Hallucinating mice bring us one step closer to what’s going on in the brain

Enlarge / Dumbo and Timothy Q. Mouse hallucinate pink elephants on parade in a famous animated sequence from Disney's Dumbo (1941). Scientists have imaged neurons of mice under the influence of a hallucinogen for a new study. (credit: YouTube/Disney)

People under the influence of hallucinogenic drugs like LSD often experience vivid visual hallucinations. But exactly what is happening within the brain to induce such a state remains a mystery. According to a new paper in Cell Reports, experiments with mice under the influence of a hallucinogenic drug showed evidence that the hallucinations may be triggered by reduced signaling between neurons in the visual cortex, along with changes in the timing at which they fire.

This might seem counterintuitive, according to co-author Cris Niell, a neuroscientist at the University of Oregon. "You might expect visual hallucinations would result from neurons in the brain firing like crazy or by mismatched signals," he said. "We were surprised to find that a hallucinogenic drug instead led to a reduction of activity in the visual cortex. But in the context of visual processing, it made sense."

In short, the brain may just be over-interpreting a lack of information. When we dream, for instance, there are no visual signals entering the brain, and yet the brain still creates visual patterns.

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