The search for the function of individual areas is understandable. This gave rise to a number of localization theories. But these could not and cannot explain the function of the brain. The function lies in the network, is one conclusion from the dilemma. Nevertheless, local searches continue. It has long been known that during functional activity, it is not areas but connectome fibers that become active across the board. Excitation runs via synaptically connected neurons to the successful organ. These synaptic fibers become active with all their divergence and convergence, not specialized areas in the network.
Thesis: These specially shaped fibers carry out brain functions. These are the functional parts.
This means that the astrocytes are not located in functional parts, but act between them. An astrocyte nourishes neurons belonging to different functional parts. In this way, the astrocyte registers the need. If one neuron uses a lot, the other neurons supplied have less, and this in detail. Neurons wait for signals from astrocytes. Without these commands, the neurons are helpless and atrophy. Theoretically, the number of connectome fibers can exceed the number of neurons.
Given current knowledge, the paradigm shift to connectome structure (also called communication chains) is long overdue. The intensive influence of localization theories makes it difficult to rethink things.
The neurons are not supplied directly, but the astrocytes. This is interpreted as Blood-Brain Barrier. An astrocyte nourishes several neurons with its cell processes and a neuron is supplied by several astrocytes.
How to explain this fact? I don't know of any thesis on this.
If the supplied neurons are now functionally dependent, this special supply regulates the functional activity. This follows in more detail in German language