142 Abstracts /International Journal of Psychophysiology 30 (1998) 95-271 emergence of the dissociated state the accessibility for re- trieval of some memory traces takes place with suppression of another ones. Pharmacological influence over just processes of engram selection and retrieval could result in memory dissoci- ation phenomena. It is well known that different forms of memory have non-equal vulnerability to amnesic influences. Analysis of literature and own data resulted in conclusion that declarative (explicit) memory is the form that especiulEyvulnera- ble to the dmginduced dissociation. Functioning of temporal lobe structures is most essential both in declarative memory and in memory dissociation processing. It is broadly con- sidered that state-dependent learning/retrieval of responses results from the inlhtence of high doses of drugs with toxic effects. Nevertheless, the dose of memory dissociation is prin- cipally determined by the tasks used in the experiment. Tasks based on declarative memory provide the opportunity for state-dependent retrieval of memory traces when moderate doses are used. This conclusion suggests the revision of the rarity of dissociate phenomena in normal and pathological memory processing. Supported by RFBR (98-04-48301). 368 ERP CORRELATES OF IMPLICIT AND EXPLICIT MEMORY H.L. Sharpe*, A.R. Mayes, D.D. P0tterfC.B. Barrow Division of Psychology and Biology, Bolton Institute, Deane Road, Bolton, BL3 5AB England In the present study event-related potentials (ERPS) were recorded in conjunction with behavioural -measures to clarify the dissociation between implicit and explicit memory. Explicit memory can be defined as requiring the conscious recollection of a prior learning episode whereas implicit memory does not. The distinction between these two types of memory has only really begun to be appreciated within the last two decades and has important implications for contemporary theories of me- mory. ERP research has already revealed that recognition (explicit memory) can be driven by a familiarity-based process or a recollective process. Other ERP studies are also begin- ning to highlight brain areas which may be involved in implicit memory e.g. occipital areas seem to be implicated in perceptu- ally-based implicit memory. Despite these results, however, and those of neuroimaging investigations, the quest for a suitable theory of such memory phenomena continues. The debate currently focuses on ‘processing’ versus ‘systems’ ac- counts of the dissociation between implicit and explicit me- mory. Processing accounts argue that the two types of memory utilise a single memory system whereas systems accounts stress that they rely on processes which are computationally unique to each type of memory. However, ERP studies have not yet been able to distinguish fully between these two theories. This is due to the fact that the issue of contamina- tion of implicit memory by explicit processes has yet to be adequately addressed. Moreover, a recent theory of memory proposed by Mayes, Gooding and van Eijk (1997) challenges the systems and processing accounts. Mayes et al argue that implicit and explicit memory do have certain processes in common but the type of information encoded in a memory representation will determine which parts of the neocortex will be involved in forming memories. Results of a behaviou- ral/ERP paradigm designed to address the issue of explicit memory contamination and ultimately test the predictions of this theory will be presented. 369 INTERFERENCE EFFECTS OF BACKGROUND MUSIC ON WORKING MEMORY TASK AND P300 Tatsuya lwaki, Shogo Sadamitsu, Mitsuo Hayashi, Tadao Hori Faculty of Behavioral Science, Hiroshima University, Ka- gamiyama l-7-1, Higashi-Hiroshima, 739-8521 Japan The present study explores the interference effects of back- ground music on working memory task using the P300 compo- nent of ERPs (event-related potentials). In experiment 1, sixteen subjects participated in the control and the music sessions. EEG (Fz, Cz, Pz> and EOG were recorded during periods of (1) pre-music, (2) music (silence or music presenta- tion), (3) post- music. They listened to music (gJupiter h from a suite by Gustav Holst entitled g The Plants h,7 min. 16 s.) during the music period in the music session. All subjects performed a working memory task consecutively through the control and the music sessions and performance data were collectedThe hit ratio of working memory task decreased during music period in music session compared with that in the control session. Similarly, the P300 amplitude of ERPs decreased during the music period in music session, while such changes did not occur in the controlsession. The P300 latency was not changed by presentation of music. In experi- ment 2, the other sixteen subjects participated in the control and music sessions of which procedures were the same as those in experiment 1 with the exception that different musi- cal stimulus was presented. Reverse replay of musicalpiece (gJupiter h) was used in experiment 2 as comparison stimuli to confirm the results of experiment 1. For the reverse replay music, the information processing load of the musical struc- ture and meaning of stimulus would be lower than those of the forward replayed original music. There were no effects of reverse replay of musical piece on the hit ratio of working memory task and P300 ComponentThese findings imply that the background music interferes the performance of working memory task and musical information load of the musical structure and meaning may consume processing capacity. 370 ERPs ASSOCIATED WITH A SHORT-LONG TERM MEMORY TASK THE SCRABBLE PARADIGM S. Cansino*, A. Ruiz and V. Lopez-Alonso National Autonomous University of Mexico, Psychology Fac-