Primary Somatosensory Cortex

Last update: Oct 17th, 2022

The primary somatosensory cortex (SI) of the brain is located just posterior to the central sulcus in the postcentral gyrus of the parietal lobe (Broadmann areas 3, 1, and 2).

An image showing lateral view of the right hemisphere and medial view of the left hemisphere

An image showing lateral view of the right hemisphere and medial view of the left hemisphere, the Primary Somatosenory Cortex is highlighted

Using tactile stimuli from the skin, the somatosensory cortex produces sensations of touch, pressure, pain, temperature, and proprioception (or the somesthetic sensations), which it then localizes to specific body regions.
This area also assesses the size, shape, and texture of objects based on their feel and helps judge body position (proprioception) using sensory input from the joints, muscles, and skin.
Similar to the motor cortex, the primary somatosensory cortex is somatotopically organized (or functionally organized by body region).
The medial and superior portions of the cortex image sensations from the genitals, feet, legs, hips, trunk, head and arm regions.

An image showing Lateral view of the right hemisphere and Coronal view of the right hemisphere, the Primary Somatosenory Cortex is highlighted

An image showing the genitals, feet, legs, hips, trunk, head and arm sensation regions, Lateral view of the right hemisphere and Coronal view of the right hemisphere, the Primary Somatosenory Cortex is highlighted

The lateral portions of the cortex image sensations from the hands, face, teeth, tongue, pharynx and intraabdominal regions.

Each somatosensory cortex receives sensory input from the opposite side of the body.
Neurons that carry information about touch cross over in medulla oblongata portion of the brain stem.

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An image showing the stimulation of the skin generating action potential in the 1st sensory neuron of the touch pathway

An image showing the action potential moving through the first sensory neuron, from the receptor to the spinal cord, part of the touch pathway

An image showing the action potential moving through the second sensory neuron, from the spinal cord to the thalamus passing through medial lemniscus of the medulla, part of the touch pathway

An image showing the action potential moving through the third sensory neuron, from the thalamus to the cerebral cortex, part of the touch pathway

Neurons that carry information about temperature and pain cross over in the spinal cord, near their point of entry.

An image showing stimulation of the somatic sensory nervous system by sharp object

An image showing the action potential moving through the first sensory neuron of the somatic nervous system

An image showing the action potential moving through the second and third sensory neurons of the somatic nervous system pathway

Neuronal pathway of a signal traveling from the skin via a sensory neuron to the spinal cord, medulla oblongata and the sensory cortex of the brain to transmit pain sensation.

If this area is damaged, an individual may ignore certain body regions (or neglect syndrome) or not be able to recognize objects from their feel (or agnosia).

Primary Somatosensory Cortex

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