How cocaine hijacks memory

Memories associated with drug use are a leading suspect in driving the impulses behind drug addiction and researchers have now found the mechanism that helps cocaine influence memory.

The findings could lead to targeted therapy that could alter or disable the mechanism and make drug addiction less compulsive.

Turning off the mechanism is "diminishing the emotional impact or the emotional content of the memory, so it decreases the motivation to relapse," said Barbara Sorg, professor of neuroscience at the Washington State University, Vancouver.

Drug use creates memories so powerful that they hijack the system, the researchers noted.

They gave male rats cocaine in a specific setting, a drug cage, conditioning them to associate the experience with that place.

With each new experience, the rats would draw memories of previous experiences there, reconsolidate them with new information and in effect reinforce the memory.

With one group of rats, the researchers removed structures called perineuronal nets that surround a group of neurons in the medial prefrontal cortex, a high-order area of the brain important for attention, cognition and inhibitory behaviour, as well as learning and memory.

The nets are believed to regulate the ability to strengthen or weaken as memories are recalled and reconsolidated.

Indeed, the rats with their nets removed were less interested in being in the drug cage.

"When we manipulated them and removed these nets from the prefrontal cortex, we saw that our animals had poorer memories," Slaker pointed out.

Sorg noted that the procedure probably did not erase the drug memory but blunted its emotional power.

The finding opens the possibility of developing a way to target, for example, a protein of the perineuronal nets, to counteract cocaine's influence over memories.

The study appeared in the Journal of Neuroscience.