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Visual evoked potentials (VEPs) were recorded in a group of 20 operators aged 25-45 years during two sessions, before and after a 5-hour work at computer terminals, in order to assess visual system fatigue. The outcomes were referred to the norms established for the age-matched population of 30 subjects not exposed to professional contact with computers. Most of the examined operators suffered various complaints concerning not only the organ of vision but the central nervous system as well. VEPs were elicited by means of monocular stimulation using the reversal checkerboard pattern and recorded simultaneously from the scalp electrodes placed over the right and the left cerebral hemisphere. Only recording acquired after finishing of a working day demonstrated significant statistically abnormalities of the VEPs waveforms, which suggests their transient character. The changes mentioned above included prolongation of peaks P100 and N2 latency with concomitant attenuation of their amplitudes and a decrease of the correlation coefficient values for the recordings from the hemispheres. The preliminary findings presented in this paper seem to justify a conclusion that the non-invasive VEPs method can be considered as the objective indicator of the central visual fatigue induced by the workload at computer terminals.

Research on body surface potential mapping concerned predominantly the ventricular excitation process. There is only very limited data available documenting surface potential distribution during atrial electric events. The goal of this study was to establish the pattern and criteria of the atrial potential maps in the healthy population, which is substantial for a prospective usefulness of the noninvasive registrations of surface maps in atrial arrhythmias. A group of 54 subjects in whom there was no clinical evidence of cardiac dysfunction underwent a procedure of body surface potential mapping. The recordings were performed using the HPM-7100 system simultaneously from 87 leads covering the entire thorax. Isopotential maps registered during the P wave were subjected to the statistical analysis by means of the own system "Heart Map" enabling the qualitative and quantitative estimation of the atrial maps. To avoid a problem of variable heart rate, a time standardization, by the division of the P wave into 10 time intervals, was applied. In order to eliminate an interindividual variability of heart location in the thorax, a distribution of the constituent values without subordinating them to the individual electrodes was proposed. In consequence, the group-mean isopotential maps of the wave P for the normal subjects were created. According to the migration of the maximum throughout the thoracic surface during the P wave, three phases of the isopotential atrial maps were determined: phase 1 (P1-P4) comprising initial 40% of the P wave, phase 2 (P5,P6)-next 20% of the P wave and phase 3 (P7-P10)-the terminal 40% of the P wave duration. These phases reflect the successive sequences of atrial excitation. During the whole atrial depolarization the minimum of potential, changing its value, was located around lead D7. Furthermore, in the results of the analysis of the constituent values sequences, for the P wave time intervals the additional quantitive parameters were calculated, i.e. areas designated by positive and negative potential and the ratio of these areas. The presented findings revealed that surface maps give the precious insight into spread of atrial excitation. Establishing of the distribution pattern and the criteria of the atrial potential maps for normals enables to undertake the further research on the use of this technique in a various atrial pathology.