As a part of the study to elucidate the influence of exteroceptive stimulation on the excitability of the brain stem reticular formation (RF) in the presence of flash stimuli, the effect of hippocampus stimulation on the recruiting response was investigated in the rabbit and the following observed.
1) The recruitin g response in the cerebral cortex EEG induced by 8 Hz stimulation of the nucleus ventralis anterior (VA), belonging to the diffuse thalamocortical projection system, was inhibited by simultaneous 100 Hz stimulation of the hippocampus.
2) The recruiting response by 8 Hz stimulation of th e VA was inhibited or facilitated following simultaneous 8 Hz stimulation of the hippocampus.
3) The recruiting response induced by 8 Hz stimulation of the VA was facilitated by 3 Hz stimulation of the hippocampus
.4) The rate of change in the amplitude of this recruiting response following stimulation of the hippocampus was analyzed quantitatively by determination of the wave pattern, using the digital computor (ATAC-201).
The findings suggest that the previously reported (I) increase in excitability of the RF by attachment of contact lens in the presence of the flash stimulus, corresponds to the effect of 100 Hz stimulation of the hippocampus and the decrease in excitability of the RF by contact lens in the absence of the flash stimulus corresponds to the effect of 3 Hz stimulation of the hippocampus, respectively.
