Regular articleThe elusive concept of brain connectivity
Section snippets
Functional and effective connectivity—a very brief history
To frame the issues that make defining brain connectivity so difficult, a brief historical review is necessary. Investigations of the brain during the last century have been marked by a peculiar dichotomy: whereas many neuroanatomists worked diligently to ascertain how different neuronal populations were connected to one another so as to form networks,2
Definitional difficulties
As can be seen from this brief historical overview, numerous investigators over the years have claimed that they were examining something akin to functional or effective connectivity. However, the multiple types of data that are used to evaluate functional interactivity differ from one another in many features, including spatial and temporal resolution, and whether the data represent neuron activities, neural ensemble activities, or activities (electrical or hemodynamic) of macroscopic brain
Acknowledgements
I want to thank Karl Friston and Rolf Kotter for an extremely interesting round of discussions on the issue of connectivity.
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