The thalamus: controller of cortical functional connections (a model based on EEG and brain imaging)

A model of control of cortico-cortical functional connections (FCs) by the thalamo-cortical neurons (TNs) is proposed based on EEG-coherence functions, regional cerebral blood flow (rCBF) from brain-imaging techniques and computer models. In our model, cortical modules can “sleep”, be “alert” or “relaxed”, if they “imitate” these behavioral and electrical patterns of the brain, First, we classify the FCs of the cortex and their progressive establishment and later we postulate that TNs not only control activation degrees of cortical modules but also are responsible for establishing particular FCs among them, always creating connected graphs. Intralaminar neurons (INs) produce cortical activation and a variety of TNs induce the different types of FCs (coincident detection, frequency tuning, or phase synchrony). Frontal input activates/inactivates FCs by inhibition/excitation of reticular neurons (RNs) or resetting TNs oscillations. A fuzzy logic description is formulated. The role of the thalamus in a cyclic process travelling through the cortex is discussed and a new long-term-periodic-change of FCs is suggested in the context of childhood development, adult life and Alzheimer disease