Abnormal striatal circuitry and intensified novelty seeking among adolescents who abuse methamphetamine and cannabis

It has been hypothesized that changes in striatal-mediated dopamine modulation during adolescence may increase risk for initiating substance abuse as a result of its fundamental role in arbitrating reward sensitivity and motivation during learning and decision making. However, substance abuse during adolescence may also significantly modify striatal structure and function and concomitantly alter reward sensitivity and action control while this brain region is undergoing remodeling. In the present investigation, to assess the relationship of methamphetamine or methamphetamine and cannabis abuse to regional striatal morphology, we acquired structural magnetic resonance images (MRI), using a 3T Siemens Trio scanner, from three groups of adolescents composed of healthy controls (N=10), methamphetamine abusers (Meth, N=9), and combined methamphetamine and cannabis abusers (Meth+CA, N=8). We also assessed novelty seeking using the novelty seeking subscale from Cloninger’s Tridimensional Character Inventory. The results indicate that adolescent Meth+CA abusers have increased regional striatal volume and show intensified novelty seeking in contrast to controls. Degree of Meth exposure was also positively correlated with regional striatal volume and novelty seeking in both Meth and Meth+CA users. These preliminary findings support theories that propose a role for the striatum in adolescent substance abuse and further indicate that novelty seeking may be related to initiation or sustained drug use.