Influence of subject-performed tasks on memory in healthy individuals using fMRI study comparison of verbal tasks with subject-performed tasks

The subject-performed tasks (SPT), in which an individual actually performs presented actions while learning, is known to be associated with better recall as compared to verbal learning of action sentences. Such superiority of the SPT or the enactment effect is believed to result from a multimodal encoding process; however, its mechanism still remains unclear. In this study, to examine the neural basis of the SPT effect, brain activation during recognition phase of the task was evaluated using functional magnetic resonance imaging (fMRI). Eight right-handed healthy individuals participated in the study. The participants learned action sentences under two learning conditions, i.e., verbal tasks (VT) and SPT. In VT, the participants orally read and learned the sentences. In SPT, the participants performed each action with an object. The 1.5 T GE SIGNA MRI was used and EPI BOLD images were obtained during the recognition phase. The left retrosplenial cortex activation was observed while the participants were recognizing the verbally learned materials. From this result, the left retrosplenial cortex appeared to be associated with the processing of memory generation. In contrast, the bilateral motor cortex and the left supramarginal gyrus were activated during the recognition phase of materials learned under SPT. The bilateral motor cortex observed in SPT suggests that these regions associated with motor information, presumably with tactile and spatial information, were stronger as a result of SPT, leading to greater activation of the above mentioned motor-related areas during the recognition phase. In addition, we found greater activation of the supramarginal gyrus during recognition of SPT-encoded material compared with VT. Results support the findings by Russ et al, 2003, and such a specific activation pattern for enactment may suggest complex multi-modal associative processing of SPT.