Baycrest Center for Geriatric Care

Canada

Baycrest Center for Geriatric Care

Canada
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Lee A.C.H.,University of Toronto | Lee A.C.H.,Baycrest Center for Geriatric Care | Lee A.C.H.,University of Oxford | Brodersen K.H.,ETH Zurich | And 2 more authors.
Journal of Cognitive Neuroscience | Year: 2013

Although the role of the hippocampus in spatial cognition is well accepted, it is unclear whether its involvement is restricted to the mnemonic domain or also extends to perception. We used fMRI to scan neurologically healthy participants during a scene oddity judgment task that placed no explicit demand on long-term memory. Crucially, a surprise recognition test was administered after scanning so that each trial could be categorized not only according to oddity accuracy but also according to subsequent memory. Univariate analyses showed significant hippocampal activity in association with correct oddity judgment, whereas greater parahippocampal place area (PPA) activity was observed during incorrect oddity trials, both irrespective of subsequent recognition performance. Consistent with this, multivariate pattern analyses revealed that a linear support vector machine was able to distinguish correct from incorrect oddity trials on the basis of activity in voxels within the hippocampus or PPA. Although no significant regions of activity were identified by univariate analyses in association with memory performance, a classifier was able to predict subsequent memory using voxels in either the hippocampus or PPA. Our findings are consistent with the idea that the hippocampus is important for processes beyond long-term declarative memory and that this structure may also play a role in complex spatial perception. © 2013 Massachusetts Institute of Technology.


Fidalgo C.O.,The University of Toronto | Changoor A.T.,The University of Toronto | Page-Gould E.,The University of Toronto | Lee A.C.H.,The University of Toronto | And 3 more authors.
Hippocampus | Year: 2016

There is an ongoing debate regarding the nature of memory deficits that occur in the early stages of mild cognitive impairment (MCI). MCI has been associated with atrophy to regions that process objects, namely perirhinal and lateral entorhinal cortices. However, it is currently unclear whether older adults with early MCI will show memory deficits that are specific to objects, or whether they will also show memory deficits for other stimulus classes, such as scenes. We tested 75 older adults using an object and scene recognition task with stimulus-specific interference (i.e., exposure to irrelevant object or scene stimuli). We found an interaction (P = 0.05) whereby scores on the Montreal Cognitive Assessment, a neuropsychological test with high sensitivity to MCI, shared a stronger relationship with object recognition than with scene recognition performance. Interestingly, this relationship was not modulated by the stimulus category of interfering items. To further explore these findings, we also tested an amnesic patient (DA) with known medial temporal lobe damage. Like older adults with early signs of MCI, DA showed poorer object recognition than scene recognition performance. Additionally, his performance was not modulated by the stimulus category of interfering material. By demonstrating that object memory is more predictive of cognitive decline than scene memory, these findings support the notion of perirhinal and lateral entorhinal cortex dysfunction in the early stages of MCI. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.


Fernandes M.A.,University of Waterloo | Wammes J.D.,University of Waterloo | Priselac S.,Baycrest Center for Geriatric Care | Moscovitch M.,Rotman Research Institute | Moscovitch M.,University of Toronto
Neuropsychologia | Year: 2016

We examined the effect of different distracting tasks, performed concurrently during memory retrieval, on recall of a list of words. By manipulating the type of material and processing (semantic, orthographic, and phonological) required in the distracting task, and comparing the magnitude of memory interference produced, we aimed to infer the kind of representation upon which retrieval of words depends. In Experiment 1, identifying odd digits concurrently during free recall disrupted memory, relative to a full attention condition, when the numbers were presented orthographically (e.g. nineteen), but not numerically (e.g. 19). In Experiment 2, a distracting task that required phonological-based decisions to either word or picture material produced large, but equivalent effects on recall of words. In Experiment 3, phonological-based decisions to pictures in a distracting task disrupted recall more than when the same pictures required semantically-based size estimations. In Experiment 4, a distracting task that required syllable decisions to line drawings interfered significantly with recall, while an equally difficult semantically-based color-decision task about the same line drawings, did not. Together, these experiments demonstrate that the degree of memory interference experienced during recall of words depends primarily on whether the distracting task competes for phonological representations or processes, and less on competition for semantic or orthographic or material-specific representations or processes. © 2016 Elsevier Ltd


St-Laurent M.,Toronto Western Hospital | St-Laurent M.,University of Toronto | Moscovitch M.,University of Toronto | Moscovitch M.,Rotman Research Institute | And 3 more authors.
Cortex | Year: 2016

We assessed whether perceptual richness, a defining feature of episodic memory, depends on the engagement and integrity of the hippocampus during episodic memory retrieval. We tested participants' memory for complex laboratory events (LEs) that differed in perceptual content: short stories were either presented as perceptually rich film clips or as perceptually impoverished narratives. Participants underwent functional magnetic resonance imaging (fMRI) while retrieving these LEs (narratives and clips), as well as events from their personal life (autobiographical memories). In a group of healthy adults, a conjunction analysis showed that both real-life and laboratory memories engaged overlapping regions from an autobiographical memory (AM) retrieval network, indicating that laboratory memories mimicked autobiographical events successfully. A direct contrast between the film clip and the narrative laboratory conditions identified regions activated by the retrieval of perceptual memory content, which included the right hippocampus, parahippocampal gyrus, middle occipital gyrus and precuneus. In individuals with medial temporal lobe epilepsy (mTLE) originating from the right hippocampus, the magnitude of this “perceptually rich” signal was reduced significantly, which is consistent with evidence of reduced perceptual memory content in this clinical population. In healthy controls, right hippocampal activation also correlated positively with a behavioral measure of perceptual content in the clip condition. Thus, right hippocampal activity contributed to the retrieval of perceptual episodic memory content in the healthy brain, while right hippocampal damage disrupted activation in regions that process perceptual memory content. Our results suggest that the hippocampus contributes to recollection by retrieving and integrating perceptual details into vivid memory constructs. © 2016 Elsevier Ltd


Park L.,Rotman Research Institute | St-Laurent M.,University of Toronto | McAndrews M.P.,University of Toronto | Moscovitch M.,Rotman Research Institute | And 2 more authors.
Neuropsychologia | Year: 2011

Objectively measuring the experiential phenomenon of " reliving" a personal memory without relying on the retrieval of specific contents such as richness/vividness of perceptual details is difficult. There are, however, some circumstances in which an indirect measure that does not require conscious retrieval or deliberate assessment of such information, would be quite useful (e.g., in very young children, in patients with poor fluency or inappropriate use of rating scales). Here, we examined the use of the historical present (HP), defined as a present tense that refers to a past action, in autobiographical narratives. The HP indexes a sense of reliving because the memory of the event is vividly re-experienced as occurring again in the current moment. We compared the use of the HP in narratives from neurologically intact controls and from patients with unilateral temporal lobe excisions or epilepsy (TLE). Results indicate that patients used fewer instances of the HP than healthy controls. Also, the use of the HP correlated positively with other measures of recollection, such as the total number of perceptual details contained in a narrative. We provide the first empirical evidence that a linguistic construct can be used to assess the conscious experience that accompanies recollection. © 2011 Elsevier Ltd.


St-Laurent M.,University of Toronto | St-Laurent M.,University of Western Ontario | Moscovitch M.,University of Toronto | Moscovitch M.,Baycrest Center for Geriatric Care | And 3 more authors.
Hippocampus | Year: 2011

Medial temporal lobe epilepsy (TLE), a condition known to affect the integrity and function of medial temporal lobe structures such as the hippocampus, has been shown to disrupt memory for real-life episodes. Here, patients with unilateral TLE, patients who received a unilateral temporal lobe resection to cure TLE, and healthy controls produced free narratives of autobiographical memories (AMs). To assess temporal resolution, narratives were segmented into bits of information, or details, which were classified according to how precisely they could be located within the time course of the AM. Categories included details corresponding to the entire AM, to parts or subevents within the AM, and to actions taking place within seconds to minutes. The number of details per category was tallied and compared between patients and controls. Temporal order was assessed by determining the correct (internally consistent) chronological order of the sequence of events within the narrative. Results indicate that while patients' memory for the parts or subevents of personal episodes was intact, as was their temporal order, their memory for the minute-by-minute unraveling of the episode was impaired. We believe this loss of temporally specific details may contribute to the reduced vividness of AM recollection in TLE patients. Our findings provide further evidence that patients with hippocampal damage retrieve skeletal AMs for which the gist of the memory is maintained, but the specific details are lost. © 2010 Wiley-Liss, Inc.


Monette M.C.E.,University of Windsor | Leach L.,Baycrest Center for Geriatric Care
Canadian Journal of Neurological Sciences | Year: 2013

Objective: The current study sought to determine if the Kaplan-Baycrest Neurocognitive Assessment (KBNA) was capable of discriminating individuals with subjective memory complaints associated with depression from individuals with mild cognitive impairment (MCI). Methods: Scores on 12 subtests of the KBNA were compared for 27 participants with MCI and 28 participants being treated for depression using Bonferroni correct between-group comparisons for each subtest. KBNA subtest scores were corrected for age and education. Results: Significant between-group differences were obtained on six subtests with large effect sizes (Cohen's d) ranging from 1.19-1.58. The six subtests involved encoding and delayed episodic memory for verbal and visual information. Using logistic regression analysis, five subtests of the KBNA were able to correctly classify 96.4% of study participants. Conclusion: The results from this preliminary investigation indicate that the KBNA has the potential to serve as a brief and reliable assessment tool capable of distinguishing individuals with subjective memory complaints associated with depression from individuals with MCI in a clinical setting. Limitations of the current study and future research are discussed.


Zakzanis K.K.,University of Toronto | McDonald K.,University of Toronto | Troyer A.K.,Baycrest Center for Geriatric Care
Journal of Clinical and Experimental Neuropsychology | Year: 2011

We set out to examine the sensitivity of switching and clustering component scores of verbal fluency in patients with mild traumatic brain injury (mTBI). Clustering and switching scores were compared between patients with mTBI and healthy normal controls as well as those with moderate TBI and severe TBI. Fifty-four healthy controls along with 20 mild TBI, 8 moderate TBI, and 12 severe TBI patients were included in the study. Our findings demonstrate that component score effect sizes were larger than those of total words generated for both phonemic and semantic fluency. This pattern of finding held true regardless of comparison group. In addition, semantic fluency component scores were found to correspond to larger component score effect sizes than did phonemic fluency component scores. Our findings demonstrate that component scores derived from the Controlled Oral Word Association Test may be sufficient to reliably capture the effects of unremitting injury (i.e., more than 3 months post status) to the frontal and temporal brain as evinced in cases of unremitting mTBI. This differential pattern of performance provides preliminary evidence for the potential usefulness of switching and clustering in the assessment of mTBI. Given the small sample sizes employed in our study, however, future studies are needed to determine whether component measures of verbal fluency have discriminative ability. © 2011 Psychology Press.


Patent
Baycrest Center For Geriatric Care | Date: 2012-10-05

The present invention provides methods and systems for assessing cognitive function by comparing a subjects eye movements within and across distinct classes of images.


Patent
Baycrest Center For Geriatric Care | Date: 2013-08-02

In one aspect the application relates to a computing system for providing data for modelling a human brain comprises a database including a plurality of datasets (or allow access to a plurality of datasets), each dataset including at least a dynamical model of the brain including at least one node and a neurodataset of a neuroimaging modality input. The at least one node include a representation of a local dynamic model and a parameter set of the local dynamic model.

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