From uncertainty to reward: BOLD characteristics differentiate signaling pathways.
BACKGROUND
Reward value and uncertainty are represented by dopamine neurons in monkeys by distinct phasic and tonic firing rates. Knowledge about the underlying differential dopaminergic pathways is crucial for a better understanding of dopamine-related processes. Using functional magnetic resonance blood-oxygen level dependent (BOLD) imaging we analyzed brain activation in 15 healthy, male subjects performing a gambling task, upon expectation of potential monetary rewards at different reward values and levels of uncertainty.


RESULTS
Consistent with previous studies, ventral striatal activation was related to both reward magnitudes and values. Activation in medial and lateral orbitofrontal brain areas was best predicted by reward uncertainty. Moreover, late BOLD responses relative to trial onset were due to expectation of different reward values and likely to represent phasic dopaminergic signaling. Early BOLD responses were due to different levels of reward uncertainty and likely to represent tonic dopaminergic signals.


CONCLUSIONS
We conclude that differential dopaminergic signaling as revealed in animal studies is not only represented locally by involvement of distinct brain regions but also by distinct BOLD signal characteristics.
Abler
Birgit
B
Department of Psychiatry, University of Ulm, Leimgrubenweg 12-14, 89075 Ulm, Germany. birgit.abler@uni-ulm.de
Herrnberger
Bärbel
B
Grön
Georg
G
Spitzer
Manfred
M
D000328:Adult; D001479:Basal Ganglia / Q000502:physiology*; D003463:Cues; D004298:Dopamine / Q000378:metabolism; D005715:Gambling; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D015233:Models, Statistical; D009474:Neurons / Q000378:metabolism; D010100:Oxygen / Q000097:blood*; D011336:Probability; D011930:Reaction Time; D012016:Reference Values; D012201:Reward; D015398:Signal Transduction; D035501:Uncertainty; D055815:Young Adult
D010100:Oxygen; D004298:Dopamine