The FN400 is functionally distinct from the N400.
ABSTRACT The FN400 refers to the early midfrontally-distributed difference between ERPs elicited by old and new items, which operates in a way consistent with a neural marker of familiarity-based recognition. Double dissociations between the FN400 and a later ERP index of recollection provide some of the most compelling evidence in support of dual-process models to date. It has recently been claimed, however, that there is no evidence that the FN400 is functionally distinct from the N400 index of implicit semantic priming (Voss, J., and Federmeier, K., FN400 potentials are functionally identical to N400 potentials and reflect semantic processing during recognition testing, Psychophysiology, 48, 532-546, 2011), challenging inferences made on the basis of this effect. We argue that the design employed to make this claim is flawed because it comprised a semantic priming manipulation embedded within a continuous recognition test which enabled recognition contrasts to be confounded by semantic processes in a number of ways. Here, ERPs were recorded from a design which avoided these confounds by employing a semantic priming paradigm which also served as the encoding phase for a surprise subsequent recognition test phase. An N400 effect elicited in the semantic priming task demonstrated the established centro-parietal maximum, whereas the difference between correctly responded to old and new ERPs in the recognition test was maximal over frontal sites in the same time window. When direct comparisons of the electrophysiological correlates of semantic priming and episodic recognition are recorded in a paradigm in which the two are not confounded, the FN400 reflects a qualitatively distinct effect from the N400.
Article: Letter search and relatedness proportion: further electrophysiological evidence for the automaticity of semantic activation.[show abstract] [hide abstract]
ABSTRACT: Automatic semantic activation was recently called a myth when the behavioral semantic priming effect was found to be subject to task demands. Semantic priming effects as measured by lexical decision times are typically reduced to the point of being absent when a letter search has to be performed on the prime word. It seems premature to draw any definite conclusion from this behavioral result as ERP recordings show that the same prime task leaves N400 priming effects unaffected. It is still a matter of debate whether N400 priming effects are generated chiefly by automatic or by cognitively controlled priming processes. In the present study we therefore recorded both lexical decision times and ERPs while we varied the ratio of related to unrelated prime-probe pairs (25% vs. 75% related) and thus manipulated the degree to which controlled mechanisms contribute to the semantic priming effect. Behavioral measures revealed reliable semantic priming effects only when RP was high and the influence of controlled processes hence increased. The modulation of the N400, however, provided clear-cut evidence of semantic processing at both RPs, indicating that semantic activation occurred even when RP was low and the involvement of controlled mechanisms was thus minimal.Neuroscience Letters 09/2010; 482(1):26-30. · 2.11 Impact Factor
Article: Electrophysiological correlates of exemplar-specific processes in implicit and explicit memory.[show abstract] [hide abstract]
ABSTRACT: The present ERP study investigated the retrieval of task-irrelevant exemplar-specific information under implicit and explicit memory conditions. Subjects completed either an indirect memory test (a natural/artificial judgment) or a direct recognition memory test. Both test groups were presented with new items, identical repetitions, and perceptually different but conceptually similar exemplars of previously seen study objects. Implicit and explicit memory retrieval elicited clearly dissociable ERP components that were differentially affected by exemplar changes from study to test. In the indirect test, identical repetitions, but not different exemplars, elicited a significant ERP repetition priming effect. In contrast, both types of repeated objects gave rise to a reliable old/new effect in the direct test. The results corroborate that implicit and explicit memory fall back on distinct cognitive representation and, more importantly, indicate that these representations differ in the type of stimulus information stored. Implicit retrieval entailed obligatory access to exemplar-specific perceptual information, despite its being task irrelevant. In contrast, explicit retrieval proved to be more flexible with conceptual and perceptual information accessed according to task demands.Cognitive Affective & Behavioral Neuroscience 03/2012; 12(1):52-64. · 3.57 Impact Factor