Short duration power changes in the EEG during recognition memory for words and faces.

Although memory has been widely studied using event-related potentials, memory-related changes in the electroencephalogram (EEG) have been relatively neglected. The aim of this study was to determine whether evidence could be found for memory-related changes in the EEG. EEG was recorded from a sample of healthy volunteers while they performed word and face recognition memory tasks. Data were analyzed using the method of event-related desynchronization. In the theta frequency range there was a short-duration increase in power that occurred in the first 250 ms that was maximal at temporal sites (T5/T6). For words, but not faces, there was a repetition effect in theta such that new words elicited greater synchronization than old words at the midline frontal electrode (Fz). In the alpha frequency range there was a lateralized repetition effect, which occurred from 750 ms. In upper alpha this effect was lateralized in the expected way with greater desynchronization at temporo-parietal sites on the left for words and on the right for faces. For lower alpha, the lateralization was reversed. The meanings of these findings are interpreted in the light of existing models of recognition memory.