Primary motor cortex
From Psy3241
Picture of Primary Motor Cortex
Contents |
Background
• Primary motor cortex is also called M1
• One of the principle areas involved in motor function
• Located in the frontal lobe of the brain along the precentral gyrus
• The role is to generate neural impulses that control the execution of movement
• Signals from M1 cross the body’s midline to activate skeletal muscles on the opposite side of the body
• The right hemisphere controls the left side of the body
• The left hemisphere controls the right side of the body
Somatotopic Representation
• Every part of the body is represented in the primary motor cortex
• Body part representations are arranged somatotopically
• The foot is next to the leg, next to the trunk, next to the arm, which is next to the hand
• The amount of brain matter devoted to a particular body part represents the amount of control that the primary motor cortex has over that body part
• A lot of cortical space is devoted to complex hand and finger movements; therefore, they have larger representations in M1
Corticospinal Tract
• Neurons in M1, supplementary motor area, and premotor cortex give rise to fibers of the corticospinal tract
• The corticospinal tract is the only direct pathway from the cortex to the spine
• This tract is composed of over a million fibers
• The fibers descend through the brainstem and cross to the opposite side of the body
• The fibers then continue to descend through the spine, terminating at the appropriate spinal levels
• This tract is the main pathway for control of voluntary movement in humans
Damage to Primary Motor Cortex
• Lesions in the primary motor cortex result in paralysis of the contralateral side of the body
