The interplay between theta and alpha oscillations in the human electroencephalogram reflects the transfer of information between memory systems

The exchange of information between the working and long-term memory system (WMS and LTMS) was investigated. We analyzed evoked theta and upper alpha desynchronization in a special memory task, designed to study the transfer of information between both memory systems. The results show that during attempts to retrieve information from the LTMS, evoked theta oscillations spread from anterior to posterior recording sites. When information actually is retrieved, the direction reverses and theta spreads to frontal sites. This time point—when direction reverses—varies between subjects to a large extent but is significantly correlated with memory performance and the onset of upper alpha desynchronization. We conclude that this phenomenon reflects the transfer of information between the WMS and LTMS