In a new study published in the scientific journal Drug and Alcohol Dependence, researchers led by the University of Minnesota found that moderate alcohol consumption scrambles and hinders brain-wide communication, keeping signals localized to specific brain regions, thus making your brain less efficient, which your failed sobriety test proved undeniably.
The team recruited 107 healthy adults between 21 and 45. In two separate sessions, participants were given either a placebo or enough alcohol to reach the U.S. legal driving limit of 0.08 blood-alcohol concentration. About 30 minutes later, they underwent MRI scans measuring communication across 106 brain regions.
The team found that alcohol increased “local efficiency” and clustering, meaning nearby brain regions communicated more tightly with each other while decreasing “global efficiency,” or long-range communication across the brain. To put it in a stupid but easy-to-understand kind of way, brains soaked in alcohol were running in small circles, while sober brains can run across a city without breaking a sweat.
Those network changes tracked closely with how drunk people felt. Even though participants reached similar blood-alcohol levels, those whose brains showed greater global disconnection reported feeling more intoxicated. The findings may help explain why two people with the same breathalyzer reading can experience different levels of impairment.
Let’s Scan the Brain During a Drunken Brawl Next
Certain regions were particularly affected. The occipital lobe is responsible for processing visual information. Researchers found that it had reduced global connectivity, offering a potential explanation for why a few drinks blur your vision and turn you into an uncoordinated mess.
The scans were taken while participants were at rest, so the study doesn’t capture how alcohol affects the brain during active tasks like going streaking or getting into a barroom brawl. It also doesn’t address how alcohol affects brain communication over the long term. The researchers also note that people with chronic alcohol use disorders could potentially have more disorganized patterns of brain connectivity, but more research is needed before anything like that can be definitively claimed.
So, if you’ve ever had a few drinks and felt your brain slowing, there’s a chance that your brain’s architecture is temporarily forgetting how to communicate with itself.
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