Lower scores of older adults on intelligence tests could be partially explained by

A preliminary version of this report was presented as a poster at the 1995 annual meeting of the National Academy of Neuropsychology, San Francisco, CA. The study was partially supported by a grant from the National Institute of Mental Health (MH43960), and was completed while the first author was a postdoctoral fellow at Harbor-UCLA Medical Center, Torrance, CA.

Abstract

Base rates of deficient neuropsychological test performance were evaluated among 132 neurologically healthy older normal adults using a variety of measures commonly employed in the “flexible-battery”approach to neuropsychological assessment. Subjects were divided into three age groups (50 to 59, 60 to 69, and 70 to 79 years). Despite the healthy status of our sample, most tests yielded at least some proportion of subjects earning scores in the borderline and impaired ranges (1.3 and 2.0 standard deviations below the age-group mean, respectively). Across the battery of measures, 73% of subjects earned a borderline score on at least one measure, and 20% of subjects earned at least two scores in the impaired range on separate tests. The proportion of subjects consistently earning borderline or impaired scores across multiple measures within specific cognitive domains was generally lower. Results illustrate the problems in interpreting isolated low scores, and the need to consider false-positive base rates in drawing inferences from poor test performance.

Copyright © 1998 National Academy of Neuropsychology. Published by Elsevier Ltd. All rights reserved.

Volume 46, September–October 2014, Pages 94-106

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

Under a Creative Commons license

Open access

Highlights

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We assess overlap between ‘frontal’ tests and fluid intelligence (gf) in old age.

We also examine how units of common score variance relate to frontal lobe volumes.

gf-common variance was linked with variance in some left frontal lobe regions.

gf-independent variance was linked with homotopic right frontal regions.

We identify two biologically-meaningful components of complex cognition 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.

Keywords

Ageing

Frontal lobes

Intelligence

Neuropsychology

MRI

Crown copyright © 2014 Published by Elsevier Inc.