Age-related differences in white matter microstructure: Region-specific patterns of diffusivity

Abstract

We collected MRI diffusion tensor imaging data from 80 younger (20-32 years) and 63 older (60-71 years) healthy adults. Tract-based spatial statistics (TBSS) analysis revealed that white matter integrity, as indicated by decreased fractional anisotropy (FA), was disrupted in numerous structures in older compared to younger adults. These regions displayed five distinct region-specific patterns of age-related differences in other diffusivity properties: (1) increases in both radial and mean diffusivity; (2) increases in radial diffusivity; (3) no differences in parameters other than FA; (4) a decrease in axial and an increase in radial diffusivity; and (5) a decrease in axial and mean diffusivity. These patterns suggest different biological underpinnings of agerelated decline in FA, such as demyelination, Wallerian degeneration, gliosis, and severe fiber loss, and may represent stages in a cascade of age-related degeneration in white matter microstructure. This first simultaneous description of age-related differences in FA, mean, axial, and radial diffusivity requires histological and functional validation as well as analyses of intermediate age groups and longitudinal samples.

Age-related changes in human and non-human primate white matter: from myelination disturbances to cognitive decline

“…Since FA also declined with age in the genu and the ventromedial prefrontal WM with an increase of mean diffusivity (MD), axial diffusivity (AxD), and RD, this data supports the idea that the frontal cortex is particularly vulnerable to agerelated myelin loss (i.e., is age-sensitive; Michielse et al 2010). A number of studies, using similar techniques, have proposed that the timing and combination of agerelated changes in FA, MD, AxD, and RD may reflect a progression of mild to severe WM changes, including demyelination, axonal loss/damage, inflammation, and gliosis (Bennett et al 2010;Burzynska et al 2010;Sala et al 2010;Zhang et al 2010).…”

Socioeconomic status is positively correlated with frontal white matter integrity in aging

“…An increased understanding of the neurobiological bases for potential SES-WM integrity relationships can be gained from the joint consideration of FA, radial diffusivity (DR), and axial diffusivity (DA) (Assaf and Pasternak 2008;Burzynska et al 2010;Gold et al 2012). For example, an SES-DR relationship would suggest that SES may help to preserve myelin integrity (Song et al 2002(Song et al , 2005, whereas an SES-DA relationship would suggest a relationship between SES and gross tissue characteristics (Sen and Basser 2005).…”

Mechanisms of white matter changes induced by meditation

“…Fractional anisotropy (FA) is an important index for measuring the integrity of white matter fibers. In general, a higher FA value has been related to improved performance, and reduced FA has been found in normal aging and in neurological or psychiatric disorders (1,(6)(7)(8).FA alterations originate from several factors, such as changes in myelination, axon density, axonal membrane integrity, axon diameter, and intravoxel coherence of fiber orientation and others changes (1, 9). To understand the mechanisms of FA change, several DTI studies have examined axial diffusivity (AD) and radial diffusivity (RD), the most important indices associated with FA (6-8).…”

“…Fractional anisotropy (FA) is an important index for measuring the integrity of white matter fibers. In general, a higher FA value has been related to improved performance, and reduced FA has been found in normal aging and in neurological or psychiatric disorders (1,(6)(7)(8).…”

“…To understand the mechanisms of FA change, several DTI studies have examined axial diffusivity (AD) and radial diffusivity (RD), the most important indices associated with FA (6)(7)(8). Usually, alterations in AD are associated with axon morphological changes, such as changes in axonal density or caliber (10,11).…”