function and the cellular architecture of the neurons in the cerebral cortex of the brain (Khaitovich, Muetzel, She, Lachmann, Hellmann, & Dietzsch, 2004; Naumova, et al., unpublished data). For example, only one of the 4,998 genes with detectable expression differences between Broca’s area (inferior frontal cortex) and the left prefrontal cortex, was identified in three human individuals analyzed in a study comparing the dorsolateral prefrontal cortex, anterior cingulate cortex, primary visual cortex, and Broca’s area (Khaitovich, Muetzel, She, Lachmann, Hellmann, Dietzsch, et al., 2004). The high variability and low concordance of gene expression within the cortical regions between individuals might reflect genetic heterogeneity, differential responses of different individuals to the environment, brain plasticity in the realization of higher cognitive functions throughout the lifetime and in different environments, among many other “unknowns.” Only the systematic study of the gene expression variation among distinct functional cortical areas will be able to resolve these intriguing questions on the interindividual differentiation of the cerebral cortex in terms of gene expression, as well as to provide a better understanding of the molecular mechanisms underlying the distinct behavioral functions controlled by the CNS and the typical and atypical (pathological) development of these functions.
