Functional cortical areas
1) Frontal lobe:
Its posterior part (precentral area) is responsible for motor functions, while its anterior part (prefrontal area) is responsible for higher mental functions.
Premotor area:
It plans the movements, inhibits muscle tone, and adjusts the posture to start the movement.
Primary motor area:
It initiates skilled voluntary movements for contralateral ½ of body which are planned in premotor area.
Frontal eye field:
It is responsible for voluntary conjugate eye movements (to contralateral side), and NOT reflex eye movements.
prefrontal area:
It is responsible for intelligence and normal expression of emotions. Also has a role in ability to predict consequences of actions.
Broca’s area (motor speech area):
It receives data from sensory speech area (Wernicke’s area) to create sequence of muscle contractions to be sent to motor area to produce intelligible words.
N.B:
- Supplementary motor area: it is an area on the medial surface of cerebral hemisphere (medial frontal gyrus).
- The body is represented bilaterally in this area (its stimulation evokes movements in limbs on both sides).
- It stores programmed sequences for stereotyped movements and contains superior speech center.
- Motor homunculus: it is the body representation within the cortical areas.
- The primary motor cortex corresponds point by point with specific regions of the contralateral side of the body.
- This means that activity of certain portion in the primary motor cortex results in contraction of specific peripheral muscles.
- The contralateral side of the body is represented upside down (face is down, while foot area is in paracentral lobule).
- The body representation depends on skill, not the size of the organ (parts with fine skilled movements occupy larger areas (hands)).
2) Parietal lobe:
It contains general sensory areas (1ˢᵗ and 2ⁿᵈ somatosensory areas, sensory association area, and sensory speech center of Wernicke’s).
1ˢᵗ somatosensory area:
It receives sensory information about the contralateral ½ of the body from anterior thalamic nuclei. Its anterior part receives cutaneous stimuli, while its posterior part receives proprioceptive impulses.
2ⁿᵈ somatosensory area:
It is located on the upper lip of lateral sulcus just behind the central sulcus. It receives transient sensory stimuli from both sides of the body (brush strokes).
Gustatory (taste) area:
It is located in parietal operculum of insula (upper lip of lateral sulcus). It receives ipsilateral solitario-thalamo-cortical fibers.