Induced gamma band responses: an early marker of memory encoding and retrieval

Although mnemonic processes have been widely studied using event-related potentials (ERPs), memory-related oscillatory changes in the EEG have been relatively neglected. The aim of this study was to investigate memory encoding- and retrieval-related changes in the frequency domain. In particular, we focused on induced gamma band responses (GBRs), which are a candidate for the establishment and activation of widespread cell assemblies. At encoding, results revealed increased GBRs for subsequently recognised relative to subsequently forgotten items. At retrieval, recognised old stimuli were associated with higher GBRs compared to new stimuli. During encoding and retrieval GBR modulation preceded that of ERPs. Thus, GBRs might be a correlate of processes that onset earlier to those responsible for memory encoding and retrieval ERP effects.