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A mechanism for suppression of optokinesis
Abstract
We have studied optokinetic responses to oscillating patterns of dots, and the suppression of these responses by a foveally stabilized target. Such a target suppressed most of the optokinetic response, although the target provided neither retinal target motion nor target offset from the fovea. This indicates that suppression of OKN can occur by other means than smooth pursuit eye movements to traditional stimuli. We studied the form of the suppression for different optokinetic stimulus strengths and stimulus frequencies (0.25-1.0 Hz). The results show that over this frequency range the optokinetic response is substantial, and also that the suppression continues to operate. We also examined the time-course of suppression: it begins to appear within 150-200 msec of the appearance of a fixation target in motion relative to the optokinetic stimulus field.
... In our initial investigation of suppression of optokinesis (Wyatt & Pola, 1984), we asked subjects to actively look at a small round (l.5 0) target stabilized at the fovea, presented against the sinusoidal motion of an optokinetic field. Clear suppression of optokinesis was observed, even though retinal slip of the foveal target was absent. ...
... A significant feature of these findings is that the onset of suppression is quite rapid, occurring within about 100-200 msec (Wyatt & Pola, 1984), suggesting the existence of a well-developed, relatively automatic control process. However, little is known about this process except for its behavior with 0.25-and 0.5-Hz sinusoidal field motion (Wyatt & Pola, 1984; and unidirectional field motion . ...
... A significant feature of these findings is that the onset of suppression is quite rapid, occurring within about 100-200 msec (Wyatt & Pola, 1984), suggesting the existence of a well-developed, relatively automatic control process. However, little is known about this process except for its behavior with 0.25-and 0.5-Hz sinusoidal field motion (Wyatt & Pola, 1984; and unidirectional field motion . In the present study, we attempted to determine the overall dynamic properties of the suppression mechanism. ...
Subjects gazed passively at a sinusoidally oscillating optokinetic stimulus. They made no attempt to look at a target which appeared, stabilized on the retina at one of several locations, yet the appearance of the target caused rapid and prolonged suppression of optokinesis. Suppression declined (optokinesis increased) as target eccentricity increased, but could be observed for eccentricities up to 15-20 deg. We propose that a target moving relative to a background is a stimulus for suppression of optokinesis, depending substantially on the visual properties of the target and not the act of attending to it.
... The feedback loop is opened in such experiments with the anticipation that if the background motion exerts some control over the oculomotor system during fixation of the target, its effects will become more clearly manifest in the absence of visual feedback about the target position. Using such a stimulus arrangement both counterphase eye movements (Pola and Wyatt 1980; Wyatt and Pola 1984) as well as eye movements lagging the background by less than 90 deg have been observed (Collewijn and Tamminga 1986; Wyatt and Pola 1984) which have been interpreted as pursuit of apparent motion induced by the background movement and an optokinetic influence of the background , respectively. In contrast, Mack et al. (1982) found in a similar experiment that no eye movements related to the movement of the background or apparent motion of the target occurred. ...
... In all these experiments the target was stabilized horizontally only. It has been suggested that the different responses may have resulted from differences in the number of contours, the location and the size of the background (Wyatt and Pola 1984) or the waveform of the background motion (Collewijn and Tamminga 1986). Such explanations cannot account for the large idiosyncratic differences in the response in a single experiment as reported by Wyatt and Pola (1984). ...
... It has been suggested that the different responses may have resulted from differences in the number of contours, the location and the size of the background (Wyatt and Pola 1984) or the waveform of the background motion (Collewijn and Tamminga 1986). Such explanations cannot account for the large idiosyncratic differences in the response in a single experiment as reported by Wyatt and Pola (1984). The results of our first experiment suggested that the influence of volition might partly explain the prior inconsistent results. ...
We investigated the capacity of 6 humans to make voluntary smooth eye movements with a horizontally stabilized foveal point target. When the target was viewed on a dark field, all subjects were able to make smooth oscillatory eye movements when they attempted to imitate their own normal pursuit of sinusoidal target movement (0.2-0.7 Hz) directly preceding the stabilization on the fovea. The frequency of the imitating eye movement was in general lower than the frequency of normal pursuit by 2-35%. While fixating a foveally stabilized point target superimposed on a large, sinusoidally moving non-stabilized background, all subjects were able to make either no eye movements, eye movements nearly in phase with or eye movements nearly in counterphase with the background movement depending on the instruction to imagine the target as head-stationary, moving in phase, or moving in counterphase with the background. The accuracy of the frequency of the smooth eye movement with the stabilized target on the moving background was higher than during imitation of pursuit on the dark field but the precision of the frequency was lower than during normal pursuit. When the background moved pseudo-randomly all subjects could voluntarily inhibit their smooth eye movements or could make smooth eye movements in phase with the background. Only 2 subjects showed a limited ability to make smooth eye movements opposite to the pseudo-random background movement. The results suggest that with predictable background movement the volition of the subject rather than the movement of the background determines the eye movements when the subject looks at the foveally stabilized target.
... Les humains ne peuvent supprimer volontairement leur OKN que si un élément immobile est superposé sur l'arrière-plan en mouvement (Ilg, 1997 ;Pola, Wyatt, & Lustgarten, 1992 ;Pola, Wyatt, & Lustgarten, 1995 ;Rubinstein & Abel, 2011 ;Waespe & Schwarz, 1987 ;Williams, Mulhall, Mattingley, Lueck, & Abel, 2006 ;Wyatt & Pola, 1984 ;Wyatt, Pola, & Lustgarten, 1988). Dans ce cas, l'individu peut fixer cet élément et supprimer l'OKN de manière complète et rapide dans un délai de 100 à 200 ms (Pola et al., 1992 ;Wyatt & Pola, 1984). ...
... Les humains ne peuvent supprimer volontairement leur OKN que si un élément immobile est superposé sur l'arrière-plan en mouvement (Ilg, 1997 ;Pola, Wyatt, & Lustgarten, 1992 ;Pola, Wyatt, & Lustgarten, 1995 ;Rubinstein & Abel, 2011 ;Waespe & Schwarz, 1987 ;Williams, Mulhall, Mattingley, Lueck, & Abel, 2006 ;Wyatt & Pola, 1984 ;Wyatt, Pola, & Lustgarten, 1988). Dans ce cas, l'individu peut fixer cet élément et supprimer l'OKN de manière complète et rapide dans un délai de 100 à 200 ms (Pola et al., 1992 ;Wyatt & Pola, 1984). Le niveau de suppression de l'OKN (en termes d'amplitude ou de fréquence du déplacement oscillatoire des yeux) peut être variable, et dépend notamment des caractéristiques des éléments que peut fixer l'individu. ...
... En résumé, l'influence du mouvement de l'arrière-plan est généralement négative sur la performance et l'expérience subjective ressentie par l'utilisateur. Le mouvement peut être sans effet visible si la tâche requiert beaucoup d'attention, plus particulièrement si de nombreux objets statiques sont disposés sur l'arrière-plan et utilisés de manière soutenue (Pola et al., 1992 ;Wyatt & Pola, 1984 ...
Les jeux vidéo occupent une place importante dans notre société. Cependant, leur conception ne prend aujourd'hui que peu en compte les spécificités de l'interaction joueur-jeu vidéo, qui sont déterminantes pour une expérience de jeu optimale. L'objectif de cette thèse était de comprendre l'influence de différents choix de conception des interfaces visuelles des jeux vidéo sur la performance et le comportement du regard des joueurs. Ces interfaces, généralement dynamiques et complexes, sont composées de trois sources d'information : les objets avec lesquels le joueur interagit et l'arrière-plan, qui composent la scène d'action principale, ainsi que les informations contextuelles superposées à la scène principale. Sept expériences ont été réalisées pour comprendre le partage attentionnel entre ces sources dans le cadre d'une activité de jeu vidéo. Les caractéristiques de l'arrière-plan, des informations contextuelles et de la tâche ont été manipulées. La performance et les mouvements du regard des joueurs ont été enregistrés. Les résultats ont montré que le partage attentionnel entre deux sources d'information (e.g., scène d'action et informations contextuelles) est facilité lorsqu'elles ne se chevauchent pas. Lorsque qu'elles se chevauchent nécessairement (e.g., objets et arrière-plan), les caractéristiques de mouvement et de complexité de l'arrière-plan et la difficulté de la tâche modulent très largement la dégradation de la performance. Un modèle théorique de partage attentionnel entre deux sources visuelles d'information superposées est proposé. Des recommandations sont établies pour la conception des jeux vidéo, mais aussi des environnements virtuels en général.
... Yet, the question of how the oculomotor control system manages to switch oV the OKR during SPEM in such an ecologically plausible manner has still to be answered. At present, there is only preliminary experimental evidence implying that either the relative motion between the pursuit target and the background, or, alternatively, the pursuit-induced background image motion per se might be used as purely visual cues to suppress the OKR in the direction of self-produced image motion (Kodaka et al., 2004;Suehiro et al., 1999;Wyatt & Pola, 1984). We, therefore, tried to test thoroughly whether such visual information is suYcient for the direction-speciWc cancellation of the OKR during SPEM or whether extra-retinal information like for instance an eVerence copy (von Holst & Mittelstaedt, 1950) or corollary discharge (Sperry, 1950) of the voluntary eye movement motor command might be additionally needed. ...
... However, as the latter information can be used to recover motion information in world-centered coordinates (e.g., see von Holst & Mittelstaedt, 1950;Ilg, Schumann, & Thier, 2004) and because the cancellation of the OKR does not refer to such an allocentric frame of reference (see Lindner et al., 2001), it seemed to us rather unlikely that extra-retinal signals are engaged in OKR suppression. In contrast, purely retinal signals, namely the pursuit-induced image motion of a background per se (Suehiro et al., 1999) or its motion relative to the pursuit target (Wyatt & Pola, 1984), were suggested as possible candidates. Suehiro and coworkers (1999) used a stimulus, in which a background was moving with the same speed as the pursuit target before an additional background shift was applied in any of the four cardinal directions. ...
... In another study Wyatt and Pola (1984) stressed the role of relative motion for the suppression of the OKR. They were able to show that presenting a pursuit target during an ongoing OKR was able to suppress this gaze-stabilizing reXex within 150-200 ms. ...
When our eyes track objects that are moving in a richly structured environment, the retinal image of the stationary visual scene inevitably moves over the retina in a direction opposite to the eye movement. Such self-motion-induced global retinal slip usually provides an ideal stimulus for the optokinetic reflex. This reflex operates to compensate for global image flow. However, during smooth pursuit eye movements it must be shut down so that the reflex does not counteract the voluntary pursuit of moving targets. Here, we asked if retinal information is sufficient for this cancellation of the optokinetic reflex during smooth pursuit eye movements. In a series of experiments, we show that neither the eye movement-induced retinal image motion per se nor the relative motion between the pursuit target and the background are sufficient for suppression of optokinesis. We, therefore, conclude that extra-retinal information about smooth pursuit eye movements is required for the cancellation of the optokinetic reflex.
... In our initial investigation of suppression of optokinesis (Wyatt & Pola, 1984), we asked subjects to actively look at a small round (l.5 0) target stabilized at the fovea, presented against the sinusoidal motion of an optokinetic field. Clear suppression of optokinesis was observed, even though retinal slip of the foveal target was absent. ...
... A significant feature of these findings is that the onset of suppression is quite rapid, occurring within about 100-200 msec (Wyatt & Pola, 1984), suggesting the existence of a well-developed, relatively automatic control process. However, little is known about this process except for its behavior with 0.25-and 0.5-Hz sinusoidal field motion (Wyatt & Pola, 1984; and unidirectional field motion . ...
... A significant feature of these findings is that the onset of suppression is quite rapid, occurring within about 100-200 msec (Wyatt & Pola, 1984), suggesting the existence of a well-developed, relatively automatic control process. However, little is known about this process except for its behavior with 0.25-and 0.5-Hz sinusoidal field motion (Wyatt & Pola, 1984; and unidirectional field motion . In the present study, we attempted to determine the overall dynamic properties of the suppression mechanism. ...
Subjects viewed a foveally stabilized target presented against a background field of dots moving sinusoidally. Several different modes of viewing the target were used (subjects were instructed to gaze, look, or hold), and the frequency of sinusoidal field motion was varied from 1/32 to 2 Hz. In line with previous findings, the presence of a stabilized target resulted in substantial suppression of optokinesis. The characteristics of this suppression (gain and phase of slow residual eye movements) were dependent on both the mode of viewing the target and the frequency of field motion. When subjects used an imaginary target, little suppression occurred. These findings provide an overall profile of dynamic characteristics of mechanisms involved in the suppression of optokinesis. They support the view that this suppression is significantly determined by the presence of a target against a moving background (even without retinal slip), and by the mode of attending to the target.
... In our initial investigation of suppression of optokinesis (Wyatt & Pola, 1984), we asked subjects to actively look at a small round (l.5 0) target stabilized at the fovea, presented against the sinusoidal motion of an optokinetic field. Clear suppression of optokinesis was observed, even though retinal slip of the foveal target was absent. ...
... A significant feature of these findings is that the onset of suppression is quite rapid, occurring within about 100-200 msec (Wyatt & Pola, 1984), suggesting the existence of a well-developed, relatively automatic control process. However, little is known about this process except for its behavior with 0.25-and 0.5-Hz sinusoidal field motion (Wyatt & Pola, 1984; and unidirectional field motion . ...
... A significant feature of these findings is that the onset of suppression is quite rapid, occurring within about 100-200 msec (Wyatt & Pola, 1984), suggesting the existence of a well-developed, relatively automatic control process. However, little is known about this process except for its behavior with 0.25-and 0.5-Hz sinusoidal field motion (Wyatt & Pola, 1984; and unidirectional field motion . In the present study, we attempted to determine the overall dynamic properties of the suppression mechanism. ...
The oculomotor "twitch" is a small, transient eye movement that occurs in response to onset of target motion during both passive and active regard of the target (Wyatt and Pola 1985 a, 1987). Among the properties described here, primarily tested with subjects remaining passive, the twitch (i) is elicited extrafoveally, but maximally at and near the fovea, (ii) often persists as a distinct early transient response even when target motion is onset of a simple ramp, and (iii) remains approximately constant over a wide range of target motions, varying only with direction. We suggest that the twitch reflects the working of a mechanism analyzing the direction in which a target starts to move.
... Although this viewpoint would appear to account for fixation of a small target in the presence of a homogeneous background (such as in the dark or with a Ganzfeld) and perhaps a textured stationary background, it may not be sufficient to account for our ability to fixate a target in more complex stimulus situations. This is suggested by recent experiments in which subjects looked at a small target stabilized at the fovea in the presence of horizontal sinusoidal motion of an optokinetic field (Wyatt & Pola, 1984;Pola, Wyatt & Lustgarten, 1992). A primary result of these studies was that the eyes were not dragged along in the direction of motion of the optokinetic stimulus, i.e. optokinesis was substantially suppressed without "retinal-slip" of the target relative to fovea. ...
... Instead, we suggested that, to a substantial extent, it might involve mechanisms responding to relative target-field motion and the mode of attending to the target (such as looking at the target). An important result of these experiments was that eye movements were not completely absent: subjects typically made residual smooth eye movements that were roughly counterphase to the field motion (Wyatt & Pola, 1984;Pola et al., 1992). We wanted to explore the relationship between these results and fixation of a target in the real world, where targets of regard are not stabilized. ...
... Many of the methods have been described previously (e.g. Wyatt & Pola, 1984;Wyatt, Pola & Lustgarten, 1988;Pola et al., 1992). We will briefly recapitulate and emphasize the special conditions used here. ...
The ability to maintain foveal fixation of a target with either a stationary or moving background is often assumed to depend primarily on a difference (in velocity and/or position) between fovea and target. However, when subjects look at a target stabilized at the fovea presented against sinusoidal motion of an optokinetic stimulus field, optokinetic nystagmus (OKN) is suppressed. This suppression is not simply the absence of movement but instead most subjects show some amount of residual slow eye movements roughly counterphase to the field motion. We have varied the visual feedback of the target from 0 (stabilized) to -1 (stationary in space); as feedback increased, amplitude and phase lag of residual eye movements decreased systematically. The mechanism responsible for residual movements appears to operate for all feedback values (including the "real world" value of -1), which suggests a new view of the role played by retinal slip during fixation of a target and suppression of OKN.
... However, the OKN triggered by lateral background motion apparently had no impact on visual search performance. This might be because the shapes were used to cancel out the OKN (Ilg 1997;Pola, Wyatt, and Lustgarten 1992;Rubinstein and Abel 2011;Wyatt and Pola 1984). ...
... Visual performance is apparently not affected by background motion if the task involves enough stationary objects on which the observer has to maintain his or her attention. As in other complex tasks such as reading (Menozzi and Koga 2004), people performing visual searches must fixate the different items in the display and this would be sufficient to attenuate or suppress OKN and/or the sensation of vection (Ilg 1997;Pola, Wyatt, and Lustgarten 1992;Rubinstein and Abel 2011;Wyatt and Pola 1984), and cancel out any negative impact they may have on the task (Menozzi and Koga 2004;Seno, Ito, and Sunaga 2011). ...
The visual interfaces of virtual environments such as video games often show scenes where objects are superimposed on a moving background. Three experiments were designed to better understand the impact of the complexity and/or overall motion of two types of visual backgrounds often used in video games on the detection and use of superimposed, stationary items. The impact of background complexity and motion was assessed during two typical video game tasks: a relatively complex visual search task and a classic, less demanding shooting task. Background motion impaired participants' performance only when they performed the shooting game task, and only when the simplest of the two backgrounds was used. In contrast, and independently of background motion, performance on both tasks was impaired when the complexity of the background increased. Eye movement recordings demonstrated that most of the findings reflected the impact of low-level features of the two backgrounds on gaze control.
... Such context image motion on the retina drives a passive pursuit or OKN response into the opposite direction. To smoothly track the target, the OKN response will have to be suppressed (Lindner and Ilg 2006; Worfolk and Barnes 1992; Wyatt and Pola 1984), possibly causing a delay in initiating pursuit. Regarding cognitive mechanisms, it has been suggested that latency effects result from the observer's inability to attend to the target in the presence of a textured context because the context renders the target less salient (Masson et al. 1995). ...
... To initiate a smooth-pursuit response , the resulting OKN has to be suppressed. OKN suppression was previously shown to occur at an early stage before or during pursuit onset (Wyatt and Pola 1984) and can be stronger for a context moving into the direction opposite to that of the pursuit target (see Lindner and Ilg 2006 for a discussion on pursuit–OKN interaction). In our experiment, OKN suppression was not perfect, as indicated by the high number of saccades, in particular backward saccades during pursuit initiation in the presence of a context drifting opposite to that of the pursuit target. ...
Segregating a moving object from its visual context is particularly relevant for the control of smooth-pursuit eye movements. We examined the interaction between a moving object and a stationary or moving visual context to determine the role of the context motion signal in driving pursuit. Eye movements were recorded from human observers to a medium-contrast Gaussian dot that moved horizontally at constant velocity. A peripheral context consisted of two vertically oriented sinusoidal gratings, one above and one below the stimulus trajectory, that were either stationary or drifted into the same or opposite direction as that of the target at different velocities. We found that a stationary context impaired pursuit acceleration and velocity and prolonged pursuit latency. A drifting context enhanced pursuit performance, irrespective of its motion direction. This effect was modulated by context contrast and orientation. When a context was briefly perturbed to move faster or slower eye velocity changed accordingly, but only when the context was drifting along with the target. Perturbing a context into the direction orthogonal to target motion evoked a deviation of the eye opposite to the perturbation direction. We therefore provide evidence for the use of absolute and relative motion cues, or motion assimilation and motion contrast, for the control of smooth-pursuit eye movements.
... In the present study, a 30× 11° stimulus field was used and the possibility exists that with a small field, stare instructions may have caused OKN suppression to occur. OKN suppression is reflected by a loss of slow phase eye movement in the direction of stimulus motion together with a decrease in the number of oppositely-directed quick phases (Wyatt and Pola, 1984, 1988; Pola et al., 1992). However, previous OKN suppression studies (Dieterich et al., 1998, 2000) had to add a fixation point in the stimulus field in order to suppress OKN. ...
... Also, the experienced OKN subject in the current study reported the ocular motor sensation of stare OKN during the stare OKN portion of the study. It has been noted that even with a fixation point to induce OKN suppression, residual smooth eye movements are present in humans (Wyatt and Pola, 1984, 1988; Pola et al., 1992) and nystagmus is present in monkeys (Waespe and Schwarz, 1986, 1987). The pilot eye movement recording data also clearly demonstrate that the stare OKN instructions did not suppress OKN. ...
... However, 250 msec before the target crossed the 0 deg position, target luminance increased, which signalled the subjects to stop looking and instead to gaze passively, i.e., to avoid any deliberate attempt to attend to or follow the moving target. We have used both look and passive instructions in previous studies (Pola & Wyatt, 1980;Pola et al., 1992Pola et al., , 1995Wyatt & Pola, 1979, 1984. ...
... With closedloop ramp target motion (Wyatt & Pola, 1987), onset oscillations and pursuit gain were greater with looking than with gazing. Attention (looking, gazing and pushing) also affected eye movements when subjects viewed a target stabilized at the fovea against sinusoidal motion of a background field (Pola et al., 1992;van den Berg & Collewijn, 1987;Wyatt & Pola, 1984). An important difference between the present and previous studies is that in the present study there were no retinal error signals (during pursuit offset), whereas in the previous studies there was retinal error from either target or field motion. ...
Subjects made smooth pursuit eye movements with a target moving horizontally at 15 deg/sec. At a specified location the target either: (1) suddenly vanished; or (2) jumped to the fovea with target retinal velocity and feedback becoming 0 (target stabilized at the fovea). In each type of trial, the subjects either: "looked" at the target, "pushed" the target, or "passively" gazed. When the target vanished, eye velocity decreased exponentially with a short time-constant (tau approximately 0.10 sec), regardless of whether the subjects were "looking," "pushing" or "passively" gazing. However, some subjects while "pushing" (using an imaginary target) did generate low velocity smooth movement (1-2.5 deg/sec) late in the offset. When the target was stabilized at the fovea, eye velocity also decreased, but with a relatively long time-constant (tau = 0.4-0.8 sec). The time-constant was the same with both "looking," and "pushing", but was shorter for some subjects with "passive" gazing (tau = 0.1-0.5 sec). These findings show that smooth pursuit offset is influenced by the presence of a target, but is relatively independent of attentional mode. All of the pursuit offset responses can be simulated using a model of the pursuit system with target velocity and position inputs, and an internal positive feedback loop enabled by target presence.
... For example, some cells in the rostral superior colliculus in monkeys become active both during smooth pursuit and fixation (Munoz & Wultz, 1993a,b; Krauzlis, Basso, & Wultz, 1997). The other related phenomenon is the residual smooth eye movement under OKN suppression (Tamminga & Collewijn, 1981; Wyatt & Pola, 1984; Collewijn & Tamminga, 1986; Waespe & Schwarz, 1986, 1987 van den Berg & Collewijn, 1987; Wyatt, Pola, Lustgarten, & Aksionoff, 1995). When the optokinetic motion field changes in a sinewave fashion, small residual smooth eye movements, which are roughly counter-phase to the field motion (i.e., toward the in-coming field), can be observed (Wyatt & PolaPola, Wyatt, & Lustgarten, 1992). ...
During optokinetic nystagmus (OKN) the mean eye position of gaze (the beating field) shifts in the direction of the fast phases. The function of this shift may be to re-orient the eyes in the direction of self-motion which optic flow implies (in-coming field). This idea leads to the hypothesis that visual attention may be directed toward the In-coming field. In Experiment 1, subjects detected a visual flash presented against unidirectional field motion. The OKN beating field was shifted toward the In-coming field, and manual reaction times were shorter when the target appeared in the In-coming field. Experiment 2 revealed that this In-coming field advantage occurred even when OKN (and thus the mean eye-position shift) was suppressed. Subsequent experiments showed that the In-coming field advantage is not due to a local motion interaction (Experiment 3), survives subject's voluntary allocation of attention (Experiment 4), and develops over less than 320 ms after the onset of the motion field (Experiment 5). These results suggest that unidirectional field motion tends to automatically shift visual attention toward the In-coming field.
... A variety of evidence exists to show that people can voluntarily control many aspects of oculomotor behavior through directed attention, as revealed by their ability to follow particular instructions to do so under conditions where visual stimuli are absent or held constant. Saccades can be directed to imaginary or remembered targets (Becker, 1991), pursuit movements can be generated by directing attention to targets that are stabilized on the retina (Grtisser, 1986), and optokinetic nystagmus (OKN) responses are modulated substantially by the effort to track the stimulus or to fixate steadily (Wyatt & Pola, 1984;1987). With respect to disparity vergence, Erkelens & Collewijn (1991) reported, under conditions of image stabilization, that instructions to attend to a line nearer or farther than a fixation line produced appropriate vergence responses. ...
Previously it has been reported that horizontal disparity vergence is strongly influenced by subject instructions to vary attention or tracking effort. This paper describes experiments which compared these instruction effects on horizontal and vertical disparity vergence. Within-trial comparisons were made possible by use of oblique (combined horizontal and vertical) disparity modulation. Subjects viewed a flat, fully correlated, dynamic random noise stereogram pattern through stationary circular apertures, with a small stationary fixation cross superimposed in the center. The disparity of the noise pattern was either modulated sinusoidally or changed abruptly. Subjects were instructed either to (1) hold fixation on the cross and ignore the disparity modulation of the noise pattern; or (2) follow the movement of the noise pattern as accurately as possible. Subjects showed clear effects of instruction on the horizontal component of tracking, but showed little or no effect on the vertical component. Horizontal and vertical components of oblique vergence tracking appear to be largely independent, and vertical vergence is affected minimally, if at all, by an effort to track.
... In cats and primates, the initial fast rise is of large amplitude and has been associated with the oculomotor mechanisms for pursuit movements (see Bi.ittner & Bi.ittner-Ennever,1988), although, even in humans, it has been suggested that there is no clear distinction between the OK and pursuit systemsin the control of eye movements (Wyatt & Pola, 1984 ). Such pursuit movements are thought to be of very small amplitude, if present at all, in animals other than primates and to involve the visual and other areas of the cerebral cortex. ...
Horizontal optokinetic responses of pigmented rats were studied both in intact animals and in animals that had received lesions of the visual area of the cerebral cortex. In response to uniform velocity stimulation, there was an initial phase of rapid acceleration, larger than that reported in earlier studies, followed by a period of fairly uniform acceleration until the eye velocity approached that of the stimulus. As reported previously, responses to monocular stimulation were highly asymmetric, with the responses to nasotemporal stimulation being much weaker than those to temporonasal stimulation. Responses to sinusoidal stimulation were also studied. No significant effect of cortical lesions on the responses was seen.
... The method is similar to that used in studies of OKN suppression (e.g. Wyatt & Pola, 1984, 1987, in which a drifting stimulus is su~~rnpo~ on a steady fixation mark and the attempt to fixate reduces, but does not abolish optokinetic nystagmus. By putting the surround stimulus in conflict with the fixation target, the relative effectiveness of the two can be assessed. ...
In previous reports, we developed a metric for describing the signal strength of a dynamic random-dot stereogram (DRDS) stimulus at binocular (cyclopean) levels of the human visual system, which takes both contrast and interocular correlation into account. In this study we tested the generality of that metric in relation to the control of horizontal vergence eye movements. Signal strength was assessed by measuring the extent to which a DRDS stimulus could elicit involuntary vergence responses from a subject who was attempting to fixate steadily. Results for both step and sinusoidal disparity modulation paradigms showed that vergence velocity increased when either interocular correlation (IOC) or contrast was increased. Furthermore, IOC and contrast were found to contribute to signal strength for vergence in the same proportion as was found psychophysically. In general, the results indicate that the signals that drive this passive form of vergence are derived according to the same binocular combination rules as the signals that give rise to the perception of surfaces in DRDS stimuli.
... Interestingly, the straight optic flows did not significantly increase the error angles in our data. The test rod placed in the center of the test screen could act as a visual target superimposed on the moving visual background, which suppressed the horizontal optokinetic ocular response [38][39][40] . However, the test rod could not effectively suppress the background rotational optic flows probably because it was placed in the center of the concentric circular optic flow. ...
This study assessed the pupil responses in the sensory integration of various directional optic flows during the perception of gravitational vertical. A total of 30 healthy participants were enrolled with normal responses to conventional subjective visual vertical (SVV) which was determined by measuring the difference (error angles) between the luminous line adjusted by the participants and the true vertical. SVV was performed under various types of rotational (5°/s, 10°/s, and 50°/s) and straight (5°/s and 10°/s) optic flows presented via a head-mounted display. Error angles (°) of the SVV and changes in pupil diameters (mm) were measured to evaluate the changes in the visually assessed subjective verticality and related cognitive demands. Significantly larger error angles were measured under rotational optic flows than under straight flows ( p < 0.001). The error angles also significantly increased as the velocity of the rotational optic flow increased. The pupil diameter increased after starting the test, demonstrating the largest diameter during the final fine-tuning around the vertical. Significantly larger pupil changes were identified under rotational flows than in straight flows. Pupil changes were significantly correlated with error angles and the visual analog scale representing subjective difficulties during each test. These results suggest increased pupil changes for integrating more challenging visual sensory inputs in the process of gravity perception.
... 13 Early open-loop experiments appeared to confirm this idea, 14 but later work has shown that the pursuit/OKR interaction is not a straightforward linear summation. 15 It is clear, however, that OK suppression is not simply the result of an attentional "switch," in which the presence of the fixation target totally shuts off the OKR. l6 It may be expected, therefore, that subjects with deficient pursuit should not be able to exert such a significant suppressive effect on their OKR. ...
Abnormalities of foveal smooth pursuit and the monocular optokinetic response (OKR) have often been reported in subjects with latent nystagmus (LN) and manifest latent nystagmus (MLN). This abnormality typically takes the form of a monocular asymmetry with a deficit in the response to nasal-to-temporal (N-T) motion in the visual field. Previous studies have each presented different interpretations of this finding, depending on whether the characteristics of the spontaneous oscillation were considered when analyzing the measured eye movement response: one report has suggested that these asymmetries are in fact the cause of the spontaneous nystagmus. In this study, pursuit and OKRs were examined separately and, when working synergistically and antagonistically, to attempt to overcome this difficulty. Results suggest that pursuit and the OKR could be symmetric in LN and MLN for both binocular and monocular viewing, which leads to the conclusion that the asymmetric patterns of response often reported in LN/MLN result from either shifts in the zone of minimum-intensity oscillation or from non-stimulus-specific increases in the spontaneous nystagmus.
... However, moving visual backgrounds do not always have a negative impact on performance, most likely because human observers are able to voluntarily suppress the OKN by fixating any visual item that is superimposed on the moving background [e.g., 19,[29][30][31]. Menozzi and Koga [32] compared how people read a text displayed on a laterally moving, patterned background to a fixed version of the same background. ...
In many virtual environments, such as those of video games, the scene background moves to give the illusion of movement. In the present study, two experiments were designed to investigate the combined impact of lateral background motion and task difficulty on players’ performance in a target-shooting task. Participants had to perform the task on either the moving or the stationary version of a patterned background that was either green (Experiment 1) or black-and-white (Experiment 2). The difficulty of the task was manipulated by varying the number of visual features shared between the target and distractor items. In accordance with the literature, the participants’ performance was worse, and the number and duration of participants’ fixations increased when the task was difficult. Background motion had an additive, negative impact on performance. When the background was black-and-white, background motion had an impact only when the task was easy but not when it was difficult. Design recommendations based on manipulations of the background characteristics are proposed to establish the level of difficulty in simple video games that use lateral background motion.
... It is triggered either by visual (optokinetic) or vestibular inputs and is implicated in the sensation of circular vection (Cohen et al. 1977; Lafortune et al. 1986; Waespe and Schwartz 1986; Cannon and Robinson 1987). In condition of gaze Wxation or pursuit of a visual target against the moving background, there has been described a cancelation of OKN responses either by perceptual feedback from the relative target/background motion (Wyatt and Pola 1984; Suehiro et al. 1999; Kodaka et al. 2004) or by extra-retinal inputs from the smooth pursuit system (Pola et al. 1995; Lindner and Ilg 2006). Interestingly, after such OKN inhibition, OKAN is still present and often occurs with a reversal of the slow components in the opposite direction of the visual stimulus (Brandt et al. 1974; Kudo et al. 2002). ...
When the visual background is moving while subject fixate a visual target, optokinetic eye movements (OKN) are suppressed and the after response, called optokinetic after nystagmus (OKAN), occurring at the stimuli offset is often inverted as compared to the situation when the OKN movements are allowed. In this study, we investigated whether this reversal of OKAN results from a perceptual or extra-retinal feedback in relation with the pursuit system and/or the vestibular indirect system. Optokinesis performance was studied in normal subjects in four experiments always using the same background motion (1) to characterize the OKN and OKAN performance elicited by the whole visual field motion while fixating or not a central visual target, (2) to investigate the 3D characteristics of the OKAN reversal by using different orientations of the visual stimulation, (3) to correlate the occurrence of an inverted OKAN with functional asymmetry of the visuo-vestibular system, by studying the effects of ocular fixation deviations and finally (4) to examine the effects of the depth plane of gaze fixation on the OKAN characteristics. In Experiments 1 and 2, we observed that the visual fixation during full-field motion induced either a dumping effect or an inversion of the OKAN response that could occur in the different planes of eye movements. The time constant was significantly increased in the inverted after-responses as compared to the not inverted ones. In Experiment 3, we found that the occurrence of an OKAN reversal after eye movement inhibition was significantly related to the presence of right/left asymmetrical OKAN responses. Moreover, the OKAN time constant was strikingly dependent on the eye fixation position during the visual stimulation and this time constant/eye position relation diverged between OKAN responses with and without inversion. Finally, Experiment 4 showed that the OKAN inversion tended to disappear when the visual target to fixate was in the near space as compared to the far space included in the background. These results argue in favor of an extraretinal influence in relation to the dynamics of the vestibulo-motor system, rather than for a perceptual influence on the inverted OKAN mechanisms. More precisely, we postulate that the reversal of OKAN could be linked to an inhibition issued from pursuit signals combined with an asymmetrical activity in the VSM vestibular complex.
... Such context-induced retinal image motion drives a passive pursuit or slow-phase optokinetic response into the opposite direction. In order to smoothly track the target, the OKN has to be suppressed (Lindner and Ilg, 2006; Worfolk and Barnes, 1992; Wyatt and Pola, 1984), possibly causing the delay in initiating pursuit. For moving backgrounds, most studies provide evidence for a spatial averaging of motion signals (motion assimilation). ...
Smooth pursuit eye movements are continuous, slow rotations of the eyes that allow us to follow the motion of a visual object of interest. These movements are closely related to sensory inputs from the visual motion processing system. To track a moving object in the natural environment, its motion first has to be segregated from the motion signals provided by surrounding stimuli. Here, we review experiments on the effect of the visual context on motion processing with a focus on the relationship between motion perception and smooth pursuit eye movements. While perception and pursuit are closely linked, we show that they can behave quite distinctly when required by the visual context.
Subjects regarded targets which executed step-ramp motion in one of two conditions, either active (looking at the target) or passive (similar to the subject condition in passive or stare optokinetic nystagmus). The targets jumped 2 deg to one side and returned at a constant velocity. Targets were single round targets or extended targets with a high edge content. Many subjects showed substantial smooth eye movement responses in the passive condition, suggesting that a substantial component of initial smooth movement responses can occur independent of attention. Additional features of the smooth eye movement responses included (i) oculomotor "twitches" (brief, short-latency smooth eye movements in the step direction), (ii) overshoots (eye velocity greater than target velocity), and (iii) oscillations. Most of the response features can be accounted for by a model with a gain that is dependent on the subject's attentional level and on stimulus parameters.
Eye movements were recorded precisely with a scleral-coil method under three experimental conditions: fixation of a central, stationary target; pursuit of a central, moving target; pursuit of eccentric, moving targets. Subjects were instructed to attend to and fixate the target and to pursue it when it moved. The target was presented either in darkness (no visible background), on a diffusely lighted background, or on a large, structured background. Target and/or background could be moved independently with single sinusoids, pseudo-random mixtures of sinusoids or triangular waves. The target was usually presented under normal viewing conditions, but in some measurements (interleaved with normal ones) retinal target motion was uncoupled from eye motion by electronical addition of the eye position to the target position (open-loop conditions). The gain and phase relations of eye movements induced by motion of the target and/or background were calculated for the total, composite (smooth and saccadic) eye movement and for the reconstructed cumulative smooth component separately. Horizontal motion of a large, structured background induced correlated smooth eye movements while subjects fixated a stationary point target. The induced horizontal movements were very small (gain about 0.05) when the target was seen normally, and larger (gain about 0.20) when the target was horizontally stabilized on the retina. The phase lag of the induced eye movements relative to the background movements was usually smaller than 90 deg. When the target moved vertically and the background horizontally, vertical pursuit was similar to that with a stationary background, but in addition horizontal smooth eye movements, correlated with the background movements, were elicited with a gain of about 0.1 and a phase lag which was usually smaller than 90 deg. Imposed pseudo-random retinal motion of a central target under open-loop conditions (retinal image motion uncoupled from eye movements) elicited highly idiosyncratic responses which varied too much among subjects to allow any general conclusions, other than that open-loop stimulation seems unsuitable as a tool for analysing the response characteristics of the smooth pursuit system. In the absence of a background, an eccentric target configuration (two vertically aligned arrows with the points localized 5 deg above and 5 deg below the fovea) in horizontal motion was pursued equally well as a central target.(ABSTRACT TRUNCATED AT 400 WORDS)
Optokinetic nystagmus is often thought of as a "primitive" oculomotor response, while smooth pursuit is thought of as a "higher" one. We have used conditions that are usually thought of as eliciting optokinetic responses; i.e., large-field stimuli confined to the retinal periphery, and instructions to subjects to respond passively. In spite of this, the responses showed predictive behavior similar to that described for smooth pursuit.
We compared the quality of monocular smooth pursuit obtained with either a single point, a full-field stripe pattern or their combination as the target for unidirectional stimulus motion at velocities between 9 and 90 deg/sec. A point target moving in a fixed trajectory maximally constrains target selection as well as pursuit trajectory, whereas a full-field multicontoured pattern leaves the subject maximal freedom in these respects. To unconfound effects of pattern extent from those of spatial and temporal constraints, we presented point targets under conditions in which the subject was free to choose the location, extent and temporal structure of his pursuit trajectory ("free range"). Pursuit velocity gains were lowest for the point target moving in a fixed trajectory. Gain improved when the subject was free to pursue the same target moving at the same velocity in his own preferred range and rhythm. A further improvement was reached by showing the stripe pattern in addition to, and moving in conjunction with the spot. A final increase in gain occurred when the spot was removed, and the subject was allowed to pursue any feature of the uniformly moving, multicontoured pattern. No asymmetries were found between monocular pursuit with the right or the left eye, pursuit of rightward and leftward motion or between nasal- and temporalward motion. Effects of the type of target on the structure of the nystagmoid pursuit eye movements were slight or absent.
We reported earlier that occlusion of the central retina and stationary edges have highly interactive effects on the gain of optokinetic nystagmus (OKN; Murasugi, Howard, & Ohmi, 1986). In this study, we explored this effect in more detail. A central occluding band of variable height, flanked by vertical bars, was superimposed onto an array of dots moving at 30 degrees per second. The height of the occluding band required to abolish OKN increased with the separation of the vertical bars. For bars 3.5 degrees apart, OKN was abolished in most subjects when a band only 6' high ran between them. For bars 75 degrees apart, a band at least 20 degrees in height was required to abolish the response. The effects of the stationary figure depended to some extent on the subject's attention, but only at intermediate values of bar separation. Both low- and high-level mechanisms are proposed to account for the results.
Optokinetic nystagmus (OKN) is suppressed if attention is directed to a centrally placed afterimage superimposed on a moving display. Imagining a stationary object has little or no effect. An afterimage does not provide the retinal slip and misfoveation error signals provided by a stationary object and we have shown that an effective error signal does not arise from occlusion or masking of the display by the afterimage. Although a lack of relative motion between afterimage and moving display could indicate when OKN gain is one, there is no unique relative motion signal associated with a gain of zero. Subjects could partially inhibit the vestibulo-ocular reflex (VOR) in the dark when they imagined a head-fixed object. They could suppress the response more effectively by attending to an afterimage, but the suppression was still only partial. When OKN and VOR were evoked simultaneously, pursuit movements of the eyes could not be suppressed until the vestibular inputs had subsided. We conclude that signals associated with OKN, are fully available to the mechanism that assesses the headcentric motion of objects but that signals associated with VOR are only partially available to that mechanism.
In previous work, subjects looked at a target stabilized at the fovea, superimposed on a sinusiodally moving OKN stimulus. The stabilized target (no retinal-slip) suppressed OKN leaving residual eye movements that were often in counterphase with the OKN stimulus motion. In the present study we explored how this type of suppression of OKN is influenced by OKN stimulus predictability: OKN stimulus motion was either sinusoidal or a random walk of half-sinusoids. During fixation of a stabilized target with sinusoidal stimulus motion, OKN was suppressed leaving residual eye movement whose amplitude was typically less than OKN and with a phase lag of about 180 deg (roughly in counterphase with stimulus motion). With random-walk stimulus motion, the residual movement amplitude was even smaller, and at higher frequencies the phase lag decreased to become the same as for OKN. For both stimulus motions, OKN was suppressed when the target was present, but counterphase residual movements appear to depend on stimulus predictability.
Induced motion (IM) was observed in a fixated target in the direction opposite to the real motion of a moving background. Relative to a fixation target located straight ahead, IM decreased when fixation was deviated 10 degrees in the same direction as background motion and increased when fixation was deviated 10 degrees opposite background motion. These results are consistent with a "nystagmus-suppression" hypothesis for subjective motion of fixated targets: the magnitude of illusory motion is correlated with the amount of voluntary efference required to oppose involuntary eye movements that would occur in the absence of fixation. In addition to the form of IM studied, this explanation applies to autokinesis, apparent concomitant motion, and the oculogyral illusion. Accounts of IM that stress visual capture of vection, afferent mechanisms, egocenter deviations, or phenomenological principles, although they may explain some forms of IM, do not account for the present results.
To investigate the effects of an imaginary and a visual target on torsional optokinetic nystagmus (tOKN) and directional symmetry of tOKN.
Torsional OKN was induced by a rotating random dot pattern (52 degrees in diameter, constant angular velocity: +/-30 deg/sec to +/-52 deg/sec) with an imaginary or a visual target in 11 eyes of 10 healthy humans by dual-search coil methods.
Intorsional OKN and extorsional OKN were symmetrical in their slow-phase gain. The mean slow-phase gain (0. 037/0.041, intorsion/extorsion) of tOKN during fixation on a visual target at the center of the rotating random dot pattern was significantly (P: < 0.002) smaller than that (0.051/0.052, intorsion/extorsion) during fixation on an imaginary target at the center of the rotating random dot pattern. The mean tOKN slow-phase beat duration (840 msec/724 msec, intorsion/extorsion) during fixation on the visual target was significantly (P: < 0.002) longer than that (585 msec/543 msec, intorsion/extorsion) during fixation on the imaginary target. In seven eyes of six subjects, the mean slow-phase gain and beat duration (0.034 and 812 msec) of tOKN during fixation on a visual target 6.5 degrees left or right from the center of the rotating random dot pattern were not significantly different from those (0.037 and 825 msec) with a visual target at the center of the rotating random dot pattern (P: > 0.3).
A visual target spot suppresses tOKN by a nonpursuit visual system. Intorsional and extorsional OKNs were symmetrical.
A subgroup of individuals with vestibular dysfunction and visual motion hypersensitivity (VMH) become dizzy and imbalanced in response to movement of the visual environment. The purpose of this study was to investigate ocular fixational stability during gaze on a target, with and without visual background movement. Binocular vision functions were also examined as possible contributory factors to the dizziness and imbalance.
Twenty-four individuals with VMH, 20 with vestibular disorders without VMH and 20 healthy subjects were tested. Assignment to the experimental group was by symptoms of VMH. Outcome measures included electro-oculogram recordings of horizontal fixation and blink. Four clinical binocular vision functions were also tested. The Dizziness Handicap Inventory was used to assess the level of dizziness.
Subjects with VMH made significantly more refixational eye movements and had higher levels of dizziness than those in the other 2 diagnostic groups. There were abnormalities of binocular function in both the VMH and vestibular dysfunction groups compared with the control group. Individuals with VMH were unable to maintain stable gaze and inhibit eye movements to background motion. The large number of subjects with diagnosis of fluctuating vestibular function in the VMH group compared with the vestibular dysfunction group may indicate that VMH is a maladaptation of the system.
In Experiment 1 we investigated the independent and combined effects of horizontal OKN of stationary edges and occlusion of the central retina. For a display 60° wide moving at 30 °/sec a symmetrically placed pair of vertical nonoccluding bars suppressed OKN when near the center of the display but had no effect when 30° apart. A 7°-high 60°-wide central occluder reduced OKN gain by 37%. However, a central occluder with edges only 30° wide abolished OKN. In Experiment 2 this interaction between central occlusion and stationary edges was confirmed with a wider display over a range of stimulus velocities and configurations. A functional explanation of this interaction is presented.
We reported earlier that occlusion of the central retina and stationary edges have highly interactive effects on the gain
of optokinetic nystagmus (OKN; Murasugi, Howard, & Ohmi, 1986). In this study, we explored this effect in more detail. A central
occluding band of variable height, flanked by vertical bars, was superimposed onto an array of dots moving at 30° per second.
The height of the occluding band required to abolish OKN increased with the separation of the vertical bars. For bars 3.5°
apart, OKN was abolished in most subjects when a band only 6’ high ran between them. For bars 75° apart, a band at least 20°
in height was required to abolish the response. The effects of the stationary figure depended to some extent on the subject’s
attention, but only at intermediate values of bar separation. Both low- and high-level mechaisms are proposed to account for
the results.
It is generally believed that a target offset from the direction of gaze can only be fixated with a saccadic jump in eye position. By preventing saccadic eye movements from fixating a target, we have observed slow eye movements to both stationary and moving eccentric targets. This supports the view that target offset plays a role in guilding slow eye movements.
Horizontal and vertical small-field optokinetic nystagmus (OKN) were examined in persons with strabismic or anisometropic amblyopia. Reduced velocity for the slow phase of OKN driven by temporalward and upward target motion presented monocularly was observed in both the amblyopic and nonamblyopic eyes of some subjects. Several experiments were conducted in search of a sensory disturbance of perceived motion sensitivity which could account for the abnormal OKN. Comparisons between the frequency response for OKN and the contrast sensitivity function for perceived motion revealed that amblyopes with asymmetric OKN had equal sensitivity to nasal and temporal target motion. Contrast thresholds for driving the temporal slow phase of OKN were elevated by over 1 log unit above contrast thresholds for perceived temporal target motion, whereas contrast thresholds for stimulating nasal movement and driving the nasalward slow phase of OKN were equal. Contrast sensitivity to nasal and temporal target motion was symmetrical at the fovea and parafovea of the amblyopic eye. These studies did not reveal a sensory a /mso observed in both eyes of persons with congenital strabismus without amblyopia and in the nondeprived eye in monocular congenital cataract. These observations suggest a relationship between directional asymmetries of OKN and the incomplete development of binocular vision.
Previous investigations have challenged the generality of the claim that perceived motion is an effective stimulus for smooth pursuit eye movements. The experiments extend the scope of these investigations. Three experiments test the hypothesis that perceived motion can serve as the stimulus for pursuit when the eye movement does not generate constraining retinal error information. Observers viewed retinally stabilized displays that elicited the perception that a stationary target was moving or that a moving target was moving faster than it was actually moving. The results failed to confirm the hypothesis. Relevant literature is reviewed. We conclude that perceived movement can act as a stimulus for pursuit only when the “perceptual target” has no retinal counterpart.
1. Velocity characteristics of optokinetic nystagmus (OKN) and optokinetic after-nystagmus (OKAN) induced by constant velocity full field rotation were studied in rhesus monkeys. A technique is described for estimating the dominant time constant of slow phase velocity curves and of monotonically changing data. Time constants obtained by this technique were used in formulating a model of the mechanism responsible for producing OKN and OKAN.2. Slow phase velocity of optokinetic nystagmus in response to steps in stimulus velocity was shown to be composed of two components, a rapid rise, followed by a slower rise to a steady-state value. Peak values of OKN slow phase velocity increased linearly with increases in stimulus velocity to 180 degrees /sec. Maximum slow phase eye velocities in the monkey are 2-3 times as great as in humans.3. At the onset of OKAN, slow phase velocity falls by about 10-20%, followed by a slower decline to zero. Peak OKAN slow phase velocities were linearly related to optokinetic stimulus velocities up to 90-120 degrees /sec. Above 120 degrees /sec OKAN slow phase velocity saturated although OKN slow phase velocity continued to increase.4. The charge and discharge characteristics of OKAN were studied. The OKAN mechanism charged in 5-10 sec and discharged over 20-60 sec in darkness. The time constants of decay in OKAN slow phase velocity decreased as stimulus velocities increased. They also decreased on repeated testing. In several monkeys there was a consistent difference in the rate of decay of OKAN slow phase velocity to the right and left.5. Extended visual fixation discharged the activity responsible for producing OKAN. Short fixation times caused only a partial discharge of the OKAN mechanism. Following brief periods of fixation, OKAN resumed but with depressed slow phase velocities.6. A model based on a state realisation of a peak detector was formulated which approximately reproduces the salient characteristics of OKN and OKAN. This model predicts the three dominant characteristics of OKAN: (1) charge over 5-7 sec, (2) slow discharge in darkness, and (3) rapid discharge with visual fixation. With the addition of direct fast forward pathways, it also correctly predicts the rapid and slow rise in OKN. We postulate that OKAN is produced by a central integrator which is also active during OKN. Presumably this integrator acts to maximize velocities during OKN and to smooth and stabilize ocular following during movement of the visual surround.
We examined responses of the smooth pursuit system under open-loop conditions:(1) Subjects tracked an isolated target, oscillating sinusoidally at frequencies 0.3–1.5 Hz. When a variation of the Duncker illusion increasedperceived target motion (leavingretinal target motion unaltered), pursuit responses increased.(2) Measurements of perceived target motion during open-loop pursuit support the hypothesis that pursuit eye movementsper se contribute to perceived motion.(3) We interpret these results as evidence for a positive feedback loop in the pursuit system, related to perception. This loop may account for the high gain of the open-loop pursuit system.
The role of different parts of the human retina in eliciting optokinetic pursuit was investigated with continuously moving random dot or grid patterns (dia up to 30°). The retinal location and velocity of the stimulus could be fixed by servo control of the stimulus position by the eye position, and artificial scotomata could be inserted into the stimulus. Under these conditions (opened optokinetic feedback loop) pursuit velocity became much larger than the stimulus velocity. With a central stimulus, pursuit velocity (gain) in the 8 principal directions showed individual, but no systematic differences. In the periphery, a centrifugal stimulus movement was much more effective than a centripetal movement. This directional preference may assist foveation. Pursuit open-loop gain was only moderately diminished by a decrease of the stimulus diameter, but much more severely by deleting small parts in the centre. This indicates that the fovea is more powerful than the periphery in eliciting optokinetic pursuit. The distribution of fast and slow nystagmic phases with respect to the primary position was unaffected by the use of open-loop conditions or central scotomata. For all peripheral stimuli, the responses were strongly enhanced by the subject's specific attention.
Nystagmic eye movements in response to selective optokinetic stimulation of different parts of the retina were studied in normal human subjects by two methods: 1. a digital computer controlled by the eye movement signal was used to generate an optokinetic display which stimulated only the peripheral retina, simulating a central scotoma, and 2. a single dot of 0.6 degrees in diameter was used as the stimulus during maintained forward gaze. The results show that stimulation of the central or peripheral retina alone can produce optokinetic nystagmus in man, and that essentially the same type of nystagmus is produced in both cases. The slow phase velocity of nystagmus evoked from the peripheral retina falls off rapidly with distance from the fovea but can be facilitated by attention. Results are compared with other findings and a possible explanation is offered for the observed variation in slow phase speed which occurs during constant velocity optokinetic stimulation.
The spatial and temporal characteristics of optokinetic nystagmus (OKN) were investigated in the alert rhesus monkey under open and closed-loop conditions. One eye of each animal was immobilized by transection of the 3rd, 4th and 6th nerve intracranially. On optokinetic stimulation of the paralytic eye (open-loop) with the monkey's head restrained, eye movement records of the occluded, moving eye demonstrate a gradually increasing OKN, its slow phase reaching angular velocities much faster than pattern speed. This runaway effect is discussed in terms of the "corollary discharge" concept. Similarities of optokinetic and post-rotatory vestibular after-nystagmus are discussed. Investigation of the spatial parameters shows that the size of perifoveal areas successfully stimulated to elicit optokinetic nystagmus is relatively small under open-loop conditions and that this size depends on the distance of the stimulated area from the fovea, the minimum field diameter being an exponential function of excentricity. The preparation is shown to be useful for objective measurements of visual functions in the experimental monkey.
Certain significant differences have been shown to occur in the character of the optokinetic response of a subject gazing actively and passively at a moving striped drum which suggest that different nervous mechanisms subserve each. Image motion across the retina appears to be the stimulus inducing the passive variety and is moreover largely responsible for the illusory sensations of self rotation. This same mechanism may be invoked by way of explanation of the phenomenon of reversed optokinetic nystagmus. The occurrence of this phenomenon in patients with non congenital as well as congenital nystagmus lends support to this explanation. Eye movements induced in the normal eye of subjects with unilateral ophthalmoplegia following stimulation of the paretic eye provide additional support for the contention that peripheral vision contributes to the control of normal ocular movements.
Slow phase velocities of optokinetic eye movements due to constant rotation or sinusoidal movement of surroundings were measured under normal and open loop conditions. Speeds from 0.03-1°/sec were followed with a closed loop gain of 0.7-0.9. Higher eye speeds were reached at an acceleration of no more than 1°/sec2 and lower gain. Open loop gain was better than 10 for stimulus velocities up to 0.1°/sec. Phase lag in sinusoidal movement was very small even at low gain. No evidence for a genuine position servo was found.
The human optokinetic response to a horizontally moving stripped pattern surrounding the subject was investigated under quasi-open and closed loop conditions. Open loop conditions were produced by the addition of an external signal from measured slow phase eye velocity to stripe velocity. A comparison of open and closed loop responses to step and sinusoidal changes of stripe velocity indicates that the central nervous system controlling slow phase optokinetic following can be described as a simple first order lag (Ka/(s + a)) where K is 4.7 and the time constant, 1/a, is 1.25 s.
Smooth pursuit eye movements are usually thought to be guided only by target velocity. We studied the effectiveness of target velocity and target position (offset from the fovea) as stimuli for pursuit movements. Under open-loop conditions, we used induced (apparent) sinusoidal motion as a “velocityonly” stimulus, and square-wave motion as a “position-only” stimulus. Over a range of frequencies, position stimuli tended to give larger responses, and response velocity increased linearly with target offset. When open-loop sinusoidal target motion was synthesized using appropriate position-only and velocity-only “components”, the response was about the same as for real sinusoidal motion, suggesting a dominant role for target position in both cases. Using non-periodic step-ramp stimuli as devised by Rashbass, but in the open-loop, we have commonly observed position-directed pursuit movements.
Untersuchungen uber op-tokinetischen Nystagmus. Arc/w Neerb The role of nerceived motion ;n smooth pursuit kye movements
- J W C Braak
- H J Wyatt
- J Pola
Braak J. W. C. ter (1936) Untersuchungen uber op-tokinetischen Nystagmus. Arc/w Neerb. Physiol. 21, Wyatt H. J. and Pola J. (19791 The role of nerceived motion ;n smooth pursuit kye movements. 'Vision Res. 19, 613-618.
Uber induzierte Bewegung (Ein Bietrag zur Theorie optisch whargenommener Bewegung)
- Duncker
Suppression of OKN during visual fixation and pursuit
- Pola
Introduction: an appreciation of early work on gaze control in man and of visuo-vestibular research before 1940
- Jung
Results of electronystagmography in man: the value of optokinetic. vestibular, and spontaneous nystagmus for neurologic diagnosis and research
- Jung
Pursuit eye movements in response to stimulus velocity may be OKN
- Pola