Effect of stimulation in three subcortical sites on the thalamocortical augmenting response in the cat

The thalamocortical augmenting response is a complex multineuronal response which can be elicited by repetitive stimulation of the ventrolateral thalamus. A major function of the ventrolateral thalamus is known to be a result of its participation in central nervous system activity related to motor behaviour. The significance of the thalamocortical augmenting response itself is not known. Since it would be reasonable to relate that response to motor behaviour, we evaluated the effect on the thalamocortical augmenting response of the stimulation of two other central nervous system structures which are also thought to participate in motor control, the cerebellum and the red nucleus. We conclude that at least part of the effect of red nucleus stimulation on the thalamocortical augmenting response is exerted through a rubro-olivo-cerebellar pathway. We then compared the effects of red nucleus and of cerebellar stimulation to the effect of stimulating a non-motor mesencephalic site, the periaqueductal gray. The changes induced in the thalamocortical augmenting response appear not to be fully explicable solely in terms of changes in motor behaviour.