Fig. 3.

Neuronal message passing On the left are the equations describing a gradient descent on variational free energy. On the right, we show how these equations map to a neuronal message passing scheme for the generative model outlined above. To do so, we have simply assigned the terms on the left hand side of each equation to a neuronal population, and mapped the influences between each population with excitatory and inhibitory connections. We have separated the states representing positions and velocities into right and left components; for consistency with the representation of each hemifield on the contralateral side of the sagittal plane in the brain. The numbers in little blue circles refer to the anatomical designation of expectation and error units in Fig. 5.