Abstract
Interactions between the slow negativity component of the photically evoked potential and the regular 5-7/sec wave of the spontaneous EEG were systematically investigated in rabbit's cortex with chronically and acutely implanted electrodes. The following interaction was seen:
1. As the evoked slow negativity developed, the relative amplitudes of the simultaneously elicited spontaneous regular waves, as related to the control, gradually decreased. When the apex of the regular wave was coincident with the peak of the slow negativity, the relative amplitudes of the spontaneous regular wave to the control was minimum, with maximum occlusion. At the end of the falling phase of the slow negativity, the regular wave was briefly facilitated.
2. As the regular wave ascended to the surface-negative phase, the relative amplitude of the slow negativity to the control decreased. At the apex of the regular wave, the occlusion became maximum, and then as the regular wave descended the occlusion weakened. The slow negativity elicited at the end of falling phase of the regular wave was briefly facilitated. This curve of excitability change was very similar with that of the regular wave in reference to the slow negativity.
3. The interaction between two slow negativities showed the same pattern of facilitation and occlusion in the excitability curve as that between the slow negativity and the spontaneous regular wave.
From the present findings it was concluded that the neural elements which contribute to the generation of the spontaneous regular EEG include those concerning the generation of the slow negativity of the evoked potential.
