This paper, by V. J. Schmithorst, M. Wilke, B. J. Dardzinski, and S. K. Holland Imaging Research Center, Children’s Hospital Medical Center Cincinnati, OH, USA, uses Diffusion Tensor Imaging (DTI) to check on the connection of cerebral white matter to measured (Wechsler) IQ in normal children. ANd they found very strong correlations! You might also want to look at the plots shown at the link; The link is only two pages long (PDF). I know that "IQ is not real" is a frequent and popular meme on this forum, but gee! how much evidence does it take?