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The frontal eye field (FEF) and superior colliculus (SC) are thought to form two parallel systems for generating saccadic eye movements. The SC is thought classically to mediate reflex-like orienting movements. Thus it can be hypothesized that the FEF exerts a higher level control on a visual grasp reflex. To test this hypothesis we have studied the(More)
Gaze, the direction of the visual axis in space, is the sum of the eye position relative to the head (E) plus head position relative to space (H). In the old explanation, which we call the oculocentric motor strategy, of how a rapid orienting gaze shift is controlled, it is assumed that 1) a saccadic eye movement is programmed with an amplitude equal to the(More)
1. In this paper we describe the movement-related discharges of tectoreticular and tectoreticulospinal neurons [together called TR (S) Ns] that were recorded in the superior colliculus (SC) of alert cats trained to generate orienting movements in various behavioral situations; the cats' heads were either completely unrestrained (head free) or immobilized(More)
The purpose of this investigation was to describe the neural constraints on three-dimensional (3-D) orientations of the eye in space (Es), head in space (Hs), and eye in head (Eh) during visual fixations in the monkey and the control strategies used to implement these constraints during head-free gaze saccades. Dual scleral search coil signals were used to(More)
The objective of system identification methods is to construct a mathematical model of a dynamical system in order to describe adequately the input-output relationship observed in that system. Over the past several decades, mathematical models have been employed frequently in the oculomotor field, and their use has contributed greatly to our understanding(More)
The goal of this study was to identify and model the three-dimensional (3-D) geometric transformations required for accurate saccades to distant visual targets from arbitrary initial eye positions. In abstract 2-D models, target displacement in space, retinal error (RE), and saccade vectors are trivially interchangeable. However, in real 3-D space, RE is a(More)
The superior colliculus has long been recognized as an important structure in the generation of saccadic displacements of the visual axis. Neurons with presaccadic activity encoding saccade vectors are topographically organized and form a "motor map." Recently, neurons with fixation-related activity have been recorded at the collicular rostral pole, at the(More)
The dynamic behavior of primate (Macaca fascicularis) inhibitory burst neurons (IBNs) during head-fixed saccades was analyzed by using system identification techniques. Neurons were categorized as IBNs on the basis of their anatomic location as well as by their activity during horizontal head-fixed saccadic and smooth pursuit eye movements and vestibular(More)
1. Orienting movements, consisting of coordinated eye and head displacements, direct the visual axis to the source of a sensory stimulus. A recent hypothesis suggests that the CNS may control gaze position (gaze = eye-relative-to-space = eye-relative-to-head + head-relative-to-space) by the use of a feedback circuit wherein an internally derived(More)
1. We recorded from electrophysiologically identified output neurons of the superior colliculus (SC)--tectoreticular and tectoreticulospinal neurons [together called TR(S)Ns]--in the alert cat with head either unrestrained or immobilized. A cat actively exploring its visual surrounds typically makes a series of coordinated eye-head orienting movements that(More)