232 BRAINS OF RATS AND MEN 



Now, still in front of this premotor field the human 

 brain possesses an extreme prefrontal cortex which is 

 scarcely represented at all in lower mammals and no- 

 where approaches the human development. This re- 

 gion is in especially intimate relation with the thala- 

 mus through the so-called anterior peduncle of the 

 thalamus, probably by both descending and ascend- 

 ing fibers. Keeping in mind that the thalamus ap- 

 pears to be the organ par excellence of affective ex- 

 perience (p. 145)5 this thalamo-frontal connection 

 may provide for the addition within the prefrontal 

 field of affective impulses of thalamic origin. 



The emotional drive which is so powerful a com- 

 ponent of much intentionally directed effort is here 

 knit into the cortical process in the field where motor 

 patterns are in process of fabrication. Affective ex- 

 perience thus co-operates with cognitive experience 

 in shaping the course of action and giving the re- 

 sponse its dynamic power and volitional motivation 

 (Tilney and Riley, 1923, pp. 611, 799). This is a very 

 attractive hypothesis, though, it must be admitted, 

 not adequately supported anatomically or physio- 

 logically. 



It is significant that in many of the reported cases 

 of injury to the frontal pole two classes of symptoms 

 are encountered clinically. These are disorientation 

 in space (inability to find one's way about) and emo- 

 tional instability. For striking cases of the former, 

 see the papers by Marie and his colleagues (1919, 



