title: Dissociating N400 effects of prediction from association in single-word contexts.
abstract: When a word is preceded by a supportive context such as a semantically associated word or a strongly constraining sentence frame, the N400 component of the ERP is reduced in amplitude. An ongoing debate is the degree to which this reduction reflects a passive spread of activation across long-term semantic memory representations as opposed to specific predictions about upcoming input. We addressed this question by embedding semantically associated prime-target pairs within an experimental context that encouraged prediction to a greater or lesser degree. The proportion of related items was used to manipulate the predictive validity of the prime for the target while holding semantic association constant. A semantic category probe detection task was used to encourage semantic processing and to preclude the need for a motor response on the trials of interest. A larger N400 reduction to associated targets was observed in the high than the low relatedness proportion condition, consistent with the hypothesis that predictions about upcoming stimuli make a substantial contribution to the N400 effect. We also observed an earlier priming effect (205-240 msec) in the high-proportion condition, which may reflect facilitation because of form-based prediction. In summary, the results suggest that predictability modulates N400 amplitude to a greater degree than the semantic content of the context.
authors.affiliation: Massachusetts General Hospital, Massachusetts, USA. ellenlau@umd.edu
authors.forename: Ellen F
authors.initials: EF
authors.lastname: Lau
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Holcomb
authors.forename: Gina R
authors.initials: GR
authors.lastname: Kuperberg
mesh_terms: D000328:Adult; D004569:Electroencephalography / Q000295:instrumentation / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology*; D053483:Eye Movement Measurements; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D011578:Psycholinguistics / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology; D060865:Repetition Priming / Q000502:physiology; D012660:Semantics; D055815:Young Adult