Figure 9.
Alternate models of neural control of saccades. A, One version of the traditional local feedback loop model. Key elements or processes include computing a desired displacement command (ΔEd) from SC population activity, using a comparator (red summation symbol) to compute dynamic motor error (m.e.), and using a resettable neural integrator (RNI; red text) to convert the eye velocity signal (E′EBN (t)) to current eye displacement (ΔE). Also, the EBN performs a nonlinear transform on motor error signal to determine eye velocity. B, Our revised conceptual model is void of the comparator and resettable neural integrator elements and therefore no longer computes dynamic motor error. The EBN output is a linear transform of the SC input. The eye velocity feedback signal (E′EBN (t)) projects to the SC. The spatiotemporal pattern of population SC activity is pivotal in determining the instantaneous eye velocity. MN, Motoneuron.