title: Underlying mechanisms of the P3a task-difficulty effect.
abstract: In three-stimulus oddball studies, even typical deviant stimuli elicited a large P3a event-related brain potential (ERP) when target/standard discrimination was difficult. To investigate the underlying mechanisms, the effects of task difficulty on early deviant-related ERPs were assessed. Four visual stimuli defined by an orthogonal combination of task-relevant size (nontarget 80%, target 20%) and task-irrelevant luminance (standard 80%, deviant 20%) were presented randomly, where two task difficulties (easy, difficult) were defined by target/nontarget discriminability. An increase in task difficulty enhanced P3a as well as a posterior negativity (change-related negativity) and an anterior positivity (frontal positivity) elicited by deviant nontarget stimuli. These results suggest that attentional modulation of refractoriness-based rareness detection and an attention-triggering process underlie the P3a task-difficulty effect.
authors.affiliation: Graduate School of Education, Hokkaido University, Sapporo, Japan. m-kimura@edu.hokudai.ac.jp
authors.forename: Motohiro
authors.initials: M
authors.lastname: Kimura
authors.forename: Jun'ichi
authors.initials: J
authors.lastname: Katayama
authors.forename: Harumitsu
authors.initials: H
authors.lastname: Murohashi
mesh_terms: D000328:Adult; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000502:physiology; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*