Where does the third-order neuron send the signal?

Where does the third-order neuron send the signal?

• A. To the spinal cord
• B. To the cerebellum
• C. To the thalamus
• D. To the primary somatosensory cortex (postcentral gyrus)

Answer: (D)

In somatosensory pathways the third-order neuron carries the signal from the thalamus to the cerebral cortex. After receptors send the message via first- and second-order neurons to the thalamus (ventral posterior lateral nucleus for body, ventral posterior medial for face), the third-order neuron projects from the thalamus to the primary somatosensory cortex in the postcentral gyrus. This is where we consciously perceive and localize touch, proprioception, pain, and temperature. Signals directed to the spinal cord or cerebellum are involved in earlier processing or coordination, not conscious cortical perception, so the thalamus-to-cortex projection is the correct pathway.

In somatosensory pathways the third-order neuron carries the signal from the thalamus to the cerebral cortex. After receptors send the message via first- and second-order neurons to the thalamus (ventral posterior lateral nucleus for body, ventral posterior medial for face), the third-order neuron projects from the thalamus to the primary somatosensory cortex in the postcentral gyrus. This is where we consciously perceive and localize touch, proprioception, pain, and temperature. Signals directed to the spinal cord or cerebellum are involved in earlier processing or coordination, not conscious cortical perception, so the thalamus-to-cortex projection is the correct pathway.