Postural Control: Learning to Balance Is a Question of Timing Stefan Glasauer, Hans Straka  Current Biology  Volume 27, Issue 3, Pages R105-R107 (February 2017) DOI: 10.1016/j.cub.2016.12.021 Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 1 Postural re-adjustment of larval zebrafish and potential underlying control mechanisms. (A) Body orientations before and after gravity-induced disturbance, and during subsequent postural re-adjustment within the water column by swimming bouts. (B) The dependency of swim bout probability on body orientation. (C) The increase of postural sensitivity during post-embryonic development. (D) Continuous control: the desired state of the organism is compared to the output of a state estimator, which receives sensory feedback and motor efference copies; the error between estimated and desired states is sent to a controller, which computes optimal motor commands for error minimization. The state of the body as well as the sensory feedback, which includes delays that complicate continuous control, are influenced by the environment (see for example [9]). (E) Intermittent control: the simplified scheme here is similar to (D), except that a switch prevents error signals from being transmitted to the controller such that the latter acts only if the trigger closes the switch. The closing of the switch is triggered when the error between the estimated and desired states exceeds a particular threshold. Note that the state usually consists of multiple variables such as velocity and position. Current Biology 2017 27, R105-R107DOI: (10.1016/j.cub.2016.12.021) Copyright © 2017 Elsevier Ltd Terms and Conditions