Thalamic projections from lateral cervical nucleus in monkey. A degeneration study.

The projection from the lateral cervical nucleus (LCN) to the thalamus has been investigated in macaque monkeys. After electrolytic lesions of the LCN, the degeneration was studied in sections impregnated by the Wiitanen method. The cervicothalamic fibers cross the midline at their level of origin and ascend to the thalamus in the medial lemniscus. A small ipsilateral projection may also exist. The tract terminates in the posteromedial (POm) and ventralis posterolateralis (VPL) nuclei. Termination in the POm is indicated by the presence of a small number of thin preterminal fibers. In the VPL the cervicothalamic fibers are unevenly distributed, forming patches of moderately dense preterminal networks, mainly in the medial two-thirds of the nucleus. Rostrocaudally the termination is restricted to areas corresponding to Olszewski's VPLc. Compared to cat, the cervicothalamic projection to the VPL in the monkey appears considerably smaller. It is also much smaller than the spinothalamic projection to the VPL in the monkey. The results neither confirm nor exclude a small projection to the nucleus ventralis posteromedialis (VPM) from the lateral cervical nucleus.