The involvement of the striatum in numerous forms of learning and memory is likely to be based on changes in neuronal activity when specific behavioral tasks are being learned. Striatal neurons show distinctive changes when animals learn the significance of stimuli that predict rewards and induce the preparation of movements. These changes resemble some of the simultaneous, learning-related changes in closely associated areas of the frontal cortex. The striatal changes might assist in adapting existing reward expectations and behaviors to novel or changing environmental conditions and they could contribute to the functions of the basal ganglia in learning, reward expectation and movement preparation.