What are the functions of the precentral and postcentral gyri?

Functions of the Precentral and Postcentral Gyri

The precentral gyrus serves as the primary motor cortex controlling voluntary movement, while the postcentral gyrus functions as the primary somatosensory cortex processing tactile sensation, proprioception, and pain.

Precentral Gyrus (Primary Motor Cortex)

The precentral gyrus is the anatomical location of the primary motor area and represents one of the most functionally critical brain regions 1.

Motor Function

• Controls voluntary motor movements through direct corticospinal projections, with the lateral two-thirds supplied by the middle cerebral artery and the medial one-third by the anterior cerebral artery 1
• Encodes motor representations of body parts in a somatotopic organization, with finger movements specifically represented in distinct patterns 2
• Integrates motor planning and execution, showing activation during both actual motor performance (2.1% signal increase) and motor imagery (0.8% signal increase) 3

Functional Connectivity

• Contains both motor and tactile finger representations that integrate finger-specific motor and tactile information through distinct connectivity patterns 2
• Demonstrates activation in the anterior bank and crown of the central sulcus during motor tasks, representing the primary motor cortex proper 3

Postcentral Gyrus (Primary Somatosensory Cortex)

The postcentral gyrus processes sensory information from the body in a somatotopic arrangement.

Sensory Function

• Processes primary somatosensory information including touch, pressure, proprioception, and pain from the contralateral body 4
• Shows functional activation during motor tasks (1.2% signal increase during motor performance, 0.4% during motor imagery), indicating sensorimotor integration 3
• Contains tactile finger representations organized according to perceived hand structure rather than actual anatomical arrangement 2

Sensorimotor Integration

• Shares overlapping neural networks with the precentral gyrus for motor and sensory processing, with approximately 30% of motor imagery activation occurring in regions also active during actual movement 3
• Demonstrates distinct but interconnected motor and tactile representations supported by finger-specific anatomical and functional connectivity patterns 2

Clinical Relevance

Anatomical Identification

• Can be identified on CT and MR imaging using the medullary pattern of cerebral white matter, particularly useful when space-occupying lesions blur sulcal anatomy 5
• The central sulcus separates these gyri, serving as a reliable landmark for neurosurgical planning 5

Vascular Supply

• Precentral gyrus receives dual arterial supply: medial third from anterior cerebral artery (callosomarginal or pericallosal arteries) and lateral two-thirds from middle cerebral artery branches 1
• Strokes affecting this territory cause contralateral hemiparesis and sensory deficits due to involvement of these motor and sensory structures 6

Pathological Considerations

• In opioid use disorder, altered connectivity patterns involve the postcentral gyrus, with increased dorsal anterior cingulate connectivity to surrounding regions including sensory areas 7
• Tactile processing abnormalities in various neurological conditions show differential activity in the primary somatosensory cortex (BA2) located in the postcentral gyrus 4

Functional Organization

Both gyri encode body representations based on perceived hand anatomy rather than actual anatomical structure, representing an adaptive process that harmonizes functional and structural features 2. This organization extends to the paracentral lobule medially, where the precentral and postcentral gyri continue to represent lower limb and perineal sensorimotor functions 8.