In Hoogland et al. (2010) a different Tower of London version was used (Foltynie et al., 2004b), and no functional MRI was conducted, perhaps limiting the sensitivity to an effect of COMT. Interestingly, there was an interaction between LEDD and COMT on verbal reasoning consistent with a genotype interaction with dopaminergic medication to influence frontal cognitive ability in Parkinson’s disease. This evidence concerns the gene COMT and Parkinson disease.