Anatomical and Functional Relations of the Cerebral Cortex to the Thalamus and Other Lower

Centers. All areas of the cerebral cortex have extensive to-and-fro efferent and afferent connections with deeper structures of the brain. It is especially

Figure 57-1

Structure of the cerebral cortex, showing: I, molecular layer; II, external granular layer; III, layer of pyramidal cells; IV, internal granular layer;V, large pyramidal cell layer;and VI, layer of fusiform or polymorphic cells. (Redrawn from Ranson SW, Clark SL [after Brodmann]: Anatomy of the Nervous System. Philadelphia: WB Saunders Co, 1959.)

Figure 57-1

Structure of the cerebral cortex, showing: I, molecular layer; II, external granular layer; III, layer of pyramidal cells; IV, internal granular layer;V, large pyramidal cell layer;and VI, layer of fusiform or polymorphic cells. (Redrawn from Ranson SW, Clark SL [after Brodmann]: Anatomy of the Nervous System. Philadelphia: WB Saunders Co, 1959.)

important to emphasize the relation between the cerebral cortex and the thalamus. When the thalamus is damaged along with the cortex, the loss of cerebral function is far greater than when the cortex alone is damaged because thalamic excitation of the cortex is necessary for almost all cortical activity.

Figure 57-2 shows the areas of the cerebral cortex that connect with specific parts of the thalamus. These connections act in two directions, both from the thalamus to the cortex and then from the cortex back to essentially the same area of the thalamus. Furthermore, when the thalamic connections are cut, the functions of the corresponding cortical area become almost entirely lost. Therefore, the cortex operates in close association with the thalamus and can almost be considered both anatomically and functionally a unit with the thalamus: for this reason, the thalamus and the cortex together are sometimes called the thalamocortical system. Almost all pathways from the sensory receptors and sensory organs to the cortex pass through the thalamus, with the principal exception of some sensory pathways of olfaction.

Figure 57-2

Areas of the cerebral cortex that connect with specific portions of the thalamus.

Supplementary motor synergies

Supplementary motor synergies

Figure 57-3

Functional areas of the human cerebral cortex as determined by electrical stimulation of the cortex during neurosurgical operations and by neurological examinations of patients with destroyed cortical regions. (Redrawn from Penfield W, Rasmussen T: The Cerebral Cortex of Man: A Clinical Study of Localization of Function. New York: Hafner Co, 1968.)

Figure 57-3

Functional areas of the human cerebral cortex as determined by electrical stimulation of the cortex during neurosurgical operations and by neurological examinations of patients with destroyed cortical regions. (Redrawn from Penfield W, Rasmussen T: The Cerebral Cortex of Man: A Clinical Study of Localization of Function. New York: Hafner Co, 1968.)

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