Towards a physiological explanation of behavioral data on human short-term memory: The role of theta-gamma oscillations

Psychological studies have suggested that there is both a short-term, limited-capacity (similar to 7 digits) memory buffer and a much larger long-term memory store. The psychological and physiological data for and against the idea of a separate multi-item STM store is reviewed. Recent theoretical work has postulated that an STM is organized by known brain oscillations in the theta and gamma range. The serial activation of memories in sequential gamma cycles is related to ideas that emerged from the Sternberg memory recognition test. Furthermore, network simulations reveal that known neural mechanism could produce a multiplexing STM buffer capable of actively holding similar to 7 memories. Recent work has attempted to study the role of brain oscillations in humans using subdural electrode arrays in epileptic patients. This work has demonstrated the existence of large-amplitude theta oscillations in the temporal lobe. Preliminary work indicates a close involvement of theta oscillations in the Sternberg STM task.