Rutgers-Newark Researchers Link Individual Preferences To Neuronal Activity In Brain

In the article, "Preference for cocaine-versus pup-associated cuesdifferentially activates neurons expressing either Fos or CART inlactating, maternal rodents," which is in press for the September 2005volume of the journal Neuroscience (the article currently appearsonline at www.sciencedirect.com)Rutgers-Newark neuroscience professor Joan Morrell and her colleagueBrandi Mattson reveal that individual preferences can be linked to theactivation of specific sets of neurons within the brain. Theresearchers used postpartum rats in order to establish preferences andanalyze how the mother rats' brains functioned when they selected anenvironment associated with their pups or another environmentassociated with the drug cocaine. In the experiment, rats learned overfour days in which distinct environments they had access to their pupsversus where they had access to cocaine. Following a 24-hour wait, therats were given the opportunity to choose either the environment wherethey anticipated they would find either their pups or where they wouldfind cocaine.

Using a computer program, the researchers recorded the rats'time and activity in each chamber as a means of determining theirpreferences for pups or cocaine. Then, the researchers analyzed andrecorded the rats' brain activity at the time of their environmentalchoice.

According to Dr. Morrell, the analysis revealed clear patternsof neuronal activity when the rats made their choices and showed thatspecific brain regions were active when the animals were making onechoice (pup-associated environment) in favor of another one(drug-associated environment). The researchers determined this bytracking the presence of proteins that demonstrate the activity ofneurons within the brain.

"This approach provides a snapshot of what was going on in thebrain at decision time, which is preferred pups or cocaine," Dr.Morrell notes. "The different brain regions are arranged in a circuit,with some regions more active or less active depending on what therat's preference is. Understanding what is going on in the brain atdecision time is crucial since preference for the environment relatedto her pups is likely to lead to pup care by the mother rat whilepreference for the environment related to cocaine is likely to lead topup neglect."

These findings may be significant because they establish a linkbetween individual preferences and innate brain activity, but Dr.Morrell cautioned that it would be a leap to use these results toprovide a model for the higher cognitive processes such as criticalthinking and belief systems that humans possess."

"However, my results do demonstrate the general principles ofhow the nervous system mediates such important decisions and theseprinciples apply in the nervous system of all mammals includinghumans," Dr. Morrell explains. "With this approach we can determine theground rules for the function of the mammalian brain in such decisions."