Effects of fixation target timing on smooth-pursuit initiation

1996 ◽  
Vol 111 (2) ◽  
Author(s):  
MarkJ. Morrow ◽  
NancyL. Lamb
Keyword(s):  
Smooth Pursuit ◽  
Fixation Target ◽  
Pursuit Initiation

Predicting 2D Target Velocity Cannot Help 2D Motion Integration for Smooth Pursuit Initiation

2006 ◽  
Vol 96 (6) ◽  
pp. 3545-3550 ◽  
Author(s):  
Anna Montagnini ◽  
Miriam Spering ◽  
Guillaume S. Masson
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Object Motion ◽  
Line Orientation ◽  
Motion Direction ◽  
Direction Error ◽  
Pursuit Eye Movements ◽  
Pursuit Initiation ◽  
Motion Integration ◽  
Tracking Direction

Smooth pursuit eye movements reflect the temporal dynamics of bidimensional (2D) visual motion integration. When tracking a single, tilted line, initial pursuit direction is biased toward unidimensional (1D) edge motion signals, which are orthogonal to the line orientation. Over 200 ms, tracking direction is slowly corrected to finally match the 2D object motion during steady-state pursuit. We now show that repetition of line orientation and/or motion direction does not eliminate the transient tracking direction error nor change the time course of pursuit correction. Nonetheless, multiple successive presentations of a single orientation/direction condition elicit robust anticipatory pursuit eye movements that always go in the 2D object motion direction not the 1D edge motion direction. These results demonstrate that predictive signals about target motion cannot be used for an efficient integration of ambiguous velocity signals at pursuit initiation.

scholarly journals Functional specialization in the middle temporal area for smooth pursuit initiation

2019 ◽  
Vol 2 ◽  
pp. 6 ◽  
Author(s):  
Shahab Bakhtiari ◽  
Christopher C. Pack
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Sensory Information ◽  
Target Velocity ◽  
Multiple Sources ◽  
Temporal Area ◽  
Middle Temporal ◽  
Mt Neurons ◽  
Pursuit Eye Movements ◽  
Pursuit Initiation

Smooth pursuit eye movements have frequently been used to model sensorimotor transformations in the brain. In particular, the initiation phase of pursuit can be understood as a transformation of a sensory estimate of target velocity into an eye rotation. Despite careful laboratory controls on the stimulus conditions, pursuit eye movements are frequently observed to exhibit considerable trial-to-trial variability. In theory, this variability can be caused by the variability in sensory representation of target motion, or by the variability in the transformation of sensory information to motor commands. Previous work has shown that neural variability in the middle temporal (MT) area is likely propagated to the oculomotor command, and there is evidence to suggest that the magnitude of this variability is sufficient to account for the variability of pursuit initiation. This line of reasoning presumes that the MT population is homogeneous with respect to its contribution to pursuit initiation.  At the same time, there is evidence that pursuit initiation is strongly linked to a subpopulation of MT neurons (those with strong surround suppression) that collectively generate less motor variability. To distinguish between these possibilities, we have combined human psychophysics, monkey electrophysiology, and computational modeling to examine how the pursuit system reads out the MT population during pursuit initiation. We find that the psychophysical data are best accounted for by a model that gives stronger weight to surround-suppressed MT neurons, suggesting that variability in the initiation of pursuit could arise from multiple sources along the sensorimotor transformation.

scholarly journals Smooth pursuit preparation modulates neuronal responses in visual areas MT and MST

2015 ◽  
Vol 114 (1) ◽  
pp. 638-649 ◽  
Author(s):  
Vincent P. Ferrera
Keyword(s):  
Smooth Pursuit ◽  
Motor Response ◽  
Visual Motion ◽  
Neuronal Response ◽  
Direction Selectivity ◽  
Relative Strength ◽  
Target Motion ◽  
Motion Onset ◽  
Pursuit Initiation ◽  
Visual Cortical

Primates are able to track small moving visual targets using smooth pursuit eye movements. Target motion for smooth pursuit is signaled by neurons in visual cortical areas MT and MST. In this study, we trained monkeys to either initiate or withhold smooth pursuit in the presence of a moving target to test whether this decision was reflected in the relative strength of “go” and “no-go” processes. We found that the gain of the motor response depended strongly on whether monkeys were instructed to initiate or withhold pursuit, thus demonstrating voluntary control of pursuit initiation. We found that the amplitude of the neuronal response to moving targets in areas MT and MST was also significantly lower on no-go trials (by 2.1 spikes/s on average). The magnitude of the neural response reduction was small compared with the behavioral gain reduction. There were no significant differences in neuronal direction selectivity, spatial selectivity, or response reliability related to pursuit initiation or the absence thereof. Variability in eye speed was negatively correlated with firing rate variability after target motion onset during go trials but not during no-go trials, suggesting that MT and MST activity represents an error signal for a negative feedback controller. We speculate that modulation of the visual motion signals in areas MT and MST may be one of the first visual cortical events in the initiation of smooth pursuit and that the small early response modulation may be amplified to produce an all-or-none motor response by downstream areas.

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

2019 ◽  
Author(s):  
Stuart Behling ◽  
Stephen G. Lisberger
Keyword(s):  
Steady State ◽  
Eye Movements ◽  
Smooth Pursuit ◽  
Smooth Pursuit Eye Movements ◽  
Target Speed ◽  
Pursuit Eye Movements ◽  
Pursuit Initiation ◽  
Visual Motor ◽  
State Tracking ◽  
Eye Velocity

AbstractSmooth 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 towards 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 creates less reliable target motion that impacts pursuit initiation by changing the gain of visual-motor transmission and perturbs steady-state tracking by modulation of the motor corollary discharges that comprise eye velocity memory.

Smooth pursuit initiation in young and elderly subjects

1993 ◽  
Vol 33 (2) ◽  
pp. 203-210 ◽  
Author(s):  
Mark J. Morrow ◽  
James A. Sharpe
Keyword(s):  
Smooth Pursuit ◽  
Elderly Subjects ◽  
Pursuit Initiation ◽  
Young And Elderly Subjects

Smooth Pursuit Eye Movements to Isoluminant Targets

2008 ◽  
Vol 100 (3) ◽  
pp. 1287-1300 ◽  
Author(s):  
D. I. Braun ◽  
N. Mennie ◽  
C. Rasche ◽  
A. C. Schütz ◽  
M. J. Hawken ◽  
...  
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Small Difference ◽  
Luminance Contrast ◽  
Sine Wave ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements ◽  
Pursuit Initiation ◽  
All Speeds ◽  
Sine Wave Gratings

At slow speeds, chromatic isoluminant stimuli are perceived to move much slower than comparable luminance stimuli. We investigated whether smooth pursuit eye movements to isoluminant stimuli show an analogous slowing. Beside pursuit speed and latency, we studied speed judgments to the same stimuli during fixation and pursuit. Stimuli were either large sine wave gratings or small Gaussians blobs moving horizontally at speeds between 1 and 11°/s. Targets were defined by luminance contrast or color. Confirming prior studies, we found that speed judgments of isoluminant stimuli during fixation showed a substantial slowing when compared with luminance stimuli. A similarly strong and significant effect of isoluminance was found for pursuit initiation: compared with luminance targets of matched contrasts, latencies of pursuit initiation were delayed by 50 ms at all speeds and eye accelerations were reduced for isoluminant targets. A small difference was found between steady-state eye velocities of luminance and isoluminant targets. For comparison, we measured latencies of saccades to luminance and isoluminant stimuli under similar conditions, but the effect of isoluminance was only found for pursuit. Parallel psychophysical experiments revealed that different from speed judgments of moving isoluminant stimuli made during fixation, judgments during pursuit are veridical for the same stimuli at all speeds. Therefore information about target speed seems to be available for pursuit eye movements and speed judgments during pursuit but is degraded for perceptual speed judgments during fixation and for pursuit initiation.

scholarly journals Activation and Inactivation of Rostral Superior Colliculus Neurons During Smooth-Pursuit Eye Movements in Monkeys

2000 ◽  
Vol 84 (2) ◽  
pp. 892-908 ◽  
Author(s):  
Michele A. Basso ◽  
Richard J. Krauzlis ◽  
Robert H. Wurtz
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Smooth Pursuit ◽  
Superficial Layer ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements ◽  
Pursuit Initiation ◽  
Intermediate Layers ◽  
Deep Layers ◽  
Stimulation Of

Neurons in the intermediate and deep layers of the rostral superior colliculus (SC) of monkeys are active during attentive fixation, small saccades, and smooth-pursuit eye movements. Alterations of SC activity have been shown to alter saccades and fixation, but similar manipulations have not been shown to influence smooth-pursuit eye movements. Therefore we both activated (electrical stimulation) and inactivated (reversible chemical injection) rostral SC neurons to establish a causal role for the activity of these neurons in smooth pursuit. First, we stimulated the rostral SC during pursuit initiation as well as pursuit maintenance. For pursuit initiation, stimulation of the rostral SC suppressed pursuit to ipsiversive moving targets primarily and had modest effects on contraversive pursuit. The effect of stimulation on pursuit varied with the location of the stimulation with the most rostral sites producing the most effective inhibition of ipsiversive pursuit. Stimulation was more effective on higher pursuit speeds than on lower and did not evoke smooth-pursuit eye movements during fixation. As with the effects on pursuit initiation, ipsiversive maintained pursuit was suppressed, whereas contraversive pursuit was less affected. The stimulation effect on smooth pursuit did not result from a generalized inhibition because the suppression of smooth pursuit was greater than the suppression of smooth eye movements evoked by head rotations (vestibular-ocular reflex). Nor was the stimulation effect due to the activation of superficial layer visual neurons rather than the intermediate layers of the SC because stimulation of the superficial layers produced effects opposite to those found with intermediate layer stimulation. Second, we inactivated the rostral SC with muscimol and found that contraversive pursuit initiation was reduced and ipsiversive pursuit was increased slightly, changes that were opposite to those resulting from stimulation. The results of both the stimulation and the muscimol injection experiments on pursuit are consistent with the effects of these activation and inactivation experiments on saccades, and the effects on pursuit are consistent with the hypothesis that the SC provides a position signal that is used by the smooth-pursuit eye-movement system.

Visuomotor Velocity Transformations for Smooth Pursuit Eye Movements

2010 ◽  
Vol 104 (4) ◽  
pp. 2103-2115 ◽  
Author(s):  
Gunnar Blohm ◽  
Philippe Lefèvre
Keyword(s):  
Eye Movements ◽  
Reference Frame ◽  
Smooth Pursuit ◽  
Eye Position ◽  
Smooth Pursuit Eye Movements ◽  
Velocity Transformation ◽  
Pursuit Eye Movements ◽  
Pursuit Initiation ◽  
Retinal Motion ◽  
Frame Transformation

Smooth pursuit eye movements are driven by retinal motion signals. These retinal motion signals are converted into motor commands that obey Listing's law (i.e., no accumulation of ocular torsion). The fact that smooth pursuit follows Listing's law is often taken as evidence that no explicit reference frame transformation between the retinal velocity input and the head-centered motor command is required. Such eye-position-dependent reference frame transformations between eye- and head-centered coordinates have been well-described for saccades to static targets. Here we suggest that such an eye (and head)-position-dependent reference frame transformation is also required for target motion (i.e., velocity) driving smooth pursuit eye movements. Therefore we tested smooth pursuit initiation under different three-dimensional eye positions and compared human performance to model simulations. We specifically tested if the ocular rotation axis changed with vertical eye position, if the misalignment of the spatial and retinal axes during oblique fixations was taken into account, and if ocular torsion (due to head roll) was compensated for. If no eye-position-dependent velocity transformation was used, the pursuit initiation should follow the retinal direction, independently of eye position; in contrast, a correct visuomotor velocity transformation would result in spatially correct pursuit initiation. Overall subjects accounted for all three components of the visuomotor velocity transformation, but we did observe differences in the compensatory gains between individual subjects. We concluded that the brain does perform a visuomotor velocity transformation but that this transformation was prone to noise and inaccuracies of the internal model.

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