Large-diameter myelinated axons of the trigeminal ganglion conveying discriminative touch information terminate in the principal trigeminal nucleus.
The axons of these cells then cross the midline, join the medial lemniscus, and terminate in the medial division of the Ventro-Posterior Nucleus (VPM).
Small diameter lightly-myelinated and unmyelinated axons of the trigeminal ganglion conveying thermal and nociceptor information descend in the spinal trigeminal tract and terminate in the spinal trigeminal nucleus.
The axons of these cells then project to VPM and to the posterior and intralaminar thalamic nuclei (i.e., rather like the anterolateral system).
Hence, we have a separation again of mechanoreceptors from thermoreceptors.