The research combines the expertise of a chemist, Dr. Joseph Justice, and a biobehavioral scientist, Dr. Darryl Neill, in the study of the relationship between neurochemistry and behavior. A long standing impediment to understanding the brain has been the inability to actually observe the changes that occur in the chemistry of the brain during behavior. To address this problem, the investigators have developed a new methodology for in vivo measurement of the neurotransmitter dopamine. They will continue to develop this sytem and apply it to neurchemical dynamics. Sensors which sample the chemical environment of the brain will be used to observe neurochemistry during behavior. These studies will contribute fundamental knowledge about the relationship between the neurochemisrty of identified neural systems and well characterized behaviors.