Lab 8 - Higher Motor Function

Review of the Cerebral Cortex (continued)

View and identify the structures in the illustration.

Start by looking for the longitudinal fissure, lateral sulcus, and central sulcus.

The primary motor area (also called the primary motor cortex) is located within the precentral gyrus. The premotor area is within the precentral gyrus rostral to the primary motor cortex and extends rostrally to include the caudal half of the frontal lobe. The premotor area is thought to be involved with preparation for movement and developing appropriate motor strategies.

The supplementary motor area occupies the medial aspect of the superior frontal gyrus rostral to the precentral sulcus. This area appears to be important for programming motor sequences involved in complex motor tasks.

The frontal eye-fields are located within the caudal part of the middle frontal gyrus. Electrical stimulation of this region elicits conjugate movement of the eyes to the contralateral side; lesions of this area result in deviation of the eyes towards the side of the lesion and inability to voluntarily, but not reflexively, move the eyes contralaterally.

Broca's speech area is located within the caudal part of the inferior frontal gyrus, i.e., in the triangular and opercular parts inferior frontal gyrus of the dominant hemisphere. The dominant hemisphere is the hemisphere that is important for the comprehension and production of speech and language. Normally, it is the left hemisphere of right-handed people. Broca's speech area is important for the production of speech and language.

In addition to the motor cortical areas in the frontal lobe, cortical areas within the parietal lobe also are important for the control of voluntary movement. Parietal regions, along with frontal cortex, contribute axons to the pyramidal tract-the direct pathway linking the cerebral cortex and spinal cord. The primary somatosensory cortex in the postcentral gyrus is also substantially interconnected with the primary motor cortex in the precentral gyrus. The superior parietal lobule and the precuneus are interconnected with premotor and supplementary motor cortex.