The findings that inhalable marijuana boosts working memory surprised the researchers, who were expecting subjects to be impaired.
While prior findings show that marijuana can temporarily impair working memory, a new study published in the journal Neurobiology of Learning and Memory suggests the exact opposite.
To investigate marijuana’s effects on working memory, researchers from the University of Florida trained 32 rats (15 male, 16 female) in a food-motivated delayed response task. They then had the animals perform the test again after being exposed to either inhalable cannabis smoke or a placebo.
The researchers assessed the rats’ performances in the tests, looking to see whether exposure to cannabis at all affected their working memory and ability to complete the task.
In male rats, the researchers found that exposure to cannabis smoke had no effect on the performance of male rats.
Female rats, however, surprisingly demonstrated enhanced working memory accuracy in the task after they had consumed marijuana.
“Cannabis smoke improved working memory accuracy,” the study’s authors wrote. Meanwhile, “placebo smoke did not affect working memory accuracy” in both male and female rats.
It’s the lack of impact caused by placebo smoke that prompted the researchers to believe cannabis played a role in enhancing the performance of female rats.
“Exposure to placebo smoke had no effect on performance, suggesting that the cannabinoid content of cannabis smoke was critical for its effects on working memory,” the wrote.
The researchers did note that baseline performances, prior to cannabis and placebo exposure, were lower in female rats compared to males. They suggest this “raises the possibility that the enhancing effects in females were due to their relatively worse baseline performance rather than to sex differences in the effects of cannabis per se.”
Findings Run Counter to Earlier Research
The new study’s findings fly in the face of earlier research and the consensus that marijuana can temporarily impair cognitive performance.
Marijuana contains tetrahydrocannabinol (THC), an intoxicating cannabinoid that interacts with the body’s native systems to elicit temporary euphoric effects. Some of the effects of this temporary “high” include altered physical senses and perception of time, feelings of euphoria and relaxation, impaired body movement, and short-term recall difficulties.
“The overwhelming majority of research in both animal models and human subjects shows that acute administration of cannabis and cannabinoids induces deficits in tests of cognitive function, including working memory,” the researchers wrote.
“In contrast, the current experiments show that acute exposure to cannabis smoke enhanced working memory performance in a delayed response task in rats, particularly in females in which baseline levels of task performance were lower than those in males,” they added.
The researchers suggest that their surprising findings could indicate that marijuana’s effect on memory may be dependent on THC dose, and that the amount given to the test subjects elicited a memory-boosting effect.
Additionally, they also proposed that the cognitive impacts of cannabis might be different based on consumption method. Most studies that have looked into the effects of THC on working memory have subjects consume either synthetic or non-smokable marijuana products.
You can access the abstract of the new study, “Enhancing effects of acute exposure to cannabis smoke on working memory performance,” at ScienceDirect.
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