Enactment effect in memory: evidence concerning the function of the supramarginal gyrus

Experimental behavioral data show that written action descriptions are remembered better when encoded by enacting them compared with merely verbal encoding. To explore this facilitating effect of encoding by performing actions ('enactment effect'), a functional magnetic resonance imaging (fMRI) study was conducted with n=18 normal subjects. During a learning condition, subjects encoded action phrases like 'cut the bread' either by reading aloud or by enacting them. The same phrases plus additional distractors were presented during fMRI scanning, and the task was to decide (yes/no key press) whether a displayed phrase was previously learned or whether it was a new one. Retrieval--independent of encoding type--activated anterior cingulate, SMA, and visual cortex bilaterally. Activations of the inferior frontal and sensorimotor cortex, and the precentral sulcus, were only left sided. The right cerebellum was also activated. The subtraction of the brain activations in the verbal condition from the enactment condition resulted in significant clusters located in middle temporal and inferior parietal left cortical areas, and, on the right side, in superior temporal, postcentral and inferior parietal cortical areas. Most striking were the bilateral inferior parietal activations, covering the supramarginal gyrus (SMG). Therefore it is concluded that SMG may be a central structure in a neurofunctional explanation of the enactment effect.