as dendritic maturation and synaptogenesis, continue to occur postnatally, with the most rapid changes occurring in the first few years of life. (Goldman-Rakic et al., 1983; Anderson et al, 1995; Huttenlocher and Dabholkar, 1997). In rats, the medial prefrontal cortex (mPFC) consists of the anterior cingulate, prelimbic and infralimbic regions (Jerison, 1997; Uylings et al., 2003; Heidbreder & Groenewegen, 2003). Neurogenesis of the most superficial cortical cells occurs just prior to birth (Bayer and Altman, 2004) with some of the latest neurons still migrating to mature positions during the first few days of postnatal life (Van Eden et al., 1990). Although the process of entering the cortical plate starts just before birth (Kalsbeek et al., 1988), there is an increase in the number of dopaminergic fibers from the mediodorsal nucleus of the thalamus, the major afferent of the PFC, during the first postnatal week (Van Eden et al., 1986) suggesting that significant differentiation and maturation of prefrontal cortex occurs postnatally in the rat brain. These fibers reach and terminate in the developing Layer III and it is suggested that their early presence may play an important role in the laminar development of the prefrontal cortex (Van Eden et al., 1986).
