Rotman Research Institute
Rotman Research Institute
Bialystok E.,York University |
Bialystok E.,Rotman Research Institute |
Craik F.I.M.,Rotman Research Institute
Trends in Cognitive Sciences | Year: 2012
Building on earlier evidence showing a beneficial effect of bilingualism on children's cognitive development, we review recent studies using both behavioral and neuroimaging methods to examine the effects of bilingualism on cognition in adulthood and explore possible mechanisms for these effects. This research shows that bilingualism has a somewhat muted effect in adulthood but a larger role in older age, protecting against cognitive decline, a concept known as 'cognitive reserve'. We discuss recent evidence that bilingualism is associated with a delay in the onset of symptoms of dementia. Cognitive reserve is a crucial research area in the context of an aging population; the possibility that bilingualism contributes to cognitive reserve is therefore of growing importance as populations become increasingly diverse. © 2012 Elsevier Ltd.
Deco G.,University Pompeu Fabra |
Jirsa V.K.,Aix - Marseille University |
McIntosh A.R.,Rotman Research Institute
Trends in Neurosciences | Year: 2013
Resting-state networks (RSNs), which have become a main focus in neuroimaging research, can be best simulated by large-scale cortical models in which networks teeter on the edge of instability. In this state, the functional networks are in a low firing stable state while they are continuously pulled towards multiple other configurations. Small extrinsic perturbations can shape task-related network dynamics, whereas perturbations from intrinsic noise generate excursions reflecting the range of available functional networks. This is particularly advantageous for the efficiency and speed of network mobilization. Thus, the resting state reflects the dynamical capabilities of the brain, which emphasizes the vital interplay of time and space. In this article, we propose a new theoretical framework for RSNs that can serve as a fertile ground for empirical testing. © 2013 Elsevier Ltd.
Churchill N.W.,University of Toronto |
Strother S.C.,Rotman Research Institute
NeuroImage | Year: 2013
The presence of physiological noise in functional MRI can greatly limit the sensitivity and accuracy of BOLD signal measurements, and produce significant false positives. There are two main types of physiological confounds: (1) high-variance signal in non-neuronal tissues of the brain including vascular tracts, sinuses and ventricles, and (2) physiological noise components which extend into gray matter tissue. These physiological effects may also be partially coupled with stimuli (and thus the BOLD response). To address these issues, we have developed PHYCAA. +, a significantly improved version of the PHYCAA algorithm (Churchill et al., 2011) that (1) down-weights the variance of voxels in probable non-neuronal tissue, and (2) identifies the multivariate physiological noise subspace in gray matter that is linked to non-neuronal tissue. This model estimates physiological noise directly from EPI data, without requiring external measures of heartbeat and respiration, or manual selection of physiological components. The PHYCAA. + model significantly improves the prediction accuracy and reproducibility of single-subject analyses, compared to PHYCAA and a number of commonly-used physiological correction algorithms. Individual subject denoising with PHYCAA. + is independently validated by showing that it consistently increased between-subject activation overlap, and minimized false-positive signal in non gray-matter loci. The results are demonstrated for both block and fast single-event task designs, applied to standard univariate and adaptive multivariate analysis models. © 2013 Elsevier Inc.
Ghosh V.E.,Rotman Research Institute |
Gilboa A.,Rotman Research Institute
Neuropsychologia | Year: 2014
The term "schema" has been used to describe vastly different knowledge structures within the memory neuroscience literature. Ambiguous terminology hinders cross-study comparisons and confounds interpretation of the suggested role of the ventromedial prefrontal cortex (vmPFC) in schema functions. Based on an extensive review of the psychological literature, we propose a framework for distinguishing memory schemas from other knowledge structures. The framework includes a definition of schema as possessing four necessary and sufficient features, and four additional features schemas are sensitive to, which are not required but do play a frequent and central role in schema functions. Necessary schema features are (1) an associative network structure, (2) basis on multiple episodes, (3) lack of unit detail, and (4) adaptability. Features schemas are sensitive to are (5) chronological relationships, (6) hierarchical organization, (7) cross-connectivity, and (8) embedded response options. Additionally, we suggest that vmPFC activity observed in studies of schemas corresponds with participants' coordination of existing schemas with ongoing task demands. © 2013 Elsevier Ltd.
Grady C.,Rotman Research Institute
Nature Reviews Neuroscience | Year: 2012
The availability of neuroimaging technology has spurred a marked increase in the human cognitive neuroscience literature, including the study of cognitive ageing. Although there is a growing consensus that the ageing brain retains considerable plasticity of function, currently measured primarily by means of functional MRI, it is less clear how age differences in brain activity relate to cognitive performance. The field is also hampered by the complexity of the ageing process itself and the large number of factors that are influenced by age. In this Review, current trends and unresolved issues in the cognitive neuroscience of ageing are discussed. © 2012 Macmillan Publishers Limited. All rights reserved.
Craik F.I.M.,Rotman Research Institute |
Rose N.S.,Rotman Research Institute
Neuroscience and Biobehavioral Reviews | Year: 2012
This review article surveys the evidence for age-related changes in memory from cognitive and neuroimaging studies. It is probable that the observed declines in episodic memory with increasing age are a consequence of impairments in both acquisition (encoding) and retrieval - possibly for similar reasons - but the present review focuses on the former set of processes. An additional emphasis is on a processing approach to understanding age-related encoding deficiencies; we suggest that many problems stem from a decline in the ability to self-initiate deeper semantic processing operations. The article briefly discusses the role of declining sensory and perceptual abilities, but focuses primarily on the nature of processing resources, their consequences for memory acquisition, and on age-related changes in cognition and neural functioning. We also survey the evidence for neuroplasticity in the older brain, and how compensatory activities at behavioral and neural levels can reduce age-related problems. Finally, we review recent studies of brain and cognitive training procedures. Age-related memory problems are real, but there are also grounds for optimism. © 2011 Elsevier Ltd.
McIntosh A.R.,Rotman Research Institute
NeuroImage | Year: 2012
This article provides a personal perspective of the adoption of path analysis (structural equation modeling) to neuroimaging. The paper covers the motivation stemming from the need to merge functional measures with neuroanatomy and early innovations in its application. The use of path analysis as a means to test directional hypotheses about networks is presented along with the development of the complementary method, partial least squares. A method is useful when it provides insights that were previously inaccessible, and reflecting this, the paper concludes with a synopsis of the theoretical developments that arose for the routine use of methods like path analysis. © 2011 Elsevier Inc.
Paus T.,Rotman Research Institute
Hormones and Behavior | Year: 2013
This article is part of a Special Issue "Puberty and Adolescence".This review provides a conceptual framework for the study of factors - in our genes and environment - that shape the adolescent brain. I start by pointing out that brain phenotypes obtained with magnetic resonance imaging are complex traits reflecting the interplay of genes and the environment. In some cases, variations in the structural phenotypes observed during adolescence have their origin in the pre-natal or early post-natal periods. I then emphasize the bidirectional nature of brain-behavior relationships observed during this period of human development, where function may be more likely to influence structure rather than vice versa. In the main part of this article, I review our ongoing work on the influence of gonadal hormones on the adolescent brain. I also discuss the importance of social context and brain plasticity on shaping the relevant neural circuits. © 2013 Elsevier Inc.
Stuss D.T.,Rotman Research Institute
Journal of the International Neuropsychological Society | Year: 2011
Proceeding from the assumptions that specific frontal regions control discrete functions and that very basic cognitive processes can be systematically manipulated to reveal those functions, recent reports have demonstrated consistent anatomical/functional relationships: dorsomedial for energization, left dorsolateral for task setting, and right dorsolateral for monitoring. There is no central executive. There are, instead, numerous domain general processes discretely distributed across several frontal regions that act in concert to accomplish control. Beyond these functions, there are two additional "frontal" anatomical/functional relationships: ventral-medial/orbital for emotional and behavioral regulation, and frontopolar for integrative-even meta-cognitive-functions. © 2011 The International Neuropsychological Society.
Stuss D.T.,Rotman Research Institute
Current Opinion in Neurology | Year: 2011
Purpose of Review: This review examines the applicability of a framework of frontal lobe functioning to understand the sequelae of traumatic brain injury (TBI). Recent Findings: TBI research illustrates the need for improved phenotyping of TBI outcome. The functions of the frontal lobes are divisible into four distinct anatomically discrete categories: executive functions, speed of processing, personality changes, and problems with empathy and social cognition. Research on the outcome after TBI demonstrates several different types of impairment that map onto this framework. Summary: TBI predominantly causes damage to the frontal/temporal regions, regardless of the pathophysiology. Limiting the spotlight to the frontal lobes, a model is presented describing four separate general categories of functions within the frontal lobes, with specific types of processes within each category. A selective review of TBI literature supports the importance of evaluating TBI patients with this framework in mind. In addition, there is growing evidence that rehabilitation of TBI patients must consider this broader approach to direct rehabilitation efforts and improve outcome. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.