It’s All in the Wiring

Paul Thompson of UCLA asks questions that some people think are unaskable, or should be–like what is the genetic and anatomical basis of human intelligence? First of all, psychologists still maintain a lively debate about the nature of intelligence. Is it a single factor, like Spearman’s g? Or do we have multiple intelligences? Is intelligence simply the factor that intelligence tests test? If we do find the genetic basis for intelligence, will that lead to determinism? Reduced opportunities for education for some?

Now Thompson and his group are using diffusion-tensor imaging (DTI), a form of MRI that allows you to image white matter, to compare the brains of identical and fraternal twins. White matter “integrity” and performance on a standardized IQ test were positively correlated. The correlations were not uniform, with a range of heritability from 85% in the parietal lobe to 45% in the temporal lobe. Previous studies had focused on gray matter volume, but white matter is of interest due to its deterioration in Alzheimer’s disease, alcoholism, and traumatic brain injury.

DTI Images of White Matter

Thompson’s group is also looking at genes that might contribute to the differences in white matter they observed, and variations in a gene that produces BDNF has emerged as an important candidate.

Will we have the wisdom to use new findings about the biological bases of intelligence responsibly?  As Thompson points out, knowing something is largely genetic doesn’t mean that it cannot be influenced. Both the mediocre and elite athlete benefit from practice.

Ming-Chang Chiang, Marina Barysheva, David W. Shattuck, Agatha D. Lee, Sarah K. Madsen, Christina Avedissian, Andrea D. Klunder, Arthur W. Toga, Katie L. McMahon, Greig I. de Zubicaray, Margaret J. Wright, Anuj Srivastava, Nikolay Balov, and Paul M. Thompson
Genetics of Brain Fiber Architecture and Intellectual Performance
J. Neurosci., Feb 2009; 29: 2212 – 2224 ; doi:10.1523/JNEUROSCI.4184-08.2009