What is the Difference Between Primary and Association Cortex

The main difference between primary cortex and association cortex is that the primary cortex is composed of the primary motor and primary sensory cortex, whereas the association cortex is composed of most cerebral surfaces. 

The primary and association cortex are two areas of the cerebral cortex. Also, they perform different functions. 

Key Areas Covered

1. What is the Primary Cortex
– Definition, Structure, Function
2. What is Association Cortex
– Definition, Structure, Function
3. Similarities Between Primary and Association Cortex
– Outline of Common Features
4. Difference Between Primary and Association Cortex
– Comparison of Key Differences

Key Terms 

Association Cortex, Primary Cortex, Primary Motor Cortex, Primary Sensory Cortex

What is the Primary Cortex

The primary cortex is the brain area that includes the primary motor and sensory cortex. 

Primary Motor Cortex

The primary motor cortex is the part of the cerebral cortex that controls the body’s voluntary movements. Also, it is one of the three areas of the motor cortex, while the other two include the supplementary motor area and the premotor cortex. It occurs in the precentral gyrus, on the medial surface of the cerebrum. The primary motor cortex functions to send electrical signals from the motor cortex. Importantly, the voluntary movements controlled by the primary motor cortex are skilled and refined. Additionally, it controls muscular movements on both sides of the body.

Figure 1: Primary Cortex

Primary Sensory Cortex

The primary somatosensory cortex, along with the secondary somatosensory cortex, is located in the parietal lobe of the brain. The primary somatosensory cortex occurs just behind the central sulcus. It receives sensory information from specific areas of the body. However, it requires a secondary somatosensory cortex to store, process, and retain information. 

What is Association Cortex

The association cortex is a part of the cerebral cortex responsible for the complex processing of cognitive functions. It is responsible for cognition, the ability to attend to external stimuli or internal motivation. Also, it integrates complex functions, including perception, language, and thought. In addition, the association cortex has two regions: unimodal association cortex and hetero modal association cortex. The unimodal association cortex receives information from a single sensory modality. The output of the unimodal association cortex is largely to hetero modal areas. For example, the occipital lobe and the visual association cortex process visual information. Also, the temporal lobe and the auditory association cortex process auditory information.

Figure 2: Visual Association Cortex

Moreover, the hetero-modal association cortex or polymodal association cortex integrates information from multiple sensory modalities. It involves higher cognitive functions such as attention, memory, language, and conscious thought. 

Similarities Between Primary and Association Cortex

• The primary and association cortex are two parts of the brain.
• But they perform different functions.
• They integrate information from various sources. 

Difference Between Primary and Association Cortex

Definition

Primary cortex refers to a brain region that is located in the dorsal portion of the frontal lobe. In contrast, the association cortex refers to most of the cerebral surface of the human brain and is largely responsible for the complex processing between the arrival of input in the primary sensory. 

Composed of

The primary cortex is composed of the primary motor cortex and primary sensory cortex, while the association cortex is composed of most of the cerebral surface. 

Function

The primary motor cortex generates nerve impulses that direct the body’s movement, while the primary sensory cortex processes afferent somatosensory input and contributes to the integration of sensory and motor signals necessary for skilled movement. In contrast, the associate cortex performs complex cognitive functions. 

Conclusion

In brief, the primary and associate cortex are two regions of the brain that perform different functions. The primary cortex is composed of two regions: the primary motor cortex and the primary sensory cortex. The primary motor cortex is responsible for directing movements of the body. Also, the primary sensory cortex integrates sensory and motor signals. In comparison, the associate cortex is composed of most of the cerebral surface. Additionally, it performs complex cognitive functions. Therefore, the main difference between primary and associate cortex is their structure and function. 

References:

1. Stewart, S. (2022b, November 10). Motor cortex. Kenhub. https://www.kenhub.com/en/library/anatomy/motor-cortex
2. Raju H, Tadi P. Neuroanatomy, Somatosensory Cortex. [Updated 2022 Nov 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-
3. Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. Chapter 26, The Association Cortices.

Image Courtesy:

1. “Blausen 0102 Brain Motor&Sensory” By BruceBlaus – Own Work (CC-BY 3.0) via Commons Wikimedia
2. “BA19 – Visual association cortex (V3) – lateral view” By Polygon data were generated by Database Center for Life Science (DBCLS) – Own work (CC BY-SA 2.1 jp) via Commons Wikimedia