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INTRODUCTION TO NEUROLOGY 



with a specific region in the cerebral cortex, viz., the optic, 

 auditory, and somesthetic projection centers (see p. 273). 

 These tracts are known as the optic, auditory, and somesthetic 

 radiations (see Fig. 80). 



The old thalamus (palaeothalamus) comprises the more 

 medial thalamic centers, which were differentiated for the 

 primitive thalamic correlations which are present in fishes and 

 other lower vertebrates which lack the cerebral cortex. Clinical 



Lateral (Sylvian) 



fissure 

 Internal capsule 



Island of Reil 

 Lentiform nucleus 



External capsule 



Corpus callosum 

 Fornix 



Chorioid plexus 



Stria medullaris 



Nuc. ant. thai. 



Nue. medial, thai. 



Nuc. lateral, thai. 



Nuc. ventral, thai. 



Subthalamus 



Mammillary body 



Optic tract 



Amygdala- 



Lateral ventricle 



Fig. 79. Cross-section through the human cerebral hemisphere and 

 thalamus, including the mammillary body and the posterior end of the an- 

 terior nucleus of the thalamus (cf. Fig. 78). At this level the epithalamus 

 is represented only by the stria medullaris and the chorioid plexus of the 

 third ventricle, the hypothalamus by the mammillary body. The old 

 thalamus (pala;othalamus) is represented by the anterior and medial nuclei 

 and the subthalamus, the new thalamus (neothalamus) by the lateral and 

 ventral nuclei. 



evidence (see especially Head and Holmes, 1911) seems to show 

 that many of these primitive functions are retained in the old 

 thalamus in man, and that some of the conscious activities are 

 served by these thalamic centers. In other words, the activity 

 of the cerebral cortex is not essential for all conscious processes, 

 though its participation is necessary for others, particularly 

 all intellectual and voluntary activities. The thalamus, on the 

 other hand, can act independently of the cortex in the case of 



