THE THALAMUS 145 



thalamus (or better, the diencephalon as a whole) per- 

 forms two very different kinds of function. First, 

 there are the intrinsic thalamic reflexes and their mu- 

 tual adjustment locally; and, second, there are thal- 

 amo-striatal and thalamo-cortical relations of diverse 

 sorts. Normally in higher animals these two kinds of 

 function are probably never performed independently 

 of each other; and yet it is clear that these are inde- 

 pendent variables, and when the matter is viewed 

 comparatively the second kind of activity becomes 

 progressively more important relatively to the first 

 as the vertebrate series is ascended from fishes to men. 



Nevertheless, the local or intrinsic thalamic func- 

 tions are probably not less, but more, important in 

 man than in lower forms. In certain diseased condi- 

 tions where the thalamus is isolated from its cortical 

 connections by destruction of the thalamic radiations 

 the functions of the thalamus itself come into the 

 foreground of the clinical picture. In this "thalamic 

 syndrome" pure affective experience is intensified. 

 The slightest stimulus may be extremely painful, but 

 there is no intelligent analysis of the experience or 

 localization of the stimulus. It is sheer pain, uninter- 

 preted and better expressed by "it hurts" than by "I 

 feel a pin prick in my hand." 



That the thalamus, even in man, plays a large 

 role in the fabrication of conscious experience is sug- 

 gested by many clinical cases. Head (1920, vol. 2, p. 

 600) is of the opinion that here are localized, not only 



