboration risk of bias tool. We summarized the efficacy of citalopram compared to other antidepressants by examining rates of depression remission, depression response and change in depression symptom scores. Medication tolerability was assessed through trial withdrawals due adverse events and withdrawals due to any cause. We used meta-analysis to determine the odds ratios (OR) of efficacy and tolerability outcomes for citalopram compared to other antidepressants. Results Seven studies comparing citalopram (N = 647) to other antidepressants (N = 641) for LLD were identified including four studies with tricyclic comparators and three studies with non-tricyclic comparators. Most of the studies had methodological limitations that placed them at risk for potential bias. The majority of studies reported no significant differences between citalopram and comparator medications for depression efficacy or tolerability outcomes. Meta-analysis did not find any significant differences between citalopram and other antidepressants for depression remission [OR = 0.84; 95%CI: 0.56-1.28] or for trial withdrawals due to adverse effects [OR = 0.70; 95%CI: 0.48-1.02]. Conclusions Currently there are few studies directly comparing citalopram to other antidepressants for LLD. The small number of studies and methodological issues in many studies limit any conclusions about the relative efficacy and tolerability of citalopram compared to other antidepressants. Well-designed studies comparing citalopram to other antidepressants for LLD are required. Copyright © 2010 John Wiley & Sons, Ltd.

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