A classic finding of the psychology of memory is the “serial position effect.” Immediate free recall of a word list is more efficient for items presented early (primacy effect) or late (recency effect), with respect to those in the middle. In an event-related, randomized block design, we interfered with the encoding of unrelated words lists with brief trains of repetitive TMS (rTMS), applied coincidently with the acoustic presentation of each word to the left dorsolateral pFC, the left intraparietal lobe, and a control site (vertex). Interference of rTMS with encoding produced a clear-cut double dissociation on accuracy during immediate free recall. The primacy effect was selectively worsened by rTMS of the dorsolateral pFC, whereas recency was selectively worsened by rTMS of the intraparietal lobe. These results are in agreement with the double dissociation between short-term and long-term memory observed in neuropsychological patients and provide direct evidence of distinct cortical mechanisms of encoding in the human brain.

Observing actions made by others activates the cortical circuits responsible for the planning and execution of those same actions. This observation–execution matching system (mirror-neuron system) is thought to play an important role in the understanding of actions made by others. In an fMRI experiment, we tested whether this system also becomes active during the processing of action-related sentences. Participants listened to sentences describing actions performed with the mouth, the hand, or the leg. Abstract sentences of comparable syntactic structure were used as control stimuli. The results showed that listening to action-related sentences activates a left fronto-parieto-temporal network that includes the pars opercularis of the inferior frontal gyrus (Broca's area), those sectors of the premotor cortex where the actions described are motorically coded, as well as the inferior parietal lobule, the intraparietal sulcus, and the posterior middle temporal gyrus. These data provide the first direct evidence that listening to sentences that describe actions engages the visuomotor circuits which subserve action execution and observation.

Long-term, episodic memory processing is supposed to involve the prefrontal cortex asymmetrically. Here we investigate the role of the dorsolateral prefrontal cortex (DLPFC) in encoding and retrieval of semantically related or unrelated word pairs. Subjects were required to perform a task consisting of two parts: a study phase (encoding), in which word pairs were presented, and a test phase (retrieval), during which stimuli previously presented had to be recognized among other stimuli. Consistently with our previous findings using pictures, repetitive transcranial magnetic stimulation (rTMS) had a significant impact on episodic memory. The performance was significantly disrupted when rTMS was applied to the left or right DLPFC during encoding, and to the right DLPFC in retrieval, but only for unrelated word pairs. These results indicate that the nature of the material to be remembered interacts with the encoding–retrieval DLPFC asymmetry; moreover, the crucial role of DLPFC is evident only for novel stimuli.