Lifting Brain Fog

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T cell. Wellcome Institute.

Ten years ago, Jonathan Kipnis decided to run an experiment to see how well mice can learn new things. He suspected that the immune system was important to cognition, and so he wanted to compare mice with normal immune systems to mice with deficient ones. Kipnis engineered mice that lacked T cells, a type of white blood cell that fights pathogens. At the time, Kipnis was getting his Ph.D. at the Weizman Institute in Israel, and the lab he was working in didn’t have the equipment necessary for the test. So he shipped off his mice–a group of normal ones and a group lacking T cells–to Ben-Gurion University. There, his colleague Hagit Cohen put the mice through their paces.

Cohen gave the mice a task known as the Morris water maze. She put them in a pool of water, where they started to swim frantically. Just under the surface of the water there was a hidden stand. If the mice could find the stand, they could climb onto it and stop their desperate swimming. Over several rounds, the mice learned where the stand was hidden and swam straight for it.

Once she had tested the animals, Cohen gave Kipnis a call. “She said, ‘One of the groups of the mice you sent me are real idiots. I’ve never seen such idiotic mice,’” Kipnis told me when I talked to him about his research.

The idiot mice were the ones without a T cell between them.

Kipnis, who is now at the University of Virginia, has spent the past decade following up on his discovery, exploring the potential influence of the immune system on the brain. It may help to explain all sorts of puzzles, such as why getting sick can put our minds in a fog. His work is the subject of my column in the latest issue of Discover. This piece is my final one as a Discover columnist, and I’m particularly happy to end with such intriguing research, which encourages us to understand the brain by looking beyond it. Check it out.