The corpus callosum as anatomical marker of intelligence? A critical examination in a large-scale developmental study

René Westerhausen,Darius A. Rohani,Anders M. Fjell,Jon S. Skranes,Kristine B. Walhovd,Charline-Marie Friesen,Stine K. Krogsrud,Christian K. Tamnes,Asta K. Håberg

doi:10.1007/s00429-017-1493-0

Abstract

Intellectual abilities are supported by a large-scale fronto-parietal brain network distributed across both cerebral hemispheres. This bihemispheric network suggests a functional relevance of inter-hemispheric coordination, a notion which is supported by a series of recent structural magnetic resonance imaging (MRI) studies demonstrating correlations between intelligence scores (IQ) and corpus-callosum anatomy. However, these studies also reveal an age-related dissociation: mostly positive associations are reported in adult samples, while negative associations are found in developing samples. In the present study, we re-examine the association between corpus callosum and intelligence measures in a large (734 datasets from 495 participants) developmental mixed cross-sectional and longitudinal sample (6.4–21.9 years) using raw test scores rather than deviation IQ measures to account for the ongoing cognitive development in this age period. Analyzing mid-sagittal measures of regional callosal thickness, a positive association in the splenium of the corpus callosum was found for both verbal and performance raw test scores. This association was not present when the participants’ age was considered in the analysis. Thus, we did not reveal any association that cannot be explained by a temporal co-occurrence of overall developmental trends in intellectual abilities and corpus callosum maturation in the present developing sample.

Highlights

Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Intellectual and general cognitive abilities are supported by a large-scale brain network encompassing association cortices in frontal, parietal, and temporal lobes (Deary 2012; Deary et al 2010; Jung and Haier 2007; Luders et al 2009; Shaw 2007)
We reexamine the association between corpus callosum and intelligence measures in a large (734 datasets from 495 participants) developmental mixed cross-sectional and longitudinal sample (6.4–21.9 years) using raw test scores rather than deviation IQ measures to account for the ongoing cognitive development in this age period
The verbal raw test scores (v-Raw subscale (RS)) analysis revealed a negative association in the genu of the corpus callosum, that is, in segment 13

Summary

Introduction

Electronic supplementary material The online version of this article (doi:10.1007/s00429-017-1493-0) contains supplementary material, which is available to authorized users. Brain Struct Funct (2018) 223:285–296 interpretation, a common genetic origin for corpus callosum size and intelligence has been suggested in studies on healthy twins and siblings (Hulshoff Pol et al 2006) This general notion is supported by a series of recent magnetic resonance imaging (MRI) studies demonstrating correlations between intelligence coefficients (IQ; as measured with standard intelligence tests) and measures of mid-sagittal callosal area (e.g., Allin et al 2007; Ganjavi et al 2011; Hutchinson et al 2009; Peterson et al 2001), thickness (Luders et al 2007, 2011), and microstructural integrity (i.e., fractional anisotropy; Chiang et al 2009; Dunst et al 2014; Hutchinson et al 2009; Navas-Sanchez et al 2014; Tang et al 2010). This was necessary as raw intelligence test scores (Neisser 1997; Tamnes et al 2010) and callosal thickness (e.g., Giedd et al 1996; Luders et al 2010b; Westerhausen et al 2016, 2011) are characterized by a continuous age-related increase in the studied age period, and the temporal cooccurrence of these two developmental trends could confound the association (see e.g. Salthouse 2011)

Participants

Results

Discussion