page_title: Trigeminal nerve
section_title: Sensory pathways
hierarchical_section_title: Trigeminal nerve / Function / Sensory pathways
caption_attribution_description: English: Diagram of sensory nerve pathways for touch and pain
context_page_description: The trigeminal nerve is a nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the most complex of the cranial nerves. Its name derives from the fact that each of the two nerves has three major branches: the ophthalmic nerve, the maxillary nerve, and the mandibular nerve. The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory functions. Adding to the complexity of this nerve is the fact that autonomic nerve fibers as well as special sensory fibers are contained within it.
  The motor division of the trigeminal nerve derives from the basal plate of the embryonic pons, and the sensory division originates in the cranial neural crest. Sensory information from the face and body is processed by parallel pathways in the central nervous system.
context_section_description: Sensory pathways from the periphery to the cortex are separate for touch-position and pain-temperature sensations. All sensory information is sent to specific nuclei in the thalamus. Thalamic nuclei, in turn, send information to specific areas in the cerebral cortex. Each pathway consists of three bundles of nerve fibers connected in series:
  The secondary neurons in each pathway decussate (cross the spinal cord or brainstem), because the spinal cord develops in segments. Decussated fibers later reach and connect these segments with the higher centers. The optic chiasm is the primary cause of decussation; nasal fibers of the optic nerve cross (so each cerebral hemisphere receives contralateral—opposite—vision) to keep the interneuronal connections responsible for processing information short. All sensory and motor pathways converge and diverge to the contralateral hemisphere.
  Although sensory pathways are often depicted as chains of individual neurons connected in series, this is an oversimplification. Sensory information is processed and modified at each level in the chain by interneurons and input from other areas of the nervous system. For example, cells in the main trigeminal nucleus (Main V in the diagram below) receive input from the reticular formation and cerebral cortex. This information contributes to the final output of the cells in Main V to the thalamus.
  Touch-position information from the body is carried to the thalamus by the medial lemniscus, and from the face by the trigeminal lemniscus (both the anterior and posterior trigeminothalamic tracts). Pain-temperature information from the body is carried to the thalamus by the spinothalamic tract, and from the face by the anterior division of the trigeminal lemniscus (also called the anterior trigeminothalamic tract).
  Pathways for touch-position and pain-temperature sensations from the face and body merge in the brainstem, and touch-position and pain-temperature sensory maps of the entire body are projected onto the thalamus. From the thalamus, touch-position and pain-temperature information is projected onto the cerebral cortex.
caption: C = Cervical segment, S = Sacral segment, VPL = Ventral posterolateral nucleus, SI = Primary somatosensory cortex, VM = Ventromedial prefrontal cortex, MD = Medial dorsal thalamic nucleus, IL = Intralaminar nucleus, VPM = Ventral posteromedial nucleus, Main V = Main trigeminal nucleus, Spinal V = Spinal trigeminal nucleus
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