Dissociable ERP profiles for processing rules vs instances in a cognitive sequencing task

A hotly debated question in cognitive neuroscience is whether individual in stances of perceptual sequences, and the rules that describe them, are proc essed by the same brain mechanisms. We tested the hypothesis that such rule s and instances are processed by dissociable brain mechanisms. We analyzed event-related brain potentials (ERPs) evoked during cognitive sequencing ta sks that assessed surface (instance) vs abstract (rule) structure learning. Sequence instances ABCBAC and DEFEDF have different serial order or surfac e structure, but share the same rule or abstract structure, 123213. Nine he althy subjects were first trained to learn a set of surface and abstract st ructures in sequences of visually presented stimuli. During the subsequent ERP recording, for surface and abstract structures, they then discriminated between acceptable and unacceptable sequences, based on the pre-learned re gularities. Abstract structure processing evoked a late positivity around 5 00 ms, which was not seen in the surface structure processing, supporting o ur hypothesis of dissociable processes. We discuss implications for the rul e vs instance debate, and similarities between this late positivity and the P600 observed in previous studies of syntactic processing. NeuroReport 11: 1129-1132 (C) 2000 Lippincott Williams & Wilkins.