Termination of a separate (proprioceptive?) cuneothalamic tract from external cuneate nucleus in monkey.

The termination of a pathway recently discovered in monkey, from the external cuneate nucleus (ECN) to the thalamus, has been investigated with the degeneration method. A previous HRP study showed that the projection is crossed. The ECN fibers terminate a wedge-shaped zone located dorsally in the rostral half of the contralateral nucleus ventralis posterolateralis (VPL). This zone occupies the dorsolateral corner of the forelimb division of the VPL. The main cuneate nucleus also projects to this zone, most of which has the cytoarchitectonic characteristics of Olszewski's VPLc24. The ECN pathway may be phylogenetically recent, and it may be a direct route for proprioceptive information to the cerebral cortex.