MODULATION OF EVENT-RELATED POTENTIALS BY THE REPETITION OF DRAWINGS OF NOVEL OBJECTS

In experiment 1, event-related potentials (ERPs) were recorded from 13 scalp sites while subjects viewed a series of line drawings of novel objects. Most of the drawings were of objects that were structurally p ossible, while the remainder were of structurally impossible objects; the task was to respond to each presentation of an impossible object. Approximately one third of the possible objects were repetitions of th e immediately preceding drawing. Compared to the ERPs elicited by firs t presentations, the ERPs elicited by repetitions were more negative-g oing. This negative repetition effect comprised two temporally and top ographically distinct components. In experiment 2, subjects monitored drawings of unstructured patterns, so as to detect occasional 'targets ' containing a pair of parallel lines. Repetitions of 'non-target' pat terns elicited ERPs which were largely indistinguishable from those el icited by first presentations. Thus, the negative repetition effects f ound in experiment 1 are not merely a consequence of repeating visual patterns in a demanding discrimination task. Possible reasons why nove l objects should elicit ERP repetition effects opposite in polarity to those observed in tasks employing verbal or meaningful pictorial stim uli are discussed.