Scientific Understanding of Consciousness
Dopamine Signaling Altered by Drugs of Abuse
Science 22 May 2009: Vol. 324. no. 5930, pp. 1080 - 1084
Phasic Firing in Dopaminergic Neurons Is Sufficient for Behavioral Conditioning
Hsing-Chen Tsai,1,2, Feng Zhang,2, Antoine Adamantidis,3 Garret D. Stuber,4 Antonello Bonci,4 Luis de Lecea,3 Karl Deisseroth2,3,
1 Neuroscience Program, W080 Clark Center, 318 Campus Drive West, Stanford University, Stanford, CA 94305, USA.
Natural rewards and drugs of abuse can alter dopamine signaling, and ventral tegmental area (VTA) dopaminergic neurons are known to fire action potentials tonically or phasically under different behavioral conditions. However, without technology to control specific neurons with appropriate temporal precision in freely behaving mammals, the causal role of these action potential patterns in driving behavioral changes has been unclear. We used optogenetic tools to selectively stimulate VTA dopaminergic neuron action potential firing in freely behaving mammals. We found that phasic activation of these neurons was sufficient to drive behavioral conditioning and elicited dopamine transients with magnitudes not achieved by longer, lower-frequency spiking. These results demonstrate that phasic dopaminergic activity is sufficient to mediate mammalian behavioral conditioning.
Dopaminergic (DA) neurons have been suggested to be involved in the cognitive and hedonic underpinnings of motivated behaviors. Changes in the firing pattern of DA neurons between low-frequency tonic activity and phasic bursts of action potentials could encode reward prediction errors and incentive salience. Consistent with the reward prediction-error hypothesis, DA neuron firing activity is depressed by aversive stimuli.
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