DUAL PROJECTIONS OF THE VENTROMEDIAL LAMINA-VI AND THE MEDIAL LAMINA-VII NEURONS IN THE 2ND SACRAL SPINAL-CORD SEGMENT TO THE THALAMUS AND THE CEREBELLUM IN THE CAT

Neurons of origin of the crossed spinocerebellar and/or spinothalamic tracts giving off axon collaterals at supraspinal levels were antidromically identified and labeled with horseradish peroxidase in lower sacral spinal cord segments of cats. Their cell bodies were located mainly in the medial part of lamina VII and rarely in the ventromedial aspect of lamina VI. In the S2 segment 77 neurons with axons in the opposite dorsolateral funiculus were recorded; 36 of them were invaded from only the thoracic level, 21 from both the thoracic level and the restiform body, 3 from both the thoracic level and the thalamus, and 17 from both the thoracic level, the restiform body and the thalamus on the contralateral side. These termination areas suggest that the S2 neurons under study transmit peripheral signals of proprioceptive, exteroceptive and nociceptive sensations.