Expectancy modulates a late positive ERP in an artificial grammar task

ÁNGEL TABULLO; YAMILA SEVILLA; GUILLERMO PASQUALETTI; SERGIO VERNIS; ENRIQUE SEGURA; ALBERTO YORIO; SILVANO ZANUTTO; ALEJANDRO WAINSELBOIM

BRAIN RESEARCH

ELSEVIER SCIENCE BV

Año: 2011 vol. 1373 p. 131 - 143

0006-8993

Awide range of studies have found late positive ERP components in response to anomaliesduring processing of structured sequences. In language studies, this component is namedSyntactic Positive Shift (SPS) or P600. It is characterized by an increase in potential peakingaround 600 ms after the appearance of the syntactic anomaly and has a centroparietaltopography. Similar late positive components were found more recently in non-linguisticcontexts. These results have led to the hypothesis that these components index thedetection of anomalies in rule-governed sequences, or the access to abstract rulerepresentations, regardless of the nature of the stimuli. Additionally, there is evidenceshowing that the SPS/P600 is sensitive to probability manipulations, which affect thesubjects’ expectancy of the stimuli. Our aim in the present work was to address thehypothesis that the late positive component is modulated by the subject´s expectancy ofthe stimuli. To do so, we employed an artificial grammar learning task, and controlled thefrequency of presentation to different kind of sequences during training. Results showedthat certain sequence types elicited a late positive component which was modulated bydifferent factors in two distinct time windows. In an earlier window, the component washigher for sequences which had a low or null probability of occurrence during training,while in a later window, the component was higher for incorrect than correct sequences.Furthermore, this late window effect was absent in those subjects whose performance wasnot significantly above chance. Two possible explanations for this effect are suggested.