# A measure for brain complexity: relating functional segregation and integration in the nervous system #

This controversy mirrors two contrasting properties that coexist in the brains of higher vertebrates: the functional segregation of different brain regions and their integration in perception and behavior.

A balance can "arise naturally through constructive and correlative properties of reentry" see Reentry

Different neuronal groups are functionally segregated if their activities tend to be statistically independent when these groups are considered a few at a time. Conversely, groups are functionally integrated if they show a high degree of statistical dependence when considered many at a time.

$$I(X)$$ is defined as the difference between the sum of the entropies of all individual components ... considered independently and the entropy of $$X$$ considered as a whole:

$$I(X) = \sum_{i=1}^{n} H(x_i) - H(X).$$