Stimulus-classification traces are dominant in response learning

Priming can reflect the stimulus-driven retrieval of output-related memory traces, commonly referred to as stimulus-response associations. The purpose of the current study was to investigate which aspects of the output exactly are preserved in these traces using electroencephalography (EEG). We orthogonally manipulated the repetition of action and classification whilst participants performed one of the two semantic tasks according to the cue. We found no evidence of stimulus-action associations but significant effects relevant to the retrieval of stimulus-classification associations in participants' accuracy and RT. Event-related potential (ERP) and oscillatory analysis further revealed a classification-related modulation at around 200. ms after stimulus onset, which appeared much earlier than the one reported in previous studies. These classification effects possibly indicate the modification of memory traces which requires the dynamic interaction of temporal and frontal cortices. The finding of classification effects across behavioural and EEG data suggested that the formation of stimulus-classification traces is rather spontaneous and may be dominant in single trial stimulus-response binding.