Somatosensory Cortex

Before discussing the role of the cerebral cortex in somatic sensation, we need to give an orientation to the various areas of the cortex. Figure 47-5 is a map of the human cerebral cortex, showing that it is divided into about 50 distinct areas called Brodmann's areas based on histological structural differences. This map is important because virtually all neurophysiologists and neurologists use it to refer by number to many of the different functional areas of the human cortex.

Note in the figure the large central fissure (also called central sulcus) that extends horizontally across the brain. In general, sensory signals from all modalities of sensation terminate in the cerebral cortex immediately posterior to the central fissure. And, generally, the anterior half of the parietal lobe is concerned almost entirely with reception and interpretation of somatosensory signals. But the posterior half of the parietal lobe provides still higher levels of interpretation.

Visual signals terminate in the occipital lobe, and auditory signals in the temporal lobe.

Conversely, that portion of the cerebral cortex anterior to the central fissure and constituting the posterior half of the frontal lobe is called the motor cortex and is devoted almost entirely to control of muscle contractions and body movements. A major share of this motor control is in response to somatosensory

Projection of the dorsal column-medial lemniscal system through the thalamus to the somatosensory cortex. (Modified from Brodal A: Neurological Anatomy in Relation to Clinical Medicine. New York: Oxford University Press, 1969, by permission of Oxford University Press.)

Structurally distinct areas, called Brodmann's areas, of the human cerebral cortex. Note specifically areas 1, 2, and 3, which constitute primary somatosensory area I, and areas 5 and 7, which constitute the somatosensory association area.
Somatosensory Areas
Two somatosensory cortical areas, somatosensory areas I and II.

Upper lip

Figure 47-7

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