In the facial touch pathway, the primary neurons in the trigeminal ganglion synapse with second-order neurons in which structure?

• A. Pons
• B. Medulla
• C. Thalamus
• D. Cortex

Answer: (A)

In facial touch, the first-order neurons in the trigeminal ganglion connect to second-order neurons in the brainstem, specifically the principal (main) sensory nucleus of the trigeminal complex, which sits in the pons. This is the site where discriminative touch signals from the face undergo the crucial synapse that relays them onward. From there, the second-order neurons project to the ventral posteromedial nucleus of the thalamus, and then third-order neurons reach the somatosensory cortex. The spinal trigeminal nucleus in the medulla handles other modalities like pain and temperature, while the thalamus and cortex are higher processing stations. So the second-order synapse for facial touch is in the pons.