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Electric activity of the brain during prolonged mental work

Z. Bujas ; Institut za higijenu rada Zagreb
B. Petz ; Institut za higijenu rada Zagreb
A. Krković ; Institut za higijenu rada Zagreb

Puni tekst: hrvatski pdf 10.366 Kb

str. 125-137

preuzimanja: 290



The problem the authors desired to solve was to determine how prolonged mental work influences the alpha-waves of the brain. This problem is not new and much research work was been done in connection with it. However, the relation between mental work and brain waves has by far not been precisely established because the results of the different examinations were contradictory. The authors have recorded brain waves of the parietal-occipital part of the left hemisphere by means of an electroencephalograph (type Grass). The recording was bipolar. The fluctuations of the brain potentials m S subjects were measured continuously: before, during and after mental work, consisting in adding pairs of two-digit numerals read out to them during one hour. The subject was able to signalize with one of the channels the moment when he completed the addition so that he was immediately given another addition. In computing the results the so-called alpha-index was taken into account (i. e. percentual relation between clearly perceptible alpha-waves and all waves registered within a period of lime). The alpha-index was investigated also in tile stage of the so-called »blocks« i. e. in additions lasting twice or more as long as the average of all additions. The results showed that the alpha-index rapidly decreased at the beginning of mental work, its rate of decrease diminishing gradually with the progress of work: towards the end of mental work, a tendency of increasing of alpha-index was noticeable. After the end of the work the alpha-index rose again. Individual differences between various subjects have been noticed, especially with regard to the degree of depression of alpha-waves during mental work. In respect of blocks, their number increased on the average in the beginning and then stabilized. The alpha-index in blocks showed no significant differences from the general alpha-index during mental work. The authors try lo explain the average curve of the changes of the alpha-index during mental work by means of the antagonistic influence of two factors: exercise and fatigue. After the initial fall caused by mental strain and emotional disturbance, the alpha-index - under the influence of the exercise - has the tendency of rising; however, the fatigue, increasing during work, causes the fall of the alpha-index. The curve thus obtained is a result of the interaction of those two factors. This interpretation is sup-ported by the authors' experience with some of the subjects tested, in whom the alpha-index showed during the second experiment a continuous rise after the initial fall, because the work by then represented a minor strain and the technique of the work became somewhat automatic. On the other hand, in another case the alpha-index decreased right down to the cud of the work because the subject got very tired by the experiment. The authors point out that the above results and their interpretation represent only the first stage in the systematic research of the influence of mental work on the alpha-rhythm. New experiments, now in progress, are to fill up various gaps and give more information on the influence of exercise and fatigue on alpha-waves, not only in regard to their depression, but also to their amplitude.

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