9. Visual stimulation for long-term monitoring of brain functions via evoked potentials evaluation

Abstract

Introduction At present, predominantly stationary visual stimulators are used for diagnostic examination of visual evoked potentials (VEPs). They cover significantly the central visual field of the tested subject and such examination does not allow any other parallel activity during the stimulation. Therefore, it cannot be used e.g. for a long-term monitoring and evaluation of functional changes of CNS functions – for continual assessment of visual perception. Methods We have introduced a visual stimulator (Czech Republic patent No. 303192 pending), the principle of which is that the source of light stimuli is in periphery of the visual field – a row of light emitting diodes (LEDs) is placed on the head of a stimulated subject on a standard peak (a part of a baseball cap). A control unit switches individual LEDs (flash or motion stimuli are generated) and synchronizes VEPs evaluation. The set of LEDs is located about 20° from the center of the stimulus field. There are several variants of stimulation available because of significant inter-individual differences in reactivity of subjects to particular stimuli. The motion stimuli have similar parameters as stimulations used for clinical diagnostic purposes (see Kuba, M., Kubova, Z., Kremlacek, J., et al. Motion-onset VEPs: Characteristics, methods, and diagnostic use. Vision Res., 2007, vol. 47, p. 189–202 – http://dx.doi.org/10.1016/j.visres.2006.09.020 ). Recording of VEPs (with the use of built-in amplifiers) and on-line evaluation of their parameter changes can be done via “blue-tooth” transmission to a standard computer or in a built-in microprocessor (in preparation). Results Since using of this kind of VEPs examination does not interfere with common human activities, it is possible to use it not only for standard diagnostic purposes in neuro-ophthalmological diseases but also for monitoring of CNS function changes or level of vigilance/fatigue, e.g. in drivers or some other professions. Supported by EU project CZ.1.05/3.1.00/13.0284 and by Charles University project PRVOUK P37/07.