Lingual mechanoreceptive information. II. An evoked-potential study of the central projections of low-threshold lingual nerve afferent information.

The extent to which the known trigeminothalamic projections are related to afferents from specific peripheral branches of the trigeminal nerve is not clearly revealed by degeneration studies involving lesions of the various trigeminal nuclei. This study examines the ascending projections related to the lingual branch of the trigeminal nerve using the evoked-potential technique in pentobarbital anesthetized rhesus monkeys. The distribution of potentials within the medulla, pons, and midbrain was determined by recording with macroelectrodes following single-pulse stimulation of the lingual nerve. Results show that two pathways from the main sensory nucleus convey lingual nerve information to the thalamic ventral posteromedial nucleus: an ipsilateral projection which in position corresponds to the dorsal trigeminal tract, and a larger contralateral projection which in position corresponds to the to the crossed ventral trigeminal tract, or trigeminal lemniscus. Additionally, the spinal trigeminal nucleus contributes fibers of lingual nerve origin to the contralateral medial lemniscus. The role of low-threshold mechanoreceptive information in lingual sensorimotor activity is discussed in relation to current concepts of somatosensory system function.