Brain imaging correlates of general intelligence in UK Biobank

Abstract

The associations between indices of brain structure and measured intelligence are not clear. In part, this is because the evidence to date comes from mostly small and heterogenous studies. Here, we report brain structure-intelligence associations on a large sample from the UK Biobank study. The overall N = 29,004, with N = 18,363 participants providing both brain MRI and cognitive data, and a minimum N = 7318 providing the MRI data alongside a complete four-test battery. Participants' age range was 44-81 years (M = 63.13, SD = 7.48). A general factor of intelligence (g) was extracted from four varied cognitive tests, accounting for one third of the variance in the cognitive test scores. The association between (age-and sex-corrected) total brain volume and a latent factor of general intelligence is r = 0.275, 95% C.I. = [0.252, 0.299]. A model that incorporated multiple global measures of grey and white matter macro-and microstructure accounted for more than double the g variance in older participants compared to those in middle-age (13.4% and 5.9%, respectively). There were no sex differences in the magnitude of associations between g and total brain volume or other global aspects of brain structure. The largest brain regional correlates of g were volumes of the insula, frontal, anterior/superior and medial temporal, posterior and paracingulate, lateral occipital cortices, thalamic volume, and the white matter microstructure of thalamic and association fibres, and of the forceps minor.

Multi-group analysis using generalized additive kernel canonical correlation analysis

“…Consistent with previous studies investigating the structural brain correlates of IQ 26 , 27 , we defined that there are significant relationships between the neurodevelopmental and the neurophysiological domains (Empirical contribution coefficient is 0.463 with p-value 0.048). Also, a trend toward significance (p = 0.077) is also reported in the clinical and neurophysiological domains (Empirical contribution coefficient is 0.463).…”

Neurology-related protein biomarkers are associated with general fluid cognitive ability and brain volume in older age

“…No proteins or protein-PCs were associated with WMH or PVS score (all p>0.0029). Twenty-two proteins and protein-PC1 were associated with general cognitive function in LBC1936; some of these were also associated with brain volume (total brain [5], grey matter [4], normal appearing white matter [2]), and gMD [1] (p<0.0029).…”

“…Aging-related cognitive changes are thought to be drivenat least in part -by structural changes in the brain 1 . For example, global atrophy, grey matter and white matter volumes, white matter microstructure, and measures such as white matter hyperintensities (WMH) and perivascular spaces (PVS)-which are markers of cerebral small vessel disease (SVD)-have been associated with reduced cognitive ability and risk of dementia in both cross-sectional and longitudinal studies [2][3][4][5][6][7] .…”

Birth weight is associated with brain tissue volumes seven decades later, but not with age-associated changes to brain structure

“…To better understand the value of birth weight value as a perinatal indicator of later life brain health, it is important to establish the neurobiological correlates of birth weight into older age. We investigated the following global measures, each of which is reliably associated with cognitive ability in later life with modest effect sizes: total brain (TB) (24,25), grey matter (GM) and normal appearing white matter (NAWM) which are also linked to cognition (26,27), as well as white matter hyperintensity (WMH) volume, a marker of cerebrovascular disease in older age, is associated with cognitive decline (26,28,29). In older age, brain volume may be affected both by the degree of soft tissue atrophy that has occurred and by maximal healthy brain size (indexed by intracranial volume (ICV), an archaeological measure of maximal brain volume that is invariant with age (25,30).…”

“…As birth weight is also associated with greater adult height and weight (31), we controlled for these variables to investigate whether a relationship with brain volumes may be due to overall body dimension, rather than to a specific effect on brain or head growth (32). We selected two global measures of white matter microstructure: gFA, which reflects the pattern of covariance of FA values among white matter pathways of the brain and is correlated with preterm birth (33), ageing (34), and cognitive functioning in older age (27), and PSMD, which is effective at capturing diffuse pathology in otherwise normal appearing white matter (36)(37)(38). We further investigated regional associations between birth weight and cortical thickness, volume and surface area and explicitly tested the contribution of head size and body size.…”