Abstract
The traditional belief is that brain oscillations are important for human long-term memory, because they induce synchronized firing between cell assemblies which shapes synaptic plasticity. Therefore, most prior studies focused on the role of synchronization for episodic memory, as reflected in theta (∼5 Hz) and gamma (>40 Hz) power increases. These studies, however, neglect the role that is played by neural desynchronization, which is usually reflected in power decreases in the alpha and beta frequency band (8–30 Hz). In this paper we present a first idea, derived from information theory that gives a mechanistic explanation of how neural desynchronization aids human memory encoding and retrieval. Thereby we will review current studies investigating the role of alpha and beta power decreases during long-term memory tasks and show that alpha and beta power decreases play an important and active role for human memory. Applying mathematical models of information theory, we demonstrate that neural desynchronization is positively related to the richness of information represented in the brain, thereby enabling encoding and retrieval of long-term memories. This information via desynchronization hypothesis makes several predictions, which can be tested in future experiments.
Highlights
One of the most influential ideas in memory research has been that memories are stored in the synaptic weights of neural assemblies (Hebb, 2002), which are shaped by synchronized activity (Markram et al, 1997)
In this paper we present a first idea, derived from information theory that gives a mechanistic explanation of how neural desynchronization aids human memory encoding and retrieval
The main purpose of this paper is to offer a first, plausible mechanistic explanation for the role of alpha and beta power decreases, which are robustly observed and, call for an explanation
Summary
One of the most influential ideas in memory research has been that memories are stored in the synaptic weights of neural assemblies (Hebb, 2002), which are shaped by synchronized activity (Markram et al, 1997). Thereby, brain oscillations index graded excitatory or inhibitory postsynaptic potentials, which are picked up by EEG/MEG sensors. These synchronous fluctuations between excitation and inhibition have been shown to induce synchronized firing patterns (Lee et al, 2005; Jacobs et al, 2007; Haegens et al, 2011). Several studies using intracranial EEG, surface EEG, and MEG have shown that brain oscillations play a crucial role for long-term memory (see Axmacher et al, 2006; Düzel et al, 2010; Nyhus and Curran, 2010, for recent reviews). The overriding theme in these studies is that increases in synchronized activity in the theta (around 5 Hz) and gamma (>40 Hz) frequency ranges play an important role for memory formation and retrieval via shaping synaptic plasticity and coordinating the reactivation of memories
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