Neuroimaging intelligence testing: Difference between revisions

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Using MRI, researchers are able to acquire volumetric measurements of [[brain size]]. Some studies have tried to explain the relationship between brain size (meaning volume) and intelligence, specifically in terms of IQ. In general, it has been found that Full Scale IQ and Verbal IQ have a stronger correlation with brain size than Performance IQ. It is thought by some that grey and white matter specifically relate to different IQs (grey matter with Verbal IQ and white matter with Performance IQ), but the results have not been consistent. It has been found that within the cortex, the correlation with IQ was very influenced by the volume of prefrontal grey matter.<ref name=deary2 />

A 2009 study examined intracerebral volumetric relationships in twins. Making use of high resolution MRI data, they found strong genetic connections correlations between cerebral structures. Specifically, the study suggests that a strong correlation exists between the tissue type or spatial proximity and genes. By examining the differences or lack thereof between the brain size of twin children, the researchers drew conclusions that individuals that share genes (i.e. twins) will show similar physiological brain properties compared to genetically-unrelated individuals.<ref>{{cite journal|last=Schmitt|first=JE|author2=Wallace, GL |author3=Lenroot, RK |author4=Ordaz, SE |author5=Greenstein, D |author6=Clasen, L |author7=Kendler, KS |author8=Neale, MC |author9= Giedd, JN |displayauthors=9 |title=A twin study of intracerebral volumetric relationships.|journal=Behavior genetics|date=March 2010|volume=40|issue=2|pages=114–24|pmid=20112130|doi=10.1007/s10519-010-9332-6|pmc=3403699}}</ref> This study provides evidence of the genetic influence of the brain structure and size, which are believed to both influence intelligence in some way.

Another study in 2006 examined 100 postmortem brains, seeking a relationship between an individual’s Full Scale Wechsler Adult Intelligence Scale score and the volume of their brain regions. Prior to death, the subjects had completed the WAIS test, which measures verbal and visuospatial abilities. The factors considered important to the relationship between brain size and intelligence were age, sex and hemispheric functional lateralization. They found that general verbal ability was correlated with cerebral volume in women and right-handed men. It was not possible to find a relationship between ability and volume in with every group, however.<ref>{{cite journal|last=Witelson|first=S. F.|title=Intelligence and brain size in 100 postmortem brains: sex, lateralization and age factors|journal=Brain|date=26 October 2005|volume=129|issue=2|pages=386–398|doi=10.1093/brain/awh696|pmid=16339797}}</ref>