The primary function of the nervous system is to produce behavior. Behaviors promote survival, but in some instances, alterations within the nervous system have deleterious effects; schizophrenia and Parkinson's disease are examples. Behavioral neuroscientists study the effects of genetics, the environment and their interaction with behavior. The goals are to discover the important physiological, neurochemical and molecular factors that govern behavior, and to provide insight into the treatment of behavioral disorders. Methods include the use of inbred mice strains to locate and identify genes controlling behavioral phenotypes, molecular genetics to measure changes in gene expression correlated to behavioral changes, extracellular electrical recording in vivo, in situ and in vitro analysis of neurotransmitter turnover, histochemical localization of neurotransmitters and their receptors, brain imaging techniques, and cognitive testing of specific human populations.