SUMMARY OF CORTICAL EVOLUTION 261 



pathways from the lower centers to the cortex are 

 activated and the cortex participates in the reaction. 



From this it follows that the nervous impulses that 

 reach the cortex are the resultants of the interaction 

 of more or less complicated subcortical dynamic pat- 

 terns, some of the participating peripheral sensory 

 systems being reinforced and others wholly or partial- 

 ly inhibited. The nervous impulses that stream into 

 the cortex are overflows from subcortical centers 

 whose simpler reflex outlets are inadequate. These 

 nervous currents may, accordingly, be thought of as 

 carrying a quale of subcortical origin in that they are 

 already organized into incipient reflex patterns. It 

 may be that this quale is what gives subjectively to 

 some cortical activities of man their affective coloring 

 and also (sometimes) an impulsive tone or "drive" 

 (Herrick, 1913). 



8. The cortex in its most primitive form seems to 

 exert a dynamogenic influence upon the activities of 

 lower centers. This is in part a non-specific (equipo- 

 tential) tonic effect upon such activities as may be in 

 process, comparable with the tonic influences of the 

 cerebellum; in part (and progressively more so in 

 higher animals) it is a selective phasic action upon 

 some particular functional components of lower re- 

 flex patterns, namely, those which are the key factors 

 in problem solution by the conditioned-response 

 method. These functions are shared by the corpus 

 striatum, and in higher mammals (especially man) the 



