WHAT WE DO WITH OUR BRAINS 9 



connections are really in action, but as the patterns 

 of cortical associations change from moment to 

 moment the total of anatomically present inter- 

 cellular connections that may be activated is so 

 large a number that it seems futile to attempt to 

 express it in figures. These are the possible combina- 

 tions, not those actually working. 



During a few minutes of intense cortical activity 

 the number of interneuronic connections actually 

 made (counting also those that are activated more 

 than once in different associational patterns) may 

 well be as great as the total number of atoms in the 

 solar system. Certainly not all anatomically present 

 connections of nervous elements are ever used, but 

 the potentialities of diversity of cortical associational 

 combinations are practically unHmited and the 

 personal experience of the individual is probably an 

 important factor in determining which of these 

 possibilities will be actually realized. 



The efficiency of the cortex, what practical use 

 we can make of these potential intercellular associa- 

 tional connections, seems to depend in the first place 

 upon the number and character of the associational 

 patterns that are laid down as enduring structural 

 records of past experience (that is, the number and 

 character of our memory vestiges — what we have 

 learned), and in the second place upon the facility 

 with which these memory patterns can be reactivated 

 in useful combinations (that is, the extent to which 



