Final answer:
Trigeminal 3rd order neurons originate in the thalamus, travel via the trigeminothalamic tract, and connect to the primary somatosensory cortex, where the perception of facial sensation occurs.
Step-by-step explanation:
Trigeminal 3rd order neurons originate in the thalamus, ascend in the trigeminothalamic tract, and terminate in face representations of the primary somatosensory cortex.
The trigeminal nerve is the fifth cranial nerve and is responsible for transmitting somatosensory information from the face, head, mouth, and nasal cavity to the brain. The pathway of the trigeminal nerve includes three orders of neurons. After synapsing in the thalamus, the third-order neurons send projections to the somatosensory areas of the cortex, where facial sensation is processed and perceived.