260 INTRODUCTION TO NEUROLOGY 



ties and with a minimum of objective reference, excite within the brain, 

 probably in the medial thalamic nuclei, a general non-localized pleasurable 

 or unpleasant feeling, a feeling of well-being or malaise, as the case may be. 

 These thalamic receptive centers are in very intimate relation with the 

 visceral efferent systems of the hypothalamus and a reflex response in the 

 viscera follows a typical organic circuit. So long as this circuit involves 

 only the viscera and their thalamic centers the peripheral reference will be at 

 a minimum, and the feeling remains an unlocalized change in the affective 

 consciousness. 



The higher emotional and esthetic activities are so charged with intellec- 

 tual content also as to require the ^participation of the association centers of 

 the cerebral cortex. But no pleasure-pain centers are known in the cortex 

 and the evidence at present available seems to negative the presence of such 

 centers. The agreeable or disagreeable components of the higher emotional 

 processes are very probably due to the colligation of thalamic activities 

 with cortical associational processes. In case these emotional or esthetic 

 processes are of cortical origin, that is, excited in the first instance by the 

 activity of cortical associational centers, their affective content may be due 

 to the involvement of the subcortical pleasure-pain apparatus in the asso- 

 ciational process, and this apparatus would, as above described, generate 

 efferent impulses from the related visceral centers, thus causing the charac- 

 teristic visceral movements, which in turn would reinforce the visceral activ- 

 ities of the brain centers, and thus by a "back-stroke" action strengthen 

 the emotional con ten t of the primary associational complex. Thus the com- 



Eletion of the circular reaction may reinforce the affective consciousness so 

 >ng as it is operative. 



That pleasure is correlated with free discharge of nervous energy is sug- 

 gested further by the fact that in most of the pleasurable emotions and senti- 

 ments there is present a large factor of recall of previous experiences. The 

 esthetic enjoyment of a given situation is in large measure proportional to 

 the wealth of associated memories incorporated within it, especially when 

 these are recombined into new patterns. The pleasure experienced in listen- 

 ing to a complicated musical production like a symphony may be enhanced 

 many fold after one has become thoroughly familiar with it, and still more 

 so if the listener has himself played it or parts of it. 



In concluding this discussion of pleasure-pain we quote the following 

 paragraph from Sherrington's account of Cutaneous Sensations, already 

 referred to (Schafer's Physiology, 1900, vol. ii, p. 1000): 



"Affective tone is an attribute of all sensation, and among the attribute 

 tones of skin sensation is skin-pain. Affective tone inheres more intensely 

 in senses which refer to the body than in those which refer to the environ- 

 ment, that is, it is strongest in the non-pro jicient senses. It is, therefore, 

 strong in the cutaneous senses, and in them is inversely as their projicience, 

 therefore least in touch spots, more in thermal spots, most in the so-called 

 'pain-spots.' . . . Stimuli evoking skin-pain are broadly such as injure 

 or threaten injury to the skin; the skin may be said to have gone far toward 

 developing a special sense of its own injuries. The central conducting 

 path concerned with these skin feelings seems a side-path into which the 

 impressions from the various skin spots embouch with various ease, those 

 from the 'pain spots' especially easily. The physiological reactions connected 

 with this side-path are characterized by tendency to 'summation, ' tendency 

 to 'collateral irradiation,' slow culmination, and slow subsidence. They 

 often involve with their own activity that of adjacent sensory channels (as- 



