Walking down the same street a person used to smoke on can trigger memories that could make them want to light up.
When we enter a restaurant, exposure to food cues such as seeing and smelling it can boost our appetite and make us crave it, even if we are already full.
These reward pathways involve the release of the hormone dopamine.
This is also known as the "sex, drugs, and rock 'n' roll" neurotransmitter because our brains release it during pleasurable activities.
Dopamine, however, also plays a crucial role in learning and motivation. Older studies have shown that in the absence of dopamine, mice find it more difficult to learn and remember new things.
So, what happens with learning and memory formation in addiction, during which the brain is used to getting "overexcited" in anticipation of receiving a drug?
Scientists from the Department of Psychology and Collaborative Program in Neuroscience at the University of Guelph in Ontario, Canada, set out to investigate.
Prof. Francesco Leri is the last and corresponding author of the new study.
How drug-related cues affect memory
Specifically, Prof. Leri and his colleagues wanted to investigate the effects of nicotine and cocaine addiction cues on memory formation.
As the study authors explain, past research had shown that addiction-related environmental cues activate brain areas associated with emotional processing and response to stimuli.
This is why the sight of a smoking area may trigger smoking, which, in turn, makes a person who smokes temporarily feel good.
However, Prof. Leri and team were interested in the links between memory and learning. Previous studies had demonstrated that cocaine and nicotine enhance long-term memory formation, the scientists note.
In their new experiments, they gave rats cocaine and nicotine and tested their memory by putting them in test chambers and examining how well they remembered new objects.
Then, they conditioned the rats so that they would associate the drugs with certain environmental stimuli. Finally, they tested the rats' memories when they had not received any drugs but did have exposure to the stimuli.
These experiments revealed that the rodents' memories were more active in chambers where the scientists had given them drugs and conditioned them to drug-associated cues, but it was less active in environments free from drug associations.
This suggested to the team that when nicotine and cocaine are associated with environmental cues, these cues can boost learning and strengthen memories.
"Those cues acquire powerful cognitive effects," says Prof. Leri, which "could be used to enhance learning of the recovery process."
These memory-strengthening effects make it harder to recover from addiction, the study authors explain. However, understanding the mechanism could make cognitive behavioral therapy more effective in treating addiction.
"Stimuli in our environment such as buildings, objects, and places are normally fairly innocuous, [but] when they're associated with drugs of abuse, they can become modifiers of memory function."
Prof. Francesco Leri