Topographic EEG maps by various normal visual functions

Abstract

Characteristic EEG topograms which were evoked by various visual functions and often appeared with high reproducibility were classified for standardization in clinical use. The following seven types of topograms were selected. Retinal potentials on the prefrontal region were obtained in flash visual evoked potential (VEP), which included short latency VEPs. It appeared only in the frontal region and never extended to the posterior region. Optic pathway potentials were demonstrable as very weak negative far field potentials appearing after each oscillatory potential of the retina. Brainstem potentials were represented by the far field potentials in the short latency VEP at about 50 msec and this seemed to be related to pupillary light reaction. The premotor spike positive potential was also detected as a brainstem potential. Occipital potentials appeared as visual cortex responses represented by P₁₀₀. Wide field stimuli provoked convex discharge indicating an excitation of the whole visual cortex. Occipito-frontal inverse potentials were recognized in pattern reversal VEP and seemed to be the result of frontal negative and occipital positive discharges at the time of P₁₀₀. A parietal positive focus appeared during the occurrence of P₂₀₀ and P₃₀₀. As another parietal potential, strong negative focus was demonstrated in stereopsis. In pattern VEP, occipital positive change moved to the temporal region, suggesting that pattern recognition takes place in the temporal lobe. It was concluded that various kinds of visual function may be generated from the activity of whole brain.

Key Words:

• EEG topogram
• visual evoked response
• eye movement
• brainstem potential
• visual evoked potential