Natasha Rajah

CIHR New Investigator Award

2007-09-01

Academic Salary Award from CIHR, New Investigator Competition (2007-2012)

Awarded FRQS Junior 2 Chercheurs Boursier

2013-09-01

Academic Salary Award Received from FRQS (2013-2015)

Top 50 Under 50 Scientists in Quebec

2012-09-01

Selected as one Quebec's top 50 scientists under the age of 50 by Quebec Science Magazine in 2012

University of Toronto

Ph.D. (NSERC PGS A & B)

Psychology

2003

Supervisor: A. R. McIntosh

U. C. Berkely

Post-doctoral fellowship (NSERC)

Cognitive Neuroscience

2005

Supervisor: M. D'Esposito

Changes in the correlation between spatial and temporal source memory performance and BOLD activity across the adult lifespan.

2017-01-16

Abstract
Studies investigating age-related functional differences associated with source memory have recently focused on the importance of clarifying the relationship between effects of age and performance on memory-related brain activations. One methodological challenge has been in discriminating between effects of age on memory-related brain activations that are independent from age-related differences in performance. In the current study, event-related functional magnetic resonance imaging (fMRI) was used to identify brain activity during spatial and temporal source encoding and retrieval across the adult lifespan. We used multivariate behavior partial least squares (B-PLS) to identify patterns of brain activity during source encoding and source retrieval that were associated with age and/or retrieval accuracy. The PLS analysis identified three significant effects. The first effect indicated that encoding and retrieval activity in fusiform, middle occipital–temporal and inferior parietal cortices increased with age and decreased with performance. The second effect showed that dorsolateral prefrontal cortex and limbic activity increased with age at encoding, and increased with performance at retrieval. The third effect indicated that activity in right ventrolateral prefrontal and bilateral hippocampus increased with age during retrieval and was differentially related to performance during encoding versus retrieval. We conclude that although some age-related differences in brain activity observed during source encoding and retrieval are associated with individual differences in performance, age-related differences in prefrontal and hippocampal areas exhibit more complex patterns of interactions between age, performance, and phase-related activity.

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Region-specific changes in prefrontal function with age: a review of PET and fMRI studies on working and episodic memory

2005-09-01

Abstract
Several neuroimaging studies of cognitive ageing have found that age-related deficits in working memory (WM) and episodic memory abilities are related to changes in prefrontal cortex (PFC) function. Reviews of these neuroimaging studies have generally concluded that with age there is a reduction in the hemispheric specialization of cognitive function in the frontal lobes that may either be due to dedifferentiation of function, deficits in function and/or functional reorganization and compensation. Moreover, previous reviews have considered the PFC as homogeneous in function and have not taken into account the possibility that region specific changes in PFC function may occur with age. In the current review we performed a qualitative meta-analytic review of all the functional magnetic resonance imaging ageing studies and positron emission tomography ageing studies of WM and episodic memory that report PFC activation, to determine if any region-specific changes occur. The results indicated that in normal ageing distinct PFC regions exhibit different patterns of functional change, suggesting that age-related changes in PFC function are not homogeneous in nature. Specifically, we hypothesize that normal ageing is related to the differentiation of cortical function in a bilateral ventral PFC and deficits in function in right dorsal and anterior PFC. As a result of these changes, functional compensation in left dorsal and anterior PFC may occur. We hope that future studies will be conducted to either confirm or counter these hypotheses.

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Family history and APOE4 risk for Alzheimer's Disease impact the neural correlates of episodic memory by early midlife

2017-01-24

Abstract
Episodic memory impairment is a consistent, pronounced deficit in pre-clinical stages of late-onset
Alzheimer’s disease (AD). Individuals with risk factors for AD exhibit altered brain function several
decades prior to the onset of AD-related symptoms. In the current event-related fMRI study of spatial
context memory we tested the hypothesis that middle-aged adults (MA; 40-58yrs) with a family history
of late onset AD (MA+FH), or a combined +FH and apolipoprotein E ε4 allele risk factors for AD
(MA+FH+APOE4), will exhibit differences in encoding and retrieval-related brain activity , compared to –
FH –APOE4 MA controls. We also hypothesized that the two at-risk MA groups will exhibit distinct
patterns of correlation between brain activity and memory performance, compared to controls. To test
these hypotheses we conducted multivariate task, and behavior, partial least squares analysis of fMRI
data obtained during successful context encoding and retrieval. Our results indicate that even though
there were no significant group differences in context memory performance, there were significant
differences in brain activity and brain-behavior correlations involving hippocampus, left angular gyrus,
cingulate, and precuneus in MA with AD risk factors, compared to controls. In addition, we observed
that brain activity and brain-behavior correlations in anterior-medial PFC and in ventral visual cortex
differentiated the two MA risk groups from each other, and from MAcontrols. This is the first study to
show that there are differences in the brain areas engaged during context memory encoding and
retrieval in middle-aged adults with +FH and +APOE-4 risk factors for late onset AD, compared to
controls.

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