They know what you’re thinking (Image: Brad Wilson/The Image Bank/Getty)

A miniature brain scanner small enough for rats to wear is enabling researchers to watch how the brain influences behaviour for the first time.

Animals usually have to be anaesthetised before they can be scanned, so the “ratCAP” makes it possible to see in real time how sexual, addictive and depressive behaviours affect, and are affected by brain chemistry.

“It means we can watch how the animals behave and observe their brain chemistry at the same time,” says David Schlyer, co-leader of the team that developed the mini-scanner at Brookhaven National Laboratory in Upton, New York.


“We can start to understand the brain chemistry involved in behaviour to a much greater extent than before in rodents,” says Schyler.

The scanner is shaped like an Elizabethan “ruff” and encircles the rat’s head between the eyes and ears, while still allowing the animal to see ahead through the hole in the middle.

Balancing act

Because it weighs about 250 grams, which would be too much for the animals to bear, the researchers have rigged it to a counterbalance which takes the weight while the animal moves around. “It doesn’t feel the weight of the device, although it will feel a little inertia as it moves,” says Schlyer.

As a positron-emission tomography (PET) scanner, the device constantly images the activity of vital brain chemicals such as dopamine and serotonin. “Dopamine is our first choice neurotransmitter to monitor because as a reward chemical it’s associated with addiction and other types of behaviour that we’re studying,” says Schlyer.

The team demonstrated that the scanner gives reliable signals, when the collar registered an expected increase in dopamine activity known to arise after the rats received amphetamines, which increase physical activity.

Schlyer says that though the animals initially found wearing the scanners stressful they did get used to them and happily wore them for 3 to 4 hours without any further signs of stress.

Schlyer says that the scanner could also be fitted to other lab animals such as rabbits or guinea pigs, but they’ve yet to make one small enough to fit on mice.

The team is also hoping to develop wearable scanners for people and monkeys, so they too can move around and engage in activities while their brains are being scanned. “We’re considering this at the moment,” says Schlyer. “It would be something like a football helmet.”

Next, the team is hoping to study sexual interactions between rats, but Schlyer admitted that although the animals showed the expected behaviours and brain chemistry leading up to sex, the devices did appear to inhibit actual mating.

Journal reference: Nature Methods, DOI: 10.1038/nmeth.1582