Given the extent of brain maturation occurring during this phase in life, adolescents who use substances appear to be vulnerable to alterations in brain functioning, cognition and behavior. Indication that alcohol and marijuana use may detrimentally influence the developing brain comes from studies showing diminutions in neurocognitive functioning, especially attention, visuospatial functioning, and learning and retrieval of verbal and nonverbal information (Brown et al. 2000; Medina et al. 2007b; Tapert and Brown 1999, 2000; Tapert et al. 2002); morphological changes (Medina et al. 2008; Nagel et al. 2005); anisotropic differences in white matter (De Bellis et al. 2008); and a more distributed functional network and recruitment of alternate brain regions (see Table 1) (Jacobsen et al. 2007; Schweinsburg et al. 2008; Schweinsburg et al. 2005a; Tapert et al. 2001a, 2004, 2007). Table 1Brain correlates of heavy alcohol and marijuana use in adolescenceSubstanceWhite matterCortical volumesBOLD responseNeuropsychological functioningAlcohol↓ FA in the SCR, ILF, FOF, and SLF (Jacobus et al. 2009)↑ PFC volume in males and ↓ PFC volume in females compared to same-gender controls (Medina et al. 2008)↑ Response in frontal and
