Fig. 6.

Predictive routing model. Arrows and connections represent functional (not anatomical) connections between areas/layers. Thick lines represent effective connections with increased influence; thin lines represent effective connections with decreased influence. The Upper boxes represent superficial layers (1 to 4) and the Lower boxes represent deep layers (5/6). (Left subpanel) Sensory cortex is dynamically prepared to process its preferred stimulus, stimulus A, by feedback which inhibits MUA and enhances alpha/beta in deep layers. Enhanced deep-layer alpha/beta functionally inhibits superficial-layer processing of stimulus A by reducing spiking and gamma, reducing feedforward outputs. (Right subpanel) When a strong prediction for stimulus B is present and stimulus A is presented (as in the first few trials of an unpredictable block after a predictable block where “B” was the repeated/predicted sample), there is less feedback alpha/beta inhibition to the A column. Deep-layer to superficial-layer inhibition is weak or absent. The A column is more excitable and responds to stimulus A with more gamma/spiking and enhanced feedforward output from superficial layers (a prediction error). Although we hypothesize this mechanism occurs at the level of cortical columns, it could apply to any pathway that processes the specific predicted stimulus. We also hypothesize that this mechanism can be graded to reflect varying strengths of prediction.