Fig. 2.

(a) A typical hierarchical processing unit presented in Fig. 1 with an input from its previous layer (incoming red arrow on the left) and an output to its next layer (outgoing red arrow on the right). The precision-weighting signal is illustrated by a green arrow. According to this model, the intrinsic connectivity of local microcircuits and extrinsic connectivity between cortical regions become integrated: Abnormal precision signalling can lead to aberrant intrinsic connectivity and increased local functional connectivity, with decreased extrinsic connectivity, as observed for example in focal epilepsy. (b) A normal free-energy minimisation cycle associated with the hierarchical processing unit presented in (a). The input and output signals (red arrows) of panel (a) are also illustrated in this cycle. The blue circles show where precision (i.e., neuronal excitability or postsynaptic gain) may be subverted by focal epilepsy. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)