"Rats wearing the device appear to adapt well and move freely about their environment," Woody said.
To validate the use of the wearable scanner for simultaneous studies of brain function and behavior, the scientists conducted tests with 11C-raclopride, a commonly used PET radiotracer, which incorporates a radioactive, positron-emitting isotope of the element carbon. When the positrons interact with electrons in ordinary matter, they immediately annihilate one another, emitting back-to-back gamma rays. Detectors in the circular PET scanner pick up the signals from these back-to-back gamma rays to identify the location and concentration of the tracer in the body.
The tracer 11C-raclopride binds to receptors for dopamine, a brain chemical involved in movement, reward, and memory formation. A higher signal from the tracer means that less natural dopamine is in that particular part of the brain; a low signal indicates that that particular part of the brain has released dopamine (which binds to its receptors, thus blocking the tracer from binding).
The main test was to see if the wearable scanner could be used to correlate dopamine levels with behavior - in this case, the rats' activity (i.e., movement) within their chambers. Surprisingly the level of activity was inversely related to dopamine levels - that is, the more active the animals were, the lower the level of dopamine (as indicated by a stronger tracer signal).
"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 and lead author of the paper. "So our method provides data which may challenge traditional paradigms and ultimately improve our understanding of the dopamine system."
"But regardless of the direction, the results clearly demonstrate that RatCAP can correlate brain function meas
|Contact: Karen McNulty Walsh|
DOE/Brookhaven National Laboratory