New animal studies suggest that memory and other cognitive problems experienced by cocaine-addicted people can result directly from the cocaine abuse in addition to pre-existing traits or lifestyle factors.
The findings were presented at Neuroscience 2009, the annual meeting of the Society for Neuroscience and the world's largest source of emerging news about brain science and health.
"Our results clearly demonstrate the negative impact that even limited access to cocaine can have on cognitive function," said senior author Charles W. Bradberry, PhD, of the University of Pittsburgh. "These findings may lead to the development of therapies for cognitive impairments as a way to improve addiction treatment."
Cocaine users display a range of cognitive deficits, including problems with decision-making, planning, and memory. The greater these deficits, the more likely treatment will fail. The current finding is part of a multi-year longitudinal study of cognitive assessment in cocaine-exposed rhesus monkeys, which offer an ideal model for study because their brain structure and function are similar to that of humans.
For the study, 14 animals were trained to perform two tasks on a touch screen. One test first assessed how well the animals learned to associate pictures with rewards and then measured cognitive flexibility by reversing high- and low-reward pictures. The other task was a visual working memory task, in which animals had to remember an abstract stimulus for varying periods of delay. After initial training they were separated into two groups, with one group self-administering cocaine on Tuesdays through Fridays. Cognitive testing for both groups was conducted on Mondays, after the cocaine-administering animals had been drug-free for about 72 hours.
The animals showed impairments in learning, cognitive flexibility, and, to a lesser degree, working memory. "The types of errors suggest that poor attention and distractibility were significant contributors to the deficits, for they were similar to those made on cognitive tasks by people with attentional deficit disorders," Bradberry said. His lab plans to investigate whether the brain mechanisms that lead to impaired attention in people with attention deficit disorders may be causing similar problems in people chronically addicted to cocaine.
Research was supported by the Veteran's Administration Medical Research Service and the National Institute on Drug Abuse.
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