scholarly journals Saccade Adaptation Specific to Visual Context

2009 ◽  
Vol 101 (4) ◽  
pp. 1713-1721 ◽  
Author(s):  
James P. Herman ◽  
Mark R. Harwood ◽  
Josh Wallman
Keyword(s):  
Target Stimulus ◽  
Separate Experiment ◽  
Physical Parameters ◽  
Visual Context ◽  
Saccade Amplitude ◽  
Repair Mechanism ◽  
Adaptive Process ◽  
Differential Adaptation ◽  
Saccade Adaptation ◽  
Visual Properties

When saccades consistently overshoot their targets, saccade amplitudes gradually decrease, thereby maintaining accuracy. This adaptive process has been seen as a form of motor learning that copes with changes in physical parameters of the eye and its muscles, brought about by aging or pathology. One would not expect such a motor-repair mechanism to be specific to the visual properties of the target stimulus. We had subjects make saccades to sudden movements of either of two targets—a steadily illuminated circle or a flickering circle—one of which stepped back during each saccade it elicited, simulating the effect of a hypermetric saccade. Saccade gain (saccade amplitude/target amplitude) decreased by 15% for the target that stepped back versus 6% for the target that did not step back. Most of the change in gain between successive blocks of trials of each type occurred on the first saccade of the block, decreasing by 0.12 on the first trial of a step-back block and increasing by 0.1 on the first trial of a no-step-back block. The differential adaptation of the two targets required postsaccadic feedback of both target types, as shown in a separate experiment, in which saccades to only one target received feedback, and the gain did not differ between the two target types. This demonstration that a context defined by a visual stimulus can serve as an effective cue for switching saccade gain between states suggests that saccade adaptation may have a heretofore unsuspected dimension of adaptability.

Mislocalization of stationary and flashed bars after saccadic inward and outward adaptation of reactive saccades

2012 ◽  
Vol 107 (11) ◽  
pp. 3062-3070 ◽  
Author(s):  
Fabian Schnier ◽  
Markus Lappe
Keyword(s):  
Saccade Target ◽  
Saccade Amplitude ◽  
Presentation Duration ◽  
Target Presentation ◽  
Adaptation Mechanisms ◽  
Long Duration ◽  
Neuronal Mechanisms ◽  
The Difference ◽  
Saccade Adaptation

Recent studies have shown that saccadic inward adaptation (i.e., the shortening of saccade amplitude) and saccadic outward adaptation (i.e., the lengthening of saccade amplitude) rely on partially different neuronal mechanisms. There is increasing evidence that these differences are based on differences at the target registration or planning stages since outward but not inward adaptation transfers to hand-pointing and perceptual localization of flashed targets. Furthermore, the transfer of reactive saccade adaptation to long-duration overlap and scanning saccades is stronger after saccadic outward adaptation than that after saccadic inward adaptation, suggesting that modulated target registration stages during outward adaptation are increasingly used in the execution of saccades when the saccade target is visually available for a longer time. The difference in target presentation duration between reactive and scanning saccades is also linked to a difference in perceptual localization of different targets. Flashed targets are mislocalized after inward adaptation of reactive and scanning saccades but targets that are presented for a longer time (stationary targets) are mislocalized stronger after scanning than after reactive saccades. This link between perceptual localization and adaptation specificity suggests that mislocalization of stationary bars should be higher after outward than that after inward adaptation of reactive saccades. In the present study we test this prediction. We show that the relative amount of mislocalization of stationary versus flashed bars is higher after outward than that after inward adaptation of reactive saccades. Furthermore, during fixation stationary and flashed bars were mislocalized after outward but not after inward adaptation. Thus, our results give further evidence for different adaptation mechanisms between inward and outward adaptation and harmonize some recent research.

scholarly journals Deconstructing multimodality: visual properties and visual context in human semantic processing

2019 ◽  
Author(s):  
Christopher Davis ◽  
Luana Bulat ◽  
Anita Lilla Vero ◽  
Ekaterina Shutova
Keyword(s):  
Semantic Processing ◽  
Visual Context ◽  
Visual Properties

Visual Versus Motor Vector Inversions in the Antisaccade Task: A Behavioral Investigation With Saccadic Adaptation

2008 ◽  
Vol 99 (5) ◽  
pp. 2708-2718 ◽  
Author(s):  
Thérèse Collins ◽  
Dorine Vergilino-Perez ◽  
Laura Delisle ◽  
Karine Doré-Mazars
Keyword(s):  
Eye Movement ◽  
Visual Target ◽  
Antisaccade Task ◽  
Saccade Amplitude ◽  
Stimulus Position ◽  
Target Vector ◽  
Saccadic Adaptation ◽  
Vector Inversion ◽  
Adaptation Field ◽  
Saccade Adaptation

In the antisaccade task, subjects must execute an eye movement away from a visual target. Correctly executing an antisaccade requires inhibiting a prosaccade toward the visual target and programming a movement to the opposite side. This movement could be based on the inversion of the visual vector, corresponding to the distance between the fixation point and the visual target, or the motor vector of the unwanted prosaccade. We dissociated the two vectors by means of saccadic adaptation. Adaptation can be observed when systematic targeting errors are caused by the displacement of the visual target during the saccade. Adaptation progressively modifies saccade amplitude (defined by the motor vector) such that it becomes appropriate to the postsaccadic stimulus position and thus different from the visual vector of the target. If antisaccade preparation depended on visual vector inversion, rightward prosaccade adaptation should not transfer to leftward antisaccades (which are based on the same visual vector) but should transfer to rightward antisaccades (which are based on a visual vector inside the adaptation field). If antisaccade preparation depended on motor vector inversion, rightward prosaccade adaptation should transfer to leftward antisaccades (which are based on the same, adapted motor vector) but should not transfer to rightward antisaccades (which are based on a nonadapted motor vector). The results are in line with the first hypothesis, showing that vector inversion precedes saccadic adaptation and suggesting that antisaccade preparation depends on the inversion of the visual target vector.

scholarly journals Discharge of Monkey Nucleus Reticularis Tegmenti Pontis Neurons Changes During Saccade Adaptation

2005 ◽  
Vol 94 (3) ◽  
pp. 1938-1951 ◽  
Author(s):  
N. Takeichi ◽  
C.R.S. Kaneko ◽  
A. F. Fuchs
Keyword(s):  
Saccade Amplitude ◽  
Nucleus Reticularis Tegmenti Pontis ◽  
Adaptation Mechanisms ◽  
Nucleus Reticularis ◽  
Oculomotor Vermis ◽  
Adaptive Mechanisms ◽  
Direct Input ◽  
Induced Changes ◽  
Saccade Adaptation ◽  
Amplitude Decrease

Saccade accuracy is maintained by adaptive mechanisms that continually modify saccade amplitude to reduce dysmetria. Previous studies suggest that adaptation occurs upstream of the caudal fastigial nucleus (CFN), the output of the oculomotor cerebellar vermis but downstream from the superior colliculus (SC). The nucleus reticularis tegmenti pontis (NRTP) is a major source of afferents to both the oculomotor vermis and the CFN and in turn receives direct input from the SC. Here we examine the activity of NRTP neurons in four rhesus monkeys during behaviorally induced changes in saccade amplitude to assess whether their discharge might reveal adaptation mechanisms that mediate changes in saccade amplitude. During amplitude decrease adaptation (average, 22%), the gradual reduction of saccade amplitude was accompanied by an increase in the number of spikes in the burst of 19/34 neurons (56%) and no change for 15 neurons (44%). For the neurons that increased their discharge, the additional spikes were added at the beginning of the saccadic burst and adaptation also delayed the peak-firing rate in some neurons. Moreover, after amplitude reduction, the movement fields changed shape in all 15 open field neurons tested. Our data show that saccadic amplitude reduction affects the number of spikes in the burst of more than half of NRTP neurons tested, primarily by increasing burst duration not frequency. Therefore adaptive changes in saccade amplitude are reflected already at a major input to the oculomotor cerebellum.

scholarly journals Modification of saccadic gain by reinforcement

2011 ◽  
Vol 106 (1) ◽  
pp. 219-232 ◽  
Author(s):  
Laurent Madelain ◽  
Céline Paeye ◽  
Josh Wallman
Keyword(s):  
Target Location ◽  
Error Signal ◽  
Saccade Amplitude ◽  
Learning Mechanisms ◽  
Progressive Change ◽  
Compensatory Process ◽  
Amplitude Criterion ◽  
Original Target ◽  
Saccade Adaptation ◽  
Visual Error

Control of saccadic gain is often viewed as a simple compensatory process in which gain is adjusted over many trials by the postsaccadic retinal error, thereby maintaining saccadic accuracy. Here, we propose that gain might also be changed by a reinforcement process not requiring a visual error. To test this hypothesis, we used experimental paradigms in which retinal error was removed by extinguishing the target at the start of each saccade and either an auditory tone or the vision of the target on the fovea was provided as reinforcement after those saccades that met an amplitude criterion. These reinforcement procedures caused a progressive change in saccade amplitude in nearly all subjects, although the rate of adaptation differed greatly among subjects. When we reversed the contingencies and reinforced those saccades landing closer to the original target location, saccade gain changed back toward normal gain in most subjects. When subjects had saccades adapted first by reinforcement and a week later by conventional intrasaccadic step adaptation, both paradigms yielded similar degrees of gain changes and similar transfer to new amplitudes and to new starting positions of the target step as well as comparable rates of recovery. We interpret these changes in saccadic gain in the absence of postsaccadic retinal error as showing that saccade adaptation is not controlled by a single error signal. More generally, our findings suggest that normal saccade adaptation might involve general learning mechanisms rather than only specialized mechanisms for motor calibration.

Activity Changes in Monkey Superior Colliculus During Saccade Adaptation

2007 ◽  
Vol 97 (6) ◽  
pp. 4096-4107 ◽  
Author(s):  
Norihito Takeichi ◽  
Chris R. S. Kaneko ◽  
Albert F. Fuchs
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Brain Stem ◽  
Neuronal Activity ◽  
Great Majority ◽  
Behavioral Adaptation ◽  
Saccade Amplitude ◽  
Common Pathway ◽  
Movement Field ◽  
Saccade Adaptation

Saccades are eye movements that are used to foveate targets rapidly and accurately. Their amplitude must be adjusted continually, throughout life, to compensate for movement inaccuracies due to maturation, pathology, or aging. One possible locus for such saccade adaptation is the superior colliculus (SC), the relay for cortical commands to the premotor brain stem generator for saccades. However, previous stimulation and recording studies have disagreed as to whether saccade adaptation occurs up- or downstream of the SC. Therefore we have reexamined the behavior of SC burst neurons during saccade adaptation under conditions that were optimized to produce the biggest possible change in neuronal activity. We show that behavioral adaptation of saccade amplitude was associated with significant increases or decreases, in the number of spikes in the burst and/or changes in the shape of the movement field in 35 of 43 SC neurons tested. Of the 35, 29 had closed movement fields and 14 were classified indeterminate because the movement field could not be definitively diagnosed. Changes in the number of spikes occurred gradually during adaptation and resulted from correlated changes in burst lead and duration without consistent changes in peak burst rate. These data indicate that the great majority of SC neurons show a change in discharge in association with saccade amplitude adaptation. Based on these and previous results, we speculate that the site for saccade adaptation resides in the SC or that the SC is the final common pathway for adaptive changes that occur elsewhere in the saccade system.

Differential Adaptation of the Linear and Nonlinear Components of the Horizontal Vestibuloocular Reflex in Squirrel Monkeys

2002 ◽  
Vol 88 (6) ◽  
pp. 3534-3540 ◽  
Author(s):  
Richard A. Clendaniel ◽  
David M. Lasker ◽  
Lloyd B. Minor
Keyword(s):  
Squirrel Monkeys ◽  
Linear Component ◽  
Vestibuloocular Reflex ◽  
Nonlinear Component ◽  
Adaptive Process ◽  
Gain Enhancement ◽  
High Acceleration ◽  
Differential Adaptation ◽  
Linear And Nonlinear ◽  
Nonlinear Components

Previous work in squirrel monkeys has demonstrated the presence of linear and nonlinear components to the horizontal vestibuloocular reflex (VOR) evoked by high-acceleration rotations. The nonlinear component is seen as a rise in gain with increasing velocity of rotation at frequencies more than 2 Hz (a velocity-dependent gain enhancement). We have shown that there are greater changes in the nonlinear than linear component of the response after spectacle-induced adaptation. The present study was conducted to determine if the two components of the response share a common adaptive process. The gain of the VOR, in the dark, to sinusoidal stimuli at 4 Hz (peak velocities: 20–150°/s) and 10 Hz (peak velocities: 20 and 100°/s) was measured pre- and postadaptation. Adaptation was induced over 4 h with ×0.45 minimizing spectacles. Sum-of-sines stimuli were used to induce adaptation, and the parameters of the stimuli were adjusted to invoke only the linear or both linear and nonlinear components of the response. Preadaptation, there was a velocity-dependent gain enhancement at 4 and 10 Hz. In postadaptation with the paradigms that only recruited the linear component, there was a decrease in gain and a persistent velocity-dependent gain enhancement (indicating adaptation of only the linear component). After adaptation with the paradigm designed to recruit both the linear and nonlinear components, there was a decrease in gain and no velocity-dependent gain enhancement (indicating adaptation of both components). There were comparable changes in the response to steps of acceleration. We interpret these results to indicate that separate processes drive the adaptation of the linear and nonlinear components of the response.

scholarly journals Adaptation of naturally paced saccades

2014 ◽  
Vol 111 (11) ◽  
pp. 2343-2354 ◽  
Author(s):  
Michael J. Gray ◽  
Annabelle Blangero ◽  
James P. Herman ◽  
Josh Wallman ◽  
Mark R. Harwood
Keyword(s):  
Eye Movement ◽  
Learning Process ◽  
Main Sequence ◽  
Intertrial Interval ◽  
Peak Velocity ◽  
Saccade Amplitude ◽  
Sequence Relationship ◽  
Saccade Adaptation ◽  
Interval Observers ◽  
Surprising Finding

In the natural environment, humans make saccades almost continuously. In many eye movement experiments, however, observers are required to fixate for unnaturally long periods of time. The resulting long and monotonous experimental sessions can become especially problematic when collecting data in a clinical setting, where time can be scarce and subjects easily fatigued. With this in mind, we tested whether the well-studied motor learning process of saccade adaptation could be induced with a dramatically shortened intertrial interval. Observers made saccades to targets that stepped left or right either ∼250 ms or ∼1,600 ms after the saccade landed. In experiment I, we tested baseline saccade parameters to four different target amplitudes (5°, 10°, 15°, and 20°) in the two timing settings. In experiments II and III, we adapted 10° saccades via 2° intrasaccadic steps either backwards or forwards, respectively. Seven subjects performed eight separate adaptation sessions (2 intertrial timings × 2 adaptation direction × 2 session trial lengths). Adaptation proceeded remarkably similarly in both timing conditions across the multiple sessions. In the faster-paced sessions, robust adaptation was achieved in under 2 min, demonstrating the efficacy of our approach to streamlining saccade adaptation experiments. Although saccade amplitudes were similar between conditions, the faster-paced condition unexpectedly resulted in significantly higher peak velocities in all subjects. This surprising finding demonstrates that the stereotyped “main sequence” relationship between saccade amplitude and peak velocity is not as fixed as originally thought.

Some Results of the Spectroscopic Study of Four Close Binary Systems of Early Spectral Types

1965 ◽  
Vol 5 ◽  
pp. 120-130
Author(s):  
T. S. Galkina
Keyword(s):  
Spectroscopic Study ◽  
Spectral Type ◽  
Spectroscopic Investigation ◽  
Binary Systems ◽  
Quantitative Information ◽  
Close Binary ◽  
Physical Parameters ◽  
Absorption And Emission ◽  
Close Binary Systems ◽  
Quantitative Estimates

It is necessary to have quantitative estimates of the intensity of lines (both absorption and emission) to obtain the physical parameters of the atmosphere of components.Some years ago at the Crimean observatory we began the spectroscopic investigation of close binary systems of the early spectral type with components WR, Of, O, B to try and obtain more quantitative information from the study of the spectra of the components.

A theory of contamination in electron microscopes by surface diffusion

1978 ◽  
Vol 36 (1) ◽  
pp. 116-117
Author(s):  
J.T. Fourie
Keyword(s):  
Electron Beam ◽  
Surface Diffusion ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Physical Parameters ◽  
Carbon Compounds ◽  
Hydrocarbon Molecules ◽  
Electron Microscopes ◽  
Primary Electrons ◽  
Long Chain

Contamination in electron microscopes can be a serious problem in STEM or in situations where a number of high resolution micrographs are required of the same area in TEM. In modern instruments the environment around the specimen can be made free of the hydrocarbon molecules, which are responsible for contamination, by means of either ultra-high vacuum or cryo-pumping techniques. However, these techniques are not effective against hydrocarbon molecules adsorbed on the specimen surface before or during its introduction into the microscope. The present paper is concerned with a theory of how certain physical parameters can influence the surface diffusion of these adsorbed molecules into the electron beam where they are deposited in the form of long chain carbon compounds by interaction with the primary electrons.

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