Top-down inhibitory influence on memory by posterior alpha oscillation: An MEG study

Abstract

In our daily lives, we are confronted with large amount of information. Since only a small fraction can be encoded in long-term memory, the brain must rely on powerful mechanisms to filter out the irrelevant information. To understand the neuronal mechanisms underlying the gating of information into long-term memory, I employed a memory paradigm where the encoding of pictorial stimuli was directed by a Remember or a No-Remember cue. I found that posterior alpha activity increased prior to the presentation of the irrelevant No-Remember stimuli, whereas it decreased prior to the Remember stimuli. Subjects with a larger cue-modulation of posterior alpha activity had better memory for the relevant items. The sources of the alpha activity were localized in the posterior parietal cortex included in the dorsal attention network. The individual ability to control posterior alpha activity was predictive of memory performance. During the presentation of the memory items, there was more gamma activity for the Remember compared to the No-Remember stimuli in the same regions. Importantly, the anticipatory alpha power modulation during the cue interval predicted the gamma power during item presentation. These findings suggest that top-down controlled alpha activity in the posterior dorsal attention network serves to gate sensory information to long-term memory. This gating is achieved by inhibiting the processing of visual information reflected by neuronal synchronization in the gamma band. In conclusion, the functional architecture reflected by alpha band activity reflects modulations in attention which has consequences for long-term memory encoding.