Quite often, on the effects of cannabis on human behavior and cognition are done while the user is engaged in various activities. We know, for instance, that THC changes the way information is processed, which may impair judgment, and affects memory, making it difficult to remember things when you're high.
A new study, however, investigated what marijuana does to the brain when it's at rest -- when a person isn't engaged in any particular task.
Shikha Prashad of the Center for BrainHealth at the University of Texas at Dallas, along with colleagues, used electroencephalography (EEG) to monitor electrical activity in the cortex of the brain of 17 cannabis users and 21 non-cannabis users.
The researchers found that the participants who used cannabis showed increased activity and connectivity compared to the control group, even when not engaged in a task. This sort of neural signature is reduced during resting state and enhanced when performing a task. In other words, marijuana makes the brain act like it's 'wired' all the time.
However, the researchers claim that this kind of heightened resting-state brain activity isn't more efficient, but rather more 'noisy'. For instance, the researchers found that neural connectivity in cannabis users was associated with craving. It's possible that differences in neural activity may be related to the sort of cognitive impairments described in earlier studies.
"These results suggest that there are differences in cortical activity and connectivity between cannabis users and non-using controls in the resting state that may be related to putative cognitive impairments and can inform effectiveness of intervention programs," the authors wrote in their study's abstract.
This isn't the last word on the matter, as the findings present some caveats. The sample size is rather small to draw immediate conclusions and the results must be replicated on a broader audience. Of course, it's always difficult to involve a lot of people in cannabis studies, a substance which is still illegal at the federal level and notoriously challenging to research despite being virtually legal in over a dozen states.
“It is essential to interpret every study within its limitations,” Prashad noted. “As is standard in our studies, we required participants to be abstinent from cannabis for 24 hours to avoid acute intoxication during the session. Thus, it is unclear whether our results reflect ongoing cannabis use or this short-term abstinence."
Still, the study is significant because it asks a very important question: if this is true for cannabis, what other substances have similar psychoactive effects during resting-state?
The findings appeared in the journal NeuroImage.