The influence of working memory processes on the selective retrieval of episodic memory contents

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The retrieval of information from episodic memory involves the reactivation of sensory cortical representations that were active during encoding. This mechanism is called ecphory and is an important prerequisite for a conscious recollective experience. Previous studies with neuroimaging techniques such as the electroencephalogram (EEG) have shown that sensory memory content from the encoding phase is cortically reinstated in the first 200 ms of cue-based retrieval. This supports the theory of a largely automatic and unconscious ecphory process. On this basis, it is investigated to what extent cortical reinstatement during episodic memory retrieval is under cognitive or 'top-down' control. Essential for these investigations is the concept of working memory, which enables active short-term storage of sensory information and cognitive control over activated memory contents. The storage and cognitive manipulation of working memory content, like the retrieval of information from episodic memory, entails the activation of the sensory areas involved in encoding of the respective information. Both memory processes are therefore either implemented in a comparable way in sensory cortical areas, or they are based on the same mechanism. The first two experiments of the planned project will therefore investigate the role of working memory in retrieving information from episodic memory. This will be investigated on the basis of experiments in which test participants should memorize certain objects and their position for later retrieval. During the encoding phase, the objects are to be cognitively manipulated within working memory. By comparing the (oscillatory) EEG patterns between the encoding and retrieval phases, it will be examined whether episodic memory retrieval involves the early reactivation of either purely sensory representations or higher-level working memory representations. The third and fourth experiments will investigate the extent to which ecphoric information during memory retrieval is subject to attentional control. After encoding associations between visual objects and spatial positions, these are to be selectively forgotten or remembered based on visual cues. This should require a control process on working memory level. The temporal characteristics of this process can be analyzed by means of the EEG, based on both the measurement of neural oscillations and multivariate decoding techniques.