Research focus can be generally described as the influence of behavioral and environmental factors on pharmacologic action of psychostimulants like cocaine. Various rodent models of stimulant action that correlate with abuse liability are used, including locomotor activity, conditioned place preference, acoustic startle, and prepulse inhibition of startle. Effects of stimulant drugs on behavioral processes such as learning (both habituation and conditioning), as well as the effects of behavioral processes on stimulant drug actions are studied. Emphasis is on acute and chronic effects of cocaine but other abused stimulants are studied for comparative purposes. Drug interactions are of particular interest, both for investigating neuropharmacologic mechanisms and with regard to medications development. In addition to the study of behavior, experimental approaches usually integrate several levels of analyses. For example, cocaine conditioned behavioral effects are correlated with endocrine and neurochemical changes. Neuroanatomical loci of these drug-behavior interactions are characterized using neural activity related measures such as immediate early gene expression.