Describe the main route of sensory information and determine how different cortical areas contribute to somatosensation.

Question

What will be an ideal response?

Answer 1

Information about the body senses enters the spinal cord or the brain and first synapses in the thalamus. It then travels to the somatosensory cortex, located in the parietal lobes. Most of the sensory neurons that come from one side of the body cross over the opposite-side hemisphere. The somatosensory cortex contains a somatotopic map of the body, with adjacent body parts represented in adjacent parts of the cortex. The receptive fields for some of the neurons are responsible for detecting two points touching the skin (rather than the perception of just one point), while others respond to different aspects of an object or stimulus, such as orientation, direction of movement, shape, surface curvature, or texture.
The left and the right primary somatosensory cortices synapses with the secondary somatosensory cortex, which combines information from both sides of the body. Neurons in this area are particularly responsive to stimuli that have acquired meaning. The secondary somatosensory cortex then sends connections to the hippocampus, which likely contributes to memory formation when somatosensory information is involved.
The primary somatosensory cortex then synapses with the posterior parietal cortex and the secondary somatosensory cortex. In the posterior parietal area, the brain determines the body's orientation in space; the location of the limbs; and the location in space of objects detected by touch, sight, and sound. Some of its cells combine proprioception and vision to provide information about specific postures, for example, the location and positioning of the arm and the hand. Other cells contribute to reaching and grasping movements and eye movements toward targets of interest.