RT Journal
A1 Okada, Ken-ichi
A1 Toyama, Keisuke
A1 Inoue, Yuka
A1 Isa, Tadashi
A1 Kobayashi, Yasushi
T1 Different Pedunculopontine Tegmental Neurons Signal Predicted and Actual Task Rewards
JF The Journal of Neuroscience 
JO The Journal of Neuroscience 
YR 2009 
FD April 15 
VO 29 
IS 15 
SP 4858 
OP 4870 
DO 10.1523/JNEUROSCI.4415-08.2009 
UL http://www.jneurosci.org/content/29/15/4858.abstract 
AB The dopamine system has been implicated in guiding behavior based on rewards. The pedunculopontine tegmental nucleus (PPTN) of the brainstem receives afferent inputs from reward-related structures, including the cerebral cortices and the basal ganglia, and in turn provides strong excitatory projections to dopamine neurons. This anatomical evidence predicts that PPTN neurons may carry reward information. To elucidate the functional role of the PPTN in reward-seeking behavior, we recorded single PPTN neurons while monkeys performed a visually guided saccade task in which the predicted reward value was informed by the shape of the fixation target. Two distinct groups of neurons, fixation target (FT) and reward delivery (RD) neurons, carried reward information. The activity of FT neurons persisted between FT onset and reward delivery, with the level of activity associated with the magnitude of the expected reward. RD neurons discharged phasically after reward delivery, with the levels of activity associated with the actual reward. These results suggest that separate populations of PPTN neurons signal predicted and actual reward values, both of which are necessary for the computation of reward prediction error as represented by dopamine neurons.