Functional Magnetic Resonance Imaging (fMRI) Activity in the Hippocampal Region during Recognition Memory

Neuroimaging studies have often failed to observe activity in the hippocampal region during memory retrieval. Recently, two functional magnetic resonance imaging studies reported activity in the hippocampal region associated with recollective success. In both, participants studied pictures of objects and were given a recognition memory test with words that either did or did not name the studied objects. The recognition test was therefore cross-modal or associative in nature. These findings raise the question of what circumstances are required to observe activity in the hippocampal region during memory retrieval. Here, we report that robust hippocampal activity for targets relative to foils occurred during retrieval in a recognition memory task when single words were used at both study and test, as well as when pictures of single nameable objects were used at both study and test. The hippocampal region is involved not just in overtly associative tasks but more broadly in the recollection of recently occurring facts and events.