Memory entrainment by visually evoked theta-gamma coupling in the human brain

The formation of novel memories is orchestrated by the rhythmic interplay of neuronal activity within and across cell assemblies. Critically, given the correlative nature of neurophysiological recordings, the functional role of neuronal rhythms in the human brain is still unclear. Here, episodic memory encoding was entrained by a rhythmic visual stimulation at an individually adjusted theta frequency (3-8Hz), in contrast to the stimulation at an individual alpha frequency (8-12Hz). Memory enhancing effects of the theta stimulation were not explained by theta power per se, but were driven by theta coupled gamma oscillations (40-120Hz) in wide spread neocortical networks. These findings provide first evidence for a functional role of the theta-gamma neuronal code in human episodic memory. The entrainment of mnemonic network mechanisms by a simplistic visual stimulation technique demonstrates that internal rhythms can align with external pacemakers, which can entrain complex cognitive functions in the wake human brain.

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