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Developmental biology - Brain Function

Cortical thickness is link to intelligence

Brain cortical thickness appears to mediate intelligence...

Reports from several studies had previously identified a link between height and cognitive ability, or intelligence, but the mechanisms underlying this association were not well understood. Researchers from the University of Helsinki, University of California San Diego and Boston University found that this association is mediated by cortical surface area.

cortical thickness

Cortical surface area is calculated as the straightforward sum of: areas of the triangles making up the cortical surface. Image source: Hanyang University, Korea
In the study, cortical grey matter was measured with magnetic resonance imaging (MRI) focussed on total cortical surface area and mean (average) cortical thickness. Although total surface area was greater in taller persons, height did not relate to cortical thickness.

Researchers examined the association between height and cognitive ability using a model where the size of the cortical grey matter was considered a mediating factor. They found that greater height was associated with a bigger cortex, which in turn was linked with better cognitive ability.

Participants in this study were 51-60 year old American men. Researchers point out that even though genetic effects accounted for most of the individual differences between these men in height and cortical size and cognition, the contribution of environmental factors may be much larger in other similar populations yet net different results.

In this study, cognitive ability was measured with a paper-and-pencil test consisting of items measuring verbal, mathematical, spatial and reasoning abilities and published in the journal Brain Structure & Function.
"Even though taller individuals have, on average, a bigger brain compared to shorter people, the size of any given individual's brain cannot be determined by their stature alone ... cognitive ability is not simply determined by brain size. The findings do, however, shed light on the biological mechanism underlying the association between height and cognition.

"These observations are in line with recent MRI studies of cortical development suggesting that cortical surface area increases until approximately the age of 12, whereas thinning of the cortex occurs across childhood and adolescence. For example, childhood malnutrition has an impact on both height and brain growth, and also affects cognitive development."

Eero Vuoksimaa PhD, Institute for Molecular Medicine, University of Helsinki, HelsinkiFinland and author of the study.

Height and general cognitive ability are positively associated, but the underlying mechanisms of this relationship are not well understood. Both height and general cognitive ability are positively associated with brain size. Still, the neural substrate of the height-cognitive ability association is unclear. We used a sample of 515 middle-aged male twins with structural magnetic resonance imaging data to investigate whether the association between height and cognitive ability is mediated by cortical size. In addition to cortical volume, we used genetically, ontogenetically and phylogenetically distinct cortical metrics of total cortical surface area and mean cortical thickness. Height was positively associated with general cognitive ability and total cortical volume and cortical surface area, but not with mean cortical thickness. Mediation models indicated that the well-replicated height-general cognitive ability association is accounted for by individual differences in total cortical volume and cortical surface area (highly heritable metrics related to global brain size), and that the genetic association between cortical surface area and general cognitive ability underlies the phenotypic height-general cognitive ability relationship.

Authors: Eero Vuoksimaa, Matthew S. Panizzon, Carol E. Franz, Christine Fennema-NotestineDonald, J. Hagler Jr., Michael J. Lyons, Anders M. Dale, William S. Kremen.

AMD [Anders M. Dale] is a founder of and holds equity in CorTechs Laboratories, Inc., and also serves on its Scientific Advisory Board. He is a member of the Scientific Advisory Board of Human Longevity, Inc., and receives funding through research agreements with General Electric Healthcare and Medtronic, Inc. The terms of these arrangements have been reviewed and approved by the University of California, San Diego, in accordance with its conflict of interest policies. All other authors have no conflicts of interest to declare.

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May 22, 2018   Fetal Timeline   Maternal Timeline   News   News Archive

Cartoon by Eira Vuoksimaa, PhD.

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