EEG power changes reflect distinct mechanisms during long-term memory retrieval

Authors


  • This work was supported by Grant FOR254/2 and Grant KH235/1-1 of the German Research Foundation (DFG). We thank Kerstin Jost for valuable discussions and Stefan Debener, as well as two anonymous reviewers, for helpful comments on the manuscript.

Address correspondence to: Dr. Patrick H. Khader, Department of Psychology, Philipps-University, 35032 Marburg, Germany. E-mail: Khader@staff.uni-marburg.de

Abstract

The roles of theta and alpha oscillations for long-term memory (LTM) retrieval are still under debate. Both are modulated by LTM retrieval demands, but it is unclear what specific LTM functions they are related to. Here, different oscillatory correlates of LTM retrieval could be obtained for theta and alpha with a paradigm that is suited to monitor the activation of a varying number of material-specific LTM representations. Both frequency bands responded parametrically to the number of retrieved items. However, only the alpha effect dissociated topographically for material type, indicating that the activation of material-specific representations became systematically modulated. For theta, this effect was material-unspecific with mid-frontal topography. These results suggest that alpha is functionally related to the activation of stored information, whereas theta is a sign of retrieval-related control processes.

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