Scientists have been poking around in mice brains a lot recently. They’ve found that they have dreams, and that those dreams can be manipulated.
Research (paywall) by scientists at the Industrial Physics and Chemistry Higher Educational Institution in Paris has shown that scientists can influence mouse dreams, in a way reminiscent of the 2010 science fiction movie Inception. Researchers placed electrodes into a part of the mouse brain called the hippocampus, which contains cells that send electrical signals in specific places (hence their name, place cells). After monitoring mice in a specific arena, scientists were able to locate specific cells that fired in specific locations.
As the mice were sleeping, the electrodes illustrated that place cells in mice were still firing, as they dreamed about particular places. As these place cells sent out signals, the researchers used the electrodes to send a reward signal to a different part of the mice brains. Essentially, they created a positive association with that a particular place, while the mice slept. Later, when the mice woke, they went directly toward the place that had been associated with the reward signal in their dreams.
“It proves that it’s not an automatic behavior. What we create is an association between a particular place and a reward that can be consciously accessed by the mouse,” Karim Benchenane, one of the authors of the study, told the New Scientist.
Similar studies have been done to show that rats may also plan future trips while they sleep. Researchers from University College London put electrodes in four different rats’ brains, monitoring their place cells, as they navigated a T-shaped space. In one of the arms of the T, researchers placed food that the rats could see, but couldn’t access.
Then, with the electrodes still in their brains, the rats took a nap. Researchers continued to monitor their place cell activity, and saw new patterns in the ways the cells send out signals. When the rats woke up, researchers placed them back in the T-shaped apparatus and removed both the food and the barrier to the food. The rats explored the new area, and scientists saw the same patterns of firing cells that they did when the rats were asleep, as if they had planned the trip while resting.
There are a few important caveats to this rodent dream research: First, in the second study, it’s difficult to say whether these animals were actually sleeping; they could have been just resting and thinking about where they wanted to go next. And it’s hard to say whether rodents’ brains mimic our own when we sleep. To monitor place cell activity in humans, electrodes need to be placed directly on the brain, which researchers can’t do in people because it’s too invasive.
Scientists from the University of California-Davis have shown that people have place cells, though, by looking at the neurological activity of epilepsy patients undergoing seizure monitoring. So perhaps “inception” isn’t so far off.