Marijuana’s Effect On Short-Term Memory

thc brain

One of the known side effects of marijuana is short-term memory loss, why is that? Researchers of the University of Bordeaux, France, and Xia Zhang of the University of Ottawa Institute of Mental Health Research think they know why.

They have discovered how marijuana disrupts short-term memory. The drug impairs users’ working memory, the ability to retain and use information over short periods of time. The research shows that this common side effect occurs because of a previously unknown signaling mechanism between neurons and non-neuronal cells called astrocytes. Their research was published today on

This was a break-through finding on the brain. The star-shaped astrocytes have long been considered nothing more than support cells that protect neurons. “Our study provides compelling evidence that astrocytes control neurons and memory,” says Zhang.

How did they conduct their research? The psychoactive ingredient of marijuana is tetrahydrocannabinol (THC). Using micro-electrodes implanted into the brains of anesthetized rats, the researchers found that the compound weakens the connections, or synapses, between neurons in the hippocampus, a structure that is crucial for memory formation.

They repeated these experiments in two types of mice that had been genetically modified to alter their production of CB1 receptors, the molecules that interact with THC in the brain. One mouse strain lacked CB1 receptors in hippocampal neurons that synthesize the neurotransmitter glutamate; the other lacked them in those that synthesize the neurotransmitter GABA.

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