Figure 1.

Functional architecture of cortical connectivity. (A) Brain topology as a Bow-Tie organization. This brain organization arises from the connectivity profile obtained from retrograde tracer studies. It defines a heavily interconnected core of fronto-parietal areas and the ties based in feedforward (FF) and feedback (FB) connections from the core. As expected, early sensory areas are located more at the extremes of the tie. Adapted with permission from Markov et al. (2013b). (B) Representation of the directed oscillatory influences (measured by Granger causality) over the cortical column in area V1 of the monkey. Gamma (30–90 Hz) oscillations are predominantly feedforward and they target granular and supragranular layers. Alpha/beta oscillations (roughly 8–30 Hz, combined) are predominantly feedback. They originate at hierarchically higher areas and target predominantly infragranular layers. Adapted with permission from van Kerkoerle et al. (2014). (C) Long and short-range connections implementing a Predictive Coding (PC) framework of sensory processing. Under such framework, a predictive model is originated at prefrontal cortex and local areas and channeled towards early sensory areas by long and short-range connections respectively, using low frequency (alpha and beta) oscillations. Error signals, originated from sensory areas are broadcasted towards hierarchically higher brain areas using high-frequency oscillations.