A structural equation modeling investigation of age-related variance in executive function and DTI measured white matter damage

Charlton, R.A.; Landau, S.; Schiavone, F.; Barrick, T.R.; Clark, C.A.; Markus, H.S.; Morris, R.G.

doi:10.1016/j.neurobiolaging.2007.03.017

« Previous Next »Neurobiology of Aging
Volume 29, Issue 10 , Pages 1547-1555, October 2008

A structural equation modeling investigation of age-related variance in executive function and DTI measured white matter damage

R.A. Charlton
- Clinical Neuroscience, St. George's University of London, Cranmer Terrace, London SW17 0RE, UK
- Corresponding author. Tel.: +44 20 8725 5385; fax: +44 20 8725 2950.
S. Landau
- Department of Biostatistics and Computing, Institute of Psychiatry, King's College, University of London, De Crespigny Park, London SE5 8AF, UK
F. Schiavone
- Clinical Neuroscience, St. George's University of London, Cranmer Terrace, London SW17 0RE, UK
T.R. Barrick
- Clinical Neuroscience, St. George's University of London, Cranmer Terrace, London SW17 0RE, UK
C.A. Clark
- Clinical Neuroscience, St. George's University of London, Cranmer Terrace, London SW17 0RE, UK
H.S. Markus
- Clinical Neuroscience, St. George's University of London, Cranmer Terrace, London SW17 0RE, UK
R.G. Morris
- Department of Psychology, Institute of Psychiatry, King's College, University of London, De Crespigny Park, London SE5 8AF, UK

Received 31 March 2006; received in revised form 13 March 2007; accepted 17 March 2007. published online 25 April 2007.

Abstract

Cognitive changes in normal aging have been explained by the frontal-executive hypothesis, but the assumptions made by this hypothesis concerning the neurobiological causes are still a matter of debate. Executive functions (EF) may activate neural networks that include disparate grey matter regions, and rely on the integrity of white matter connections. In 118 adults (50–90 years old) from the GENIE study, white matter integrity was measured using diffusion tensor imaging, and information processing speed, fluid intelligence and EF were assessed. A theory-driven structural equation model was developed to test associations between variables. The model was revised, removing non-significant paths. The adjusted model explained well the covariance in our data; and suggested that the reduction in white matter integrity associated with age directly affected only working memory. Fluid intelligence was mediated by all measured cognitive variables. The results suggest that white matter integrity may be particularly important for abilities activating complex neural networks, as occurs in working memory. Integration of the information processing speed and frontal-executive hypotheses may provide important information regarding common, unique, and mediating factors in cognitive aging.

Keywords: Aging, Executive function, Working memory, Information processing speed, White matter, Diffusion tensor imaging, Structural equation modeling