Phasic activations of neurophysiological impulse activity of dopamine neurons. A: Phasic activations following primary rewards. B: Phasic activations following conditioned, reward predicting stimuli. C: Top: Lack of phasic activation following primary aversive air puff. Bottom: substantial activating population response following conditioned aversive stimuli when stimulus generalization by appetitive stimuli is not ruled out; grey: population response to conditioned visual aversive stimulus when appetitive stimulus is also visual; black: lack of population response to conditioned visual aversive stimulus when appetitive stimulus is auditory. D: Phasic activations following physically intense stimuli. These activations are modulated by the novelty of the stimuli but do not occur to novelty per se. E: Left: Shorter and smaller activations followed frequently by depressions induced by unrewarded control stimuli (black) compared to responses following reward predicting stimuli (grey). Right: Activations to delay predicting stimuli show initial, poorly graded activation component (left of line) and subsequent, graded value component inversely reflecting increasing delays (curves from top to bottom). Time scale (500 ms) applies to all panels A-E. Data from previous work [29, 31–33, 43, 59].