THE ASSOCIATION CENTERS 247 



discharged from lower centers of diverse sorts are ar- 

 ranged in mosaic or switchboard patterns. Localiza- 

 tion in space of these "sensory projection centers" is 

 an indispensable feature of the cortex. There is also 

 a mosaic localization of peripheral motor fields of 

 some sort in the Rolandic zone. Beyond these fields 

 mosaic localization of cortical functions is of very 

 doubtful validity. Certain of the larger fascicles of as- 

 sociational fibers, like the cingulum, are probably laid 

 down in innate patterns, but what functions they 

 serve we do not know. It is not improbable that the 

 precise functions of the more disperse associational 

 pathways of the cortical white matter are determined 

 within the postnatal experience of the individual. 

 Every enduring memory vestige involves the linkage 

 in some way of a very complex system of intracortical 

 neurons, and every time the cortex is activated from 

 lower centers more or fewer of these established pat- 

 terns are quickened. 



The function of speaking my friend's name when I 

 see his face is certainly not localized among thousands 

 of similar "memories" in any simple mosaic pattern 

 that can be mapped on the cortical surface. It is local- 

 ized, no doubt, in a very different way, for it involves 

 the reactivation of systems of neurons articulated in 

 definite anatomical patterns which may ramify from 

 pole to pole of the cerebral hemisphere. The systems 

 of neurons colligated with the other memories ramify 

 equally widely, and many of the neurons involved in 



