Changes in the Macrostructure and Microstructure of the Ageing Brain

Zahr, Natalie M.; Pfefferbaum, Adolf; Sullivan, Edith V.

doi:10.1002/9780470669600.ch4

Cited by 4 publications

(5 citation statements)

References 128 publications

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“…The orientational components of diffusivity provide additional information about axonal integrity with longitudinal or axial diffusivity (λL) and myelination and myelin integrity with transverse or radial diffusivity (λT) (Song, et al, 2002; Song, et al, 2005; Sun, et al, 2006a; Sun, et al, 2006b). DTI studies of normal adult aging, for example, have consistently observed an anterior-to-posterior gradient, where commissural and association fiber systems of frontal regions, such as the genu of the corpus callosum and frontal forceps are characterized by lower FA or higher diffusivity in older than younger adults (Ardekani, Kumar, Bartzokis, & Sinha, 2007; Bhagat & Beaulieu, 2004; Bucur, et al, 2008; Head, et al, 2004; Kennedy & Raz, 2009; Madden, Bennett, & Song, 2009; e.g., Pfefferbaum, Adalsteinsson, & Sullivan, 2005; Salat, et al, 2005; Sullivan, Adalsteinsson, & Pfefferbaum, 2006; Sullivan & Pfefferbaum, 2010; Takahashi, et al, 2004; Yoon, Shim, Lee, Shon, & Yang, 2008; for reviews, Zahr, Pfefferbaum, & Sullivan, 2010). Typically, the age effect is similar for men and women and is greater in diffusivity, especially λT, than FA (Kennedy & Raz, 2009; Sullivan, Rohlfing, & Pfefferbaum, 2010).…”

Section: Introductionmentioning

confidence: 99%

Fiber tracking functionally distinct components of the internal capsule

et al. 2010

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The internal capsule conveys information from primary and supplementary motor areas, frontopontine and thalamic peduncles to brain stem and cerebellar regions, and from thalamus to prefrontal cortex. Neurological accidents involving the internal capsule indicate differential functional correlates with its sectors. To examine the microstructural condition of this fiber system and to test functional correlates of its sectors in health and aging, 12 younger and 12 older adults were examined with diffusion tensor imaging (DTI) fiber tracking and neuropsychological tests. Greater age-related degradation was evident in the anterior than posterior limb and in the superior than inferior division of the internal capsule. The superior division age effect was especially notable in axial and radial diffusivity. Fractional anisotropy (FA) across the three (anterior, genu, posterior) fiber bundles of the inferior division accounted for 27-73% of the variance for each neuropsychological domain. Identification of a triple dissociation indicated selective correlations between anterior FA and Set Shifting, genu FA and Motor Skills, and posterior FA and Fluency. Quantitative fiber tracking combined with assessment of cognitive and motor functions enabled the identification of selective brain structure-function relations in healthy adults without lesions that were previously observed only in patients with lesions of the internal capsule.

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Section: Introductionmentioning

confidence: 99%

Fiber tracking functionally distinct components of the internal capsule

et al. 2010

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“…We and others have recently reviewed the neuroimaging findings in normal adult aging (Madden, Bennet & Song, 2009; Sullivan & Pfefferbaum, 2007, 2009; Pfefferbaum & Sullivan, 2009, 2010; Zahr, Pfefferbaum & Sullivan, 2009) based on magnetic resonance imaging (MRI), capable of yielding quantification of macrostructural characteristics (notably, size and shape) of brain tissue, and diffusion tensor imaging (DTI), designed to yield quantification of microstructural characteristics of brain tissue, typically white matter axonal and myelin integrity. Many other reviews on the radiologically-identified structural characteristics of normal aging brain are also available, and most are cross-sectional in design.…”

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confidence: 99%

Longitudinal Study of Callosal Microstructure in the Normal Adult Aging Brain Using Quantitative DTI Fiber Tracking

Sullivan

Rohlfing

Pfefferbaum

2010

Developmental Neuropsychology

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We present a review of neuroimaging studies of normal adult aging conducted with Diffusion Tensor Imaging (DTI) and data from one of the first longitudinal studies using DTI to study normal aging. To date, virtually all DTI studies of normal adult aging have been cross-sectional and have identified several patterns of white matter microstructural sparing and compromise that differentiate regional effects, fiber type, and diffusivity characteristics: 1) fractional anisotropy (FA) is lower and mean diffusivity is higher in older than younger adults, 2) aging is characterized by an anterior-to-posterior gradient of greater-to-lesser compromise also seen in superior-to-inferior fiber systems, and 3) association fibers connecting cortical sites appear to be more vulnerable to aging than projection fibers. The results of this longitudinal study of the macrostructure and microstructure of the corpus callosum yielded a consistent pattern of differences between healthy, young (20s to 30s) and elderly (60s to 70s) men and women without change over 2 years. We then divided the fibers of the corpus callosum into the midsagittal strip and the lateral distal fibers in an attempt to identify the locus of the age-related differences. The results indicated that, on average, mean values of FA and longitudinal diffusivity (λL) were lower in the distal than midsagittal fibers in both groups, but the age effects and the anterior-to-posterior gradients were more pronounced for the distal than midsagittal fibers and extended more posteriorly in the distal than midsagittal fibers. Despite lack of evidence for callosal aging over 2 years, ventricular enlargement occurred and was disproportionately greater in the elderly relative to the young group, being 8.2% in the elderly but only 1.2% in the young group. Thus, different brain regions can express different rates of change with aging. Our longitudinal DTI data indicate that normal aging is associated with declining FA and increasing diffusivity in both λL (longitudinal diffusivity) and λT (transverse diffusivity), perhaps defining the normal ontological condition rather than a pathological one, which can be marked by low FA and low diffusivity.There is little doubt that even healthy aging is marked by decline in sensory, motor, and selective cognitive functions, well delineated by hundreds of careful, quantitative, crosssectional and longitudinal assessments (for volumes of reviews, Birren & Schaie, 2001;Craik & Salthouse, 2008). Less known are the neural mechanisms responsible for involutional changes in function, but quantitative in vivo neuroimaging studies conducted over the last quarter century provide critical leads to identify the selective brain structures and systems that contribute to functional decline.We and others have recently reviewed the neuroimaging findings in normal adult aging (Madden, Bennet & Song, 2009;, 2010Zahr, Pfefferbaum & Sullivan, 2009) based on magnetic resonance imaging (MRI), Correspondence: Edith V. Sullivan, Ph.D., Stanford University School o...

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“…In older adults, we found a significant decline in prefronto-striatal white matter connectivity, particularly for connections with CA nucleus and NAC. Many studies have used dMRI to study age effects on white matter connections (O' Sullivan et al, 2001;Sullivan and Pfefferbaum, 2006;Bennett et al, 2010;Zahr et al, 2010;de Groot et al, 2016), including frontal or striatal connections (Bennett et al, 2010;Burzynska et al, 2010). More specifically, a combined measure of functional and structural prefronto-striatal connectivity was found to be a prominent predictor of chronological age (Bonifazi et al, 2018).…”

Section: Effects Of Age On Scmentioning

confidence: 99%

Prefronto-Striatal Structural Connectivity Mediates Adult Age Differences in Action Selection

et al. 2020

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In complex everyday environments, action selection is critical for optimal goal-directed behavior. This refers to the process of choosing a proper action from the range of possible alternatives. The neural mechanisms underlying action selection and how these are affected by normal aging remain to be elucidated. In the present cross-sectional study, we studied processes of effector selection during a multilimb reaction time task in a lifespan sample of healthy human adults (N = 89; 20-75 years; 48 males, 41 females). Participants were instructed to react as quickly and accurately as possible to visually cued stimuli representing single-limb or combined upper and/or lower limb motions. Diffusion MRI was used to study structural connectivity between prefrontal and striatal regions as critical nodes for action selection. Behavioral findings revealed that increasing age was associated with slowing of action selection performance. At the neural level, aging had a negative impact on prefrontostriatal connectivity. Importantly, mediation analyses revealed that the negative association between action selection performance and age was mediated by prefronto-striatal connectivity, specifically the connections between left rostral medial frontal gyrus and left nucleus accumbens as well as right frontal pole and left caudate. These results highlight the potential role of prefronto-striatal white matter decline in poorer action selection performance of older adults.

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Changes in the Macrostructure and Microstructure of the Ageing Brain

Cited by 4 publications

References 128 publications

Fiber tracking functionally distinct components of the internal capsule

Fiber tracking functionally distinct components of the internal capsule

Longitudinal Study of Callosal Microstructure in the Normal Adult Aging Brain Using Quantitative DTI Fiber Tracking

Prefronto-Striatal Structural Connectivity Mediates Adult Age Differences in Action Selection

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