A brain imaging study strongly suggests that regular users of marijuana have smaller orbitofrontal cortex (OFC) volumes. Such a deficit could make it more difficult to change counterproductive behaviors, including drug use.
June 2015 A stressed rat will seek a dose of cocaine that is too weak to motivate an unstressed rat. Researchers traced the physiological pathway that links stress and the stress hormone corticosterone to increased dopamine activity and heightened responsiveness to cocaine.
This study demonstrated that cocaine increases expression of the protein E2F3a in the brain’s reward system. The changes in E2F3a levels in the nucleus accumbens are tied to addiction-related behaviors and to altered gene expression.
January 2015 Dr. Paul E. M. Phillips spoke on “Phasic Dopamine Transmission During Substance Abuse,” describing investigations that he has led into the role of brief, seconds-long bursts of dopamine signaling in addictive processes. Dr. Rita Z. Goldstein spoke on “Targeting the Brain, Cognition, and Motivation for Intervention in Addiction.”
Researchers monitored the activity of two types of neurons in mice: “urge” neurons, which promote feelings of reward and repeating behaviors that have produced rewards, and “control” neurons, which dampen those feelings and inhibit behavior.