Afferent Projections to the Midbrain Tegmentum and Their Spinal Course

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Abstract
The potentials evoked in the midbrain tegmentum of the cat by peripheral nerve stimulation were studied. Nerves of the deep and superficial modalities of both hindlegs project to the midbrain tegmentum in a lateral and in a medial area. The effects of acute cord lesions on the evoked potentials were investigated. The results indicate that multiple pathways are available in ventrolateral funiculi of the cord for both "deep" and "superficial" sensory projections. An attempt was made to correlate these findings with the known anatomy of the pathways involved. Evidence is presented for the conclusion that sensory systems largely project in the reticular formation at medullary level and that the rostral connections of that region run through the medial and the lateral areas of the midbrain tegmentum. The possible functional significance of these findings is briefly discussed.