The effect of word repetition on evoked magnetic responses in the human brain

Stimulus repetition improves performance on word recognition tasks. We used magnetoencephalography (MEG) to investigate the brain areas associated with this word repetition effect. The participants were eight men and six women. The stimuli were 162 Japanese words each consisting of four katakana letters. The task was to read the words silently and memorize them for a subsequent recognition test. The words were presented one by one and repeated once after eight intervening words. Recordings were taken from bilateral temporal sites of the brain and the responses to the second presentations of the words were compared with those to the first presentations of the same words. Clear magnetic responses were observed in both the left and right hemispheres. In both hemispheres, the responses to the second words were significantly smaller than those to the first words, 250-600 ms after the stimulus onset: Multidipole source analyses showed that the activities were reduced by repetition in the bilateral peri-Sylvian areas, the bilateral medial temporal lobes, and the left angular gyrus.