2004). In contrast, gene expression differences in other human and chimpanzee tissues, such as the heart and liver, are nearly identical in their numbers of up-(increased expression of one or more genes) and down-(decreased expression of one or more genes) regulated genes (Caceres, et al., 2003). It has been suggested (Caceres, et al., 2003) that this increased gene expression in the brain might allow for a higher level of neuronal activity and extensive changes in the physiology and function of the human brain.
