Motor Scaling By Viewing Distance of Early Visual Motion Signals During Smooth Pursuit

2002 ◽  
Vol 88 (5) ◽  
pp. 2880-2885 ◽  
Author(s):  
Hui-Hui Zhou ◽  
Min Wei ◽  
Dora E. Angelaki
Keyword(s):  
Eye Movements ◽  
Visual Motion ◽  
Neural Substrates ◽  
Open Loop ◽  
Target Distance ◽  
Viewing Distance ◽  
Major Pathway ◽  
Gaze Stabilization ◽  
Order Of Magnitude ◽  
Eye Velocity

The geometry of gaze stabilization during head translation requires eye movements to scale proportionally to the inverse of target distance. Such a scaling has indeed been demonstrated to exist for the translational vestibuloocular reflex (TVOR), as well as optic flow–selective translational visuomotor reflexes (e.g., ocular following, OFR). The similarities in this scaling by a neural estimate of target distance for both the TVOR and the OFR have been interpreted to suggest that the two reflexes share common premotor processing. Because the neural substrates of OFR are partly shared by those for the generation of pursuit eye movements, we wanted to know if the site of gain modulation for TVOR and OFR is also part of a major pathway for pursuit. Thus, in the present studies, we investigated in rhesus monkeys whether initial eye velocity and acceleration during the open-loop portion of step ramp pursuit scales with target distance. Specifically, with visual motion identical on the retina during tracking at different distances (12, 24, and 60 cm), we compared the first 80 ms of horizontal pursuit. We report that initial eye velocity and acceleration exhibits either no or a very small dependence on vergence angle that is at least an order of magnitude less than the corresponding dependence of the TVOR and OFR. The results suggest that the neural substrates for motor scaling by target distance remain largely distinct from the main pathway for pursuit.

Context Compensation in the Vestibuloocular Reflex During Active Head Rotations

2000 ◽  
Vol 84 (6) ◽  
pp. 2904-2917 ◽  
Author(s):  
W. P. Medendorp ◽  
J.A.M. Van Gisbergen ◽  
S. Van Pelt ◽  
C.C.A.M. Gielen
Keyword(s):  
Human Subjects ◽  
Linear Regression Analysis ◽  
Head Movements ◽  
Target Distance ◽  
General Context ◽  
Vestibuloocular Reflex ◽  
Gaze Stabilization ◽  
Retinal Slip ◽  
Eye Velocity ◽  
Head Rotations

The vestibuloocular reflex (VOR) needs to modulate its gain depending on target distance to prevent retinal slip during head movements. We investigated gain modulation (context compensation) for binocular gaze stabilization in human subjects during voluntary yaw and pitch head rotations. Movements of each eye were recorded, both when attempting to maintain gaze on a small visual target at straight-ahead in a darkened room and after its disappearance (remembered target). In the analysis, we relied on a binocular coordinate system yielding a version and a vergence component. We examined how frequency and target distance, approached here by using vergence angle, affected the gain and phase of the version component of the VOR and compared the results to the requirements for ideal performance. Linear regression analysis on the version gain-vergence relationship yielded a slope representing the influence of target proximity and an intercept corresponding to the response at zero vergence (“default gain”). The slope of the fitted relationship, divided by the geometrically required slope, provided a measure for the quality of version context compensation (“context gain”). In both yaw and pitch experiments, we found default version gains close to one even for the remembered target condition, indicating that the active VOR for far targets is already close to ideal without visual support. In near target experiments, the presence of visual feedback yielded near unity context gains, indicating close to optimal performance (retinal slip <0.4°/s). For remembered targets, the context gain deteriorated but was still superior to performance in corresponding passive studies reported in the literature. In general, context compensation in the remembered target paradigm was better for vertical than for horizontal head rotations. The phase delay of version eye velocity relative to head velocity was small (∼2°) for both horizontal and vertical head movements. Analysis of the vergence data from the near target experiments showed that context compensation took into account that the two eyes require slightly different VORs. In thediscussion, comparison of the present default VOR gains and context gains with data from earlier passive studies has led us to propose a limited role for efference copies during self-generated movements. We also discuss how our analysis can provide a framework for evaluating two different hypotheses for the generation of binocular VOR eye movements.

scholarly journals Enhancement of Multiple Components of Pursuit Eye Movement by Microstimulation in the Arcuate Frontal Pursuit Area in Monkeys

2002 ◽  
Vol 87 (2) ◽  
pp. 802-818 ◽  
Author(s):  
Masaki Tanaka ◽  
Stephen G. Lisberger
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Visual Motion ◽  
Gain Control ◽  
Target Velocity ◽  
Stationary Target ◽  
Electrical Microstimulation ◽  
Eye Motion ◽  
On Line ◽  
Eye Velocity

Periarcuate frontal cortex is involved in the control of smooth pursuit eye movements, but its role remains unclear. To better understand the control of pursuit by the “frontal pursuit area” (FPA), we applied electrical microstimulation when the monkeys were performing a variety of oculomotor tasks. In agreement with previous studies, electrical stimulation consisting of a train of 50-μA pulses at 333 Hz during fixation of a stationary target elicited smooth eye movements with a short latency (∼26 ms). The size of the elicited smooth eye movements was enhanced when the stimulation pulses were delivered during the maintenance of pursuit. The enhancement increased as a function of ongoing pursuit speed and was greater during pursuit in the same versus opposite direction of the eye movements evoked at a site. If stimulation was delivered during pursuit in eight different directions, the elicited eye velocity was fit best by a model incorporating two stimulation effects: a directional signal that drives eye velocity and an increase in the gain of ongoing pursuit eye speed in all directions. Separate experiments tested the effect of stimulation on the response to specific image motions. Stimulation consisted of a train of pulses at 100 or 200 Hz delivered during fixation so that only small smooth eye movements were elicited. If the stationary target was perturbed briefly during microstimulation, normally weak eye movement responses showed strong enhancement. If delivered at the initiation of pursuit, the same microstimulation caused enhancement of the presaccadic initiation of pursuit for steps of target velocity that moved the target either away from the position of fixation or in the direction of the eye movement caused by stimulation at the site. Stimulation in the FPA increased the latency of saccades to stationary or moving targets. Our results show that the FPA has two kinds of effects on the pursuit system. One drives smooth eye velocity in a fixed direction and is subject to on-line gain control by ongoing pursuit. The other causes enhancement of both the speed of ongoing pursuit and the responses to visual motion in a way that is not strongly selective for the direction of pursuit. Enhancement may operate either at a single site or at multiple sites. We conclude that the FPA plays an important role in on-line gain control for pursuit as well as possibly delivering commands for the direction and speed of smooth eye motion.

Primate Translational Vestibuloocular Reflexes. II. Version and Vergence Responses to Fore-Aft Motion

2000 ◽  
Vol 83 (3) ◽  
pp. 1648-1661 ◽  
Author(s):  
M. Quinn McHenry ◽  
Dora E. Angelaki
Keyword(s):  
Eye Movements ◽  
Rhesus Monkeys ◽  
Viewing Distance ◽  
Functional Dependencies ◽  
Ideal Behavior ◽  
Pass Filter ◽  
Disjunctive Eye Movements ◽  
Eye Velocity ◽  
High Pass ◽  
Straight Ahead

To maintain binocular fixation on near targets during fore-aft translational disturbances, largely disjunctive eye movements are elicited the amplitude and direction of which should be tuned to the horizontal and vertical eccentricities of the target. The eye movements generated during this task have been investigated here as trained rhesus monkeys fixated isovergence targets at different horizontal and vertical eccentricities during 10 Hz fore-aft oscillations. The elicited eye movements complied with the geometric requirements for binocular fixation, although not ideally. First, the corresponding vergence angle for which the movement of each eye would be compensatory was consistently less than that dictated by the actual fixation parameters. Second, the eye position with zero sensitivity to translation was not straight ahead, as geometrically required, but rather exhibited a systematic dependence on viewing distance and vergence angle. Third, responses were asymmetric, with gains being larger for abducting and downward compared with adducting and upward gaze directions, respectively. As frequency was varied between 4 and 12 Hz, responses exhibited high-pass filter properties with significant differences between abduction and adduction responses. As a result of these differences, vergence sensitivity increased as a function of frequency with a steeper slope than that of version. Despite largely undercompensatory version responses, vergence sensitivity was closer to ideal. Moreover, the observed dependence of vergence sensitivity on vergence angle, which was varied between 2.5 and 10 MA, was largely linear rather than quadratic (as geometrically predicted). We conclude that the spatial tuning of eye velocity sensitivity as a function of gaze and viewing distance follows the general geometric dependencies required for the maintenance of foveal visual acuity. However, systematic deviations from ideal behavior exist that might reflect asymmetric processing of abduction/adduction responses perhaps because of different functional dependencies of version and vergence eye movement components during translation.

scholarly journals Different mechanisms for modulation of the initiation and steady-state of smooth pursuit eye movements

2020 ◽  
Vol 123 (3) ◽  
pp. 1265-1276 ◽  
Author(s):  
Stuart Behling ◽  
Stephen G. Lisberger
Keyword(s):  
Steady State ◽  
Eye Movements ◽  
Smooth Pursuit ◽  
Visual Motion ◽  
Smooth Pursuit Eye Movements ◽  
Target Speed ◽  
Pursuit Eye Movements ◽  
Visual Motor ◽  
State Tracking ◽  
Eye Velocity

Smooth pursuit eye movements are used by primates to track moving objects. They are initiated by sensory estimates of target speed represented in the middle temporal (MT) area of extrastriate visual cortex and then supported by motor feedback to maintain steady-state eye speed at target speed. Here, we show that reducing the coherence in a patch of dots for a tracking target degrades the eye speed both at the initiation of pursuit and during steady-state tracking, when eye speed reaches an asymptote well below target speed. The deficits are quantitatively different between the motor-supported steady-state of pursuit and the sensory-driven initiation of pursuit, suggesting separate mechanisms. The deficit in visually guided pursuit initiation could not explain the deficit in steady-state tracking. Pulses of target speed during steady-state tracking revealed lower sensitivities to image motion across the retina for lower values of dot coherence. However, sensitivity was not zero, implying that visual motion should still be driving eye velocity toward target velocity. When we changed dot coherence from 100% to lower values during accurate steady-state pursuit, we observed larger eye decelerations for lower coherences, as expected if motor feedback was reduced in gain. A simple pursuit model accounts for our data based on separate modulation of the strength of visual-motor transmission and motor feedback. We suggest that reduced dot coherence allows us to observe evidence for separate modulations of the gain of visual-motor transmission during pursuit initiation and of the motor corollary discharges that comprise eye velocity memory and support steady-state tracking. NEW & NOTEWORTHY We exploit low-coherence patches of dots to control the initiation and steady state of smooth pursuit eye movements and show that these two phases of movement are modulated separately by the reliability of visual motion signals. We conclude that the neural circuit for pursuit includes separate modulation of the strength of visual-motor transmission for movement initiation and of eye velocity positive feedback to support steady-state tracking.

scholarly journals Motion dependence of smooth pursuit eye movements in the marmoset

2015 ◽  
Vol 113 (10) ◽  
pp. 3954-3960 ◽  
Author(s):  
Jude F. Mitchell ◽  
Nicholas J. Priebe ◽  
Cory T. Miller
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Visual Motion ◽  
Genetic Model ◽  
Mental Disease ◽  
Target Velocity ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements ◽  
Slow Moving ◽  
Eye Velocity

Smooth pursuit eye movements stabilize slow-moving objects on the retina by matching eye velocity with target velocity. Two critical components are required to generate smooth pursuit: first, because it is a voluntary eye movement, the subject must select a target to pursue to engage the tracking system; and second, generating smooth pursuit requires a moving stimulus. We examined whether this behavior also exists in the common marmoset, a New World primate that is increasingly attracting attention as a genetic model for mental disease and systems neuroscience. We measured smooth pursuit in two marmosets, previously trained to perform fixation tasks, using the standard Rashbass step-ramp pursuit paradigm. We first measured the aspects of visual motion that drive pursuit eye movements. Smooth eye movements were in the same direction as target motion, indicating that pursuit was driven by target movement rather than by displacement. Both the open-loop acceleration and closed-loop eye velocity exhibited a linear relationship with target velocity for slow-moving targets, but this relationship declined for higher speeds. We next examined whether marmoset pursuit eye movements depend on an active engagement of the pursuit system by measuring smooth eye movements evoked by small perturbations of motion from fixation or during pursuit. Pursuit eye movements were much larger during pursuit than from fixation, indicating that pursuit is actively gated. Several practical advantages of the marmoset brain, including the accessibility of the middle temporal (MT) area and frontal eye fields at the cortical surface, merit its utilization for studying pursuit movements.

Neurons in the Posterior Interposed Nucleus of the Cerebellum Related to Vergence and Accommodation. I. Steady-State Characteristics

1998 ◽  
Vol 79 (3) ◽  
pp. 1255-1269 ◽  
Author(s):  
Hongyu Zhang ◽  
Paul D. R. Gamlin
Keyword(s):  
Steady State ◽  
Eye Movements ◽  
Open Loop ◽  
Binocular Viewing ◽  
Viewing Distance ◽  
Unit Recording ◽  
Accommodative Response ◽  
Electrical Microstimulation ◽  
Interposed Nucleus ◽  
Response Region

Zhang, Hongyu and Paul D. R. Gamlin. Neurons in the posterior interposed nucleus of the cerebellum related to vergence and accommodation. I. Steady-state characteristics. J. Neurophysiol. 79: 1255–1269, 1998. The present study used single-unit recording and electrical microstimulation techniques in alert, trained rhesus monkeys to examine the involvement of the posterior interposed nucleus (IP) of the cerebellum in vergence and accommodative eye movements. Neurons related to vergence and ocular accommodation were encountered within a circumscribed region of the IP and their activity during changes in viewing distance was characterized. The activity of these neurons increased with decreases in vergence angle and accommodation (the far-response) but none showed changes in activity during changes in conjugate eye position and we therefore term them “far-response neurons.” Far-response neurons were found within a restricted region of the IP that extended ∼1 mm rostrocaudally and mediolaterally and 2 mm dorsal to the fourth ventricle. Microstimulation of this far-response region of the IP with low currents (<30 μA) often elicited divergence and accommodation for far. The behavior of 37 IP far-response neurons was examined during normal binocular viewing, during monocular viewing (blur cue alone), and during binocular viewing with accommodation open-loop (disparity cue alone). The activity of all cells was modulated under all three conditions. However, the change in activity of some of these neurons was significantly different under these three viewing conditions. The behavior of 70 IP far-response neurons was compared during normal binocular viewing and during viewing in which the accommodative response was significantly dissociated from the vergence response. The data from these two conditions was pooled and multiple regression analyses for each neuron generated two coefficients expressing the activity of the neuron relative to the vergence and to accommodative response respectively. On the basis of these coefficients, the overall activity of the neurons were classified as follows: 34 positively correlated with divergence, 11 positively correlated with far accommodation, 14 positively correlated with divergence and far accommodation, 9 positively correlated with divergence and accommodation, and 2 positively correlated with convergence and far accommodation. The results of this study demonstrate the involvement of a specific region of the posterior interposed nucleus of the cerebellum in vergence and accommodation. IP far-response neurons are active for vergence and accommodation irrespective of whether or not these eye movements are elicited by blur or disparity cues. The data in the present study strongly suggest that this cerebellar region is a far-response region that is involved in vergence as well as accommodative eye movements.

Human Gaze Stabilization During Active Head Translations

2002 ◽  
Vol 87 (1) ◽  
pp. 295-304 ◽  
Author(s):  
W. P. Medendorp ◽  
J.A.M. Van Gisbergen ◽  
C.C.A.M. Gielen
Keyword(s):  
Linear Regression ◽  
Human Subjects ◽  
Linear Regression Analysis ◽  
Target Distance ◽  
Frequency Range ◽  
Gaze Stabilization ◽  
The Gaze ◽  
Low Pass ◽  
Visual Targets ◽  
Eye Velocity

This study investigated how binocular gaze is controlled to compensate for self-generated translational movements of the head where geometric requirements dictate that the ideal gaze signal needs to be modulated by the inverse of target distance. Binocular gaze (eye plus head) was measured for visual and remembered targets at various distances in six human subjects during active head translations at frequencies of 0.25, 0.5, 1.0, and 1.5 Hz. We found that, during head translations, gaze changes were achieved by a combination of eye and head rotations. Accordingly, stabilization performance was characterized by the gaze response parameters sensitivity and phase, where sensitivity is defined as the ratio of gaze velocity and translational eye velocity and where phase refers to the phase delay of gaze velocity relative to translational eye velocity. In the analysis, we used a binocular coordinate system yielding a version and a vergence component. We examined how frequency and target distance, estimated from the vergence angle, affected sensitivity and phase of the version component of the gaze signal and compared the results to the requirements for ideal performance. The relation between gaze sensitivity and the inverse of distance was characterized by a linear regression analysis. The ratio of the slope of the linear regression and the slope required for ideal stabilization provided a measure for the degree of “distance compensation.” The results show that distance compensation was better for a visual target than for remembered targets in darkness, and behaved according to low-pass characteristics in both target conditions. It declined from 1.00 to 0.84 for visual targets and from 0.87 to 0.57 for remembered targets in the frequency range 0.25–1.5 Hz. The intercept obtained from the regression yielded the gaze response at zero vergence and specified a “default sensitivity” of gaze compensation. Default sensitivity increased with frequency from 0.02 at 0.25 Hz to 0.10°/cm at 1.5 Hz for visual targets and from 0.04 to 0.16°/cm in darkness. The phase delays of the gaze response increased on average from 2 to 7° in the frequency range 0.25–1.5 Hz. In comparison with earlier passive studies, active translation compensation in the dark is superior at all frequencies where comparison was possible. We conclude that a nonvestibular signal with low-pass characteristics contributes to gaze during active head translations.

Postsaccadic Enhancement of Initiation of Smooth Pursuit Eye Movements in Monkeys

1998 ◽  
Vol 79 (4) ◽  
pp. 1918-1930 ◽  
Author(s):  
Stephen G. Lisberger
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Visual Motion ◽  
Target Position ◽  
Target Motion ◽  
Target Velocity ◽  
Smooth Pursuit Eye Movements ◽  
Motor Pathways ◽  
Pursuit Eye Movements ◽  
Eye Velocity

Lisberger, Stephen G. Postsaccadic enhancement of initiation of smooth pursuit eye movements in monkeys. J. Neurophysiol. 79: 1918–1930, 1998. Step-ramp target motion evokes a characteristic sequence of presaccadic smooth eye movement in the direction of the target ramp, catch-up targets to bring eye position close to the position of the moving target, and postsaccadic eye velocities that nearly match target velocity. I have analyzed this sequence of eye movements in monkeys to reveal a strong postsaccadic enhancement of pursuit eye velocity and to document the conditions that lead to that enhancement. Smooth eye velocity was measured in the last 10 ms before and the first 10 ms after the first saccade evoked by step-ramp target motion. Plots of eye velocity as a function of time after the onset of the target ramp revealed that eye velocity at a given time was much higher if measured after versus before the saccade. Postsaccadic enhancement of pursuit was recorded consistently when the target stepped 3° eccentric on the horizontal axis and moved upward, downward, or away from the position of fixation. To determine whether postsaccadic enhancement of pursuit was invoked by smear of the visual scene during a saccade, I recorded the effect of simulated saccades on the presaccadic eye velocity for step-ramp target motion. The 3° simulated saccade, which consisted of motion of a textured background at 150°/s for 20 ms, failed to cause any enhancement of presaccadic eye velocity. By using a strategically selected set of oblique target steps with horizontal ramp target motion, I found clear enhancement for saccades in all directions, even those that were orthogonal to target motion. When the size of the target step was varied by up to 15° along the horizontal meridian, postsaccadic eye velocity did not depend strongly either on the initial target position or on whether the target moved toward or away from the position of fixation. In contrast, earlier studies and data in this paper show that presaccadic eye velocity is much stronger when the target is close to the center of the visual field and when the target moves toward versus away from the position of fixation. I suggest that postsaccadic enhancement of pursuit reflects activation, by saccades, of a switch that regulates the strength of transmission through the visual-motor pathways for pursuit. Targets can cause strong visual motion signals but still evoke low presaccadic eye velocities if they are ineffective at activating the pursuit system.

Ocular responses to translation and their dependence on viewing distance. I. Motion of the observer

1991 ◽  
Vol 66 (3) ◽  
pp. 851-864 ◽  
Author(s):  
U. Schwarz ◽  
F. A. Miles
Keyword(s):  
Eye Movements ◽  
General Tendency ◽  
Otolith Organs ◽  
Viewing Distance ◽  
Compensatory Response ◽  
Covariance Functions ◽  
Distant Target ◽  
Full Compensation ◽  
Distance Response ◽  
Eye Velocity

1. The horizontal eye movements induced by acceleration along the interaural axis were recorded from five monkeys (Macaca mulatta) by the use of the electromagnetic search-coil technique. Animals sat on a sled that was moved briefly in darkness along a linear track (bell-shaped acceleration profile: peak, 400 mm/s2; duration, 200 ms). Immediately before acceleration, animals fixated one of five target lights located at distances ranging from 16 to 150 cm. During fixation, the horizontal positions of both eyes were used to check vergence, while accommodation was monitored with an infrared optometer. 2. Sled motion induced eye movements that were generally smooth and compensatory, e.g., rightward sled motion elicited leftward eye movement. We attribute these responses to a translational vestibuloocular reflex (TVOR) that senses the sled motion through the otolith organs. However, in three animals, these responses were preceded by weak anticompensatory movements (duration, less than 40 ms; amplitude, less than 10% of the maximum compensatory response). 3. Geometry indicates that, during brief sled motion, the eye movements required to keep gaze aligned on a particular location ("full" compensation) are inversely proportional to the viewing distance. Response measures based on the computed eye velocity profiles, such as the velocity achieved at specific times ("time slices") or the peak values of the estimated covariance functions, all indicated that compensatory responses were a linear function of the inverse of the prior viewing distance. Cross-correlation analyses indicated that the effect of the prior viewing distance was to scale responses, although detailed spectral analyses revealed that high-frequency components (greater than 10 Hz) tended to scale less vigorously than lower ones. 4. The adequacy of the compensatory eye movements was assessed by calculating the gain (response recorded/response required for full compensation). Regardless of the response measure used, gains varied considerably from one animal to another and, in some particular animals, from one direction to another but showed a general tendency to increase with viewing distance. For example, on the basis of the peak eye velocity achieved within 250 ms of the onset of sled motion, mean gain at 16 cm was 0.74 (range, 0.48-1.01), whereas at 150 cm it was 1.25 (range, 0.67-1.73). 5. Using wedge prisms to dissociate vergence and accommodation indicated that ocular responses to sled motion were sensitive to selective increases in either vergence (base-out prism with the most distant target) or accommodation (base-in prism with the nearest target). However, the magnitude of the effects showed considerable variability from one animal to another and, in some particular animals, from one direction to another.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of Lesions of the Oculomotor Cerebellar Vermis on Eye Movements in Primate: Smooth Pursuit

2000 ◽  
Vol 83 (4) ◽  
pp. 2047-2062 ◽  
Author(s):  
Mineo Takagi ◽  
David S. Zee ◽  
Rafael J. Tamargo
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Dynamic Properties ◽  
Critical Role ◽  
Open Loop ◽  
Cerebellar Vermis ◽  
Peak Acceleration ◽  
Triangular Wave ◽  
Oculomotor Vermis ◽  
Eye Velocity

We studied the effects on smooth pursuit eye movements of ablation of the dorsal cerebellar vermis (lesions centered on lobules VI and VII) in three monkeys in which the cerebellar nuclei were spared. Following the lesion the latencies to pursuit initiation were unchanged. Monkeys showed a small decrease (up to 15%) in gain during triangular-wave tracking. More striking were changes in the dynamic properties of pursuit as determined in the open-loop period (the 1st 100 ms) of smooth tracking. Changes included a decrease in peak eye acceleration (e.g., in one monkey from ∼650°/s2, prelesion to ∼220–380°/s2, postlesion) and a decrease in the velocity at the end of the open-loop period [e.g., in another monkey from a gain (eye velocity/target velocity at 100 ms of tracking) of 0.93, prelesion to 0.53, postlesion]. In individual monkeys, the pattern of deficits in the open-loop period of pursuit was usually comparable to that of saccades, especially when comparing the changes in the acceleration of pursuit to the changes in the velocity of saccades. These findings support the hypothesis that saccades and the open-loop period of pursuit are controlled by the cerebellar vermis in an analogous way. Saccades could be generated by eye velocity commands to bring the eyes to a certain position and pursuit by eye acceleration commands to bring the eyes toward a certain velocity. On the other hand, changes in gain during triangular-wave tracking did not correlate with either the saccade or the open-loop pursuit deficits, implying different contributions of the oculomotor vermis to the open loop and to the sustained portions of pursuit tracking. Finally, in a pursuit adaptation paradigm (×0.5 or ×2, calling for a halving or doubling of eye velocity, respectively) intact animals could adaptively adjust eye acceleration in the open-loop period. The main pattern of change was a decrease in peak acceleration for ×0.5 training and an increase in the duration of peak acceleration for ×2 training. Following the lesion in the oculomotor vermis, this adaptive capability was impaired. In conclusion, as for saccades, the oculomotor vermis plays a critical role both in the immediate on-line and in the short-term adaptive control of pursuit.

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