Feature binding in perceptual priming and in episodic object recognition: evidence from event-related brain potentials

It is argued that explicit remembering is based on so-called episodic tokens binding together all perceptual features of a visual object. In episodic recognition, these features are collectively reactivated. In support of this view, it has been shown that changing sensory features of a stimulus from study to test decreases subject's performance in an episodic recognition task, even though the changed features are irrelevant for the recognition judgment. On the other hand, repetition priming is unaffected by such manipulations of perceptual specificity. Implicit memory performance is therefore thought to depend on structural representations, so-called types, comprising only invariant perceptual features, but no exemplar-specific details. Event-related potentials (ERPs) in our study revealed electrophysiological evidence for the differential involvement of these perceptual memory traces in explicit and implicit memory tasks. Participants attended either a living-nonliving task or an episodic recognition task with visually presented objects. During test both groups of participants processed new objects and old objects, which were repeated either identically or in a mirror-reversed version. In the implicit task ERPs showed an occipitoparietal repetition effect, which was the same for identically repeated items and mirror reversals. In contrast, in the explicit task an early mid-frontal old/new effect for identical but not for mirror-reversed old objects was observed indicating involuntary access to perceptual information during episodic retrieval. A later portion of the old/new effect solely differentiated both types of old items from new ones.