Correlational structure of ‘frontal’ tests and intelligence tests indicates two components with asymmetrical neurostructural correlates in old age

Abstract

Both general fluid intelligence (gf) and performance on some ‘frontal tests’ of cognition decline with age. Both types of ability are at least partially dependent on the integrity of the frontal lobes, which also deteriorate with age. Overlap between these two methods of assessing complex cognition in older age remains unclear. Such overlap could be investigated using inter-test correlations alone, as in previous studies, but this would be enhanced by ascertaining whether frontal test performance and gf share neurobiological variance. To this end, we examined relationships between gf and 6 frontal tests (Tower, Self-Ordered Pointing, Simon, Moral Dilemmas, Reversal Learning and Faux Pas tests) in 90 healthy males, aged ~ 73 years. We interpreted their correlational structure using principal component analysis, and in relation to MRI-derived regional frontal lobe volumes (relative to maximal healthy brain size). gf correlated significantly and positively (.24 ≤ r ≤ .53) with the majority of frontal test scores. Some frontal test scores also exhibited shared variance after controlling for gf. Principal component analysis of test scores identified units of gf-common and gf-independent variance. The former was associated with variance in the left dorsolateral (DL) and anterior cingulate (AC) regions, and the latter with variance in the right DL and AC regions. Thus, we identify two biologically-meaningful components of variance in complex cognitive performance in older age and suggest that age-related changes to DL and AC have the greatest cognitive impact.

Bilingualism, social cognition and executive functions: A tale of chickens and eggs

“…Participants were invited based on the following inclusion criteria: completed Wave 2 within 1.5 years of the cortisol study start, male (to avoid the confound of gender-based endocrine variation), ≥24 on the Mini-Mental State Exam (MMSE; Folstein et al, 1975), <11 on the depression subscale of the Hospital Anxiety and Depression Scale (Zigmond and Snaith, 1983), not taking antidepressant or glucocorticoid medication, and no reported diagnosis of neurodegenerative disorder, stroke or mini-stroke. Of 118 eligible males, 90 (mean age=74.5 years, SD=0.32; MMSE mean=28.54, SD=1.52) consented and were administered the neuropsychological tests (described in Cox et al (2014), and also below and in Table 1). Written informed consent was obtained from each participant and the study was conducted in compliance with departmental guidelines on participant testing and the Declaration of Helsinki.…”

“…Participants provided a measure of cognitive ability in youth (the Moray House Test), and also 6 tests of executive and social cognition at ~74 years (additional information is available in Cox et al, 2014). …”

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