What is the Difference Between Primary and Secondary Somatosensory Cortex

The main difference between primary and secondary somatosensory cortex is that the primary somatosensory cortex receives sensory information from the ventral posterolateral nucleus of the thalamus, whereas the secondary somatosensory cortex processes sensory information delivered to the primary somatosensory cortex.  

Primary and secondary somatosensory cortex are two types of somatosensory cortex. The somatosensory cortex receives information from various areas of the skin.

Key Areas Covered

1. What is Primary Somatosensory Cortex
     – Facts, Features, Behaviour
2. What is the Secondary Somatosensory Cortex
     – Facts, Features, Behaviour
3. Similarities Between Primary and Secondary Somatosensory Cortex
     – Outline of Common Features
4. Difference Between Primary and Secondary Somatosensory Cortex
     – Comparison of Key Differences

Key Terms

Primary Somatosensory Cortex, Secondary Somatosensory Cortex

What is Primary Somatosensory Cortex

The primary somatosensory cortex (S1) is the region of the cerebral cortex occurring behind the central sulcus. It receives sensory information from the ventral posterolateral nucleus of the thalamus via the internal capsule and corona radiata. Another name for the primary somatosensory cortex is the postcentral gyrus. The main function of the primary somatosensory cortex is to receive sensory input from the areas of the skin. Further, the primary somatosensory cortex contains a large area of the cerebral cortex. Brodmann’s areas 3a, 3b, 1, and 2 are the areas of the primary somatosensory cortex.

Figure 1: Primary Somatosensory Cortex

Furthermore, Brodmann’s area 3b processes basic touch sensation. Meanwhile, Brodmann’s area 3a responds to the proprioceptors, the regions that sense proprioception. Brodmann’s area 3b connects areas 1 and 2. Brodmann’s area 1 senses the texture of the objects, while Brodmann’s area 2 perceives the objects’ size and shape. Moreover, the primary somatosensory cortex perceives pressure, judging the degree of pressure.

What is the Secondary Somatosensory Cortex

The secondary somatosensory cortex (S2) is the region of the cerebral cortex that occurs posterior to the primary somatosensory cortex. It occurs in the upper part of the lateral sulcus. Although the S2 region is connected to the primary somatosensory cortex, it also receives direct projections from the thalamus. However, the primary function of the secondary somatosensory cortex is to involve in tactile object recognition and memory.

Figure 2: Secondary Somatosensory Cortex

Further, the primary somatosensory cortex requires the secondary somatosensory cortex to store, process, and retain information from the primary somatosensory cortex. This brain area is vital in episodic memory, visuospatial processing, aspects of consciousness, and reflections upon self. Moreover, the secondary somatosensory cortex connects to the hippocampus and amygdala.

Similarities Between Primary and Secondary Somatosensory Cortex

• Primary and secondary somatosensory cortex are the two types of somatosensory cortex in the brain.
• They are responsible for receiving sensory information from the skin.
• They occur in the parietal lobe of the brain.

Difference Between Primary and Secondary Somatosensory Cortex

Definition

Primary somatosensory cortex refers to the area of the cerebral cortex that receives sensory information from the somatic senses, plus proprioceptive senses and some visceral senses, while secondary somatosensory cortex refers to a region of cortex in the parietal operculum on the ceiling of the lateral sulcus.

Location

The primary somatosensory cortex is located in the post-central gyrus immediately posterior to the primary motor cortex while the secondary somatosensory cortex is located in the superior bank of the Sylvian fissure, where it makes up a significant part of the parietal operculum.

Function

The primary somatosensory cortex plays a critical role in processing afferent somatosensory input. It contributes to integrating sensory and motor signals necessary for skilled movement, while the secondary somatosensory cortex is responsible for tactile object recognition and memory.

Conclusion

In brief, primary and secondary somatosensory cortexes are two types of somatosensory cortex that receive information from the skin area. The primary somatosensory cortex is the area of the cerebral cortex that receives sensory information from proprioceptive and visceral senses. It is located in the post-central gyrus immediately posterior to the primary motor cortex. Additionally, it processes afferent somatosensory input and motor signals and contributes to integrating sensory and motor signals for skilled movement. In comparison, the secondary somatosensory cortex is the region of the cerebral cortex located in the superior bank of the Sylvian fissure. The primary function of the secondary somatosensory cortex is to recognize objects, which is essential in memory. Therefore, their function is the main difference between primary and secondary somatosensory cortex.

References:

1. Evans, O. G., & Olivia Guy EvansAssociate Editor for Simply Psychology BSc (Hons). (2023, February 16). Somatosensory cortex function and location. Simply Psychology. 

Image Courtesy:

1. “Blausen 0103 Brain Sensory&Motor.” By BruceBlaus – Own work (CC-BY 3.0) via Commons Wikimedia
2. “Auditory Cortex Frequency Mapping” By Chittka L, Brockmann – Own Work (CC-BY SA 2.5) via Commons Wikimedia