Biological PsychologV 24 (1987) 141-151 North-Holland 141 zyxwvutsrq EVENT-RELATED POTENTIALS AS ASYMMETRY INDICES OF LATERALIZED COGNITIVE PROCESSES DURING MUSIC AND VERBAL TASKS Vilfredo De PASCALIS *, Francesco MARUCCI and Pietronilla M. PENNA Department of Psychology, University of Rome, Rome, Italy Accepted for publication 26 November 1986 The present study replicates and extends earlier findings by using event-related potentials (ERPs) as a means of providing information about differential hemispheric engagement in cognitive processing. ERPs were recorded from T3, T4, T5 and T6 in response to task-irrelevant tone pips superimposed on white noise, on music and on verbal passages, which are thought to differentially activate the two hemispheres. The latencies and amplitudes of three peaks (Nl, P2 and N2) were obtained in 37 women. Task-related ERP asymmetries were found only for the peak amplitude of N2 recorded at posterior-temporal scalp areas, whereas at the anterior-temporal recording, there were no interactional effects. The hemisphere assumed to be most engaged in task processing showed a smaller N2 peak amplitude to tone pips at the posterior-temporal scalp area than the hypothesized unengaged hemisphere. A result common to the three peaks in the ERP was that peak latencies were longer in the music than in the noise condition. Finally, the posterior- temporal areas produced longer N2 peak latencies in verbal and even more in music conditions compared to white noise conditions. No differences in latencies were found between hemispheres during the ongoing cognitive tasks. 1. Introduction It is still not clear whether scalp recorded event-related potentials (ERPs) are a reliable measure of the documented task-related asymmetries occurring in the human brain. A number of reviewers (e.g. Donchin, Kutas, & McCarty, 1977; Hillyard & Woods, 1979; Rugg, 1983) have discussed the studies which concern this area and have identified a number of possible reasons to explain the conflicting results: (a) Differences in the experimental paradigms; (b) task selection; (c) subject’s involvement in the task; (d) conflicting aims concerning the goal of the research. In his recent review, Rugg (1983) pointed out that the majority of the investigations on lateral distribution of the ERPs have em- ployed informational stimuli to elicit evoked potentials. According to Rugg the ‘probe’ paradigm would seem an alternative and ‘less unnatural’ approach to study lateral asymmetries in concurrent cognitive activity. The probe * Address requests for reprints to: Vilfredo De Pascalis, Dipartimento di Psicologia, Via degli Apuli 8, 00185 Roma, Italy. 0301-0511/87/$3.50 0 1987, Elsevier Science Publishers B.V. (North-Holland)