144 Abstracts 7th IOP Scientific Meeting /International Journal of Psychophysiolog>l 18 (1994) 87-159

tal influences. In S.R. Steinhauer. J.H. Gruzelier and J. Zubin (Eds.). Handbook of Schizophrenia, Vol. 5: Neuropsychology. Psychophysiology and Information Processing, Elsevier, Amsterdam/London.

Patterns of cortical lateralisation in dyslexic children

G. Rippon, Department of Psychology, University of

Warwick, Coventv CV4 7AL, UK

Heterogeneity in reading disorders has been acknowl- edged for some time among researchers interested in the cognitive aspects of dyslexia. One dichotomy that has been described concerns backward readers with auditory prob- lems (auditory-linguistic dyslexia) as opposed to a second group with mainly visual problems (visuospatial dyslexia). Such heterogeneity is frequently ignored by neuropsycho- logical and psychophysiological research although some links have been made between the two fields, e.g. children with auditory-linguistic-type problems demonstrate “left hemisphere” deficits, whereas children with visuospatial

problems demonstrate “right hemisphere” deficits. Other work points to a reduction in the normal pattern of func- tional lateralisation. This paper reports the findings from three studies with children with developmental dyslexia, compared with chronological- and reading-age-matched children. One emphasis of these studies was on the selec- tion of appropriate cognitive tasks to demonstrate the un- derlying deficit and possible variations in the degree to which these dyslexic children demonstrated such deficits. Cortical lateralisation was assessed via direct (brain electri- cal activity mapping) and indirect (degree of handiness) techniques. The findings indicate that the majority of dys- lexic children can be characterised as having phonological problems and show reduced functional lateralisation both in terms of EEG activity during task performance and in degree of handedness. There is evidence however that these children can show “appropriate” lateralisation in non- verbal tasks. A smaller group of children show adequate phonological skills although still presenting with some lit- eracy deficits. These children tend to be characterised by more “fixed” lateralisation, with a predominance of left-hemisphere activity regardless of the task they are per- forming. These data are discussed in terms of their rele- vance to the debate concerning subtypes of dyslexia.

Evidence of lateralisation in motor imagery G. Rippon, Deportment of Psychology, CJniversio of Warwick, Coventry CV4 7AL, UK

Studies of the cortical correlates of imagery have at- tempted to localise areas involved in different forms of im-

agery. The majority of such studies have involved visual imagery. Interest in other forms of imagery has mainly con- centrated on spatial image, e.g. employing tasks such as mental rotation. Movement or motor imagery has received less attention, although indirectly studies of spatial image- ry using tasks such as mental rotation have considered the movement aspects of such tasks. Studies by, for example Roland have drawn attention to the relationship between the cortical areas involved in actual movement and those involved in imaginary movement. The study reported here compares the EPs to tones preceding actual movement with those to tones preceding imaginary movement. Both are compared to a control condition where the subject has to sit Iistening passively to tones. Findings indicate that EPs in the right parietal area during imaginary movement are sig- nificantly different from the control condition and from those during actual movement where the activity is mainly frontal. This accords with the suggestion of the strong spa- tial component of movement imagery and provides further evidence for different localisation of different types of im-

agery.

N400 in poor readers M. Rodriguez, T. Harmony, J. Bernal, G. Yanez, J. Silva, T. Fernandez, L. Galan, H. Rodriguez, E. Marosi, V. Guerre- ro, A. Reyes. Notionnl University of Mexico, DGAPA IN2 I01 93, ENER Iztocaln, Mexico

Poor readers (PR) are defined as those who are reading between one and two standard deviations below grade lev- el. The purpose of this study was to characterise a group of PR studying the N400, as an electrophysiological measure of contextual processing, and the performance in a behav- ioural battery of reading. We studied two groups of chil- dren: normal readers (NR, n=23), and PR (n=16) between the ages of 10 and 12. Both groups performed a computer- ised reading battery test (BTL) that explored seven tasks from perception to semantic and syntactic levels. We regis- tered N400 according to the sentence-reading paradigm of

Kutas and Hillyard (1980). in the lo/20 system, using linked earlobes as reference. NR showed a greater negative wave at 400 msec to incongruent than to congruent sen- tences. However, in four PR the negativity was larger to the congruent than to the incongruent sentence, showing no N400 effect. If these four children were eliminated from the sample of PR. no significant differences in amplitude or in latency between both groups were observed using a per- mutation test. However, significant differences between groups were obtained in the BTL. mainly in the syntactic and word recognition tasks. One possible explanation for the contradiction between behavioural and electrophysio- logical findings may be that in the N400 paradigm sentence

Abstracts 7th IOP Scientific Meeting/International Journal of Psychophysiology 18 (1994) 87-159 145

context would help the comprehension of the PR, since they rely more on context for reading.

EEG asymmetry and the organization of the mono- and polysemantic context VS. Rotenberg, Abarbanel Mental Health Centre, Tel-Aviv University Tel-Aviv, Israel

The comparison of alpha-index with the spatial syn- chronisation of brain biopotentials in the process of mental activity is a promising method for the estimation of brain hemisphere’s functional capability. The formation of the monosemantic context based on the artificial restriction of the natural relationships between objects and events re- quires the additional activation of the left hemisphere. This activation causes the reduction of alpha-index in parallel with the increase of spatial synchronisation in the left hem- isphere. The formation of the polysemantic context which integrates numerous interrelationships between objects and forms a holistic entity is based in the right hemisphere abil- ity. It does not require an additional brain activation. In this case alpha-index is not reduced or is even increased in par- allel with the increased spatial synchronisation. If task per- formance which requires the competence of the right hem- isphere is accompanied by the decrease of alpha-index of both hemispheres without the significant increase of the spatial synchronisation in the right brain, it means that the right hemisphere function is insufficient. The hyperactiva- tion of the brain in such cases reflects the unsuccessful at- tempt to overcompensate this insufficiency. The applica- tion of this modal to the psychiatric pathology and to the al- tered states of consciousness will be discussed.

Phenytoin in hypothalamic disorders I.T. Ryabtzeva. T.G. Medvedva, K.A. Shapovalova, De-

partment of Obstetrics and Gyzaecology of St. Petersburg Medical Institute, St. Petersburg, Russia

Hypothalamic disorders can be considered in many cas-

es as a reaction to different kinds of stress. For many years a study of the effect of phenytoin in afterstress pathology has been performed in the Institute of the Human Brain of the Russian Academy of Sciences. We used their data as a basis for treatment of neuroendocrinal syndrome combined with exchange disturbances. A clinical and laboratory study of 25 patients with this pathology was performed. All these women suffered from obesity, menstrual disorders and infertility. All women received traditional complex treatment; however, they received also additional treat- ment. Those who showed a hyperglycaemic sugar curve re- ceived biguanidins (12) and those where the sugar curve was “flat” received phenytoin (13). Patients of the first

group lost 5-8 kg of body weight in 6 months, in 9 of them the menstrual cycle was restored, and 3 became pregnant. Normalisation of body weight resulted in all women being treated additionally with phenytoin; they lost 6-10 kg. In 10 of these women the menstrual cycle was restored, and 4 became pregnant. We believe that it would be useful to in- clude phenytoin, a neurotrophic medicine with a very wide spectrum of action for normalisation of gonadotrophic functions of the hypophysis. This treatment could also cause a decrease in body weight.

Convulsant EEG patterns and cardiac arrhyth- mias following central administration of some neuropsychotropic drugs in animals L. Safta. B. Cuparencu, D.N. Safta, V. Sandor, V. Arustei, Department of Pharmacology University of Medicine and Pharmacy, 3400 Cluj-Napoca, Romania

In drug-induced pathology, central nervous system changes are encountered. One of these is the reduction of the convulsant threshold and the appearance of EEG distur- bance or seizures. There are also references in the literature about EEG disturbances related to cardiac arrhythmias af- ter some central excitatory drugs as pentetrazole or picro- toxin. In urethane-anaesthetized or in curarized albino rats we investigated the effects of intracerebroventricular (i.c.v.) administration of some neurotropic drugs: (1) anal- gesics. such as morphine, tifluadom, pentazocine and bremazocine; (2) excitatory amino acids (EAA), such as glutamate, aspartate and kainate, on EEG and cardiac rhythm. Morphine induced a central arrhythmogenic activ- ity and “irritative” type changes in the EEG. They were due to the stimulation of p subtype opioid receptors, and could be antagonized by naloxone. The kappa antagonist MR.2266 cannot antagonize the arrhythmias and EEG changes induced by tifluadom and bremazocine (K-ago- nists). It appeared that the opioid receptors involved in cen- tral arrhythmogenesis were not of the K type. The investi- gated EAA in high doses induced “irritative” type changes in the EEG and cardiac arrhythmias. The origin of these modifications were likely related to the stimulation of the NMDA subtype of amino acid receptors. In conclusion, a certain parallel seems to exist between the convulsant ef- fects and the centrogenic cardiac arrhythmias induced by the investigated neurotropic drugs.

The maturational theory of brain development and Kraepelin’s endogenous psychoses L.F. Saugstad, Psy%ological Institute, University of Trondheim, Trondheim, Norway

An association has been established between rate of