Feedback signals in the caudate reflect goal achievement on a declarative memory task

The striatum has been shown to be a key region in the processing of reward-related information. The head of the caudate nucleus has been implicated in processing performance feedback, or in other words, information about the outcomes of one's actions. However, feedback provides multiple types of information, and it is not clear which of these types of information drive a caudate response. We sought to determine whether the signal in the caudate differed when feedback was informative but only arbitrarily related to performance versus when it provided information about goal achievement. To do this, we used functional magnetic resonance imaging (fMRI) to examine caudate activation during a feedback-based paired associate word-learning task. During an initial round of 60 distinct trials, participants chose one of two responses on each trial and received feedback about whether their responses were correct. On the subsequent two rounds, the 60 trials were repeated and participants chose their responses based on their memory of the correct answer. The caudate nuclei were strongly engaged only during the second two rounds, when feedback reflected the accuracy of memory. These results support the idea that feedback-based caudate activation is context dependent: the caudate can be engaged in feedback-based declarative memory tasks, but it is more strongly engaged when feedback is earned by performance than when it is informative but not tied to goal achievement. (C) 2008 Elsevier Inc. All rights reserved.