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The electroanatomy of the caudal nuclei of the thalamus was studied in 23 patients, who underwent stereotactical procedures for the treatment of intractable pain or Torticollis. As in the observations on the ventro oral nucleus of the thalamus, the dominant thalamus when stimulated would produce effects on speech. Nearly all stimulations produced synchronic muscular contractions together with sensory effects in the corresponding region. Usually a large region of the body was affected at the same time. The topographical arrangement differed from the arrangement in the ventro oral nucleus of the thalamus; the face and the inside of the mouth and throat were located highest orally and more medially and anteriorly, corresponding to the nucleus Flechsig and its borderline to the centre median. The leg was posterior, most lateral and deepest ventrally, the other body regions were arranged in between. Stimulation of the VJM produced torsion movements only. Coagulation in the dominant hemisphere often had the consequence of a long lasting Korsakov syndrom. Vegetative effects were much less outspoken than in the anterior parts of the thalamus.

Our observations confirm the rule that certain effects of stimulation have to be considered as abnormal integrations of innervation in diseased brains, similar to the peculiar effects which can be produced in Parkinsons disease and in athetosis and which are not seen in patients with normal motility. This may hold true for single observations like the peculiar light phenomena in unexpected places or the erotic behaviour which we have seen in 2 patients, once in the pallidum, once in the amygdala and the Basedow-like syndrome which could be elicited in one of our patients. Another group of phenomena may be observed with high regularity in all individuals. They are more diffuse and less colourful, for instance slowing of thought and tiredness in stimulation of the fornix and vegetative effects like those on “warm and cold” around the anterior commissure, where the production of erythema, sweatting and feeling of warmth is produced on a more dorsal level and goose skin and feeling cold in a more ventral level. This observation show the wide extension of this system which probably has to do with vasomotor control in regulating temperature but also under emotional effects. The focus of most exact functional control of this mechanism is evidently in the oral parts of the brain. The effects in the regions further behind, namely in the basal ganglia, the thalamus, the internal capsule and the hypothalamus may be produced by stimulation of fibre bundles of this system, radiating horizontally and backwards from their oral control until approximately to a point 10 mm behind the intercommissural midpoint, from where on these fibres seem to disappear caudally, so that they cannot be stimulated anymore in the caudal part of the thalamus. With great regularity we see a combination of sham movements and nausea and vomiting in the basal parts of the entire basal ganglia system.