White matter in the brain that was previously implicated in animal studies has now been suggested to be specifically impaired in the brains of people with addiction to cocaine or heroin, according to a study conducted by researchers from the Icahn School of Medicine at Mount Sinai and Baylor College of Medicine.

The study looked at the connectivity of the tract between the prefrontal cortex (PFC), a brain region critical for regulating higher-order executive functions, and the habenula, a region that plays a critical role in reward and reward-associated learning. While signaling from the PFC to the habenula is disrupted in rodent cocaine addiction models, implicating this PFC-habenula circuit in withdrawal and cue-induced relapse behaviors, until now, the PFC-habenula path has remained poorly understood in the human brain.

Using diffusion MRI tractography, the research team observed reduced coherence in the orientation of the white matter fibers in the cocaine-addicted group that comprised both current cocaine users and those with short-term abstinence. Their study extended results beyond cocaine (a stimulant) to heroin (an opioid), suggesting that abnormalities in this path may be generalized in addiction. Importantly, they found that across all addicted individuals, greater impairment was correlated with earlier age of first drug use, which points to a potential role for this circuit in developmental or premorbid risk factors.