Illusory Motion Research Articles

The Effects of 30 Minutes of Artificial Gravity on Cognitive and Sensorimotor Performance in a Spaceflight Analog Environment.

The altered vestibular signaling and somatosensory unloading of microgravity result in sensory reweighting and adaptation to conflicting sensory inputs. Aftereffects of these adaptive changes are evident postflight as impairments in behaviors such as balance and gait. Microgravity also induces fluid shifts toward the head and an upward shift of the brain within the skull; these changes are well-replicated in strict head-down tilt bed rest (HDBR), a spaceflight analog environment. Artificial gravity (AG) is a potential countermeasure to mitigate these effects of microgravity. A previous study demonstrated that intermittent (six, 5-mins bouts per day) daily AG sessions were more efficacious at counteracting orthostatic intolerance in a 5 day HDBR study than continuous daily AG. Here we examined whether intermittent daily AG was also more effective than continuous dosing for mitigating brain and behavioral changes in response to 60 days of HDBR. Participants (n = 24) were split evenly between three groups. The first received 30 mins of continuous AG daily (cAG). The second received 30 mins of intermittent AG daily (6 bouts of 5 mins; iAG). The third received no AG (Ctrl). We collected a broad range of sensorimotor, cognitive, and brain structural and functional assessments before, during, and after the 60 days of HDBR. We observed no significant differences between the three groups in terms of HDBR-associated changes in cognition, balance, and functional mobility. Interestingly, the intermittent AG group reported less severe motion sickness symptoms than the continuous group during centrifugation; iAG motion sickness levels were not elevated above those of controls who did not undergo AG. They also had a shorter duration of post-AG illusory motion than cAG. Moreover, the two AG groups performed the paced auditory serial addition test weekly while undergoing AG; their performance was more accurate than that of controls, who performed the test while in HDBR. Although AG did not counteract HDBR-induced gait and balance declines, iAG did not cause motion sickness and was associated with better self-motion perception during AG ramp-down. Additionally, both AG groups had superior cognitive performance while undergoing AG relative to controls; this may reflect attention or motivation differences between the groups.

Illusory tactile movement crosses arms and legs and is coded in external space

Humans often misjudge where on the body a touch occurred. Theoretical accounts have ascribed such misperceptions to local interactions in peripheral and primary somatosensory neurons, positing that spatial-perceptual mechanisms adhere to limb boundaries and skin layout. Yet, perception often reflects integration of sensory signals with prior experience. On their trajectories, objects often touch multiple limbs; therefore, body–environment interactions should manifest in perceptual mechanisms that reflect external space.Here, we demonstrate that humans perceived the cutaneous rabbit illusion – the percept of multiple identical stimuli as hopping across the skin – along the Euclidian trajectory between stimuli on two body parts and regularly mislocalized stimuli from one limb to the other. A Bayesian model based on Euclidian, as opposed to anatomical, distance faithfully reproduced key aspects of participants' localization behavior.Our results suggest that prior experience of touch in space critically shapes tactile spatial perception and illusions beyond anatomical organization.

Contributed Session III: Perceptual consequences of interocular imbalances in temporal integration

Temporal differences in visual information processing between the eyes can cause dramatic misperceptions of motion and depth. A simple processing delay between the eyes causes a target, oscillating in the frontal plane, to be misperceived as moving along a near-elliptical motion trajectory in depth. Here, we explain a previously reported but poorly understood variant in which the illusory near-elliptical motion trajectory appears to be rotated left- or right-side back in depth, rather than aligned with the true direction of motion. We hypothesized that this variant is caused by differences in the temporal integration periods (i.e. differences in temporal blurring) between the eyes. Differences in temporal blurring dampen the amplitude of motion in one eye relative to the other, and-in a dynamic analog of the 'geometric' effect (Ogle, 1950)-cause the apparent misalignment. A target-tracking experiment shows that temporal blurring is depends on stimulus spatial frequency. A psychophysical experiment shows that when different spatial frequencies are presented to each eye, the direction of perceived rotation is predicted by the eye with the frequency associated with more temporal blur, as assessed by the target tracking task. The current findings add to add to the body of knowledge regarding the dependence of temporal processing on stimulus properties, while highlighting the perceptual consequences of interocular imbalances in temporal processing.

The analgesic effect of localized vibration: a systematic review. Part 1: the neurophysiological basis.

The analgesic action of localized vibration (LV), which is used in rehabilitation medicine to treat various clinical conditions, is usually attributed to spinal gate control, but is actually more complex. The aim of this review is: 1) to provide neurophysiological insights into the mechanisms underlying the ways in which afferent activity set up by LV induces analgesia through interactions with the nociceptive system throughout the nervous system; 2) to give a broader vision of the different effects induced by LV, some of them still related to basic science speculation. The Medline, EMBASE, AMED, Cochrane Library, CINAHL, Web of Science and ROAD databases were searched for animal and human neurophysiological and neurohormonal studies related to the direct effects of LV on nociceptive transmission and pain perception and were supplemented by published books and theses. The spinal gate control mechanism through Aβ-fibers activation seems to be the most effective antinociceptive system activated by LV at frequencies between 100 and 250 Hz (high-frequency LV [HF-LV]) when applied in the same segment as the pain. A gating effect can be obtained also when it is applied contralaterally to the painful site or to adjacent dermatomes. Kinesthetic illusions of movement induced by HF-LV may induce a stronger analgesic effect. Activation of C-mechanoreceptors induced by a massage-like LV of low frequency and low intensity may interfere with pain through the activation of the limbic system. This action does not involve any gating mechanism. Frequency is more important than intensity as different frequencies induce activity in different cortical and cerebellar areas; these activations may be related to plastic cortical changes tentatively reversing pain-related maladaptive disorganization. Distraction/shift of attention or cortisol-mediated stress-induced analgesia are not involved in LV analgesic action in humans for both LF and HF. The release of opioidergic neuropeptides (analgesia not reversed by naloxone) as well as a reduction in substance P in the CSF does not seem to play a major role in the HF-LV action. Decrease in calcitonin and TRPV1 expression in the trigeminal ganglia in animals has been induced by HF-LV but the role of LF-LV is not completely deciphered. Both high and low LV induce the release of oxytocin, which may induce antinociceptive responses in animals and contribute to controlling pain in humans. Although many aspects of LV-induced pain alleviation deserve more in-depth basic and translational studies, there are sound neurophysiological reasons for using LV in the therapeutic armamentarium of pain control. Laboratory animal and human data indicate that LV relieves pain not only by acting on the spinal gate, but also at higher levels of the nervous system.

The reverse motion illusion in random dot motion displays and implications for understanding development.

Across two independent developmental labs, we have been puzzled by the observation that a small proportion of our child and adult participants consistently report perceiving motion in the direction opposite to that presented in random-dot motion displays, sometimes even when the motion is at 100% coherence. In this review, we first draw together existing reports of misperceptions of motion direction in random dot displays across observers in a small percentage of trials, before reporting evidence of consistent reverse motion perception in a minority of observers, including previously unreported observations from our own studies of visual development. We consider possible explanations for this reverse motion illusion, including motion induction, motion energy, correspondence noise and spatial undersampling. However, more work is required to understand the individual differences relating to this percept. We suggest that errors in perceived motion direction are likely to be more widespread than can be currently gleaned from the literature and explain why systematic study is needed, especially in children. Finally, we list some remaining open questions and call for collaborative efforts to document this phenomenon and stimulate future investigation.

Potential use of dimensionhydrinate/cinnarizine combination in the treatment of vertigo

Vertigo is a fairly common complaint with which patients present to physicians of various profiles, and especially to general practitioners, neurologists, and otorhinolaryngologists. Vertigo is a condition where a person has the illusion of movement or of surrounding objects moving when they are not. Vertigo is a symptom of a wide range of diseases, both benign and life-threatening. Vertigo can have a variety of causes, and the suggested treatment should depend on the cause. Due to the multifactorial etiology of medical care, many patients receive inadequate treatment under the primary healthcare scheme, especially during initial presentation. The main causes of vertigo are benign paroxysmal positional vertigo, Meniere’s disease, vestibular neuritis, vestibular migraine, and cerebrovascular diseases. Patients with other disorders, such as depression and hyperventilation syndrome, may present with complaints of nonrotary vertigo. Differential diagnosis of vertigo can be made using easy-to-perform tests during physical examination, including assessment of nystagmus, Dix-Hallpike maneuver, and blood pressure measurements with head-up tilt table tests. Treatment of patients with complaints of vertigo includes drug and non-drug therapy, depending on the established nosological form. However, due to the multifactorial etiology, many patients receive inadequate treatment under the primary healthcare scheme, especially during initial presentation. The dimensionhydrinate/cinnarizine combination is one of the drugs for the symptomatic treatment of vertigo of various origins in adults.

Motor Response of Mirror Therapy after Reconstruction of Extensor Mechanism Caused by Glass Cut Injury

Treatment by mirror therapy (MT) restores motion in injured limbs without invasive procedures. This process is widely accepted for rehabilitating patients with phantom limb pain, stroke victims, or patients who need therapy after nerve damage. The procedure is specifically useful in restoring motion to the hand after surgical repairs to the extensor muscle and tendons. Mirror therapy rewires the brain by making the restored limb remember hand motions by observing the motions of a normal hand. The concept of a mirror image is that the movement of the uninjured arm forms the illusion of the same movement in the affected arm. Efforts to repeat hand movements elicit the same reaction in the affected hand in what is referred to as Hebbian learning. This case study evaluated MT’s effectiveness in motion restoration after a glass injury. This case study showed restoration of normal hand motions in a patient following surgery to repair a glass cut to the arm. Surgery repaired the lacerated extensor tendon and radial nerve. The muscle belly was repaired, and a graft fixed the nerve gap. Once the arm healed, the patient underwent rehabilitation in mirror therapy to restore normal function in his hand. After conducting mirror therapy, the pain was eliminated, and the patient restored normal function of moving the hand and finger extension. In addition, the therapy could be conducted at home without needing a professional. The effectiveness of mirror therapy was seen in the functional restoration of hand and finger movement. The process is also less complicated as it can be performed at home.

Visually induced dizziness.

Visually induced dizziness (VID) is a common phenomenon in vestibular disorders of both peripheral and central causes. This article provides a review of the most updated understandings of definition, pathophysiology, and treatment options. The pathophysiology is complex and its severity or persistence may be related both to the underlying cause and heritable factors. Environmental and psychological factors may influence the degree of impact of VID on daily life function. Treatment is mostly empiric at this point but includes pharmacologic, desensitization, cognitive behavioral therapies, visual rehabilitation, and treatment of the underlying cause whenever present. Additional research is needed to clarify the best management of this vestibular symptom as well as some of the other conditions with which it is commonly associated. VID is a fairly common vestibular syndrome constitutng spatial disorientation without illusory motion. As it is seen in both peripheral and central vestibular disorders, it should be considered a syndrome or constellation of symptoms rather than a discrete disorder. In some cases, it may be the presenting symptom with no other clear disorder linked to it.

Faces behind bars: illusory eye movements induced by gratings

I describe a novel illusion in which perceived eye movements are induced by moving a vertical grating across a single image of a forward-looking face. By varying properties of the grating, a wide range of illusory eye movements can be generated including nystagmus, a ‘swirling’ motion of the eyes, and vertical scanning/blinking. I suggest that the phenomenon is closely related to the footsteps illusion, but reveals the role that object shape and grating spatial frequency together play in determining the direction of illusory motion that observers perceive. I also discuss the relationship between the current illusion, the footsteps illusion, and Moire pattern animations.

Bimanual digit training improves right-hand dexterity in older adults by reactivating declined ipsilateral motor-cortical inhibition

Improving deteriorated sensorimotor functions in older individuals is a social necessity in a super-aging society. Previous studies suggested that the declined interhemispheric sensorimotor inhibition observed in older adults is associated with their deteriorated hand/finger dexterity. Here, we examined whether bimanual digit exercises, which can train the interhemispheric inhibitory system, improve deteriorated hand/finger dexterity in older adults. Forty-eight healthy, right-handed, older adults (65–78 years old) were divided into two groups, i.e., the bimanual (BM) digit training and right-hand (RH) training groups, and intensive daily training was performed for 2 months. Before and after the training, we evaluated individual right hand/finger dexterity using a peg task, and the individual state of interhemispheric sensorimotor inhibition by analyzing ipsilateral sensorimotor deactivation via functional magnetic resonance imaging when participants experienced a kinesthetic illusory movement of the right-hand without performing any motor tasks. Before training, the degree of reduction/loss of ipsilateral motor-cortical deactivation was associated with dexterity deterioration. After training, the dexterity improved only in the BM group, and the dexterity improvement was correlated with reduction in ipsilateral motor-cortical activity. The capability of the brain to inhibit ipsilateral motor-cortical activity during a simple right-hand sensory-motor task is tightly related to right-hand dexterity in older adults.

Exploring the presence of multiple abnormal non-motor features in patients with cervical dystonia

This study’s aim was to investigate prevalence of four non-motor symptoms in patients with cervical dystonia and healthy controls to explore whether the presence of multiple non-motor features is associated with cervical dystonia diagnosis. Fifteen patients with cervical dystonia and 15 healthy controls underwent non-invasive testing of spatial discrimination threshold, temporal discrimination threshold, vibration-induced illusion of movement, and kinesthesia. All spatial discrimination threshold, temporal discrimination threshold, and vibration-induced illusion of movement measures were converted to standardized Z scores with scores >2.0 considered abnormal. Any incorrect kinesthesia response was considered abnormal. Prevalence of each abnormal non-motor feature was compared between groups using a chi-squared test. A higher proportion of patients with cervical dystonia had abnormal spatial discrimination threshold (p = 0.01) and abnormal kinesthesia (p = 0.03) scores compared to healthy control subjects. There were no significant differences between the proportion of patients with cervical dystonia versus healthy controls for abnormal temporal discrimination threshold (p = 0.07) or abnormal vibration-induced illusion of movement (p = 0.14). Forty-seven percent of patients with cervical dystonia (7/15) demonstrated one abnormal non-motor feature, 20% (3/15) displayed two abnormal features, and 13% (2/15) displayed three abnormal features. Kinesthesia was the only non-motor feature identified as abnormal in the control group (20%, 3/15). All four tests demonstrated high specificity (80–100%) and low-moderate sensitivity (13–60%). These findings suggest that non-motor feature testing, specifically for spatial discrimination threshold and kinesthesia, could be a highly specific diagnostic tool to inform cervical dystonia diagnosis. Further investigation is needed to confirm these findings.

The relationship between vection, cybersickness and head movements elicited by illusory motion in virtual reality

Cybersickness is an unpleasant side effect of Virtual Reality and is often detrimental to a user’s experience. It shows a complex relationship to vection (illusory self-motion) as well as postural instability. Three experiments were conducted presenting both expanding and rotating colourful optimised Fraser Wilcox illusions as well as grey-scaled controlled versions of the illusions. Cybersickness and vection were reported and head movements in medio-lateral and anterior-posterior direction were recorded. The experiments found that perceived visual motion (illusory motion) is sufficient to elicit vection in the absence of any stimulated visual motion. The strength of motion perceived in the illusions was related to the experience of cybersickness and vection, with illusions that were perceived as moving more eliciting stronger experiences of both. Surprisingly, rotating illusions were continuously perceived as moving more compared to expanding motion illusions, which could be related to missing stereoscopic motion-in-depth cues. Head movements were unrelated to any stimuli properties, suggesting that the motion signal elicited by the illusions might not have been strong enough to cause postural instability. Finally, dizziness has been identified as the possible link between cybersickness, vection and head movements supporting sensory conflict as well postural instability theories of cybersickness.

Improving diagnosis and treatment of benign paroxysmal positional vertigo

Background: Vertigo is defined as an illusion of motion caused by a mismatch of information between the visual, vestibular and somatosensory systems. The most common diagnosis associated with whirling vertigo is benign paroxysmal positional vertigo (BPPV), which affects approximately 3.4% of patients older than 60 years of age.
 Objective: This paper aims to educate primary care providers on how to diagnose BPPV by performing canalith repositioning maneuvers at the initial point of care. Timely treatment of BPPV in the primary care office is believed to reduce healthcare costs by way of limiting unnecessary diagnostic testing and lowering referrals for specialty care. Immediate treatment is also believed to improve the quality of healthcare delivery for the vertigo patient by reducing morbidity and resolving the condition without the need for referrals or imaging.
 Population Health: A review of the literature finds that delayed diagnosis and treatment of BPPV is associated with a host of deleterious effects on patients. Population health impacts include increasedrates of anxiety and depression; loss of work and/or change of career paths; inappropriate use of medications or emergency care resources; decreased access to healthcare services; increased healthcare costs; and reduced quality of care.
 Diagnosis: A history of positional vertigo and evidence of nystagmus with Dix-Hallpike positioning confirms the diagnosis. A detailed description of the performance of this test is elucidated.
 Treatment: The observed nystagmus is analyzed and classified based on directionality. Treatment can be initiated immediately with canalith repositioning maneuvers.

The Mechanisms of the Visual System Behind Visual Illusions: From Eye to Brain

Visual illusion is a psychological phenomenon characterized by perception that appears to differ from physical reality. Illusory perception persists even though the sufferers are aware of the physical properties of what they are observing. Thus, studying visual illusions has led to an improved understanding of the neural mechanism underlying visual information processing. Visual illusions are important tools in neuroscience. Some brightness illusions, such as the Hermann grid illusion or Chevreul illusion, can be explained by the function of the center-surround antagonistic receptive field of retinal ganglion cells. Additionally, color aftereffects were found to be produced in the retina. In addition, neurons in the primary visual cortex are responsible for the orientation-contingent color aftereffect, known as the McCollough effect. ISI reversal, a visual motion illusion, is known to be caused by a biphasic temporal mechanism located in the retinal or lower visual areas. Higher visual areas are responsible for the production of visual illusions such as the Ponzo illusion, size constancy illusion, or tabletop illusion. These illusions are perceived through the process of achieving size constancy from a two-dimensional retinal image. Thus, both low-level and high-level vision are involved in the perception of visual illusions.

Visual feedback improves movement illusions induced by tendon vibration after chronic stroke

BackgroundIllusion of movement induced by tendon vibration is commonly used in rehabilitation and seems valuable for motor rehabilitation after stroke, by playing a role in cerebral plasticity. The aim was to study if congruent visual cues using Virtual Reality (VR) could enhance the illusion of movement induced by tendon vibration of the wrist among participants with stroke.MethodsWe included 20 chronic stroke participants. They experienced tendon vibration of their wrist (100 Hz, 30 times) inducing illusion of movement. Three VR visual conditions were added to the vibration: a congruent moving virtual hand (Moving condition); a static virtual hand (Static condition); or no virtual hand at all (Hidden condition). The participants evaluated for each visual condition the intensity of the illusory movement using a Likert scale, the sensation of wrist’s movement using a degree scale and they answered a questionnaire about their preferred condition.ResultsThe Moving condition was significantly superior to the Hidden condition and to the Static condition in terms of illusion of movement (p < 0.001) and the wrist’s extension (p < 0.001). There was no significant difference between the Hidden and the Static condition for these 2 criteria. The Moving condition was considered the best one to increase the illusion of movement (in 70% of the participants). Two participants did not feel any illusion of movement.ConclusionsThis study showed the interest of using congruent cues in VR in order to enhance the consistency of the illusion of movement induced by tendon vibration among participants after stroke, regardless of their clinical severity. By stimulating the brain motor areas, this visuo-proprioceptive feedback could be an interesting tool in motor rehabilitation.Record number in Clinical Trials: NCT04130711, registered on October 17th 2019 (https://clinicaltrials.gov/ct2/show/NCT04130711?id=NCT04130711&draw=2&rank=1).

Special treatment of prediction errors in autism spectrum disorder

For autistic individuals, sensory stimulation can be experienced as overwhelming. Models of predictive coding postulate that cortical mechanisms disamplify predictable information and amplify prediction errors that surpass a defined precision level. In autism, the neuronal processing is putting an inflexibly high precision on prediction errors according to the HIPPEA theory (High, Inflexible Precision of Prediction Errors in Autism). We used an apparent motion paradigm to test this prediction. In apparent motion paradigms, the illusory motion of an object creates a prediction about where and when an internally generated token would be moving along the apparent motion trace. This illusion facilitates the perception of a flashing stimulus (target) appearing in-time with the apparent motion token and is perceived as a predictable event (predictable target). In contrast, a flashing stimulus appearing out-of-time with the apparent motion illusion is an unpredictable target that is less often detected even though it produces a prediction error signal. If a prediction error does not surpass a given precision threshold the stimulation event is discounted and therefore less often detected than predictable tokens. In autism, the precision threshold is lower and the same prediction errors (unpredictable target) triggers a detection similar to that of a predictable flash stimulus. To test this hypothesis, we recruited 11 autistic males and 9 neurotypical matched controls. The participants were tasked to detect flashing stimuli placed on an apparent motion trace either in-time or out-of-time with the apparent motion illusion. Descriptively, 66% (6/9) of neurotypical and 64% (7/11) of autistic participants were better at detecting predictable targets. The prediction established by illusory motion appears to assist autistic and neurotypical individuals equally in the detection of predictable over unpredictable targets. Importantly, 55% (6/11) of autistic participants had faster responses for unpredictable targets, whereas only 22% (2/9) of neurotypicals had faster responses to unpredictable compared to predictable targets. Hence, these tentative results suggest that for autistic participants, unpredictable targets produce an above threshold prediction error, which leads to faster response. This difference in unpredictable target detection can be encapsulated under the HIPPEA theory, suggesting that precision setting could be aberrant in autistic individuals with respect to prediction errors. These tentative results should be considered in light of the small sample. For this reason, we provide the full set of materials necessary to replicate and extend the results.

Pupil responses to implied motion in figurative and abstract paintings.

Motion can be perceived in static images, such as photos and figurative paintings, representing realistic subjects in motion, with or without directional information (e.g., motion blur or speed lines). Motion impression can be achieved even in non-realistic static images such as motion illusions and abstract paintings. It has been shown that visual motion processing affects the diameter of the pupil, responding differently to real, illusory, and implied motion in photographs (IM). It has been suggested that these different effects might be due to top-down modulations from different cortical areas underlying their processing. It is worthwhile to investigate pupillary response to figurative paintings, since they require an even higher level of interpretation than photos representing the same kind of subjects, given the complexity of cognitive processes involved in the aesthetic experience. Also, pupil responses to abstract paintings allows to study the effect of IM perception in representations devoid of real-life motion cues. We measured pupil responses to IM in figurative and abstract artworks depicting static and dynamic scenes, as rated by a large group of individuals not participating in the following experiment. Since the pupillary response is modulated by the subjective image interpretation, a motion rating test has been used to correct individual pupil data according to whether participants actually perceived the presence of motion in the paintings. Pupil responses to movies showing figurative and abstract subjects, and to motion illusions were also measured, to compare real and illusory motion with painted IM. Movies, both figurative and abstract, elicit the largest pupillary dilation of all static stimuli, whereas motion illusions cause the smallest pupil size, as previously shown. Interestingly, pupil responses to IM depend on the paintings’ style. Figurative paintings depicting moving subjects cause more dilation than those representing static figures, and pupil size increases with the strength of IM, as already found with realistic photos. The opposite effect is obtained with abstract artworks. paintings depicting motion produce less dilation than those depicting stillness. In any case, these results reflect the individual subjective perception of dynamism, as the very same paintings can induce opposite responses in observer which interpreted it as static or dynamic. Overall, our data show that pupil size depends on high-level interpretation of motion in paintings, even when they do not represent real-world scenes. Our findings further suggest that the pupil is modulated by multiple top-down cortical mechanisms, involving the processing of motion, attention, memory, imagination, and other cognitive functions necessary for enjoying a complete aesthetic experience.

No Evidence for a Single Oscillator Underlying Discrete Visual Percepts

Theories of perception based on discrete sampling posit that visual consciousness is reconstructed based on snapshot-like perceptual moments, as opposed to being updated continuously. According to a model proposed by Schneider (2018), discrete sampling can explain both the flash-lag and the Frohlich illusion, whereby a lag in the conscious updating of a moving stimulus alters its perceived spatial location in comparison to stationary stimulus. The alpha-band frequency, which is associated with phasic modulation of stimulus detection and the temporal resolution of perception, has been proposed to reflect the duration of perceptual moments. The goal of this study was to determine whether a single oscillator (e.g., alpha) is underlying the duration of perceptual moments, which would predict that the point of subjective equality (PSE) in the flash-lag and Frohlich illusions are positively correlated across individuals. Although our displays induced robust flash-lag and Frohlich effects, virtually zero correlation was seen between the PSE in the two illusions, indicating that the illusion magnitudes are unrelated across observers. These findings suggest that, if discrete sampling theory is true, these illusory percepts either rely on different oscillatory frequencies or not on oscillations at all. Alternatively, discrete sampling may not be the mechanism underlying these two motion illusions or our methods were ill-suited to test the theory.

A motion-energy-based optimization method for generating an image sequence causing four-stroke apparent motion illusion

A motion-energy-based optimization method for generating an image sequence causing four-stroke apparent motion illusion

The interaction between motion and texture in the sense of touch.

Besides providing information on elementary properties of objects, like texture, roughness, and softness, the sense of touch is also important in building a representation of object movement and the movement of our hands. Neural and behavioral studies shed light on the mechanisms and limits of our sense of touch in the perception of texture and motion, and of its role in the control of movement of our hands. The interplay between the geometrical and mechanical properties of the touched objects, such as shape and texture, the movement of the hand exploring the object, and the motion felt by touch, will be discussed in this article. Interestingly, the interaction between motion and textures can generate perceptual illusions in touch. For example, the orientation and the spacing of the texture elements on a static surface induces the illusion of surface motion when we move our hand on it or can elicit the perception of a curved trajectory during sliding, straight hand movements. In this work we present a multiperspective view that encompasses both the perceptual and the motor aspects, as well as the response of peripheral and central nerve structures, to analyze and better understand the complex mechanisms underpinning the tactile representation of texture and motion. Such a better understanding of the spatiotemporal features of the tactile stimulus can reveal novel transdisciplinary applications in neuroscience and haptics.