A recent study published in the Journal of Addiction Medicine demonstrates significant activation of the amygdala and hippocampus during marijuana cue exposure. What's this mean? It means individuals that are addicted to Marijuana's brains (specifically the amygdala and hippocampus whose jobs are memory and emotion) preferentially light up on fMRI when shown marijuana-related pictures compared to random pictures. The same has been shown with cocaine, heroin, nicotine and alcohol.