Abstracts /International Journal of Psychophysiology 25 (I 997) 17-84 59 PV (at Fzl in the chlorpheniramine group (F(t,rs, = 5.37, p = 0.0325). The results demonstrate that the antihistamine chlor- pheniramine selectively affects the automatic stimulus-change detector associated with MMN and suggest an implication of the H,-receptor in the neurochemical genesis of the MMN. SUPPORTED BY GENERALITAT DE CATALUNYA (Gerencia de Seguretat Vial) SHORT-TERM REPLICABILITY OF THE MISMATCH NEGATIVITY C. Escera, J.M. Serra*, E. Torras, A. Povedano and C. Grau Neurodynamics Laboratory, Dept. of Psychiatry and Clinical Psychobiology, University of Barcelona P. Vall d’Hebron 171, 08035 Barcelona, Catalonia, Spain A large body of empirical and theoretical knowledge has been accumulated to present on an auditory endogenous event-re- lated potential component, called mismatch negativity (MMN). The MMN is elicited by low probability deviant tones ran- domly replacing standard tones in a series of repetitive stimu- lation. The main interest of MMN in clinical contexts is that it can be obtained independently of the direction of the atten- tion of the subject, thus allowing the evaluation of sensory memory, auditory discrimination and passive attention in patients unable or unwilling to cooperate. However, in order to develop clinical tests based on MMN its reliability and replicability has to be established. The MMN was obtained to 160 deviant tones, in two different recording sessions spaced 2 hours apart, in a group of 11 normal subjects (1000 Hz, 92%, 1100 Hz, 8%; IS1 480 ms). Exogenous Nl and P2 to standard tones showed high replicability at both the individual (signifi- cant Pearson correlation) and group level (non-significant ANOVAs). At the group level, the replicability of MMN was good, reaching significance at the individual level in some of the electrodes only. This last result was, however, similar to that obtained for the Nl to deviant tones. This suggests that the number of averages should be increased in order to improve the clinical usefulness of the MMN. EXTRAVERSION, NEUROTICISM AND EMOTIONAL REACTIVITY Jari Tuuva* , Petri Naatanen, Arto Ryynlnen, Pertti Keski- vaara & Liisa Keltikangas-Jarvinen Dept. Psychology, University of Helsinki, P.O. Box 607, FIN- 00014 Helsinki, Finland Numerous studies have shown that extraversion is associated with self-rated positive emotionality and neuroticism is associ- ated with self-rated negative emotionality. The present study was carried out to examine this relationship experimentally considering all three basic components of emotion: Subjective experience was measured with self-ratings, autonomic activity with SCL and facial expressions with EMG from corrugator supercilii and zygomaticus major muscle areas. Four film-clips, two negative and two positive, were used as a mood induction procedure. Neurotics and especially neurotic introverts showed heightened emotional reactivity to negative films in self-rat- ings. However the difference in averaged SCL between posi- tive and negative films were greater among stables than neu- rotics and no differences were found in EMG-recordings. The difference in averaged corrugatoric activity between positive and negative films were greater among extraverts than intro- verts, but no other differences were found. Results suggest that neuroticism is related to negative emotional reactivity, but only at the level of subjective experience. This might be due to individual differences in perception of peripheral feed- back cues. Often reported relation between extraversion and positive emotionality might be due to greater expressivity among extraverts, which may create conditions that promote positive emotionality (e.g., positive social feedback). SIGNIFICANCE OF SEX DIFFERENCES IN RESEARCH AND CLINICAL SETTINGS S. Pogun* Ege Un Center for Brain Res. Dept. of Physiology and TUBI- TAK Basic Neuroscience Research Unit, Turkey Sex differences transcend reproductive functions, are evident in the structural and functional organization of the brain and are reflected in cognitive abilities and behavior. Sex hormones have organizational and activational effects on brain develop ment and function. Genetic sex shapes gonadal sex which in turn determines the phenotypic sex resulting from the inter- play between the sex hormones and experience throughout a span covering the embryonic, perinatal, pubertal and adult phases of life. Sexual differentiation involves not only the development of neurotransmission and communication between nerve cells but also the responsiveness of nerve cells to various input. The net result is having sexually dimorphic brains with different patterns of plasticity, adaptive responses, vulnerability to various insults and cognitive abilities. Gender differences in psychopathology and addiction demonstrate the importance of the issue in the clinical setting. Gender differ- ences are also implicated in career choices and success in employment requiring skills that show sexual dimorphism. Since sex hormones show fluctuations over the menstrual cycle in women and seasonal variations in men, their activatio- nal affects have profound influences on daily living. Sex dif- ferences in brain and behavior may have an evolutionary basis. Males and females have different neural organizational patterns for information processing and use different strate- gies in problem solving. In general, women are better in verbal and perceptual skills, arithmetic calculations and motor tasks that require manual precision, whereas men have an advan- tage in spatial tasks, mathematical reasoning and target-di- rected motor skills. Even though the average sex differences in cognitive abilities appear to be small, they are consistent and become more apparent when the upper tails of distribu- tion in related tests are compared. Research on sex differ-