Induced rotary movement during eye movements: displays with unequal spacing of pattern

In my previous (Reinhardt-Rutland, 1982) study, I suggested that eye movements enhance induced rotary movement. However, low salience of absolute displacement might also explain the results, as displays were covered with large numbers of equally spaced radial pattern elements. To test these competing hypotheses in the present study, I used an unequally spaced pattern in two displays. Common to each display was an annulus: In one display, the common annulus surrounded a disk, and in the other display the common annulus was surrounded by another annulus. In any trial, one component rotated and the other was stationary while for 40 s the subject's eyes followed a circular path concentric with the display; subjects timed those occasions when perceived stronger rotation resided in the common annulus. Despite an unequally spaced pattern, absolute displacement had a barely significant effect. Instead, perceived stronger rotation mostly resided in a display's more central component. I concluded therefore that eye movements enhance induced rotary movement.     

Induced rotation with concentric patterns

Duncker (1929) described induced rotation of a radial-line pattern when a concentric, enclosing annulus pattern rotated. This observation has not, so far, been confirmed or extended. Six experiments are described. The results from Experiments 1 and 2 showed that the frequency with which induced rotation is reported during standard observation periods is not affected by either angular velocity up to 15 deg/sec or unpatterned gaps up to 5 deg wide between the inner and outer patterns. Experiment 3 confirmed that the strength of the effect can be satisfactorily measured by cancellation of induced movement. Experiments 4–6 showed that induced rotation is very weak or absent when the inner disk rotates and the concentric annulus is stationary, increases in velocity as the number of radial lines in the rotating annulus increases by up to half the number in the stationary disk, and is only slightly stronger when the area of contrast between moving and stationary lines is poorly resolved in the peripheral visual field. The results are considered in terms of the resolution in perception of displacement ambiguity between moving and stationary elements.     

Induced movement-in-depth and induced changing-size elicited by a luminous rotating spiral

Induced movement-in-depth and induced changing-size are infrequently investigated forms of a phenomenon whereby movement is ascribed to a stationary stimulus. The present note concerns qualitative responses to a display designed to elicit both forms. The inducer was a two-arm luminous rotating linear-function spiral, and the stationary stimulus was an annulus concentric with the spiral; it was patterned with concentric luminous circles. Viewing was monocular. Among the findings, induced movement-in-depth was more frequently reported than induced changing-size, despite the lack of veridical movement-in-depth in the display. Possible lines of explanation are suggested.     

Spatial-contrast movement aftereffect can be rotary: support for link with aftereffect of induced movement.

The procedure for eliciting movement aftereffect (MAE) involves the subject's adapting to visual movement that subsequently stops. Conventionally, MAE is confined to the area of movement adaptation. However, Wohlgemuth (1911) demonstrated the existence of a type of MAE that had the opposite characteristics of an adjoining conventional MAE; the test area was unpatterned during adaptation and patterned during testing. This spatial-contrast MAE may be connected with the more recently identified induced movement MAE. Unfortunately, the eliciting movements have not necessarily been comparable; Wohlgemuth used centrifugal and centripetal movement, whereas induced movement MAE has generally been rotary. The results of this study indicate that rotary spatial-contrast MAE can be elicited by a display that, with modification, also elicits induced movement MAE and that the rotary spatial-contrast MAE is weaker than the equivalent induced movement MAE.     

Does intermittence in induced rotary movement have any explanatory significance?

Induced rotary movement has been reported to start and stop repeatedly during 1 min of observation. This has been taken as evidence for the involvement either of cyclorotational optokinetic nystagmus or of roll vection. Both assertions are dubious. Regarding cyclorotational optokinetic nystagmus, available evidence shows that it is too weak to be important in induced rotary movement. Also, induced rotary movement and cyclorotational optokinetic nystagmus are affected differently by the velocity of eliciting stimulation. Regarding roll vection, the conditions for its intermittence do not match those for induced rotary movement. Also, although aftereffects for induced rotary movement are negative, those for roll vection are positive and negative. Intermittence in induced rotary movement may be parsimoniously explained as characteristic of a weak effect.     

Anomalous induction of brightness and surface qualities: a new illusion due to radial lines and chromatic rings

When a chromatic (eg light-blue) annulus surrounds the central gap of an Ehrenstein figure so as to connect the inner ends of the radial lines, a striking new lightness effect emerges: the central white disk has both a self-luminous quality (brighter than in the regular Ehrenstein figure) and a surface quality (dense, paste-like). Self-luminous and surface qualities do not ordinarily appear co-extensively: hence, the brightness induction is called anomalous. In experiment 1, subjects separately scaled self-luminous and surface properties, and in experiment 2, brightness was nulled by physically darkening the central gap. Experiments 3 and 4 were designed to evaluate the importance of chromatic versus achromatic properties of the annulus; other aspects of the annulus (width or the inclusion of a thin black ring inside or outside the chromatic annulus) were tested in experiments 5-7. In experiments 8-12, subjects rated the brightness of modified Ehrenstein figures varying the radial lines (number, length, width, contrast, arrangement). Variation of these parameters generally affected brightness enhancement in the Ehrenstein figure and anomalous brightness induction in a similar manner, but was stronger for the latter effect. On the basis of these results, anomalous brightness induction is attributed to a surface induction process triggered by an interaction between illusory brightness enhancement (due to the radial lines) and border ownership (due to the blue annulus).     

Apparent rotation and jazzing in Leviant's Enigma illusion

In 1981 Leviant devised Enigma, a figure that elicits perceived rotary motion in the absence of real motion. However, despite its striking appearance there is no good explanation for this motion illusion to date. Gregory (1993 Proceedings of the Royal Society of London B 253 123) pointed out a similarity to MacKay's 'complementary' afterimage in his ray pattern and suggested accommodative fluctuations and small eye movements as a potential origin for these phenomena. Furthermore, Zeki et al (1993 Proceedings of the Royal Society of London B 252 215-222) found PET-activation in response to Enigma in visual area V5 and immediately surrounding areas (called V5 complex) suggesting that the illusory motion could be mediated by the same neurons as real motion. In the experiments reported here, I show that the rotary motion is perceived on coloured as well as achromatic annuli intercepting the radial lines. More importantly, the illusory streaming motion continues to be seen with a cycloplegic lens as well as through a pinhole (ie ruling out transient changes of accommodation), and in the positive after-image (ie in the absence of eye movements). Apparent rotation is strongest with radial inducers impinging at right angles onto the annuli, but persist, although to a lesser degree, when the inducing lines are tilted in opposite directions, non-collinear, or replaced by dotted lines or lines with rounded terminators. For an explanation, the Enigma illusion requires a neural mechanism that uses lines abutting an empty annulus to elicit orthogonal streaming motion in one or the other direction.     

Observations on stroboscopic induced motion

Subject-relative explanations of motion induction state that induced motion is the result of a misperceived shift of the median plane of the visual field of the subject. This theory does not require relative motion of the spot and frame, in the classical spot-and-frame condition, only asymmetrical stimulation. Three experiments are reported in which stroboscopic induced motion was investigated. The experimental arrangement was unconventional in that the induced object (spot) was presented only during the interstimulus interval between the exposures of the inducing object (frame). This allowed differentiation of the duration of the induced movement and that of the inducing one. In the first experiment it was demonstrated that perception of induced motion depends upon the duration of the interstimulus interval between the presentations of the inducing frame. In the second experiment it was shown that the perceived velocity of the induced movement can be different from that of the inducing one and depends on the duration of exposure of the induced object. In the third experiment a stimulus display was created in which the apparent displacement of an object and its induced motion are incongruous. The results are incompatible with subject-relative displacement as the sole determining factor of motion induction and they present some difficulties for the hypothesis that induced motion is the result of the apportionment of the objective displacement of the frame.     

Salience from multiple feature contrast: Evidence from saccade trajectories

We used eye tracking to quantify the extent to which combinations of salient contrasts (orientation, luminance, and movement) influence a central salience map that guides eye movements. We found that luminance combined additively with orientation and movement, suggesting that the salience system processes luminance somewhat independently of the two other features. On the other hand, orientation and movement together influenced salience underadditively, suggesting that these two features are processed nonindependently. This pattern of results suggests that the visual system does not sum sources of salience linearly, but treats some sources of salience as redundant.

     

An examination of rapid positioning movements with spatiotemporal constraints

Unidirectional positioning movements with spatiotemporal constraints were examined as a test of impulse-timing theory (Schmidt, 1976; 1980; Wallace, 1981). Movements were examined at the kinematic, kinetic, and neuromuscular levels in three experiments. In the first experiment, displacement was held constant while five different movement times were examined. Both amplitudes and durations of the EMG and the kinetic variables were related to movement time. The results generally support the impulse-timing model. In the second experiment, movements were performed to a target at each of four distances in a constant movement time. EMG and force amplitudes and, unexpectedly, accelerative-force duration were modulated to achieve changes in displacement when movement time was constant. In the third experiment, movement time and displacement were simultaneously varied resulting in four conditions with equal average velocities. The results of this experiment were not as clear and exhibited individual differences. EMG duration did not always vary with changes in movement time. The results of all three experiments could not be adequately accounted for by the impulse-timing model.     

An Examination of Rapid Positioning Movements with Spatiotemporal Constraints

Unidirectional positioning movements with spatiotemporal-constraints were examined as a test of impulse-timing theory (Schmidt, 1976; 1980; Wallace, 1981). Movements were examined at the kinematic, kinetic, and neuromuscular levels in three experiments. In the first experiment, displacement was held constant while five different movement times were examined. Both amplitudes and durations of the EMG and the kinetic variables were related to movement time. The results generally support the impulse-timing model. In the second experiment, movements were performed to a target at each of four distances in a constant movement time. EMG and force amplitudes and, unexpectedly, accelerative-force duration were modulated to achieve changes in displacement when movement time was constant. In the third experiment, movement time and displacement were simultaneously varied resulting in four conditions with equal average velocities. The results of this experiment were not as clear and exhibited individual differences. EMG duration did not always vary with changes in movement time. The results of all three experiments could not be adequately accounted for by the impulse-timing model.     

Visual search for positional relationships between pattern elements

The purpose of these experiments was to illustrate how a search for positional relationships between the elements in a stimulus pattern is effortful and serial, whereas a search for pattern elements (without requiring any positional information) takes place rapidly and in parallel. In all three experiments of this study, the target and distractor patterns consisted of two vertical line segments. In the experiment concerning the search for positional relationships between pattern elements, one of the line segments in a line pair had a gap, and the observer's task was to indicate whether the positional order of the two lines was identical in all the line pairs of the display, or whether the line segments were in a mirror-image order in one line pair (the target). In the two experiments concerning the search for pattern elements (no positional information was required), the observer's task was to look for a line pair with one gap line (the target) among line pairs containing two broken lines or among line pairs with unbroken lines. In all three tasks, the reaction time for a correct target detection was measured. The results showed that the search in the first task was highly serial, and in the second and third tasks of "feature" searches, the search time was nearly independent of the number of distractor pairs. It is suggested that this dissociation may be interpreted in the context of the quality of information processing in extrafoveal vision, i. e. the elements of a stimulus pattern can be clearly visible outside the fovea, but it is not possible to perceive accurately the positional relationships between them.     

Aftereffect of visual movement—the role of relative movement: A review

It is often believed that the aftereffect of visual movement (MAE) is more-or-less dependent on image movement. Modern explanation of MAE in terms of motion-sensitive mechanisms in the visual pathway assumes this. However, it has long been known that MAE can be influenced by other factors of stimulation, and particularly some that can be labeled asrelative. So, for example, MAE may not be observed unless more than one direction of movement is present in the eliciting stimulation, and MAE in an area may elicit an opposite MAE in an adjoining unadapted area. It is probable that the overemphasis on image movement has arisen because of the common use of multidirectional adapting movement and because of an assumption that patterned areas adjoining the MAE display do not have much effect on MAE. It is speculated that relative movement data for MAE may reflect a mechanism involved in detection of object motion: since image movement and eye movement do not in themselves adequately explain this process, it must be supposed that relative movement, in conjunction with the configuration of the retinal image, is important.     

Reinstating salience effects over time: the influence of stimulus changes on visual selection behavior over a sequence of eye movements

Recently, we showed that salience affects initial saccades only in a static stimulus environment; subsequent saccades were unaffected by salience but, instead, were directed in line with task requirements (Siebold, van Zoest, & Donk, PLoS ONE 6(9): e23552, 2011). Yet multiple studies have shown that people tend to fixate salient regions more often than nonsalient ones when they are looking at images—in particular, when salience is defined by dynamic changes. The goal of the present study was to investigate how oculomotor selection beyond an initial saccade is affected by salience as derived from changing, as opposed to static, stimuli. Observers were presented with displays containing two fixation dots, one target, one distractor, and multiple background elements. They were instructed to fixate on one of the fixation dots and make a speeded eye movement to the target, either directly or preceded by an initial eye movement to the other fixation dot. In Experiment 1, target and distractor differed in orientation contrast relative to the background, such that one was more salient than the other, whereas in Experiments 2 and 3, the orientation contrast between the two elements was identical. Here, salience was implemented by a continuous luminance flicker or by a difference in luminance contrast, respectively, which was presented either simultaneously with display onset or contingent upon the first saccade. The results showed that in all experiments, initial saccades were strongly guided by salience, whereas second saccades were consistently goal directed if the salience manipulation was present from display onset. However, if the flicker or luminance contrast was presented contingent upon the initial saccade, salience effects were reinstated. We argue that salience effects are short-lived but can be reinstated if new information is presented, even when this occurs during an eye movement.     

The effects of position cues on the appearance of stimulus elements in a bistable apparent movement display

A modified version of the Ternus display was used to assess the relative effects of element position cues on reports of group and end-to-end movement. In this display, two rows of stimulus elements are joined by connecting lines. In one version of the display, the connecting lines remain stationary across frames, facilitating the interpretation that the associated stimulus elements also remain stationary. In another version of the display, one end of the connecting lines shifts horizontally from frame to fame, facilitating the interpretation that the associated stimulus elements have also shifted. The experiment showed that when the connecting lines remain stationary, reports of end-to-end movement increase, regardless of the interstimulus interval (ISI) at which the frames alternate. When the connecting lines shift, reports of group movement increase, regardless of ISI. Theoretical interpretations of the results involving both relatively low-level motion signals and higher order perceptual influences are considered.     

错觉轮廓的适应效应

错觉轮廓反映知觉的主动建构过程, 考察其是否存在适应效应有助于理解视觉系统反馈调节的特性。我们采用Kanizsa这种典型的错觉轮廓来研究其适应过程, 结果发现：Kanizsa错觉轮廓具有适应效应, 并且这种适应主要是由主观形成的整体轮廓造成的, 而不是由Pac-Man上的线条引起的。表明依赖于高级视觉皮层反馈调节的主观建构过程和自下而上的神经元信息一样, 会随呈现时间的增加, 神经活动减弱, 体现为适应效应。     

The spatial signal for saccadic eye movements emphasizes visual boundaries

By investigating the visual processing involved when saccades are made to newly appearing targets, we show that this processing is significantly nonlinear and that texture boundary information predominates. We used the global, or center-of-gravity, effect whereby a saccadic eye movement directed to a target consisting of a pair of elements has an amplitude intermediate between that of saccades directed to the individual elements. We measured the effect using target elements with different visual characteristics, including phase-reversal checkerboard targets that had the same space-average luminance as the background. The contribution to the center-of-gravity calculation was used to measure relative salience. We found that positive and negative contrast elements contribute almost equal weightings. Thus, salience, assessed in this way, is a highly nonlinear function of luminance. The salience of checkerboard targets was found to decrease as check size was decreased and increase as the overall size of the target was increased. Checkerboards with an empty center were as effective as were full checkerboards, showing the importance of boundaries in the salience signal.     

Antagonistic effects of adjacency and apparent speed in induced movement

Two experiments concerning induced movement are reported. The hypothesis was that when outline inducing frames were used, object-relative displacement was modified by two variables, adjacency and apparent speed. Adjacency is directly related to the magnitude of induced movement. Small outline frames are high in adjacency, and so small frames should be powerful generators of induced movement. On the other hand, several investigators have found the speed of the inducing frame to be inversely related to the magnitude of induced movement. It is hypothesized here that this effect of speed was determined by apparent speed (not real speed), and if so, since small objects appeared to move faster than large ones, a small outline frame should be a relatively weak generator of induced movement. In the first experiment, this hypothesis was tested using single inducing frames. In the second experiment, this hypothesis was tested using two inducing frames presented simultaneously. The implications of these experiments were discussed with regard to other theories of induced movement.     

Skilled Motor Performance and Working Memory in Rowers: Body Patterns and Spatial Positions

Previous studies using unfamiliar laboratory tasks (e.g. Smyth & Pendleton, 1990) have shown that working memory for movements to targets external to the body (positional movements) is dissociable from working memory for movements made to recreate specific configurations of body parts (patterned movements). In Experiment 1 this dissociation is replicated using tasks that were adapted for use in Experiment 2. In Experiment 2 the timing of experienced rowers' performance of patterned and positional elements of the rowing stroke was selectively disrupted by concurrent performance of patterned and positional memory tasks, respectively. These results suggest that patterned and positional elements of well-practised everyday motor tasks, which involve a complex interaction of the two types of movement, are controlled separately and place dissociable demands on working memory.