Dopamine, Affordance and Active Inference
Figure 4
This schematic illustrates the connections between prediction units (black) and error units (red) that underlie the simulated reaching movements.
The prediction units encode conditional expectations about hidden states and causes, while the error units encode the associated prediction errors. The connections between these two sorts of units are specified by the message passing scheme in Equation 3 (cf., Figure 1). In brief, error units pass precision weighted prediction errors forward and horizontally (red connections), while prediction units sent predictions backwards and horizontally (black connections). Note that prediction units only communicate with error units and vice versa. In this figure, expectations about hidden states in the first level have been divided into two sets, corresponding to the position of the arm (motor cortex) and the affordance of the cue locations (premotor cortex). The blue circle at the bottom of this figure indicates motor neurons in the ventral horn of the spinal cord that mediate action. The cyan arrows represent various projections from the substantia nigra and ventral tegmental area (SN/VTA). Exteroceptive sensory information enters directly at parietal cortex and the superior colliculus encoding positional information about the arm and the salience of cue locations respectively.