Authors:

COX, S.M.L., Andrade, A., CUSACK, R., Russell, B. & JOHNSRUDE, I.S.

Reference:

Year of publication:

2003

CBU number:

5665

Abstract:

Introduction:Recent work in humans has shown that neutral visual stimuli can acquire affective significance through association with rewarding events. Although the brain bases of reward and of aversive conditioning have been examined in humans, little is known about the brain bases of reward conditioning2,3. Structures including the nucleus accumbens (ventral striatum), ventromedial prefrontal cortex (including the orbitofrontal cortex) and amygdala have shown to be involved in response to the presentation and/or anticipation of rewarding events 4,5,6. Here we use event-related fMRI to study the acquisition and expression of monetary reward conditioning in humans. Methods:Using a Bruker 3T scanner and whole-brain continuous imaging, we scanned 22 volunteers in two contiguous sessions. In the first, neutral visual stimuli were incidentally associated with reward or punishment in the context of a simple card game. In the following session, the conditioned stimuli were presented alone and the affective valence of these stimuli was assessed behaviourally. Finally, subjects were debriefed outside the scanner with respect to their preferences and their awareness of the stimulus-reward contingencies. Results:Participants showed a significant preference for the (previously neutral) stimulus associated with reward compared to either the stimulus paired with punishment, or to novel stimuli. The fMRI data reveal distinct patterns of neural responses following the presentation of reward compared to punishment; for example, the ventral striatum and ventro-medial prefrontal cortex (VMPFC) were active during the presentation of reward. Furthermore, activation in the VMPFC was observed during the second stage of the task when subjects passively viewed the conditioned stimulus that had been paired with reward, without the administration of an immediate reward and without subjects being aware of the conditioning manipulation. Conclusion:Our results suggest that the ventral striatum and the VMPFC are both involved in the processing of direct reward presentations, whereas the VMPFC is also involved in the representation of a rewarding value of a conditioned stimulus. References:1. Johnsrude, I. S., Owen, A. M., Zhao, W. V., & White, N. M. (1999). Conditioned preference in humans: a novel experimental approach. Learning and Motivation, 30, 250-264. 2. Johnsrude, I. S., Owen, A. M., White, N. M., Zhao, W. V., & Bohbot, V. (2000). Impaired preference conditioning after anterior temporal lobe resection in humans. J Neurosci, 20(7), 2649-2656. 3. Gottfried, J. A., O'Doherty, J., & Dolan, R. J. (2002). Appetitive and aversive olfactory learning in humans studied using event-related functional magnetic resonance imaging. J Neurosci, 22(24), 10829-10837. 4. O'Doherty, J., Kringelbach, M. L., Rolls, E. T., Hornak, J., & Andrews, C. (2001). Abstract reward and punishment representations in the human orbitofrontal cortex. Nat Neurosci, 4(1), 95-102. 5. Knutson, B., Adams, C. M., Fong, G. W., & Hommer, D. (2001). Anticipation of increasing monetary reward selectively recruits nucleus accumbens. J Neurosci, 21(16), RC159. 6. Delgado, M. R., Nystrom, L. E., Fissell, C., Noll, D. C., & Fiez, J. A. (2000). Tracking the hemodynamic responses to reward and punishment in the striatum. J Neurophysiol, 84(6), 3072-3077.