Pinging the brain with visual impulses reveals electrically active, not activity-silent, working memories

Area of Science:

• Cognitive Neuroscience
• Neuroscience
• Neurophysiology

Background:

• Working memory is traditionally thought to depend on persistent neuronal activity.
• An alternative hypothesis proposes "activity-silent" working memory, where memories are stored in synaptic changes.
• This "activity-silent" model suggests memories can be reactivated from dormant synaptic traces.

Purpose of the Study:

• To reanalyze electroencephalography (EEG) data from studies investigating "activity-silent" memory reactivation.
• To re-evaluate the evidence for "activity-silent" working memory storage based on EEG "pinging" studies.
• To reinterpret the mechanisms underlying EEG reactivations observed during memory recall.

Main Methods:

• Reanalysis of existing human electroencephalography (EEG) data from "pinging" studies.
• Application of more statistically powered analyses to the EEG data.
• Comparison of decoding based on alpha power versus raw voltage in EEG signals.

Main Results:

• The absence of memory decoding in previous studies was attributed to weak statistical power.
• Reanalysis revealed that memory decoding is possible with increased statistical power and by using alpha power.
• Visual "pinging" induces EEG "reactivations" in the presence of an electrically active code, not a silent one.

Conclusions:

• The findings challenge the "activity-silent" model for unattended memory storage in the analyzed EEG data.
• EEG "reactivations" likely reflect processes within an electrically active neural code, not dormant synaptic traces.
• The study prompts a reinterpretation of working memory mechanisms, supported by computational models and discussion of TMS-induced reactivations.