Strategic search and retrieval inhibition: the role of the frontal lobes

Recall of words from categorised lists was examined in 77 patients and 12 normal control subjects. In Experiment 1, both left temporal-lobe excisions that included the hippocampus (LTH) and left frontal-lobe removals (LF) impaired free recall, but the LF group performed normally when encoding and retrieval strategies were supplied. In Experiment 2, experimentally induced interference during cued recall abnormally hampered performance for the LF, but not for the LTH group. Subsequent removal of the interfering cues resulted in improved performance for the LF group. Thus, the integrity of the left frontal lobe seems indispensable for normal strategic retrieval and for the suppression of potentially interfering items in verbal memory.