Position, vibration, and fine touch sense information of the face, and a few other parts of the head, enters the brainstem in axons of the trigeminal nerve to synapse in an ipsilateral nucleus called the main trigeminal nucleus, which is about midway up the brainstem. Axons from this nucleus decussate and ascend in a tract called the trigeminothalamic tract to synapse in the thalamus. Abnormalities of these functions will be ipsilateral if a lesion occurs before the decussation of this pathway, or contralateral with lesions after it. Axons of the third neuron in the chain, called the somatosensory thalamocortical tract, travel from the thalamus to the primary somatosensory cortex, from which neurons project to association somatosensory cortices.

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Level 3 Unit 2 Part 12: Pain, temperature, and gross touch perception of the face