Marijuana--and its active ingredient, Δ⁹-tetrahydrocannabinol (THC)--has muddled memories for millennia. But how exactly the wacky weed interferes with remembrance of things past--as well as attention span and speech, among other things--has never been clear. Now neuroscientists have discovered that cannabinoids diminish the brain waves of rats--and disrupt the symphony of synchronous brain cell firing that may be essential for memory.

Neuroscientist David Robbe of Rutgers University and his colleagues tested the impact of THC and a synthetic cannabinoid on rats that had their heads restrained. The drugs affected certain brain waves: the theta (four to 12 hertz) and fast ripple (100 to 200 hertz) waves diminished significantly, whereas the drug had a slightly lesser impact on gamma (30 to 80 hertz) waves. Because theta and gamma oscillations are thought to play a critical role in creating and storing short-term memories--and fast ripple oscillations may allow such short-term memories to be moved into long-term storage--this suppression could mean missing memories for the rats.

In fact, rats that had been trained to follow a specific series of turns to get water--and did fine on the test before being intravenously injected with the drug--found themselves wandering in a daze under its influence. And when the researchers injected the synthetic cannabinoid directly into three rats' brains, it completely disrupted the otherwise synchronized pattern of the firing of their neurons: they fired as much as before, but in a more random pattern. And other types of brain cells, such as interneurons and pyramidal cells, fell out of step as well, although, interestingly, their overall activity actually increased (perhaps an explanation for the random nature of thoughts generated by use of the drug).

The finding suggests that this disruption of synchronized brain cell firing might be responsible for marijuana's memory distortions. "Overall, our findings indicate that under the influence of cannabinoids, neurons are liberated from population control," the researchers write in the paper presenting the finding published in the December issue of Nature Neuroscience. This, they argue, is the direct cause of memory impairment. But the research also reveals that at the highest doses of synthetic cannabinoid, the rats failed to discover the right sequence of turns altogether. In other words, there may be a threshold level of the drug that entirely prohibits learning, and that is something worth remembering very clearly.

5 Comments

1. 1. jeffjohnson 01:08 AM 11/11/08

   lol wow now i know know to inject myself with weedespecially in the brain...seriously. i like how it used the words MAY, POSSIBLY, and THOUGHT TO, which sounds like they really dont know that any of those affect memory and that are just guessing. I dont think holds any relevance at all without solid definitive proof that those brain waves do affect memory and that THC DOES or DOESNT affect memory not may possibly or even thought to enduce those effects.

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2. 2. urethanehex 02:07 PM 7/20/09

   Love how it doesn't mention at all the affects it has on alpha brain waves. You know, the kind that are lacking in every kid ever diagnosed with A.D.H.D. It's also very suspicious that the doses given to the rats are never mentioned. A rat wouldn't function correctly if it was injected with 20 times the amount of normal brain chemicals or hormones that it naturally produces either. Wonder what would happen to the rats if equivalent doses of 95% of the chemicals prescribed by doctors and pushed by drug companies were administered to them? Bet there would be a lot of dead rats. Marijuana has been proven to increase alpha wave activity. Alpha waves increase creativity, promote relaxation and help you focus.
   
   

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3. 3. 12inchfallacy 02:21 PM 1/14/10

   Dude, Jeff. I smoke hella weed, but I also study neurology. This is a clean theory, and it's more than just likely. Don't be so quick to turn down negative information about THC just because you think the media is out to kill your fun times.

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4. 4. lab.rat2000 01:42 PM 8/13/11

   By all means these test results are not faulty, they are just faulty in how the testing was administered. What pot head does anyone know thats going to inject themselves is the first issue, second issue is where does anyone for the most part besides in a lab situation, get there hands on such a refind solution of thc that can be injected.

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5. 5. belman 02:11 AM 4/20/12

   How can THC be tested on a being that is not able to think?

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