Fig. 4.

creating one’s own sensations. This figure shows the results of a simulation in which the precision (gain) of proprioceptive prediction errors was increased from a log precision of −8 to 8 (highlighted by the insert on the right). This effectively switches on reflex arcs that respond to descending proprioceptive predictions from the higher vocal centre, causing the previously perceived song to be articulated. However, when we run the simulations (ensuring that the bird can hear itself) the ensuing song is unrecognisable. This is shown in the upper panel in terms of a bizarre looking sonogram that has lost the deep hierarchical structure and tempo of the sonograms in the previous figures. The middle (resp. lower) panel shows posterior expectations about hidden states in the first (resp. second) hierarchical levels. The dynamics characteristic of the Lorentz attractor have been destroyed and low amplitude high-frequency fluctuations are evident in these traces. These reflect the impact of precise prediction errors due to sensorimotor delays in the enactment of predictions.