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EEG SLOW POTENTIAL DYNAMICS IN THE PROCESS OF A MOTOR SKILL ACQUISITION

Pashina A.Ch., Institute of Psychology, USSR Aca- demy of Sciences, Moscow, USSR

Under external observation any activity seems to be a linear sequence of actions which is conditioned by instructions and learning. However a wide spectrum of functional systems reflecting evolutional and individ- ual history of the concrete individual is actualized in his behavior at any given moment (Shvyrkov, 1985). In the process of a motor skill formation the set of elements of the initial structure of behavior changes as well as the time for realization and in the accuracy of the separate actions performance, etc. Thus, the set of systems and intersystem relations, which provide the attainment of the same results given by the instruction differs at different stages of the skill formation.

We can test intersystem changings in current activity by means of comparison of motor activity, presence of which in external behavior corresponds to the changes of sets of systems in transition from one action to another, with EEG slow potentials dynamics which reflect the dynamics of the set of actualized systems (Aleksandrov, Maksimova, 1985; Bezdeneshznykh, Pashina, 1987). It is showed that negativity reflects the functioning of the set of systems specific for the current act of behavior. Positivity corresponds to changes of intersystem relations, which occur at the bounds of successive acts of behavior, and to decreases of spe- cificity of the set of actualized systems (ibid.).

The purpose of the present paper is to obtain some information about the person’s EEC slow potentials dynamics in the process of intersystem relations dy- namics, which provides a motor skill formation. Sub- jects learned to type out various sentences consisting of 3-4 words by the forefinger on a typewriter with unknown keyboard. The EEG was recorded at Fs, F4, Ps, P4 (10-20 international system). Motoractivity was controlled by means of eyes and forefinger movement. EEG activity was averaged from the moment of a key stroke and from the onset of saccades. The averaged potentials were estimated ac- cording to their temporal and amplitude characteristics and to their connection with current behavior.

The average time of the typing of the sentence reduces in the process of learning from 30-15 to

5.5-4.5 set (for different subjects and for different sentences) as well as the average time of a letter typing - from 700-600 msec to 400-200 msec (for different letters). The coefficient of variativity decreases from 0.7 to 0.2-0.05 for different letters. The process of the formation of the typing skill of a sentence can be divided into three stages.

Stage I. The maximal frequency of motor activity changes was observed. In the interval of the typing of each letter a great amount of searching saccades and finger movements took place. The analysis of averaged EEG shows that all searching saccades and finger movements correspond to low amplitudes of positivity followed by negative waves the duration of which can be compared with the time necessary for the transfer of the finger and with the periods of gaze fixation. The most marked positivity is late to the moments of typing of each letter.

Stage II. Searching saccades an finger movements gradually disappear. The average time of letters typing and corresponding periods of gaze fixation reduces. A stable pattern of distribution of the average time of gaze fixation and letters typing which reflects the formation of groups in the form of words is forming. The elimination of unnecessary actions is accompanied by decrease of positive waves at the stage of typing of each letter. At the same time the positivity becomes more prominent in accordance to the moments of gaze transfer to the first or to the last letters in the words and to the moments of typing of these letters. Negative waves comparable in temporal aspect with the stages of typing of separate slow this positivity. The duration of both positive and negative potentials reduces (p< 0.001).

Stage III. The change of motor activity is observed only at the moment of saccade towards the certain letter and at the moment of the certain key stroke. The time of typing of each letter and of the whole sentence is stable. Sometimes there is negative wave in EEG-activity which corresponds to the typing of whole sentence. The negative waves always develop during each letters and each words typewriting. As related to negativity connected with sentence they look like the waves of 2nd and 3rd order, divided by the positive waves corresponding to the key strokes and saccades. The maximum of positivity is related to the bounds of the words.

Thus, having compared the dynamics of intersystem

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changings in sentence typing cycle, which are esti- mated on the basis of motor activity changes, with the slow potentials dynamic we can suppose the following. As related to the action of separate letter typing different stages of learning are characterized with different amount of stages of changes specificity of the set of systems in that interval; the difference in the number of the potentials reflects these processes. The comparison of amplitudes positivities in the interval of sentence typing shows that at the first stage in the interval of typing of two adjacent letters many inter- system changings take place which are connected with searching actions, but the total change of one set of systems by another one occurs only at the moment of typing. When skill performance is automatized total intersystem changing occurs only at the bounds of the words. While typing other letters only a concretization of the set of systems which realizes a certain stage occurs. Appearance of negative waves according to the sentence typing and stable reproduction of negative waves related with the words end separate letters typing demonstrate high specificity of sets of systems realizing these stages. The order of appearance and the mutual organization of negative waves in the process of learning may to some extent reflect the “history” of the formation and then the final structure of subject’s memory, related to the given motor skill.

References Aleksandrov I.O., Maksimova N.E. (1985) Functional meaning of Pa,,,, Psychol. journ., V. 76, N 3: 86-95 (in Russian) Bezdeneshznykh B.N., Pashina ACh. (1987) The structure of EEG-activity during the sentence typing. In: EEG and neuronal activity in psychophysiological studies. M. Science (in Russian). P. 185-197. Shvyrkov V.B. (1985) Psychophysiological study of subjective reflection structure. Psychol. joum., V. 76, N 3: 22-37 (in Russian)

THETA SYNCHRONIZATION IN EEG OF IN- FANTS DURING FEEDING

K. Paul, J. Dittrichova Institute for Care of Mother and Child Prague, Czecho- slovakia

Walter (1950), Maulsby (1971) and Nikitina et al. (1985) have shown that emotional stimuli could sub- stantially change the background of EEG activity evoking synchronization in theta band. This interesting phenomenon has not yet been studied in details in infants.

Studying the development of the feeding behaviour in infants we often met with that phenomenon in our polygraphic recordings. This communication deals with following aspects of the theta synchronization in infants during the first 6 months of life: 1) the situation, 2) the development, 3) the individuality.

Material 20 fullterm healthy infants which stayed during the

first six months of life in a small well-established residential unit of our institute were followed. The infants were admitted to our unit from social reasons. The mothers stayed with their infants for longer time in 10 cases and these infants were breast fed till 8 to 12 weeks.

Method The feeding behaviour of the infants was studied in

four standard successive situations: 1. before feeding, 2. with pacifier, 3. during feeding, 4. after feeding. The examinations were done in an experimental box during a morning feeding always in three successive days at the age of 2, 10, 18 and 26 weeks. The mother or a nurse had the infant on her knees during the examina- tion. Behavioural patterns were recorded by two ob- servers from an adjacent room and concurrently video- recording was taken. Simultaneously a polygraphic recording of the EEG, electrooculogram, respiration, sucking, swallowing and vocalisation was made. One minute period from each situation was analysed in detail. EEG activity from the leeds C3-P3 and C3-C, was quantified and parameters “theta index” and “mean amplitude” were statistically tested.

Results I. h&ence offeeding situation. The visual analysis

of the recordings gave an impression that the EEG activity in the situation “during feeding” differed from the other situations. The quantification revealed differ- ences that were statistically significant. “Theta index” was higher during feeding than before feeding in the 18th week (pcO,Ol) as well as in the 26th week