The cartoon above depicts the OPS: (a) Actual overt movements of the user are detected. (b) Synthetic neural activity is generated in some fashion derived from the overt movements. (c) The decoder sees only the simulated activity and provides a decoded estimate of the cursor position. (d) The cursor is placed on the screen along with the target permitting visual feedback. The flow diagrams on the right compare how data is generated in a real BCI versus the OPS and the relationship between the variables. While there is no direct link relating intended kinematics and overt movement (or volition), these variables are conditionally related. If the user desires to produce a certain decoded kinematics and doing so requires some modulations of the neural activity which are controlled by the overt movement, then the user should modulate overt movement in a way that reflects their intended kinematics.
From Merel J1, Pianto DM2, Cunningham JP3, Paninski L3. Encoder-decoder optimization for brain-computer interfaces. PLoS Comput Biol. 2015 Jun 1;11(6):e1004288. doi: 10.1371/journal.pcbi.1004288.