Experimental spike and wave EEG pattern from thalamic stimulation in anaesthetized juvenile monkeys

A bilaterally synchronous 3/sec spike and wave pattern in the EEG can be obtained during stimulation of the nucleus medialis dorsalis (nMD) and nucleus paracentralis (nPC) of the thalamus, in lightly anaesthetized juvenile monkeys. The spike and wave EEG patterns have a frequency of 2 1/2 to 3Hz and occur during low frequency stimulation, without continuing into the post-stimulatory phase. Stimulation of the mesencephalic reticular formation (MRF) at higher voltages inhibits the thalamic-induced spike and wave response. This finding has heuristic significance, as activating stimuli arrest the wave and spike EEG pattern of human absence (petit mal epilepsy) seizures. The study also demonstrates the morphological similarity of the 3/sec spike and wave thalamic induced response in experimental and clinical absence states as well as similarities in their alterations with different levels of activation.