Theta rhythm: the brain stem involvement.
This review considers the influence of brain stem transections on hippocampal theta rhythm appearance in the acute transected rat and cat. The pretrigeminal transection induces in both species continuous or almost continuous low-frequency theta rhythm while the cortex is desynchronized. The intercollicular transection induces in both species high amounts of low-frequency theta rhythm, whereas the cortex shows cortical spindle bursts of high amplitude. The precollicular transected rat generally shows high amounts of low-frequency theta rhythm while the cortex is synchronized. This theta rhythm is increased in frequency, or induced when absent, by median posterior hypothalamic stimulation. In contrast, in the cat there is no theta rhythm but the limbic rhythm is easily induced by the same hypothalamic stimulation. In the midhypothalamic transected rat there is not theta rhythm and the cortex is synchronized. These data suggest that the posterior hypothalamus could be a trigger zone for theta rhythm particularly involved during sleep.
Gottesmann
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Laboratoire de Psychophysiologie, Faculté des Sciences, Université de Nice-Sophia antipolis Parc Valrose, France.
D000818:Animals; D001933:Brain Stem / Q000502:physiology*; D002415:Cats; D051381:Rats; D013826:Theta Rhythm