BRAIN POTENTIALS WITH OLD NEW DISTINCTION OF NON-WORDS AND GEOMETRIC-FIGURES/

Event-related potentials (ERPs) were recorded in a continuous memory r ecognition task. Readable non-wards and abstract geometric figures wer e presented in an alternating manner with an inter-stimulus interval o f 2.1 s. Probability of item repetition was 0.25, a lag of one item la y between initial presentation and repetition. OLD/NEW distinction was indicated by the subject's motor response. Using linked-mastoid elect rodes for reference, material-specific hemispheric asymmetries of ERPs started 150 ms after stimulus onset in temporo-lateral and parietal r ecordings with ERPs elicited by non-words being lateralized to the lef t and those by figures to the right. Clear OLD/NEW ERP effects were fo und with non-words: Starting about 200-250 ms after stimulus presentat ion, ERPs of formerly presented (OLD) items were more positive-going i n recordings over the midline than ERPs of items that were new and to be repeated (NEW). In contrast, no local OLD/NEW ERP-difference was fo und with figures. In some brain regions, OLD/NEW ERP-differences were larger over the left hemisphere compared to the right. This finding, h owever, did not differ between non-words and figures. Copyright (C) 19 96 Elsevier Science Ireland Ltd.