Movement In Opposite Direction Research Articles

Topology-Aware Non-Rigid Point Cloud Registration.

In this paper, we introduce a non-rigid registration pipeline for pairs of unorganized point clouds that may be topologically different. Standard warp field estimation algorithms, even under robust, discontinuity-preserving regularization, tend to produce erratic motion estimates on boundaries associated with 'close-to-open' topology changes. We overcome this limitation by exploiting backward motion: in the opposite motion direction, a 'close-to-open' event becomes 'open-to-close', which is by default handled correctly. At the core of our approach lies a general, topology-agnostic warp field estimation algorithm, similar to those employed in recently introduced dynamic reconstruction systems from RGB-D input. We improve motion estimation on boundaries associated with topology changes in an efficient post-processing phase. Based on both forward and (inverted) backward warp hypotheses, we explicitly detect regions of the deformed geometry that undergo topological changes by means of local deformation criteria and broadly classify them as 'contacts' or 'separations'. Subsequently, the two motion hypotheses are seamlessly blended on a local basis, according to the type and proximity of detected events. Our method achieves state-of-the-art motion estimation accuracy on the MPI Sintel dataset. Experiments on a custom dataset with topological event annotations demonstrate the effectiveness of our pipeline in estimating motion on event boundaries, as well as promising performance in explicit topological event detection.

Rostrocaudal Distribution of the C-Fos-Immunopositive Spinal Network Defined by Muscle Activity during Locomotion.

The optimization of multisystem neurorehabilitation protocols including electrical spinal cord stimulation and multi-directional tasks training require understanding of underlying circuits mechanisms and distribution of the neuronal network over the spinal cord. In this study we compared the locomotor activity during forward and backward stepping in eighteen adult decerebrated cats. Interneuronal spinal networks responsible for forward and backward stepping were visualized using the C-Fos technique. A bi-modal rostrocaudal distribution of C-Fos-immunopositive neurons over the lumbosacral spinal cord (peaks in the L4/L5 and L6/S1 segments) was revealed. These patterns were compared with motoneuronal pools using Vanderhorst and Holstege scheme; the location of the first peak was correspondent to the motoneurons of the hip flexors and knee extensors, an inter-peak drop was presumably attributed to the motoneurons controlling the adductor muscles. Both were better expressed in cats stepping forward and in parallel, electromyographic (EMG) activity of the hip flexor and knee extensors was higher, while EMG activity of the adductor was lower, during this locomotor mode. On the basis of the present data, which showed greater activity of the adductor muscles and the attributed interneuronal spinal network during backward stepping and according with data about greater demands on postural control systems during backward locomotion, we suppose that the locomotor networks for movements in opposite directions are at least partially different.

Motion direction tuning in centre-surround suppression of contrast

The perceived contrast of a central stimulus is reduced in the presence of a high contrast surround. A number of stimulus features influence the amount of suppression. A two-mechanism model has been proposed for stationary patterns involving a narrowly-tuned process, requiring very similar stimuli in the centre and surround, and a weaker, untuned or very broadly tuned process unselective for stimulus features. This study examines whether a similar model applies to the motion pathway in human participants by varying the orientation and direction of motion of the surround relative to the centre. Four experienced observers completed a two-interval forced-choice contrast matching task. The stimuli were drifting sinusoidal grating patterns with high contrast surrounds (95%) differing in direction of motion and orientation relative to the centre grating. All surround conditions produced suppression but a common orientation and direction of motion produced significantly more suppression than either opposite direction of motion conditions or orthogonal direction conditions. The tuning for motion direction differences was assessed for same and opposite directions of motion. These findings support the extension of the two-mechanism model of contrast suppression to motion direction.

Experimental Investigation of a Spoiler’s Impact on the Flow Pattern of a High-Speed Sport Car

The relative motion of a car causes air resistance. This generates an aerodynamic force in the opposite direction of motion...

Negative Latency Recognition Method for Fine-Grained Gestures Based on Terahertz Radar

Noncontact gesture recognition is gradually being applied to emerging applications, such as smart cars and smart phones. Negative latency gesture recognition (recognition before a gesture is finished) is desirable due to the instantaneous feedback. However, it is difficult for existing methods to achieve a high precision and negative latency gesture recognition. A fragment can provide too few features to directly identify all gestures well. By observing a large number of existing gesture sets and people’s daily operating habits, we found that some high frequency used gestures are similar. To the best of our knowledge, it is the first time to redivide the gestures into two subsets according to their movement physical states. We divided the gestures with different shapes or motion states into a parent-class subset, and further divided each pair of parent-class gestures to obtain a child-class subset. In order to achieve a better tradeoff between the high-precision and negative latency, an approach of motion pattern and behavior intention (MPBI) is proposed. Taking full advantage of the characteristics of each subset, MPBI includes two models. First, pattern model coarsely classify the parent-class gestures by a convolutional network, and then intention model further classifies child-class gestures according to their opposite motion direction. MPBI is evaluated on a 340-GHz terahertz radar. With the advantage of its accurate ranging, intention model can recognize child-class gestures directly without training. MPBI is evaluated on 12 gestures and achieves a recognition accuracy of 94.13%, which only needs a 0.033-s gesture fragment as an input sample.

Accurate position exchange of stamen and stigma by movement in opposite direction resolves the herkogamy dilemma in a protandrous plant, Ajuga decumbens (Labiatae).

Herkogamy is an effective way to reduce sexual interference. However, the separation of stigma and anther potentially leads to a conflict because the pollen may be placed in a location on the pollinator different from the point of stigma contact, which can reduce pollination accuracy. Floral mechanisms aiming to resolve this conflict have seldom been explored. The floral biology of protandrous Ajuga decumbens was studied to uncover how the herkogamy dilemma can be resolved. Flower anthesis was divided into male, middle, female and wilting phases. The positions of stigma and stamen were dissimilar in different flower development stages. We measured the distance of the stamen and stigma to the lower corolla lip at different floral phases, which was the pollinators’ approaching way. The pollen viability, stigma receptivity, pollen removal and pollen deposition on stigma were investigated at different phases. During the male phase, the dehisced anthers were lower than the stigma, located at the pollinators’ approaching way, and dispersed most pollen with high viability. As the flower developed, the anthers moved upwards, making way for pollen deposition during the female phase. Meanwhile, the stigma becomes receptive by moving into the way and consequently was deposited with sufficient pollen. The position exchange of the stamen and stigma created a dynamic herkogamy at the floral phase with different sexual functions. This floral mechanism effectively avoided sexual interference and maintained pollination accuracy. In Ajuga, the movement herkogamy might be of adaptive significance in response to the changes in the pollination environment.

Do non-human primates really represent others’ ignorance? A test of the awareness relations hypothesis

Non-human primates can often predict how another agent will behave based on that agent’s knowledge about the world. But how do non-human primates represent others’ knowledge states? Researchers have recently proposed that non-human primates form “awareness relations” to attribute objectively true information to other minds, as opposed to human-like representations that track others’ ignorance or false belief states. We present the first explicit test of the awareness relations hypothesis by examining when rhesus macaques’ understanding of other agents’ knowledge falters. In Experiment 1, monkeys watched an agent observe a piece of fruit (the target object) being hidden in one of two boxes. While the agent’s view was occluded, either the fruit moved out of its box and directly back into it, or the box containing the fruit opened and immediately closed. We found that monkeys looked significantly longer when the agent reached incorrectly rather than correctly after the box’s movement, but not after the fruit’s movement. This result suggests that monkeys did not expect the agent to know the fruit’s location when it briefly and arbitrarily moved while the agent could not see it, but did expect the agent to know the fruit’s location when only the box moved while the agent could not see it. In Experiment 2, we replicated and extended both findings with a larger sample, a different target object, and opposite directions of motion in the test trials. These findings suggest that monkeys reason about others’ knowledge of objects by forming awareness relations which are disrupted by arbitrary spatial manipulation of the target object while an agent has no perceptual access to it.

Numerical study on wave phenomena produced by the super high-speed evacuated tube maglev train

With the increasing demand of faster, safer, and more comfortable rail travel, the evacuated tube maglev train (ETMT) has gradually attracted hot concerns in recent years. According to Kantrowitz limit theory, ETMT may encounter chocked flows, leading to more complex generation and development of a series of waves as ETMT moves rapidly in the tube. To study the wave phenomena produced by ETMT running at the super high-speed, the computational domain geometry model was simplified and then 2-D axisymmetric compressible N-S equation was established in the paper. Dynamic mesh method and dynamic adaptive mesh method were used to simulate the real motion of ETMT and improve the capture accuracy of the waves respectively. Results show that the wave structure is mainly composed of expansion waves, reflected shock waves and normal shock waves as ETMT moves for enough time at the speed of 1250 km/h. The intensity of the normal shock wave in front of the head car experiences four states consisting of rapid increase, initial stability, sudden drop and final stability. In the wake, the flow velocity attenuates in a fluctuating way along the opposite motion direction of ETMT due to the complicated interaction between shock waves and expansion waves.

Effect of a Semirigid Ankle Brace on the In Vivo Kinematics of Patients with Functional Ankle Instability during the Stance Phase of Walking.

An ankle brace is commonly used by patients after they suffer from initial ankle sprains, reducing the incidents of recurrent sprain or limiting laxity in joints with functional ankle instability (FAI). However, whether the application of a semirigid ankle brace can improve the abnormal ankle gait kinematics of patients with FAI remains unknown. This study aimed to determine the effect of a semirigid ankle brace on the gait kinematics of ankle joints through 3D-2D fluoroscopy image registration. A total of 8 subjects with FAI (3 males and 5 females, 10 feet) as FAI group and 10 subjects without FAI (6 males and 4 females, 10 feet) as control group were enrolled in this study. Three-dimensional bone models created from computed tomography images were matched to fluoroscopic images to compute the 6 degrees of freedom (DOF) talocrural, subtalar, and ankle joints complex kinematics for control and FAI group with or without brace during the stance phase of walking. FAI patients had significantly less ROMs in inversion/eversion rotation of the talocrural and subtalar joint after wearing semirigid ankle brace. Laxity was observed in most of the displacements of the talocrural and subtalar joints in FAI group. The brace partly altered the ankle joints movement in opposite directions, especially joint rotation, and restricted the talocrural and subtalar joints in the dorsiflexion position during the touch down phase of walking.

An integrated study on the coseismic and post-seismic deformation of the 2010 Yushu earthquake based on InSAR analysis

We carry out an integrated study on coseismic and post-seismic deformation caused by 2010 Yushu earthquake sequence, including both mainshock and aftershocks, by using multi-scene ENVISAT/ASAR data on two adjacent tracks. We map the extended deformation region to the west of mainshock and show the westward extension of seismogenic fault of mainshock. Based on our whole deformation field derived from mosaic interferograms, the total length of seismogenic fault reaches \({\sim }103\,\hbox {km}\) longer than \({\sim }71\,\hbox {km}\) suggested by the previous report. Several coseismic interferograms with different time baselines have similar deformation patterns, which indicate that the influence of aftershocks and post-seismic slip on coseismic deformation field is limited. Also, we observe a clear and separate deformation area, \({\sim }38\,\hbox {km}\) to the west of the mainshock epicentre, with maximum displacement of \({\sim }9\,\hbox {cm}\). The localised deformation is composed of two patches with opposite motion directions, where an aftershock cluster with at least 47 events (\({>}\hbox {Ms}\,3.0\)) occurred. We infer that this localised deformation is caused by aftershocks ruptured on a blind active fault. While a weak post-seismic deformation band along main rupture zone near mainshock epicentre is likely attributable to short-term afterslip.

Neuronal Correlations in MT and MST Impair Population Decoding of Opposite Directions of Random Dot Motion.

The study of neuronal responses to random-dot motion patterns has provided some of the most valuable insights into how the activity of neurons is related to perception. In the opposite directions of motion paradigm, the motion signal strength is decreased by manipulating the coherence of random dot patterns to examine how well the activity of single neurons represents the direction of motion. To extend this paradigm to populations of neurons, studies have used modelling based on data from pairs of neurons, but several important questions require further investigation with larger neuronal datasets. We recorded neuronal populations in the middle temporal (MT) and medial superior temporal (MST) areas of anaesthetized marmosets with electrode arrays, while varying the coherence of random dot patterns in two opposite directions of motion (left and right). Using the spike rates of simultaneously recorded neurons, we decoded the direction of motion at each level of coherence with linear classifiers. We found that the presence of correlations had a detrimental effect to decoding performance, but that learning the correlation structure produced better decoding performance compared to decoders that ignored the correlation structure. We also found that reducing motion coherence increased neuronal correlations, but decoders did not need to be optimized for each coherence level. Finally, we showed that decoder weights depend of left-right selectivity at 100% coherence, rather than the preferred direction. These results have implications for understanding how the information encoded by populations of neurons is affected by correlations in spiking activity.

Differential tuning of excitation and inhibition shapes direction selectivity in ferret visual cortex

To encode specific sensory inputs, cortical neurons must generate selective responses for distinct stimulus features. In principle, a variety of factors contribute to a cortical neuron’s response selectivity: the tuning and strength of excitatory1–3 and inhibitory synaptic inputs4–6, dendritic nonlinearities7–9, and spike threshold10,11. Here we employ a combination of techniques including in vivo whole-cell recording, synaptic and cellular resolution in vivo two photon calcium imaging, and GABAergic-selective optogenetic manipulation to dissect the factors contributing to direction selective responses of layer 2/3 neurons in ferret visual cortex (V1). Two-photon calcium imaging of dendritic spines12,13 revealed that each neuron receives a mixture of excitatory synaptic inputs selective for the somatic preferred or null direction of motion. The relative number of preferred- and null-tuned excitatory inputs predicted a neuron’s somatic direction preference, but failed to account for the degree of direction selectivity. In contrast, in vivo whole-cell patch clamp recordings revealed a striking degree of direction selectivity in subthreshold responses that was significantly correlated with spiking direction selectivity. Subthreshold direction selectivity was predicted by the magnitude and variance of the response to the null direction of motion, and several lines of evidence including conductance measurements demonstrate that differential tuning of excitation and inhibition suppresses responses to the null direction of motion. Consistent with this idea, optogenetic inactivation of GABAergic neurons in layer 2/3 reduced direction selectivity by enhancing responses to the null direction. Furthermore, using a new technique to optogenetically map connections of inhibitory neurons in layer 2/3 in vivo, we find that layer 2/3 inhibitory neurons make long-range, intercolumnar projections to excitatory neurons that prefer the opposite direction of motion. We conclude that intracortical inhibition exerts a major influence on the degree of direction selectivity in layer 2/3 of ferret V1 by suppressing responses to the null direction of motion.

Petrographic investigation of shatter cone melt films recovered from MEMIN impact experiments in sandstone and iSALE modeling of their formation boundary conditions

AbstractShatter cones are diagnostic for the recognition of meteorite impact craters. They are unambiguously identifiable in the field and the only macroscopic shock deformation feature. However, the physical boundary conditions and exact formation mechanism(s) are still a subject of debate. Melt films found on shatter cone surfaces may allow the constraint of pressure–temperature conditions during or immediately after their formation. Within the framework of the MEMIN research group, we recovered 24 shatter cone fragments from the ejecta of hypervelocity impact experiments. Here, we focus on silicate melt films (now quenched to glass) found on shatter cone surfaces formed in experiments with 20–80 cm sized sandstone targets, impacted by aluminum and iron meteorite projectiles of 5 and 12 mm diameter at velocities of 7.0 and 4.6 km s−1, respectively. The recovered shatter cone fragments vary in size from 1.2 to 9.3 mm. They show slightly curved, striated surfaces, and conical geometries with apical angles of 36°–52°. The fragments were recovered from experiments with peak pressures ranging from 46 to 86 GPa, and emanated from a zone within 0.38 crater radii. Based on iSale modeling and petrographic investigations, the shatter coned material experienced low bulk shock pressures of 0.5–5 GPa, whereas deformation shows a steep increase toward the shatter cone surface leading to localized melting of the rock, resulting in both vesicular as well as polished melt textures visible under the SEM. Subjacent to the melt films are zones of fragmentation and brittle shear, indicating movement away from the shatter cone apex of the rock that surrounds the cone. Smearing and extension of the melt film indicates subsequent movement in opposite direction to the comminuted and brecciated shear zone. We believe the documented shear textures and the adjacent smooth melt films can be related to frictional melting, whereas the overlying highly vesiculated melt layer could indicate rapid pressure release. From the observation of melting and mixing of quartz, phyllosilicates, and rutile in this overlying texture, we infer high, but very localized postshock temperatures exceeding 2000 °C. The melted upper part of the shatter cone surface cross‐cuts the fragmented lower section, and is accompanied by PDFs developed in quartz parallel to the {112} plane. Based on the overprinting textures and documented shock effects, we hypothesize shatter cones start to form during shock loading and remain an active fracture surface until pressure release during unloading and infer that shatter cone surfaces are mixed mode I/II fracture surfaces.

The functional effects of prior motion imagery and motion perception

The functional sensory effects and commonalties between mental imagery of different visual features such as color, form or motion remains largely unknown. Mental imagery of static visual features, including color and orientation, can have a facilitative, priming effect on subsequent perception. However, whether motion imagery can have a similar effect remains unknown. Here we used the binocular rivalry method as a measure of motion mental imagery. After imagining or viewing motion of a particular direction, participants were required to report the dominant motion direction in a brief motion rivalry stimulus. We found that motion imagery can have a facilitative priming effect on subsequent motion rivalry perception, and this effect can be attenuated by concurrent expanding and contracting perceptual motion, but not by static or flickering uniform luminance. Unlike color or orientation imagery, the effect of motion imagery on subsequent rivalry was location independent. We also observed this facilitative priming effect with prior low-contrast perceptual motion, but prior high-contrast motion induced a suppressive effect. Simultaneous imagery and perceptual motion in opposite directions induced priming, while congruent directions did not. Counter to prior findings, these results suggest motion imagery can have a priming effect on perception and that the rivalry method can be used to assess visual motion imagery. These results provide evidence for visual imagery as a multi-feature structure.

Trajectory Discrimination and Peripersonal Space Perception in Newborns.

The ability to discriminate the trajectories of moving objects is highly adaptive and fundamental for physical and social interactions. Therefore, we could reasonably expect sensitivity to different trajectories already at birth, as a precursor of later communicative and defensive abilities. To investigate this possibility, we measured newborns' looking behavior to evaluate their ability to discriminate between visual stimuli depicting motion along different trajectories happening within the space surrounding their body. Differently from previous studies, we did not take into account defensive reactions, which may not be elicited by impending collision as newborns might not categorize approaching stimuli as possible dangers. In two experiments, we showed that newborns display a spontaneous visual preference for trajectories directed toward their body. We found this visual preference when visual stimuli depicted motion in opposite directions (approaching vs. receding) as well as when they both moved toward the peripersonal space and differed only in their specific target (i.e., the body vs. the space around it). These findings suggest that at birth human infants seem to be already equipped with visual mechanisms predisposing them to perceive their presence in the environment and to adaptively focus their attention on the peripersonal space and their bodily self.

Testing of a sag of a dosimetry system rotating with a gantry using the interplay effect between detector motion and MLC motion

Abstract Purpose: An interplay between detector motion and MLC motion is a source of measurement error, when dose for dynamic arc is measured using a dosimetry system moving relative to the beam central axis during its rotation with a gantry. The purpose of this study is to develop and to evaluate a method of quantitative testing of a sag/flex of such dosimetry systems. Methods: The method is based on evaluation of relative differences between signals measured for two single arc beams, where a narrow slit field is sliding during gantry movement in opposite directions. The component of a measurement error related to the interplay effect was first assessed based on theoretical computer simulations and then on measurements for four dosimetry systems. The sag pattern of EPID and 2D array was extracted from the measurement results. Results: The simulations showed a 4 mm difference in field width and 3.3% difference in relative signals at beam axis between test beams where the slit field swept over 19 cm in opposite directions ( sinusoidal sag pattern with amplitude of 1 mm was assumed). The signal differences exceeding 4% and 5% were measured for EPID and 2D array, respectively. Conclusions: Even relatively small detector sag (less than 1 mm) can produce significant measurement error; therefore, the detector sag test should be an obligatory component of a validation of rotating dosimetry systems used for QA of dynamic arcs.

Wind-induced flow velocity effects on nutrient concentrations at Eastern Bay of Lake Taihu, China.

Shallow lakes are highly sensitive to respond internal nutrient loading due to wind-induced flow velocity effects. Wind-induced flow velocity effects on nutrient suspension were investigated at a long narrow bay of large shallow Lake Taihu, the third largest freshwater lake in China. Wind-induced reverse/compensation flow and consistent flow field probabilities at vertical column of the water were measured. The probabilities between the wind field and the flow velocities provided a strong correlation at the surface (80.6%) and the bottom (65.1%) layers of water profile. Vertical flow velocity profile analysis provided the evidence of delay response time to wind field at the bottom layer of lake water. Strong wind field generated by the west (W) and west-north-west (WNW) winds produced displaced water movements in opposite directions to the prevailing flow field. An exponential correlation was observed between the current velocities of the surface and the bottom layers while considering wind speed as a control factor. A linear model was developed to correlate the wind field-induced flow velocity impacts on nutrient concentration at the surface and bottom layers. Results showed that dominant wind directions (ENE, E, and ESE) had a maximum nutrient resuspension contribution (nutrient resuspension potential) of 34.7 and 43.6% at the surface and the bottom profile layers, respectively. Total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) average concentrations were 6.38, 1.5, and 0.03mg/L during our field experiment at Eastern Bay of Lake Taihu. Overall, wind-induced low-to-moderate hydrodynamic disturbances contributed more in nutrient resuspension at Eastern Bay of Lake Taihu. The present study can be used to understand the linkage between wind-induced flow velocities and nutrient concentrations for shallow lakes (with uniform morphology and deep margins) water quality management and to develop further models.

Phantom array and stroboscopic effects of a time-modulated moving light source during saccadic eye movement

This paper evaluates the detectability of the phantom array and stroboscopic effects during light source motion, eye movement and their combination, using time modulated light-emitting diode light sources. It is well known that the phantom array can be observed when time-modulated light sources are observed during saccadic eye movements. We investigated whether light source motion can cause similar effects when the subject has fixed eyes. In addition, we estimated the detectability threshold frequency for the combination of stroboscopic effect and the phantom array, which is named the stroboscopic-phantom array effect, during two eye movements in opposite directions under one directional rotating light source with variable speed. Our results indicate that one of the most important factors for the stroboscopic-phantom array effect is eye movement speed relative to the speed of the light source. Therefore, time-modulated moving light sources induce a stroboscopic effect in subjects with fixed eyes that is similar to the stroboscopic-phantom array effect observed during saccadic eye movement. Our findings are likely to be useful for predicting the stroboscopic effect and the stroboscopic-phantom array effect during the fast motion of time-modulated LED light sources, like multi-functional rear lamps, in automotive lighting applications.

Opposite effects of high- and low-frequency transcranial random noise stimulation probed with visual motion adaptation.

Transcranial random noise stimulation (tRNS) is a recent neuro-modulation technique whose effects at both behavioural and neural level are still debated. Here we employed the well-known phenomenon of motion after-effect (MAE) in order to investigate the effects of high- vs. low-frequency tRNS on motion adaptation and recovery. Participants were asked to estimate the MAE duration following prolonged adaptation (20 s) to a complex moving pattern, while being stimulated with either sham or tRNS across different blocks. Different groups were administered with either high- or low-frequency tRNS. Stimulation sites were either bilateral human MT complex (hMT+) or frontal areas. The results showed that, whereas no effects on MAE duration were induced by stimulating frontal areas, when applied to the bilateral hMT+, high-frequency tRNS caused a significant decrease in MAE duration whereas low-frequency tRNS caused a significant corresponding increase in MAE duration. These findings indicate that high- and low-frequency tRNS have opposed effects on the adaptation-dependent unbalance between neurons tuned to opposite motion directions, and thus on neuronal excitability.

Asymmetries and three-dimensional features of vestibular cross-coupled stimuli illuminated through modeling.

Head movements during sustained rotation can cause angular cross-coupling which leads to tumbling illusions. Even though angular vectors predict equal magnitude illusions for head movements in opposite directions, the magnitudes of the illusions are often surprisingly asymmetric, such as during leftward versus rightward yaw while horizontal in a centrifuge. This paper presents a comprehensive investigation of the angular-linear stimulus combinations from eight different published papers in which asymmetries were found. Interactions between all angular and linear vectors, including gravity, are taken into account to model the three-dimensional consequences of the stimuli. Three main results followed. First, for every pair of head yaw movements, an asymmetry was found in the stimulus itself when considered in a fully three-dimensional manner, and the direction of the asymmetry matched the subjectively reported magnitude asymmetry. Second, for pitch and roll head movements for which motion sickness was measured, the stimulus was found symmetric in every case except one, and motion sickness generally aligned with other factors such as the existence of a head rest. Third, three-dimensional modeling predicted subjective inconsistency in the direction of perceived rotation when linear and angular components were oppositely-directed, and predicted surplus illusory rotation in the direction of head movement.