Figure 1.

Schematic illustration of hypotheses for the dynamic processing underlying eye movement generation. A, Desired eye velocity commands are processed by an inverse dynamic model of the eye plant before being conveyed onto extraocular MNs. B, Parallel-pathway implementation of the inverse dynamic model. The inverse model (gray shaded box) is constructed by summing a weighted combination of desired eye velocity (top) and integrated eye velocity signals (bottom). An internal estimate of desired eye position (E*) is presumed to exist at the output of the neural integrator (∫). C, Common internal model hypothesis for extending the framework to translation (TVOR). Otolith signals, encoding linear acceleration, are presumed to be “prefiltered” before converging on the inverse model used to convert desired eye velocity signals into appropriate motor commands (supplemental text, available at www.jneurosci.org as supplemental material). D, Distributed dynamic processing hypothesis for the TVOR. The internal model is not fully implemented in the TVOR pathways. Otolith signals are presumed to be processed by only the neural integrator portion (dashed box) of the inverse model that converts linear acceleration signals into velocity. To explain the high-pass nature of the TVOR, it is assumed that the dynamic characteristics of the eye plant remain uncompensated and therefore contribute to shaping the reflex at the higher frequencies where the TVOR exhibits a robust response (see supplemental text, available at www.jneurosci.org as supplemental material).