Influences of encoding and retrieval on the steady-state visual evoked potential.

The steady-state visual evoked potential (SSVEP) is a powerful tool to study basic perceptual functions in the human electroencephalogram (EEG) (e.g. selective attention). The present study aimed at finding support for the SSVEP's sensitivity to higher cognitive functions (e.g. memory). We tagged pictures of meaningless objects with 15 Hz within a combined subsequent-memory and recognition-memory design. The EEG was recorded from 128 electrodes. The subsequent-memory design revealed that SSVEPs are influenced by encoding-related processes. In particular, successful encoding was associated with higher SSVEP amplitudes at central-parietal scalp electrodes and reduced activity at left occipital sites. Recognition memory led to higher SSVEP amplitudes at right temporal scalp regions and to an amplitude reduction at midline electrodes. For the first time it was demonstrated that the SSVEP technique is a useful tool to study memory encoding and retrieval. SSVEPs might reflect the ongoing dynamics within an externally driven and widespread task-relevant network. This offers remarkable possibilities for future research on electrophysiological correlates of mnemonic functioning.