RT Journal Article
SR Electronic
T1 Dissociable effects of surprising rewards on learning and memory
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 111070
DO 10.1101/111070
A1 N. Rouhani
A1 K. A. Norman
A1 Y. Niv
YR 2017
UL http://biorxiv.org/content/early/2017/02/23/111070.abstract
AB The extent to which rewards deviate from learned expectations is tracked by a signal known as a “reward prediction error”, but it is unclear how this signal interacts with episodic memory. Here, we investigated whether learning in a high-risk environment, with frequent large prediction errors, gives rise to higher fidelity memory traces than learning in a low-risk environment. In Experiment 1, we showed that higher magnitude prediction errors, positive or negative, improved recognition memory for trial-unique items. Participants also increased their learning rate after large prediction errors. In addition, there was an overall higher learning rate in the low-risk environment. Although unsigned prediction errors enhanced memory and increased learning rate, we did not find a relationship between learning rate and memory, suggesting that these two effects were due to separate underlying mechanisms. In Experiment 2, we replicated these results with a longer task that posed stronger memory demands and allowed for more learning. We also showed improved source and sequence memory for high-risk items. In Experiment 3, we controlled for the difficulty of learning in the two risk environments, again replicating the previous results. Moreover, equating the range of prediction errors in the two risk environments revealed that learning in a high-risk context enhanced episodic memory above and beyond the effect of prediction errors to individual items. In summary, our results across three studies showed that (absolute) prediction error magnitude boosted both episodic memory and incremental learning, but the two effects were not correlated, suggesting distinct underlying systems.