Corpus Striatum And Thalamus

The exact functions of the corpus striatum, embracing the caudate and lenticular nuclei, and of the thalamus are not known. They are most often affected in apoplexies; lesions of the corpus striatum are accompanied by disturbances of motion, and those of the thalamus by disturbances of sensation.

Corpora Quadrigemina

The anterior corpora quadrigemina are associated with sight, the posterior possibly with hearing and equilibrium. Note their proximity to the cerebellum.

Fig. 47.   The corona radiata or projection fibres which connect the cortex above with the thalamus, corpus striatum, tegmental region, pons, medulla, and spinal cord below. These fibres go to form the internal capsule.

Fig. 47. - The corona radiata or projection fibres which connect the cortex above with the thalamus, corpus striatum, tegmental region, pons, medulla, and spinal cord below. These fibres go to form the internal capsule.

Crura Cerebri

The crura cerebri transmit both sensory and motor impulses: Note their proximity to the third nerve, as they are apt to be involved by the same lesions, thus accounting for paralyses or sensory disturbances of the trunk or extremities accompanied by ocular paralysis. Pons Varolii. - The pons transmits the motor or pyramidal tract, and also the fifth, sixth, and seventh nerves. Implication of the seventh or facial nerve, together with the motor tract, has already been alluded to (page 32). If the sixth or abducent nerve is involved, the external rectus muscle on that side will be paralyzed. If the fifth, or trifacial nerve is affected, irritation of its motor root may produce trismus or clenching of the jaws, and interference with its sensory root may cause anaesthesia of one side of the face.