What hallucinating mice teach us about psychotic disorders

Schizophrenia is one of the most puzzling psychotic disorders known to man. Not only do people with Schizophrenia not know they have a mental disorder at all, but some of these patients have been known to have abnormal fingerprints, have a weak sense of body ownership, and have a puzzling array of motor disfunction that can appear decades before a diagnosis—all for a disorder that spontaneously appears in the young-adult to adult stage of life.

One of the most serious and debilitating aspects of Schizophrenia is psychosis or the loss sense of reality including visual and auditory hallucinations. If we knew how/why this happens in the brain, we could be equipped to develop treatments for this disease.

However, the problem is: how does one study hallucinations in the brain? To study hallucinations, we have to know if one is occurring which is a difficult task when studying these phenomena in lab animals like mice.

That is, until now.

Earlier this week, ground-breaking research on the neural mechanism of hallucinations was published in Science. I thought the most interesting thing about this research was the clever way they developed to know whether a mouse is hallucinating. They devised a game that both humans and mice could complete—one in which you listen for a tone amongst a bunch of background noise. If you hear a tone, you could click a button (if you’re a human) or put your nose in port for a reward (if you’re a mouse).

A hallucination, according to the researchers, is a false positive event. If you report that you heard a tone, but there wasn’t actually a tone played, then we could conclude that you’re hallucinating or “hearing things.”

The researchers used their new-found sense of mouse hallucinations to discover that excess dopamine in the striatum can be a significant driver of hallucination events. Because these hallucinations could be studied in mice, the researchers were able to manipulate the brain in ways that you could never do safely on humans. For example, if you increased the amount of dopamine in the striatum, the mouse hallucinations increased accordingly.

I think it can be tempting to believe that complex psychiatric disorders are a distinctly human thing and that it’s not even worth looking to the animal kingdom for knowledge on these fronts. But this research shows that it’s still worth trying and I