Scientists from the US Department of Energy's (DOE) Brookhaven National Laboratory have developed a new miniature, wearable Positron Emission Tomography (PET) scanner which enables the simultaneous study of brain function and behavior in animals. PET scans are much like Computed Tomography (CT) scans and have helped uncover the molecular underpinnings of conditions like drug addiction, brain diseases such as dementia and they have been used in the medical imaging of cancers.
"Positron Emission Tomography is a powerful tool for studying the molecular processes that occur in the brain" said Paul Vaska, head of PET physics at Brookhaven and leader of the development of the portable scanner. In the past, studying animals with PET scanners has required them to be immobilized by general anesthesia or other methods. Immobilizing the animals has made it impossible to study movements along with images of their neurochemistry. For the first time, it is possible to link actions with PET images of the brain.
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Called the RatCAP, for Rat Conscious Animal PET, it is a donut shaped device worn as a collar on a rat's head. Weighing 250 grams, it is counterbalanced by a system of springs and motion stabilizers to allow freedom of movement. As with other PET techniques, a rat is injected with a radioactive tracer which the RatCAP detectors can measure the concentration of and its location.
Researchers conducted a test to measure dopamine levels in rats, the brain chemical involved in movement, reward and memory formation. The RatCAP test revealed that the more active rats were the lower the level of dopamine, a conclusion which surprised the team.
"This is perhaps a counterintuitive result because behavioral activation is typically associated with an increase in dopamine release," said Daniela Schulz, a Brookhaven behavioral neuroscientist. "So our method provides data which may challenge traditional paradigms and ultimately improve our understanding of the dopamine system."