Brain grey and white matter predictors of verbal ability traits in older age: The Lothian Birth Cohort 1936

Abstract

Cerebral grey and white matter MRI parameters are related to general intelligence and some specific cognitive abilities. Less is known about how structural brain measures relate specifically to verbal processing abilities. We used multi-modal structural MRI to investigate the grey matter (GM) and white matter (WM) correlates of verbal ability in 556 healthy older adults (mean age = 72.68 years, s.d. = .72 years). Structural equation modelling was used to decompose verbal performance into two latent factors: a storage factor that indexed participants’ ability to store representations of verbal knowledge and an executive factor that measured their ability to regulate their access to this information in a flexible and task-appropriate manner. GM volumes and WM fractional anisotropy (FA) for components of the language/semantic network were used as predictors of these verbal ability factors. Volume of the ventral temporal cortices predicted participants’ storage scores (β = .12, FDR-adjusted p = .04), consistent with the theory that this region acts as a key substrate of semantic knowledge. This effect was mediated by childhood IQ, suggesting a lifelong association between ventral temporal volume and verbal knowledge, rather than an effect of cognitive decline in later life. Executive ability was predicted by FA fractional anisotropy of the arcuate fasciculus (β = .19, FDR-adjusted p = .001), a major language-related tract implicated in speech production. This result suggests that this tract plays a role in the controlled retrieval of word knowledge during speech. At a more general level, these data highlight a basic distinction between information representation, which relies on the accumulation of tissue in specialised GM regions, and executive control, which depends on long-range WM pathways for efficient communication across distributed cortical networks.

Divergent effects of healthy ageing on semantic knowledge and control: Evidence from novel comparisons with semantically impaired patients

“…However, this region exhibits little age‐related volume loss in healthy individuals, compared with other areas such as prefrontal cortex (Fjell et al ., ). Indeed, a recent study in 556 healthy older adults found that volume of the ventral temporal cortices was a positive predictor of an individual's quantity of semantic knowledge (Hoffman et al ., ). However, this association was entirely mediated by educational level and childhood IQ, suggesting that this was a lifelong association rather than an effect of the ageing process.…”

New Perspectives on the Aging Lexicon

“…These neuroimaging techniques may also be used to distinguish or compare the neural representations of linguistic and non-linguistic stimuli [86,87]. Finally, there is significant promise in linking neural biomarkers of age-related decline to both cognitive control and representational aspects of linguistic and semantic cognition (e.g., graymatter density [88]; functional connectivity [85]; AD-specific biomarkers [89]) to understand the contribution of different neural structures and processes to age differences in the mental lexicon.…”

Psychotic-like experiences, polygenic risk scores for schizophrenia and structural properties of the salience, default mode and central-executive networks in healthy participants from UK Biobank

“…We computed the trajectories of water diffusion MRI parameters (using fractional anisotropy; FA), cortical thickness (CT) and grey matter volume (GMV) of the regions involved in these networks in a large sample of healthy participants from UKBiobank in whom any such associations would not be confounded by illness-associated factors. We employed a novel approach based on ROI-ROI analysis (derived from connectome processing) which extends our previous a priori network selection methods [38,39], allowing a much finer-grained network approach than using other techniques which quantify white matter connectivity without direct subject-specific linkage to cortical or subcortical regions. In addition, previous studies have suggested that schizophrenia may be accompanied by accelerated ageing [40], indicating for instance, significant declines in white matter coherence more than twice that of age-matched controls [41].…”