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.     

Absence of color selectivity in the visual movement aftereffect

Lovegrove, Over, and Broerse (1972) reported that the magnitude of the movement aftereffect was reduced when the colors of the inducing and test stimuli differed, relative to when they were the same. Since this result is contrary to some earlier findings, four experiments were conducted to examine this claim. Neither the duration nor the magnitude (as measured by manual tracking) of the aftereffect generated by rotary or linear movement of contours were found to be affected by the color combinations of the inducing and stationary patterns.     

Interactions between spatial and spatiotemporal information in spatiotemporal boundary formation

The surface and boundaries of an object generally move in unison, so the motion of a surface could provide information about the motion of its boundaries. Here we report the results of three experiments on spatiotemporal boundary formation that indicate that information about the motion of a surface does influence the formation of its boundaries. In Experiment 1, shape identification at low texture densities was poorer for moving forms in which stationary texture was visible inside than for forms in which the stationary texture was visible only outside. In Experiment 2, the disruption found in Experiment 1 was removed by adding a second external boundary. We hypothesized that the disruption was caused by boundary assignment that perceptually grouped the moving boundary with the static texture. Experiment 3 revealed that accurate information about the motion of the surface facilitated boundary formation only when the motion was seen as coming from the surface of the moving form. Potential mechanisms for surface motion effects in dynamic boundary formation are discussed.     

An aftereffect to discrete stimuli producing apparent movement and succession

After observing the sequential flashing of two lights that produced either the perception of apparent movement or the perception of the succession of two stationary lights, the presentation of the lights in the opposite direction produced the perception of a more rapid apparent movement or of a more rapid succession of the light flashes. These aftereffects suggest the presence of neural structures for the discrimination of sequential changes in spatial position which are subject to adaptation and respond with decreased sensitivity to the repetitive presentation of the two lights in a given spatial direction. The results are interpreted to support the hypothesis that the perception of apparent movement involves the excitation of specific neural mechanisms selectively responsive to sequential changes in stimulus position. An alternative hypothesis is that the perception of apparent movement involves an inference based on the separate registrations of the position of a stimulus at one point in time and the position of that stimulus at an earlier point in time.     

Three dimensions of dialogical movement

After recalling historical and current approaches, I propose a semiotic approach to dialogicality, with a specific focus on cultural elements as markers in the flow of thinking or discourse. My core proposition is to consider dialogical dynamics as taking place in a space organised along three dimensions: 1) a temporal orientation, 2) degrees of fiction, and 3) degrees of generalization. I support my presentation with examples taken from a young woman's diary. Altogether, this raises the question of the possibility of inner dialogicality, and calls for a closer attention to the ethical underpinning of dialogical approaches.     

The spatial spread of attentional modulation of the motion aftereffect

The spatial spread of attentional modulation of selective adaptation was investigated in four experiments in which the duration of the movement aftereffect (MAE) was measured with and without processing of intermittently changing digits at the fixation point. In the first experiment, the effects of diverting attention on MAE duration were found to reduce as the distance between the fixation digits and the inner edge of the surrounding adapt/test grating was increased. A second experiment suggested that eye movements were unlikely to underlie the attentional effects. In experiment 3, the attentional effect stayed constant as the outer diameter of the adapt/test gratings was increased. In experiment 4 (as in experiment 1) the modulatory effects of attention were larger the closer the adapt/test gratings were to the locus of attention, when the area of the grating was held constant but its eccentricity varied. In experiments 1 and 4, an intermittently changing fixation digit was found to reduce MAE durations more than an unchanging digit, even when subjects were not required to process it, suggesting that exogenous as well as endogenous attentional processes modulate early motion processing.     

The auditory motion aftereffect: its tuning and specificity in the spatial and frequency domains

In this paper, the auditory motion aftereffect (aMAE) was studied, using real moving sound as both the adapting and the test stimulus. The sound was generated by a loudspeaker mounted on a robot arm that was able to move quietly in three-dimensional space. A total of 7 subjects with normal hearing were tested in three experiments. The results from Experiment 1 showed a robust and reliable negative aMAE in all the subjects. After listening to a sound source moving repeatedly to the right, a stationary sound source was perceived to move to the left. The magnitude of the aMAE tended to increase with adapting velocity up to the highest velocity tested (20 degrees/sec). The aftereffect was largest when the adapting and the test stimuli had similar spatial location and frequency content. Offsetting the locations of the adapting and the test stimuli by 20 degrees reduced the size of the effect by about 50%. A similar decline occurred when the frequency of the adapting and the test stimuli differed by one octave. Our results suggest that the human auditory system possesses specialized mechanisms for detecting auditory motion in the spatial domain.     

Interactions of speech and manual movement in a syncopated task

The present study examined interactions of speech production and finger-tapping movement, using a syncopated motor task with two movements in 10 male right-handed undergraduate students (M age = 21.0 yr.; SD = 1.4). On the syncopated task, participants were required to produce one movement exactly midway between two other movements (target interresponse interval: 250 msec.). They were divided into two groups, the tap-preceding group and speech-preceding group. The author observed that the right hand showed a more variable peak force and intertap interval than the left hand in the speech-preceding group, indicating an asymmetrical interference of two movements. On the other hand, the mean differences between onsets of speech and tapping movement were shorter than 250 msec. over all conditions (the shortest mean difference was 50 msec.), suggesting a mutual entrainment of two movements. An asymmetry of entrainment was observed in the speech-preceding group, in which speech production was more strongly entrained with movements of the right hand than with those of the left hand.     

On the relation between visual surround and motion aftereffect velocity

Two experiments examined the effect of changes in the visual surround upon the velocity of motion aftereffects. Experiment I showed that introduction or reintroduction of a patterned surround midway through the test period was sufficient to produce an increase in apparent velocity. However, a greater increase was observed when a patterned surround instead of a dark homogeneous surround had been used during the induction period. Experiment II demonstrated that luminance change was also sufficient to produce an increase in apparent velocity, although the extent of the increase was not as great as that produced through the use of the patterned surround in Experiment I. These results indicate that a change in stimulus surround is sufficient to produce an increase in the velocity of a motion aftereffect and that the extent of the increase is dependent upon the characteristics of both the induction and test surrounds.     

A low-cost system for measuring and analyzing human movement in three dimensions

This paper describes a system for measuring the three-dimensional movement of a point on the human body. The core components of the system are an ultrasonic computer mouse (The OWL), an IBM-compatible personal computer, and a suite of recording and analysis software written in National Instruments’ LabVIEW instrumentation programming language. The cost of these components is sufficiently low that we have been able to create a system for measuring human kinematics that is within the reach of a typical budget for student practical classes.     

Sequential modulations of correspondence effects across spatial dimensions and tasks

In two experiments, we explored sequential modulations of correspondence effects in a prime-target paradigm. In Experiment 1, the participants responded to the direction of target arrows that were preceded by prime arrows with a corresponding or noncorresponding direction. This produced a prime-target correspondence effect that was reduced when the preceding trial contained a noncorresponding prime-target event. This sequential modulation of the correspondence effect was observed even when neither stimuli nor responses were repeated from one trial to the next, ruling out explanations of sequential modulations in terms of stimulus or response repetitions. Experiment 2 combined the prime-target correspondence effect with a Simon-type correspondence effect. Both effects were reduced following noncorrespondence of the same type and, to a lesser extent, following noncorrespondence of the other type. Altogether, these results suggest that part of the sequential modulation of correspondence effects reflects an adaptation to a preceding response conflict independently of the peripheral stimulus events that produced this conflict.