Subjective motion and acceleration induced by the movement of the observer’s entire visual field

Three experiments were carried out to trace the developmental time course of apparent subjective rotation induced by rotating a tall striped drum around an observer. In Experiment 1, rotation of the drum led to increasingly frequent reports of subjective rotation over the first 30 sec of stimulation by the optokinetic stimulus, after which subjects experienced mostly apparent subjective rotation and a small amount of drum rotation. In Experiment 2, using a magnitude estimation technique to assess the speed of drum and subjective rotation, subjects reported subjective acceleration and drum deceleration of about the same magnitude over the first 30 sec of the 1-rain trial, followed by a steady level of subjective rotation with some residual drum movement. In Experiment 3, using three different drum speeds, it was found that the speed of steady-state rotation, as well as subjective acceleration and drum deceleration, are linear functions of the speed of the inducing stimulus. Implications of these observations towards the explanation of how we perceive a stable environment during locomotion are discussed.     

The relationship between vertical stimulation and horizontal attentional asymmetries

The original aim was to examine the effect of perceived distance, induced by the Ponzo illusion, on left/right asymmetries for line bisection. In Experiment 1, university students (n?=?29) made left/right bisection judgements for lines presented in the lower or upper half of the screen against backgrounds of the Ponzo stimuli, or a baseline. While the Ponzo illusion had relatively little effect on line bisection, elevation in the baseline condition had a strong effect, whereby the leftward bias was increased for upper lines. Experiment 2 (n?=?17) eliminated the effect of elevation by presenting the line in the middle and moving the Ponzo stimuli relative to the line. Despite this change, the leftward bias was still stronger in the upper condition in the baseline condition. The final experiment (n?=?17) investigated whether upper/lower visual stimulation, which was irrelevant to the task, affected asymmetries for line bisection. The results revealed that a rectangle presented in the upper half of the screen increased the leftward line bisection bias relative to a baseline and lower stimulation condition. These results corroborate neuroimaging research, showing increased right parietal activation associated with shifts of attention into the upper hemispace. This increased right parietal activation may increase the leftward attentional bias—resulting in a stronger leftward bias for line bisection.     

A hit-and-miss investigation of asymmetries in wheelchair navigation

In contrast to the leftward inattention caused by right parietal damage, normal brain function shows a subtle neglect of the right and left sides in peripersonal and extrapersonal space, respectively. This study explored how these attentional biases cause healthy individuals to collide with objects on the right. In Experiment 1, participants navigated manual and electric wheelchairs through a narrow doorway. More rightward collisions were observed for the electric, but not the manual, wheelchair. Experiment 2 demonstrated that the rightward deviation for electric wheelchairs increased for wider doorways. Experiment 3 established that the rightward deviation is not the result of task-related vestibular input, using a remote control device to operate the wheelchair. The rightward deviation persisted in Experiment 4 when the doorway was removed, suggesting that the bias is the result of a mis-bisection of space. In Experiment 5, the rightward bias was replicated using an electric scooter, which is steered using handlebars. Finally, Experiment 6 required participants to point to the middle of the doorway, using a laser, before moving the scooter. Rightward mis-bisection was observed in both conditions. Rightward mis-bisection of lines in extrapersonal space provides the most parsimonious explanation of the rightward collisions and deviations.     

Response suppression produced by vestibular stimulation in the rat

Seven rats were trained to stable performance levels on either Fixed Ratio 47, Variable Ratio 47, Variable Interval 1-min, or Fixed Interval 1-min schedules of food reinforcement. Subjects were then tested for sensitivity to vestibular stimulation from rotation, using an ascending method of limits technique with increments in velocity of one revolution per minute every 5 min. Centrifugal forces were minimized by locating the test chamber over the axis of rotation. Response rates decreased in all subjects as a function of increasing rotation speed. In addition, characteristic differences in the patterns of response decrement were found between subjects on ratio and on interval schedules. Repeated tests indicated high intra-subject reliability in sensitivity to rotation. Similarities of these data to "motion sickness" phenomena in other species were noted. It is suggested that this behavioral approach provides a sensitive and quantifiable technique for assessing the effects of vestibular stimulation in animals.     

Global-perspective jitter improves vection in central vision

Previous vection research has tended to minimise visual-vestibular conflict by using optic-flow patterns which simulate self-motions of constant velocity. Here, experiments are reported on the effect of adding 'global-perspective jitter' to these displays--simulating forward motion of the observer on a platform oscillating in horizontal and/or vertical dimensions. Unlike non-jittering displays, jittering displays produced a situation of sustained visual-vestibular conflict. Contrary to the prevailing notion that visual-vestibular conflict impairs vection, jittering optic flow was found to produce shorter vection onsets and longer vection durations than non-jittering optic flow for all of jitter magnitudes and temporal frequencies examined. On the basis of these findings, it would appear that purely radial patterns of optic flow are not the optimal inducing stimuli for vection. Rather, flow patterns which contain both regular and random-oscillating components appear to produce the most compelling subjective experiences of self-motion.     

Unilateral hemispheric activation does not affect free-viewing perceptual asymmetries

Strong leftward perceptual biases have been reported for the selection of the darker of two left/right mirror-reversed luminance gradients under free-viewing conditions. This study investigated the effect of unilateral hemispheric activation on this leftward bias in two groups of dextrals (N = 52 and N = 24). In Experiment 1, activation was manipulated by asking participants to tap with their left or right fingers along their midline. In Experiment 2, participants clenched their left or right hands in their respective hemispaces. Participants selected the stimulus that was darker on the left-hand side 73% of the time. Despite manipulations of activation strength and hemispace, activation had no effect on the asymmetry. If activation was important, the leftward bias should have been enhanced when the left hand/right hemisphere was active and reduced (or reversed) when the right hand/left hemisphere was active. The contribution of left-to-right scanning biases to free-viewing perceptual asymmetries is discussed as an alternative.     

Tuning of human vestibulospinal reflexes by leg rotation

Changing the foot position modifies the mechanical action exerted by the ankle extensor and flexor muscles over the body. We verified, in two groups of healthy subjects standing with the heels touching or apart, whether a 90° external rotation of the right leg and foot also changes the pattern of vestibulospinal reflexes elicited by electrical stimulation of the labyrinth. With the head oriented forward, leg rotation did not modify the labyrinthine-driven displacements of the center of pressure (CoP). When the head was rotated in the horizontal plane, either to the right or to the left, the CoP displacement increased along the y axis in all subjects. Changes in the x component in most instances appropriate to preserve unmodified the direction of body sway elicited by the stimulus were observed. Right leg rotation increased the basal EMG activity of ankle extensors and flexors on the left side, while the right side activity was unaffected. The EMG responses to labyrinthine stimulation were modified only on the left side, in a way appropriate to correct the effects of the altered torque pattern exerted on the body by right leg muscles. It appears, therefore, that somatosensory signals related to leg rotation and/or copy of the corresponding voluntary motor commands modify the pattern of vestibulospinal reflexes and maintain the postural response appropriate to counteract a body sway in the direction inferred by labyrinthine signals.     

Imagined own-body transformations during passive self-motion

Spatial perspective taking is a crucial social skill that underlies many of our everyday interactions. Previous studies have suggested that spatial perspective taking is an embodied process that involves the integration of both motor and proprioceptive information. Given the importance of vestibular signals for own-body perception, mental own-body imagery, and bodily self-consciousness, in the present study we hypothesized that vestibular stimulation due to passive own-body displacements should also modulate spatial perspective taking. Participants performed an own-body transformation task while being passively rotated in a clockwise or counter-clockwise direction on a human motion platform. A congruency effect was observed, reflected in faster reaction times if the implied mental body rotation direction matched the actual rotation direction of the chair. These findings indicate that vestibular stimulation modulates and facilitates mental perspective taking, thereby highlighting the importance of integrating multisensory bodily information for spatial perspective taking.     

Significance of paradoxical leftward error of line bisection in left unilateral spatial neglect

We intended to determine if leftward error of line bisection means "right" or "left" neglect in a patient with left unilateral spatial neglect. The patient placed the subjective midpoint to the left of the true center when bisecting lines without cueing. By contrast, when cued to the left endpoint, he showed typical rightward errors that became greater as longer lines were presented. Cueing to the right endpoint increased leftward errors compared with the bisections without cueing. The results suggest that paradoxical leftward error of line bisection is a form of "left" unilateral spatial neglect in that the shortness of the left extent is ignored.     

The angle of visual roll motion determines displacement of subjective visual vertical

The effect of full-field sinusoidal visual roll motion stimuli of various frequencies and peak velocities upon the orientation of subjective visual vertical (SV) was studied. The angle of the optokinetically induced displacement of SV was found to be a linear function of the logarithm of the stimulus oscillation angle. Interindividual slopes of this function varied between 2 and 9. The logarithmic function is independent of stimulus frequency within the range of .02 Hz to .5 Hz and of peak stimulus velocity from 7.5°/sec to 170°/sec. It holds for oscillation angles up to 100°–140°. With larger rotational angles, saturation is reached. With small stimulus angles, a surprisingly high threshold (5°-8°) was observed in our experiments. This may reflect the unphysiological combination of visual roll stimuli without corroborating vestibular and proprioceptive inputs normally present when body sway produces visual stimulation. Under natural conditions, the visual feedback about spontaneous sway stabilizes body posture by integrating rotational velocity over stimulus duration which is equal to rotational angle.     

Auditory clicks distort perceived velocity but only when the system has to rely on extraretinal signals

Previous work has found that repetitive auditory stimulation (click trains) increases the subjective velocity of subsequently presented moving stimuli. We ask whether the effect of click trains is stronger for retinal velocity signals (produced when the target moves across the retina) or for extraretinal velocity signals (produced during smooth pursuit eye movements, when target motion across the retina is limited). In Experiment 1, participants viewed leftward or rightward moving single dot targets, travelling at speeds from 7.5 to 17.5 deg/s. They estimated velocity at the end of each trial. Prior presentation of auditory click trains increased estimated velocity, but only in the pursuit condition, where estimates were based on extraretinal velocity signals. Experiment 2 generalized this result to vertical motion. Experiment 3 found that the effect of clicks during pursuit disappeared when participants tracked across a visually textured background that provided strong local motion cues. Together these results suggest that auditory click trains selectively affect extraretinal velocity signals. This novel finding suggests that the cross-modal integration required for auditory click trains to influence subjective velocity operates at later stages of processing.     

Dual adaptation and adaptive generalization of the human vestibulo-ocular reflex

In two experiments, we examined the possibility that the human vestibulo-ocular reflex (VOR) is subject todual adaptation (the ability to adapt to a sensory rearrangement more rapidly and/or more completely after repeated experience with it) andadaptive generalization (the ability to adapt more readily to a novel sensory rearrangement as a result of prior dual adaptation training). In Experiment 1, the subjects actively turned the head during alternating exposure to a visual-vestibular rearrangement (target/head gain=0.5) and the normal situation (target/head gain=0.0). These conditions produced both adaptation and dual adaptation of the VOR but no evidence of adaptive generalization when tested with a target/head gain of 1.0. Experiment 2, in which exposure to the 0.5 gain entailed externally controlled (i.e., passive) whole body rotation, resulted in VOR adaptation but no dual adaptation. As in Experiment 1, no evidence of adaptive generalization was found.     

The contribution of visual and vestibular information to spatial orientation by 6- to 14-month-old infants and adults

Although there is much research on infants' ability to orient in space, little is known regarding the information they use to do so. This research uses a rotating room to evaluate the relative contribution of visual and vestibular information to location of a target following bodily rotation. Adults responded precisely on the basis of visual flow information. Seven-month-olds responded mostly on the basis of visual flow, whereas 9-month-olds responded mostly on the basis of vestibular information, and 12-month-olds responded mostly on the basis of visual information. Unlike adults, infants of all ages showed partial influence by both modalities. Additionally, 7-month-olds were capable of using vestibular information when there was no visual information for movement or stability, and 9-month-olds still relied on vestibular information when visual information was enhanced. These results are discussed in the context of neuroscientific evidence regarding visual-vestibular interaction, and in relation to possible changes in reliance on visual and vestibular information following acquisition of locomotion.     

Lateral asymmetry and tactile sensitivity

Weinstein found in 1963 that the left female breast is more sensitive to tactile stimulation than the right breast. Saling and Cooke in 1984 hypothesized that this asymmetry in breast sensitivity underlies the well-documented leftward bias in maternal cradling behaviour, which is independent of manual specialization. Our interest in the Saling and Cooke hypothesis led to an attempt to replicate Weinstein's 1963 study. His findings were not supported. Further, a review of the literature on the lateral distribution of cutaneous thresholds showed that there is little experimental support for the widely held belief that the left side of the body is uniformly more sensitive than the right.     

Pseudoneglect for the bisection of mental number lines

Patients with unilateral neglect of the left side bisect physical lines to the right whereas individuals with an intact brain bisect lines slightly to the left (pseudoneglect). Similarly, for mental number lines, which are arranged in a left-to-right ascending sequence, neglect patients bisect to the right. This study determined whether individuals with an intact brain show pseudoneglect for mental number lines. In Experiment 1, participants were presented with visual number triplets (e.g., 16, 36, 55) and determined whether the numerical distance was greater on the left or right side of the inner number. Despite changing the spatial configuration of the stimuli, or their temporal order, the numerical length on the left was consistently overestimated. The fact that the bias was unaffected by physical stimulus changes demonstrates that the bias is based on a mental representation. The leftward bias was also observed for sets of negative numbers (Experiment 2)--demonstrating not only that the number line extends into negative space but also that the bias is not the result of an arithmetic distortion caused by logarithmic scaling. The leftward bias could be caused by a rounding-down effect. Using numbers that were prone to large or small rounding-down errors, Experiment 3 showed no effect of rounding down. The task demands were changed in Experiment 4 so that participants determined whether the inner number was the true arithmetic centre or not. Participants mistook inner numbers shifted to the left to be the true numerical centre--reflecting leftward overestimation. The task was applied to 3 patients with right parietal damage with severe, moderate, or no spatial neglect (Experiment 5). A rightward bias was observed, which depended on the severity of neglect symptoms. Together, the data demonstrate a reliable and robust leftward bias for mental number line bisection, which reverses in clinical neglect. The bias mirrors pseudoneglect for physical lines and most likely reflects an expansion of the space occupied by lower numbers on the left side of the line and a contraction of space for higher numbers located on the right.     

Pseudoneglect for the bisection of mental number lines

Patients with unilateral neglect of the left side bisect physical lines to the right whereas individuals with an intact brain bisect lines slightly to the left (pseudoneglect). Similarly, for mental number lines, which are arranged in a left-to-right ascending sequence, neglect patients bisect to the right. This study determined whether individuals with an intact brain show pseudoneglect for mental number lines. In Experiment 1, participants were presented with visual number triplets (e.g., 16, 36, 55) and determined whether the numerical distance was greater on the left or right side of the inner number. Despite changing the spatial configuration of the stimuli, or their temporal order, the numerical length on the left was consistently overestimated. The fact that the bias was unaffected by physical stimulus changes demonstrates that the bias is based on a mental representation. The leftward bias was also observed for sets of negative numbers (Experiment 2)—demonstrating not only that the number line extends into negative space but also that the bias is not the result of an arithmetic distortion caused by logarithmic scaling. The leftward bias could be caused by a rounding-down effect. Using numbers that were prone to large or small rounding-down errors, Experiment 3 showed no effect of rounding down. The task demands were changed in Experiment 4 so that participants determined whether the inner number was the true arithmetic centre or not. Participants mistook inner numbers shifted to the left to be the true numerical centre—reflecting leftward overestimation. The task was applied to 3 patients with right parietal damage with severe, moderate, or no spatial neglect (Experiment 5). A rightward bias was observed, which depended on the severity of neglect symptoms. Together, the data demonstrate a reliable and robust leftward bias for mental number line bisection, which reverses in clinical neglect. The bias mirrors pseudoneglect for physical lines and most likely reflects an expansion of the space occupied by lower numbers on the left side of the line and a contraction of space for higher numbers located on the right.     

Tactile short-term memory in relation to the two-point threshold

The purpose of the present work was to discover whether there was a relationship between the sensitivity of a body site as measured by the two-point threshold and the degree or rate of forgetting of a location stimulated at that body site. In Experiment I, it was found that the higher the two-point threshold, the greater the distance between two successive points of stimulation erroneonously thought to be identical (12 body sites). In Experiment II, it was found that forgetting over time was greater when the retention interval was filled with movement or other tactile stimulation than when the retention interval was unfilled (six body sites). It was concluded that highly sensitive areas also show the least degree of forgetting as compared with less sensitive sites, but this statement should be qualified in various ways.     

不同平面心理旋转的角色效应

本研究采用实验方法,分别在水平面和冠状面内对第一人称角色和第三人称角色心理旋转进行对比性研究。实验结果表明：空间表征转换的角色方式对心理旋转产生显著影响,第三人称角色心理旋转易于第一人称角色心理旋转,即存在心理旋转的角色效应;心理旋转的角色效应并不是在特定旋转条件下才出现的,具有更大的普遍性     

How vestibular stimulation interacts with illusory hand ownership

Artificial stimulation of the peripheral vestibular system has been shown to improve ownership of body parts in neurological patients, suggesting vestibular contributions to bodily self-consciousness. Here, we investigated whether galvanic vestibular stimulation (GVS) interferes with the mechanisms underlying ownership, touch, and the localization of one’s own hand in healthy participants by using the “rubber hand illusion” paradigm. Our results show that left anodal GVS increases illusory ownership of the fake hand and illusory location of touch. We propose that these changes are due to vestibular interference with spatial and/or temporal mechanisms of visual-tactile integration leading to an enhancement of visual capture. As only left anodal GVS lead to such changes, and based on neurological data on body part ownership, we suggest that this vestibular interference is mediated by the right temporo-parietal junction and the posterior insula.     

Subtraction by addition

University students’ self-reports indicate that they often solve basic subtraction problems (13?6=?) by reference to the corresponding addition problem (6+7=13; therefore, 13?6=7). In this case, solution latency should be faster with subtraction problems presented in addition format (6+_=13) than in standard subtraction format (13+6=_). In Experiment 1, the addition format resembled the standard layout for addition with the sum on the right (6+_=13), whereas in Experiment 2, the addition format resembled subtraction with the minuend on the left (13=6+_). Both experiments demonstrated a latency advantage for large problems (minuend > 10) in the addition format as compared with the subtraction format (13+6=_), although the effect was larger in Experiment 1 (254 msec) than in Experiment 2 (125 msec). Small subtractions (minuend ≤ 10) in Experiment 1 were solved equally quickly in the subtraction or addition format, but in Experiment 2, performance on small problems was faster in the standard format (5?3=_) than in the addition format (5=3+_). The results indicate that educated adults often use addition reference to solve large simple subtraction problems, but that they rely on direct memory retrieval for small subtractions.