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Is the pot you’re smoking rearranging your brain?

These brain scans above are from a 2005 study that compared the brain activity of 24 chronic marijuana users with that of 19 non-smokers during a series of visual attention tasks. In this study, participants were asked to to mentally track the movement of a ball on a screen as it drifted about, intermingling with other randomly moving balls.

The areas labeled in red correspond to regions of the brain that were less active in the chronic marijuana users than in non-drug users during the motion-tracking task. Interestingly, the majority of these areas correspond to parts of the brain associated with what is called the “visual-attention network,” which, as its name implies, is involved in various attention-requiring tasks. The areas labeled in blue and green, however, are regions outside the brain’s normal attention network where activity was actually higher in pot smokers than in non-drug users. According to the researchers, these altered patterns of brain activation, “suggest neuroadaptation in the attention network due to chronic marijuana exposure.” In other words, they show that heavy pot-smoking is actually associated with a reorganization in the way your brain handles tasks demanding of your attention.

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