Gamma oscillations in the human EEG as signature of use-dependent formation and activation of cortical networks related to memory processes

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One of the more fundamental puzzles in neuroscience is how the brain integrates its distributed cortical activities. A powerful associative mechanism was proposed by Hebb (1949), which stated that specific functions of different brain areas are integrated by dynamical binding of ¿cell assemblies¿. This idea has intrigued investigators since its formulation, but the technology to demonstrate its existence had been lacking until the past decade. Recently, human EEG studies on basic perceptual processing have shown that oscillatory brain activity in the garnma band (bigger as 20 Hz) correlates with the activation of such networks. Furthermore, in a series of preliminary studies, we demonstrated that gamma band responses (GBRS) are not only related to basic perception, but reflect different forms of memory. Based on these findings, the present project will examine the hypothesis that GBRs mirror the use-dependent fonnation/activation of large-scale networks related to mnemonic ftmctioning. The dynamics of these networks will be investigated in different memory systems (implicit and explicit memory) and due to multiple retrieval processes (e.g. familiarity versus recollection). In addition, we will impel the development of analysis techniques to uncover cortical (and possibly subcortical) sources of oscillatory brain activity. The outcome of the proposed project will significantly complement contemporary theoretical models of human memory.