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We present a multichip structure assembled with a medical-grade stainless-steel microelectrode array intended for neural recordings from multiple channels. The design features a mixed-signal integrated circuit (IC) that handles conditioning, digitization, and time-division multiplexing of neural signals, and a digital IC that provides control, bandwidth(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 superior colliculus (SC) is important for generating coordinated eye-head gaze saccades. Its deeper layers contain a retinotopically organized motor map in which each site is thought to encode a specific gaze saccade vector. Here we show that this fundamental assumption in current models of collicular function does not hold true during horizontal(More)
Combined eye-head movements are routinely used to orient the visual axis (gaze) rapidly in space. The gaze control system can be modeled using a feedback system in which an internally created instantaneous gaze position error signal equivalent to the distance between the target and the current gaze position is used to drive brainstem eye and head motor(More)
The superior colliculus (SC), via its projections to the pons, is a critical structure for driving rapid orienting movements of the visual axis, called gaze saccades, composed of coordinated eye-head movements. The SC contains a motor map that encodes small saccade vectors rostrally and large ones caudally. A zone in the rostral pole may have a different(More)
Rapid coordinated eye-head movements, called saccadic gaze shifts, displace the line of sight from one location to another. A critical structure in the gaze control circuitry is the superior colliculus (SC) of the midbrain, which drives gaze saccades by relaying cortical commands to brainstem eye and head motor circuits. We proposed that the SC lies within(More)
Our perception of the positions of objects in our surroundings is surprisingly unaffected by movements of the eyes, head, and body. This suggests that the brain has a mechanism for maintaining perceptual stability, based either on the spatial relationships among visible objects or internal copies of its own motor commands. Strong evidence for the latter(More)
A prominent hypothesis in motor control is that endpoint errors are minimized because motor commands are updated in real time via internal feedback loops. We investigated in monkey whether orienting saccadic gaze shifts made in the dark with coordinated eye-head movements are controlled by feedback. We recorded from superior colliculus fixation neurons(More)
Anatomical, electrophysiological and lesion studies indicate that each cortical hemisphere normally generates saccades directed to the contralateral side. In contrast, in patients who had an entire cortical hemisphere removed surgically (hemidecortication), the remaining hemicortex can generate both contraversive and ipsiversive saccades. However, current(More)
Visual neurons have spatial receptive fields that encode the positions of objects relative to the fovea. Because foveate animals execute frequent saccadic eye movements, this position information is constantly changing, even though the visual world is generally stationary. Interestingly, visual receptive fields in many brain regions have been found to(More)