Since hypoglycemia is known to influence cognitive functions, we checked whether the physiological changes in glycemia (after fasting or exertion) can explain the rather high intra-individual variability of event-related potentials (ERPs). Besides the ERPs to “change in coherence of a moving pattern” with reaction time (RT) recording, binocular pattern reversal VEPs and motion-onset VEPs (to linear and radial motion) were also examined in 14 healthy subjects prior to and after 24-h fasting that decreased glycemia from 5.3 to 3.9 mmol/l on the average. We only found one significant change in the latencies and amplitudes of VEPs and ERPs (with no change of RT). The N160 peak in the motion-onset VEPs to radial (expansive) motion (EM-VEPs) showed a larger amplitude at lower glycemia. For evaluation of the exertion influence, we tested glycemia prior to and after 90 min long exercise – bicycle ergometry with the load set to 2 W/kg in women and 2.5 W/kg in
men (average age-related values for W170/kg index). The changes of glycemia to exertion were, however, less distinct than those to fasting. We conclude that in healthy subjects the glycemia decrease due to 24-h fasting or intensive time-limited exercise never reaches the critical value to change
the VEP, ERPs and RTs.
Visual cognitive responses (P300) to moving stimuli were tested in 36 subjects with the aim to find the normal range of P300 parameters. Concomitantly, the circadian intra-individual variability of the P300 was studied in a subgroup of 6 subjects. Visual stimuli consisted of either coherent (frequent stimulus) or non-coherent motion (random stimulus). The oddball paradigm was applied for recording cognitive responses. P300 to rare stimuli had an average latency of 447.3±46.6 ms and amplitude of 12.9±6.0 mV. The average reaction time was in the range from 322 to 611 ms and there was no correlation between the reaction time and P300 latency. We did not find any significant circadian changes of the P300 parameters in the 6 subjects tested four times during the same day. Cognitive (event-related) responses (P300) displayed distinctly greater inter-individual variability (S.D. of 50 ms) when compared with pattern-reversal and motion-onset VEPs (S.D. of 6.0 ms and 14 ms, respectively). For this reason, the clinical use of P300 elicited by this kind of visual stimuli seems to be rather restricted and the evaluation of its intra-individual changes is preferable., Z. Kubová, J. Kremláček, J. Szanyi, J. Chlubnová, M. Kuba., and Obsahuje bibliografii