Figure 4.

A hypothetical anatomical circuit for homeostatic and allostatic regulation (87). The lower part represents a reflex arc in which homeostatic beliefs about bodily states (represented in hypothalamus, brainstem, spinal cord) are defended (protected) against deviations, by eliciting actions that depend on precision-weighted prediction errors. The upper part represents a cortical hierarchy for perceptual inference that is capable of modulating the homeostatic beliefs via descending connections and can implement anticipatory (allostatic) control. A top metacognitive layer (tentatively assigned to medial prefrontal cortex) holds beliefs about performance levels (i.e., levels of prediction errors at the top of the hierarchy). Colors have the same meaning throughout this figure, as indicated by the legend. It is important to keep in mind that in Bayesian treatments of inference-control loops, the direction in which predictions and prediction errors are signaled reverses when switching from the afferent branch (perception) to the efferent branch (action). For example, in the afferent branch, prediction errors are signaled upwards in the hierarchy, whereas in the efferent branch, they are used by descending projections to inform actions. post., posterior; ACC, anterior cingulate cortex; mPFC, medial prefrontal cortex. Reproduced from Figure 3 in Manjaly et al. (87), with permission from BMJ Publishing Group Ltd.