The Amygdala Plays a Role in Habitual Cocaine Seeking

June 20, 2013 · Posted in Neurobiology 

amygdalaAt a recent scientific meeting, Jennifer E. Murray et al. presented findings about the amygdala’s role in habitual cocaine seeking. The amygdala is the part of the brain that makes associations between a stimulus and a response. When a person begins using cocaine, a signal between the amygdala and the ventral striatum (also known as the nucleus accumbens), the brain’s reward center, creates a pleasurable feeling for the person. The researchers found that in mice who have learned to self-administer cocaine, as an animal progresses from intermittent use to habitual use, the amygdala connections shift away from the ventral striatum toward the dorsal striatum, a site for motor and habit memory. If amygdala connections to the dorsal striatum are severed, the pattern of compulsive cocaine abuse does not develop.

Editor’s Note: These data indicate that the amygdala is involved in cocaine-related habit memory, and that the path of activity shifts from the ventral to the dorsal striatum as the cocaine use becomes more habit-based—automatic, compulsive, and outside of the user’s awareness.

As we’ve reviewed before, the amygdala also plays a role in context-dependent fear memories, such as those that occur in post-traumatic stress disorder (PTSD). The process of retraining a person with PTSD to view a stimulus without experiencing fear is called extinction training. A study by Agren et al. published in Science in 2012 demonstrated that when extinction training of a learned fear took place within the brain’s memory reconsolidation window (five minutes to one hour after active memory recall), the training was sufficient to not only “erase the conditioned fear memory trace in the amygdala, but also decrease autonomic evidence of fear as revealed in skin conductance changes in volunteers.”

The preclinical data presented by Murray and colleagues suggest the possibility that amygdala-based habit memory traces could also be revealed via functional magnetic resonance imaging (fMRI) in subjects with cocaine addiction. Attempts at extinction of cocaine craving, if administered within the memory reconsolidation window, might likewise be able to erase the cocaine addiction/craving memory trace, as Xue et al. reported in Science in 2012.

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