In other words, the normal etiquette of the brain requires segregation among networks that have different functions, and that etiquette was blown to bits.
The focus will be on the brain's segregation into a dozen or more large-scale distributed networks and how that is balanced with the brain's need to integrate information across these networks.
Global brain network segregation was assessed using normalized clustering coefficient and modularity.
For that purpose, we analyzed parameters used in graph theory to define either brain functional segregation (M and CC) or integration (Eglob) at both the whole-brain and regional levels.
This suggests that increases of whole brain network segregation occur in the earliest stages of the neurodegenerative disease process, before symptom onset, and subsequently progress to loss of network integration in the manifest stages.
The localization of function to specific brain areas ("functional segregation") is the commonest approach to investigating function; however, an emerging, complementary approach ("functional integration") describes function in terms of the information flow across networks of areas.
Such a network architecture in the human brain facilitates efficient information segregation and integration at low wiring and energy costs, which presumably results from natural selection under the pressure of a cost-efficiency balance.
Further developments led to an ever-increased variety of neurotransmitter molecules and neurotransmitter receptors, and their functional segregation between brain regions.
Although the pattern of results was reassuringly consistent across our varied analyses, it is important to point out once again that the segregation of functional brain modules and the links between brain areas and function are based on the current state of the literature and must therefore be regarded as hypothetical and exploratory at the current stage.
Functional segregation in the brain indicates specialised processing within densely interconnected groups of brain regions, whereas functional integration implies rapid combination of specialised information from distributed brain regions [13].
