Disconnected aging: cerebral white matter integrity and age-related differences in cognition.
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2014-09
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Abstract
Cognition arises as a result of coordinated processing among distributed brain regions and disruptions to communication within these neural networks can result in cognitive dysfunction. Cortical disconnection may thus contribute to the declines in some aspects of cognitive functioning observed in healthy aging. Diffusion tensor imaging (DTI) is ideally suited for the study of cortical disconnection as it provides indices of structural integrity within interconnected neural networks. The current review summarizes results of previous DTI aging research with the aim of identifying consistent patterns of age-related differences in white matter integrity, and of relationships between measures of white matter integrity and behavioral performance as a function of adult age. We outline a number of future directions that will broaden our current understanding of these brain-behavior relationships in aging. Specifically, future research should aim to (1) investigate multiple models of age-brain-behavior relationships; (2) determine the tract-specificity versus global effect of aging on white matter integrity; (3) assess the relative contribution of normal variation in white matter integrity versus white matter lesions to age-related differences in cognition; (4) improve the definition of specific aspects of cognitive functioning related to age-related differences in white matter integrity using information processing tasks; and (5) combine multiple imaging modalities (e.g., resting-state and task-related functional magnetic resonance imaging; fMRI) with DTI to clarify the role of cerebral white matter integrity in cognitive aging.
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Bennett, IJ, and DJ Madden (2014). Disconnected aging: cerebral white matter integrity and age-related differences in cognition. Neuroscience, 276. pp. 187–205. 10.1016/j.neuroscience.2013.11.026 Retrieved from https://hdl.handle.net/10161/22538.
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David Joseph Madden
My research focuses primarily on the cognitive neuroscience of aging: the investigation of age-related changes in perception, attention, and memory, using both behavioral measures and neuroimaging techniques, including positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and diffusion tensor imaging (DTI).
The behavioral measures have focused on reaction time, with the goal of distinguishing age-related changes in specific cognitive abilities from more general effects arising from a slowing in elementary perceptual processes. The cognitive abilities of interest include selective attention as measured in visual search tasks, semantic and episodic memory retrieval, and executive control processes.
The behavioral measures are necessary to define the cognitive abilities of interest, and the neuroimaging techniques help define the functional neuroanatomy of those abilities. The PET and fMRI measures provide information regarding neural activity during cognitive performance. DTI is a recently developed technique that images the structural integrity of white matter. The white matter tracts of the brain provide critical pathways linking the gray matter regions, and thus this work will complement the studies using PET and fMRI that focus on gray matter activation.
A current focus of the research program is the functional connectivity among regions, not only during cognitive task performance but also during rest. These latter measures, referred to as intrinsic functional connectivity, are beginning to show promise as an index of overall brain functional efficiency, which can be assessed without the implementation of a specific cognitive task. From DTI, information can be obtained regarding how anatomical connectivity constrains intrinsic functional connectivity. It will be important to determine the relative influence of white matter pathway integrity, intrinsic functional connectivity, and task-related functional connectivity, as mediators of age-related differences in behavioral measures of cognitive performance.
Ultimately, the research program can help link age-related changes in cognitive performance to changes in the structure and function of specific neural systems. The results also have implications for clinical translation, in terms of the identification of neural biomarkers for the diagnosis of neural pathology and targeting rehabilitation procedures.
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