Neural signatures of test-potentiated learning in parietal cortex.

Testing, or retrieval practice, is beneficial for long-term memory both directly, by enhancing performance on tested information, and indirectly, by facilitating learning from subsequent encounters with the information. Although a wealth of behavioral research has examined the "testing effect," neuroimaging has provided little insight regarding the potential mechanisms that underlie the benefits of retrieval practice. Here, fMRI was used to examine the effects of retrieval practice on later study trials. Human subjects studied pairs of associated words, which were then tested, restudied, or neither tested nor restudied. All pairs were then studied once more in expectation of a final test. We asked how this Final Study episode was affected by prior history (whether the pair had been previously tested, restudied, or neither). The data revealed striking similarities between responses in lateral parietal cortex in the present study and those in a host of studies explicitly tapping recognition memory processes. Moreover, activity in lateral parietal cortex during Final Study was correlated with a behavioral index of test-potentiated learning. We conclude that retrieval practice may enhance learning by promoting the recruitment of retrieval mechanisms during subsequent study opportunities.