Beyond a bigger brain: Multivariable structural brain imaging and intelligence

Stuart Ritchie, Tom Booth, Maria Valdes Hernandez, Janie Corley, Susana Munoz-Maniega, Alan Gow, Natalie Royle, Alison Pattie, Sherif Karama, John Starr, Mark Bastin, Joanna Wardlaw, Ian Deary

Research output: Contribution to journalArticlepeer-review

Abstract

People with larger brains tend to score higher on tests of general cognitive ability (g). It is unclear, however, how much variance in intelligence other brain measurements would account for if included together with brain volume in a multivariable model. We examined a large sample of individuals in their seventies (n = 672) who were administered a comprehensive cognitive test battery. Using structural equation modelling, we related six common magnetic resonance imaging-derived brain variables that represent normal and abnormal features—brain volume, cortical thickness, white matter structure, white matter hyperintensity load, iron deposits, and microbleeds—to g and to ‘fluid’ intelligence. As expected, brain volume accounted for the largest portion of variance (~12%, depending on modeling choices). Adding the additional variables, especially cortical thickness (+~5%) and white matter hyperintensity load (+~2%), increased the predictive value of the model. Depending on modelling choices, all neuroimaging variables together accounted for 18-21% of the variance in intelligence. These results reveal which structural brain imaging measures relate to g over and above the largest contributor, total brain volume. They raise questions regarding which other neuroimaging measures might account for even more of the variance in intelligence.
Original languageEnglish
Pages (from-to)47–56
Number of pages10
JournalIntelligence
Volume51
DOIs
Publication statusPublished - Jul 2015

Keywords

  • g-factor
  • Intelligence
  • Brain
  • MRI
  • Structural equation modelling

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