Theta and Gamma Oscillations Predict Encoding and Retrieval of Declarative Memory

• DOI: 10.1523/jneurosci.1948-06.2006
• Publication Date: 2006-07-12T19:24:54Z
• Authors: Daria Osipova; Atsuko Takashima; Robert Oostenveld; Guillén Fernández; Eric Maris; Ole Jensen
• Keywords: Adult; Male; 160 006 Oscillations and cognitive functions; DCN 2: Functional Neurogenomics; Memory; 130 000 Cognitive Neurology & Memory; DCN 3: Neuroinformatics; Humans; 0501 psychology and cognitive sciences; UMCN 3.2: Cognitive neurosciences; Brain Mapping; 120 000 Neuronal Coherence; 05 social sciences; Brain; Magnetoencephalography; 160 000 Neuronal Oscillations; Cognitive neuroscience; Recognition, Psychology; 3. Good health; Mental Recall; 160 003 Integrated investigation in memory consilidation; Visual Perception; Female; 120 004 Integrating distributed brain processes; Photic Stimulation

Although studies in animals and patients have demonstrated that brain oscillations play a role in declarative memory encoding and retrieval, little has been done to investigate the temporal dynamics and sources of brain activity in healthy human subjects performing such tasks. In a magnetoencephalography study using pictorial stimuli, we have now identified oscillatory activity in the gamma (60–90 Hz) and theta (4.5–8.5 Hz) band during declarative memory operations in healthy participants. Both theta and gamma activity was stronger for the later remembered compared with the later forgotten items (the “subsequent memory effect”). In the retrieval session, theta and gamma activity was stronger for recognized items compared with correctly rejected new items (the “old/new effect”). The gamma activity was also stronger for recognized compared with forgotten old items (the “recognition effect”). The effects in the theta band were observed over right parietotemporal areas, whereas the sources of the effects in the gamma band were identified in Brodmann area 18/19. We propose that the theta activity is directly engaged in mnemonic operations. The increase in neuronal synchronization in the gamma band in occipital areas may result in a stronger drive to subsequent areas, thus facilitating both memory encoding and retrieval. Alternatively, the gamma synchronization might reflect representations being reinforced by top-down activity from higher-level memory areas. Our results provide additional insight on human declarative memory operations and oscillatory brain activity that complements previous electrophysiological and brain imaging studies.