The Effects of Cocaine Abuse on Functional Connectivity within the Mesolimbic Pathway

Abstract

With an estimated 1.5 million chronic cocaine users in the U.S., cocaine abuse is a considerable public health concern (Bolla et al., 2004). The mood elevation and euphoria associated with cocaine use is the result of the inhibition of the reuptake of dopamine in the mesolimbic “reward” pathway. Chronic cocaine use produces a number of distinctive biochemical adaptations within structures in this pathway, and has been the focus in numerous studies (Berhow et al 1996). A decrease in functional connectivity (i.e. the level of correlation in neural activity between distinct brain regions) in the primary motor and visual cortexes has been shown to be an acute effect of cocaine intake (Li et al 2000). The long-term effects of chronic cocaine-use on functional connectivity between structures in the mesolimbic pathway, however, has never before been investigated. Resting state functional magnetic resonance imaging (fMRI) enables researchers to observe and analyze spontaneous neural activity since the subject is not performing a task. An index of resting state functional connectivity can be created by cross-correlating activity patterns between each of the brain regions of interest (ROIs).