Abstracts 7th IOP Scientific Meeting /International Journal of Psychophysiology 18 (1994) 87-159 89

other MMN subcomponent may be generated in the frontal cortex. Furthermore, prefrontal lesions have been found to attenuate the MMN. The frontal activity contributing to the MMN might be associated with involuntary orienting of at- tention to auditory stimulus changes.

Acknowledgements

This study was supported by the Academy of Finland.

Processing of auditory stimulus changes in infants as reflected by the mismatch negativity of event-related brain potential Kimmo Alho, Cognitive Psychophysiology Research Unit, Department of Psychology, PO. Box II, FIN-00014 University of Helsinki. Finland

In adults, the mismatch negativity (MMN) component of auditory event-related brain potential (ERP) is automat- ically elicited by physically deviant sounds occurring among repetitive standard sounds even when these stimuli are not attended to. The MMN appears to reflect a compar- ison process between deviant auditory input and a neuronal sensory-memory trace representing the physical features of standard stimuli. It was recently found that an MMN-like response is also elicited in newborns by a deviant (higher-frequency) tone occurring among standard tones (Alho et al., 1990). Furthermore, in another recent study, an MMN-like response was observed in ERPs elicited in new- borns by a deviant vowel (the Finnish ‘i’) occurring among repetitive standard phonemes (the Finnish ‘y’) (Cheour-Luhtanen et al., 1994). Thus, the MMN-like re- sponse observed in newborns might provide a new tool for objective testing of auditory sensory memory, discrimina- tion, and speech perception in infants.

Acknowledgements

This study was supported by the Academy of Finland.

References

Alho, K., Sainio. K.. Sajaniemi, N.. Reinikainen. K. and NBLtlnen, R. (1990) Event-related brain potential of human newborns to pitch change of an acoustic stimulus. Electroenceph. Clm. Neurophysiol.. 77: 151-155.

Cheoor-Luhtanen. M., Alho. K., Kujala. T.. Sainio. K.. Renlund, M., Aaltonen, 0.. Eerola. 0. and NBBtSnen. R. (1994) Mismatch negativity like response in human newborns to changes in speech stimuli. Hearing Res.. in press.

Transient cognitive impairment in learning disa- bled children A. Alvarez-Amador, R. Morgades, M. Perez Abalo, J. Rojas, Y.L. Diaz Comas, Cuban Neuroscience Centre, Special Education School “Paquito Resales”. Havana,

Cuba

The disruptive effect of paroxysmal activity upon cog- nitive performance (transient cognitive impairment, TCI) has been demonstrated in epileptic patients (Binnie et al. 1980). A similar affect is also present in non-epileptic learning-disabled children (LDC) in which a high inci- dence (67.8%) of epileptiform activity has been found (Al- varez et al. 1991). The purpose of the present investigation was to assess how often and to what extent could this phe-

nomena influence the behaviour of LDC. EEG was record- ed from eight leads (F3, F4, C3, C4, P3, P4, T3, T4) while the child executed three different psychological tasks im- plemented as video games. The tasks were administered with a counterbalanced design and consisted of variants of a continuous performance test in which visual stimuli had to be classified according to colour, semantic or phonolog- ical criteria. Behavioural data for each task (error rate and reaction time) was computed separately for paroxysmal and non-paroxysmal EEG segments. According to our re- sults, TCI was found in a significant proportion of LDC. In some children the interfering effect of paroxysmal activity was evidenced in error rates, while in others reaction time values or both measures were affected. Moreover, the tasks in which TCI was present differed from one child to the other. Thus the paroxysmal activity apparently interfered with different mental processes in different children. This suggests that testing for TCI should include a battery of tests, each tapping a different cognitive ability.

Quantitative EEG analysis in children with atten- tion-deficit-hyperactivity disorder

J.W. Anderson a, R.J. Barry b, S. Clark ‘, E. Gordon a, I.

Lazzaro a, J. Leong ‘, a Cognitive Neuroscience Unit, Westmead Hospital, Westmead, Australia, b Department of Psychology, Universiv of Wollongong, Wollongong, Aus- tralia, ’ Department of Adolescent Medicine, Westmead

Hospital, Westmead, Australia

Attention deficit-hyperactivity disorder (ADHD) is rap- idly becoming recognised as perhaps the most prevalent psychiatric disorder of childhood. The behavioural hyper- activity is often ameliorated (paradoxically) by stimulant medication. In this context, quantitative EEG would appear to have much to offer in relation to diagnosis as well as the monitoring of medication effects. Previous studies have generally been carried out with electrode placements dic- tated by the desire to optimise particular event-related po- tential (ERP) components, or to explore particular hypoth- eses limited to one EEG frequency band. These have re- ported increased theta or decreased beta activity in samples of ADHD children of a wide age range (6-17 years). Evi-

90 Abstracts 7th IOP Scientific Meeting /International Journal of Psychophysiology I8 (1994) 87-I59

dence from previous studies suggests CNS hyperarousal in sources was performed by inverse solution of both data young ADHD children and hypoarousal with older chil- sets, either singly or jointly, with single equivalent current dren. Unfortunately, such studies have rarely examined a dipole models, multiple dipole models, and distributed range of EEG bands from a substantial number of sites. We source solutions. These solutions were then co-registered extended these data in a topographic study of quantitative with magnetic resonance (MR) images for each subject to EEG collected from 15 sites in both eyes-open and provide structural localisations. Principal responses oc- eyes-closed conditions in a group of adolescents (12-17 curred in the contralateral hemisphere approximately 170 years). The hypoarousal perspective in adolescent ADHD msec after the stimuli reached maximum contrast (320 was supported. Effects were more apparent in the msec after stimulus onset). At this latency the data were eyes-closed than in the eyes-open condition. The effect of well modelled by a single current dipole, implying a local- pooling the band data in a theta/beta ratio, previously sug- ised cortical generator. Co-registration with MR images re- gested to control for intrasubject variability in theta activi- vealed that this source was located in an extrastriate visual ty, is discussed in the light of these topographic findings. Il- area. The results will be compared with the known physi- lustrative data are also presented to demonstrate the nor- ology on the spatial localisation of motion centres within malising influence of stimulant medication in ADHD. the visual cortex of primates, namely areas V2 and V5.

Neuromagnetic localisation of visual evoked cor- tical activity in the magnocellular pathway in Humans S.J. Anderson, I.E. Holliday, K.D. Singh, G.F.A. Hard-

ing. Clinical Neurophysiology Unit, Department of Vi- sion Sciences, Aston UniversiQ, Birmingham B4 7ET UK

An MRI image-processing software environment that captures expert knowledge about the brain (BRAINQUERY) G. Anogianakis, M. Apostolakis, G. Nontides, Depart-

ment of Physiology? Faculty of Medicine, Aristotle Univer-

sity of Thessaloniki, 54006 Thessaloniki, Greece

There is a general consensus that the image presented at

the retina is analysed by the visual system in a number of separate cortical areas, each selective for a particular aspect of the image. Our aim in this study was to identify the spa- tial localisation and temporal sequence of activation of the cortical areas involved in the perception of motion in hu-

mans. To do this we measured evoked cortical magnetic fields and electrical potentials in response to the onset of

visual stimuli whose parameters were chosen to stimulate optimally the magnocellular (M) pathway. The parameters

so chosen were based on psychophysical and physiological data that show that neurones in the M pathway have a high luminance contrast gain, predominate at low light levels, are band-limited in spatial and temporal frequency, are sen- sitive to drifting stimuli, and provide almost exclusively the input to cortical areas involved in motion processing. All stimuli were 2D Gaussian-windowed (cr= 1.5 deg) si-

nusoids of spatial frequency 0.3-l c/deg and drift temporal frequency 4-8 Hz, presented 2.5 deg in the right visual

field along the horizontal meridian. The mean luminance of the display varied from 0.2 to 50 cd/m’. Evoked magnetic fields were measured with a 19.channel SQUID neuromag- netometer in a magnetically shielded room, and evoked electrical potentials were measured with a 20-channel rec- tangular array using 10% electrode spacing. Stimuli were presented for 600 msec, cosine-ramped to maximum con- trast over 150 msec and terminated abruptly, with an inter- stimulus interval of 1 sec. Localisation of the evoked

Computer graphics permit the 3-D visualisation of neu- roanatomical information and, together with information about the brain microstructure, are extremely important in interpreting neurophysiological data. In the framework of the European research programme MAGNOBRAIN [l] we designed and implemented a brain data base (BDB), which containselectrophysiological, neuroanatomical, neu- ropathological, neurosurgical and radiological (CT and MRI) information on the essential structures of the human brain. The present paper presents the informatics tools that were built to facilitate the collection and organisation of the necessary information within the BDB. The BDB contains a complete anatomical description of the brain in X, y and z co-ordinates with 1 nun resolution. For each co-ordinate, the known and essential brain structures or features are de-

scribed as attributes. These attributes include: (a) the no- menclature of the brain area to which it belongs; (b) the or- igin(s) of input that it receives and the destination(s) of its output; (c) any internal circuitry that it may contain and the

global brain circuits in which it participates; (d) its known functions; (e) the types of injuries or pathologies likely to

occur there, including information on the accompanying symptoms and clinical signs and their neurophysiological,

neuropsychiatric and functional assessment; (f) its micro- anatomical (quantified if possible) characteristics such as the types of neuronal and glial cells and the types of fibres contained. BRAINQUERY “extracts” the BDB contents from experts (neurologists, neuroanatomists, etc.) by que-