Cocaine use boosts learning and decision-making… but only as part of increasing dependency. By Sara Malm. dailymail.co.uk. August 25, 2013.

• Cocaine boosts brain circuits which controls planning and learning.
• However the drug-related brain growth ‘biased decision-making’.
• Study mice found that they chose environments associated with cocaine.

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Cocaine increases the brain’s ability to learn new information and make decisions, but only in ways which fuels addiction.Taking the Class A drug boosts the circuits in the frontal cortex, leading to rapid growth of the brain’s structure.American researchers injected cocaine into the brains of mice, and saw an almost immediate effect on their behaviour, where they became biased towards environments associated with the drug.
Scientists believe the research is key in understanding how users become dependent on the drug.Within two hours of the injection, the mice’s brains started growing neuron connections in the part of the brain which controls higher functions, such as planning and decision-making. It coincided with a dramatic change in the rodents’ behaviour. Given the choice of two environments, mice switched preferences to the one where they had received the cocaine shot.‘This gives us a possible mechanism for how drug use fuels further drug-seeking behaviour,’ said Dr Linda Wilbrecht, who led the research at the University of California at San Francisco.‘It’s been observed that long-term drug users show decreased function in the frontal cortex in connection with mundane cues or tasks, and increased function in response to drug-related activity or information.‘This research suggests how the brains of drug users might shift towards those drug-related associations.’The neurons directly affected by cocaine use had the ‘potential to bias decision-making’, she added.Initially the mice were given access to two adjoining ‘conditioning’ chambers, one smelling of cinnamon and the other vanilla, decorated with different patterns and textures.Free to explore both compartments, individual mice settled on one they preferred.They were then injected with cocaine while in the opposite compartment, and given the same choice.After being given cocaine, each mouse chose the compartment associated with the drug injection.When given the choice, most of the mice preferred to explore the side where they had the cocaine, which indicated that they were looking for more cocaine,’ said Dr Wilbrecht.‘Their change in preference for the cocaine side correlated with gains in new persistent spines that appeared on the day they experienced cocaine.‘The animals that showed the highest quantity of robust dendritic spines showed the greatest change in preference towards the chamber where they received the cocaine.‘This suggests that the new spines might be material for the association that these mice have learned to make between the chamber and the drug.’The findings are published in the latest edition of the journal Nature Neuroscience.Previous post-mortem studies of human brains have shown changes in dendritic spine density after weeks of repeated cocaine use.Earlier this month a study was published which showed that as well as supressing appetite, cocaine reduces the body’s ability to store fat.The increase in weight when a user stops taking the drug is thought to trigger relapses as it adds further psychological effects to withdrawal symptoms.
Journal reference: Francisco Javier Muñoz-Cuevas, Jegath Athilingam, Denise Piscopo & Linda Wilbrecht. Cocaine-induced structural plasticity in frontal cortex correlates with conditioned place preference.Nature Neuroscience (2013) doi:10.1038/nn.3498