Tilt Illusion Research Articles

AntiSox-1 Limbic Encephalitis: When A Movement Disorder Evolves Oddly And Delirium Just Does Not Feel Right

Abstract Background A 74year old male presented to a Movement Disorder service with a 15year history of a parkinsonian syndrome with asymmetric, akinetic rigidity and prominent axial features. Motor features were stable for almost 13years. Neuropsychiatric features rapidly emerged over several months including: multimodality perceptual hallucinosis, upside down and tilt illusion, akinetopsia, intractable insomnia, emotional incontinence and Othello syndrome. A marked motor, mysaesthenic pattern, deterioration occurred in conjunction with hypoactive delirium, dysphagia, pyrexias, raised inflammatory markers and weight loss, necessitating hospitalisation. Computed tomography (CT) of chest, abdomen and pelvis did not demonstrate infective or neoplastic aetiology. CT brain did not demonstrate cerebellar atrophy. Positron emission tomography did not demonstrate a vasculitis. Drg regimen alterations brought about minor improvements, but he remained very severely frail and discharged to hospice care. Unexpectedly, cognition then markedly improved and neuropsychiatric symptoms resolved over months, and he returned home, albeit now severely frail. There was persistence of hemiparkinsonian symptoms, contralateral to which, dystonia had emerged with new bilateral upper limb ataxia and nystagmus. No mysaesthenic features persisted. Methods Cerebrospinal fluid analysis and electroencephalography were not undertaken. MRI brain was not undertaken. Results Anti Sox-1 positive. Anti Zic-4 and Recoverin were equivocal. Neuronal antibodies were negative. Conclusion Limbic encephalitis as a result of AntiSox-1 onconeural antibodies is most commonly associated with small cell cancer of the lung (prevalence of 36.5% of cases). Lambert-Eaton Mysaesthenic Syndrome is a more common presentation than paraneoplastic cerebellar degeneration. Hindsight raises the possibility of non-convulsive status epilepticus as an explanation for abrupt hypoactive delirium presentation on the background of deteriorating neuropsychiatric features. Oncological or immunotherapeutic intervention was not considered appropriate by respiratory or neurology teams respectively; nor did the patient wish for these to be pursued. Case reports indicate that an underlying neoplasm is not always identified. Non-paraneoplastic autoimmune encephalitis can have a better prognosis.

The tilt illusion arises from an efficient reallocation of neural coding resources at the contextual boundary.

The tilt illusion - a bias in the perceived orientation of a center stimulus induced by an oriented surround - illustrates how context shapes visual perception. While the tilt illusion has been the subject of quantitative study for over 85 years, we still lack a comprehensive account of the phenomenon that connects its neural and behavioral characteristics. Here, we demonstrate that the tilt illusion originates from a dynamic change in neural coding precision induced by the surround context. We simultaneously obtained psychophysical and fMRI responses from human subjects while they viewed gratings in the absence and presence of an oriented surround, and extracted sensory encoding precision from their behavioral and neural data. Both measures show that in the absence of a surround, encoding reflects the natural scene statistics of orientation. However, in the presence of an oriented surround, encoding precision is significantly increased for stimuli similar to the surround orientation. This local change in encoding is sufficient to accurately predict the behavioral characteristics of the tilt illusion using a Bayesian observer model. The effect of surround modulation increases along the ventral stream, and is localized to the portion of the visual cortex with receptive fields at the center-surround boundary. The pattern of change in coding accuracy reflects the surround-conditioned orientation statistics in natural scenes, but cannot be explained by local stimulus configuration. Our results suggest that the tilt illusion naturally emerges from a dynamic coding strategy that efficiently reallocates neural coding resources based on the current stimulus context.

Behavioral and neural signatures of efficient sensory encoding in the tilt illusion

Behavioral and neural signatures of efficient sensory encoding in the tilt illusion

Tilting the balance: do balance abilities predict the body tilt illusion?

Tilting the balance: do balance abilities predict the body tilt illusion?

Stereoscopic slant contrast revisited.

The perceived slant of a stereoscopic surface is altered by the presence of a surrounding surface, a phenomenon termed stereo slant contrast. Previous studies have shown that a slanted surround causes a fronto-parallel surface to appear slanted in the opposite direction, an instance of "bidirectional" contrast. A few studies have examined slant contrast using slanted as opposed to fronto-parallel test surfaces, and these also have shown slant contrast. Here, we use a matching method to examine slant contrast over a wide range of combinations of surround and test slants, one aim being to determine whether stereo slant contrast transfers across opposite directions of test and surround slant. We also examine the effect of the test on the perceived slant of the surround. Test slant contrast was found to be bidirectional in virtually all test-surround combinations and transferred across opposite test and surround slants, with little or no decline in magnitude as the test-surround slant difference approached the limit. There was a weak bidirectional effect of the test slant on the perceived slant of the surround. We consider how our results might be explained by four mechanisms: (a) normalization of stereo slant to vertical; (b) divisive normalization of stereo slant channels in a manner analogous to the tilt illusion; (c) interactions between center and surround disparity-gradient detectors; and (d) uncertainty in slant estimation. We conclude that the third of these (interactions between center and surround disparity-gradient detectors) is the most likely cause of stereo slant contrast.

Effects of neural oscillation power and phase on discrimination performance in a visual tilt illusion

Neural oscillations reflect fluctuations in the relative excitation/inhibition of neural systems1,2,3,4,5 and are theorized to play a critical role in canonical neural computations6,7,8,9 and cognitive processes.10,11,12,13,14 These theories have been supported by findings that detection of visual stimuli fluctuates with the phase of oscillations prior to stimulus onset.15,16,17,18,19,20,21,22,23 However, null results have emerged in studies seeking to demonstrate these effects in visual discrimination tasks,24,25,26,27 raising questions about the generalizability of these phenomena to wider neural processes. Recently, we suggested that methodological limitations may mask effects of phase in higher-level sensory processing.28 To test the generality of phasic influences on perception requires a task that involves stimulus discrimination while also depending on early sensory processing. Here, we examined the influence of oscillation phase on the visual tilt illusion, in which a center grating has its perceived orientation biased away from the orientation of a surround grating29 due to lateral inhibitory interactions in early visual processing.30,31,32 We presented center gratings at participants' subjective vertical angle and had participants report whether the grating appeared tilted clockwise or counterclockwise from vertical on each trial while measuring their brain activity with electroencephalography (EEG). In addition to effects of alpha power and aperiodic slope, we observed robust associations between orientation perception and alpha and theta phase, consistent with fluctuating illusion magnitude across the oscillatory cycle. These results confirm that oscillation phase affects the complex processing involved in stimulus discrimination, consistent with its purported role in canonical computations that underpin cognition.

Specificity of tilt illusion reduction through perceptual learning.

Human perceptual ability can be improved by perceptual learning through repeated exposure or training. Perceptual learning studies have focused on achieving accurate perception of stimuli by improving perceptual sensitivity. However, eliminating illusions can also be one of the ways of accurate perception. To determine whether the illusion can be attenuated by perceptual learning, the current study used a tilt illusion where the orientation of the grating presented in the center (central grating) was misperceived because of the orientation of the grating presented in the periphery (surrounding grating). In Experiment 1, participants were trained either in the illusion training condition, in which they trained with illusory stimuli presenting both surrounding and central gratings together, or in the control training condition, where only the central grating was presented. The results confirmed that the tilt illusion was reduced only in the illusion training condition. Experiment 2 tested the transfer effect of learning, which is not often observed in perceptual learning. During training, the orientation of the surrounding grating was fixed to see whether the elimination of the illusion also occurred in the surrounding grating with an orientation that was not used during training. A decrease in the illusion was found only in the case of a surrounding grating with trained orientations, and not in the case of surrounding gratings with untrained orientations. These results suggest that the reduction in tilt illusion through training is due to perceptual learning.

Coming to grips with reality: Real grasps, but not pantomimed grasps, resist a simultaneous tilt illusion

Investigations of grasping real, 3D objects subjected to illusory effects from a pictorial background often choose in-flight grasp aperture as the primary variable to test the hypothesis that the visuomotor system resists the illusion. Here we test an equally important feature of grasps that has received less attention: in-flight grasp orientation. The current study tested a variant of the simultaneous tilt illusion using a mirror-apparatus to manipulate the availability of haptic feedback. Participants performed grasps with haptic feedback (real grasps) and without it (pantomime grasps), reaching for the reflection of a real, 3D bar atop a background grating that induced a 1.1° bias in the perceived orientation of the bar in a separate sample of participants. Analysis of the hand's in-flight grasp orientation at early, late, and end stages of the reach showed that at no point were the real grasps biased by the illusion. In contrast, pantomimed grasps were affected by the illusion at the late and end stages of the reach. At each stage, the effect on the real grasps was significantly weaker than the effect of the illusion as measured by the mean point of subjective equality (PSE) in a two-alternative forced-choice task. In contrast, the effect on the pantomime grasps was statistically indistinguishable from the mean PSE at all three stages of the reach. These findings reinforce the idea that in-flight grasp orientation, like grasp aperture to pictorial illusions of target size, is refractory to pictorial backgrounds that bias perceived orientation.

Зрительные иллюзии и восприятие классической архитектуры

<p>We carried out psychophysical experiments to study perception mechanisms of images that are elements of building projections in ancient and classical architecture. The curvature of isolated lines and lines superimposed on a fan picture (Wundt-Hering illusion), as well as the orientation of lines in the presence of distractors with varying inclination and separation (tilt illusion) were estimated. We used the methods of constant stimuli and the forced choice procedure. The experiments were carried out on three subjects with a large number of presentations of stimuli, which made it possible to evaluate the statistical significance of the obtained dependences. The values of distortions in the illusion of Wundt-Hering (WH) and in the tilt illusion were determined. It is shown that the curvature of single lines without fan lines is estimated adequately. The analysis of the results led to the conclusion that corrections of the orientation and curvature of elements in classical architecture compensate for the distortions of visual perception. At the same time, the curvature of some elements may be due to the aesthetics of perception.</p>

Contextual Modulation of Sensory Encoding in the Tilt Illusion

Contextual Modulation of Sensory Encoding in the Tilt Illusion

The simultaneous tilt illusion reveals separate yet interacting visual systems for perception and action

The simultaneous tilt illusion reveals separate yet interacting visual systems for perception and action

椎骨動脈狭窄による小脳梗塞によって浮動性めまいと一過性に視界の上下逆転を来した1例(Dizziness and reversal of vision metamorphopsia due to cerebellum infarction caused by a vertebral artery stenosis: a case report)

要旨 椎骨動脈狭窄による小脳梗塞によって一過性に視界が上下逆転する現象（reversal of vision metamorphopsia: RVM）を呈した症例を経験した。症例は狭心症，高血圧，糖尿病の既往がある71歳の男性で，浮動性めまいを主訴に救急搬送された。受診2日前と受診前日に突然誘因なく浮動性めまいが出現したが，それぞれ1時間の安静で改善した。受診当日も同様の症状が再燃し悪心も伴うため発症1時間後に救急要請した。来院時のバイタルサインは安定していた。めまいや嘔気の症状が強く可能な範囲での診察では，明らかな脳神経所見の異常はなく運動麻痺や小脳失調も認めなかったが，診察中に患者が「上下が逆に見える」と訴えた。各種画像検査から椎骨動脈狭窄を伴う急性期小脳梗塞と診断し，加療目的に脳神経外科に入院した。入院後にRVMの再燃はなかった。RVMの機序は明らかでないが，本症例では後下小脳動脈領域の梗塞により，視覚と前庭系の情報を統合する前庭小脳繊維が障害されたことが原因と考えた。またRVMの症状は一過性であることが多いとされるが，後頭葉や頭頂葉，残存した正常小脳などが持つ代償機構と，視覚的錯覚からの回復が複合的に機能しているためと考えた。RVMはとくに急性期診療を担う救急外来で遭遇しうるため救急医にとって有用な訴えとなる。RVMを認めた場合は，積極的に中枢性疾患を疑い画像検査を行うべきである。

A ‘demixing’ model explains repulsive biases in visual working memory and perception

Humans often err consistently in estimating what they see or have seen before. For example, when trying to remember one of the two similar items, the estimates of this item’s features are “repulsed” away from the other item, while for dissimilar items there is sometimes an attraction effect. This is highly reminiscent of a tilt illusion and similar biases in perception. How to explain such biases? Many models have been suggested at the mechanistic level (in Marr’s classification) but at the computational level, their rationale remains elusive. Such biases are baffling for standard Bayesian (ideal) observer models, prompting theorists to add extra components (e.g., asymmetric likelihoods or non-uniform priors). I propose an alternative based on the simple idea that observers acquire many sensory samples for each of the presented items and have to determine their causes. In other words, the observers are presented with a mixture of samples and have to ‘demix’ them to find out what the stimuli are. The mixture models are well-known in statistics, yet, their biases are seldom described, and their implications in vision science have not been explored in detail. By simulating the ideal observer behaviour, I show that the ‘demixing’ model can readily explain the repulsive-then-attractive bias pattern when the similarity between the test item and the bias inducer decreases as exemplified above. Notably, this result does not require complex priors or asymmetric likelihoods. Interestingly, depending on sensory noise levels, the observed bias pattern could change to purely repulsive or purely attractive, matching bias patterns observed in different experimental paradigms (e.g., serial dependence). This model, beautiful in its simplicity, provides a formal grounding for the intuition that repulsive biases stem from the observer’s attempt to differentiate between the items, as well as a potential way to explain other kinds of biases.

Small-angle attraction in the tilt illusion.

The tilt illusion (TI) describes the phenomenon in which a surround inducer grating of a particular orientation influences the perceived orientation of a central test grating. Typically, inducer-test orientation differences of 5 to 40 degrees cause the test orientation to appear shifted away from the inducer orientation (i.e. repulsion). For orientation differences of 60 to 90 degrees, the inducer typically causes the test grating orientation to appear shifted toward the inducer orientation, termed here “large-angle” attraction. Both repulsion and large-angle attraction effects have been observed in contrast-modulated as well as luminance-modulated grating patterns. Here, we show that a secondary, “small-angle” 0 to 10 degrees attraction effect is observed in contrast-modulated and orientation-modulated gratings, as well as in luminance-modulated gratings that are relatively low in spatial frequency, low in contrast, or contain added texture. The observed small-angle attraction, which can exceed in magnitude that of the repulsion and large-angle attraction effects, is dependent on the spatial phase relationship between the inducer and test, being maximal when in-phase. Both small-angle attraction and repulsion effects are reduced when a gap is introduced between the test and inducer. Our findings suggest that small-angle attraction in the TI is a result of assimilation of the inducer pattern into the receptive fields of neurons sensitive to the test.

Self-monitoring in schizophrenia: Weighting exteroceptive visual signals against self-generated vestibular cues

Disturbances in self-monitoring are core symptoms of schizophrenia. Some research suggests an over-reliance on exteroceptive cues and a reduced weighting of self-generated interoceptive signals to guide perception. The vestibular sense provides important self-generated information about the body in space. Alterations of vestibular function are reported in schizophrenia, but it is unknown whether internally generated vestibular information is discounted in favour of exteroceptive input. In this study, we test for evidence of an over-reliance on exteroceptive visual cues and a reduced weighting of vestibular signals in guiding perception. In a group of individuals with schizophrenia and healthy controls, we used a well-studied visual illusion – the Tilt Illusion – to probe the respective weight given to visual and vestibular cues in judging line orientation. The Tilt Illusion reveals that perceived orientation of a vertical grating is biased by the orientation in its surround. This illusion increases when the head is tilted, due to the reduced reliability of vestibular information that would otherwise provide an internally generated reference for vertical. We predicted that an over-reliance on exteroceptive cues in schizophrenia would lead to a reduced susceptibility to the effects of head position on Tilt Illusion strength. We find no difference between patients and controls. Both groups show comparable Tilt Illusion magnitudes that increase when the head is tilted. Thus, our findings suggest that chronic patients with schizophrenia adequately combine self-generated vestibular cues and exteroceptive visual input to judge line verticality. A stronger reliance on exteroceptive information over internally generated signals in guiding perception is not evident in our data. Deficits in self-monitoring might therefore be modality specific or state dependant.

Lateral inhibition between banks of orientation selective channels predicts shape context effects: A tilt-illusion field

The perceived shapes of almost circular paths are modified by concentrically placed context paths. These induced changes have previously been attributed to curvature masking. This paper shows that, instead, they can be explained by the impacts of local tilt illusions. First, the tilt-illusion was measured over the full range of orientation differences between short test and context lines and it was shown that the resulting function can be predicted by a model based on a vectorial population response of a bank of orientation selective channels, provided lateral inhibition between channels with the same orientation selectivity and adjacent receptive fields was postulated. Subsequently, it was demonstrated that, if the perceived shape of a test path were modified to accommodate the predicted local tilt-illusion, then this could account for previously reported changes in the detectability of a path sinusoidally modulated in radius. Further, we measured points of subjective vertical in test lines and points of subjective circularity in test paths when surrounded by modulated context paths. The tilt required to null the tilt-illusion approximated the maximum orientation difference from circular measured in the modulated paths at their point of subjective circularity, supporting the proposal that the illusory shape change is due to local changes in the position of the path arising from a response to local tilt illusions induced by the orientation context. An important corollary to this result is that such effects will generalize to all paths which are adjacent.

Visual illusions in Parkinson's disease: an interview survey of symptomatology

BackgroundSeveral types of visual illusions can occur in Parkinson's disease (PD). However, the prevalence and types of specific illusions experienced by patients with PD remain unclear. This study aimed to investigate the types of illusions.MethodsA questionnaire of visual illusions was developed through a literature review in consultation with clinicians and neurologists. Based on the questionnaire, 40 consecutive patients with PD were asked a series of Yes/No questions regarding 20 types of visual illusions since the onset of PD. If participants answered ‘Yes’, they were then asked to detail their experience(s).ResultsIn total, 30 patients with PD had experienced visual illusions since disease onset; among them, 25 were still experiencing them at the time of the study. The most commonly observed illusion types were dysmorphopsia, complex visual illusions, metachromatopsia, and diplopia. Other observed illusions included textural illusions, macropsia, micropsia, teleopsia, pelopsia, kinetopsia, akinetopsia, Zeitraffer/Zeitlupen phenomena, tilt illusion, upside‐down illusion, and palinopsia. Additionally, aberrant perception of surface orientation (inclination) was reported, which is yet to be reported in association with any disease. Visual illusions had detrimental effects on the patients’ daily lives in some cases.ConclusionsSystematic interviews regarding the incidence and details of visual illusions experienced by patients with PD could offer important information regarding their quality of life.

Effects of Chronic Alcohol Use Disorder on the Visual Tilt Illusion.

Rationale: Among the serious consequences of alcohol use disorder (AUD) is the reduced ability to process visual information. It is also generally agreed that AUD tends to occur with disturbed excitation–inhibition (EI) balance in the central nervous system. Thus, a specific visual behavioral probe could directly qualify the EI dysfunction in patients with AUD. The tilt illusion (TI) is a paradigmatic example of contextual influences on perception of central target. The phenomenon shows a characteristic dependence on the angle between the inducing surround stimulus and the central target test. For small angles, there is a repulsion effect; for larger angles, there is a smaller attraction effect. The center-surround inhibition in tilt repulsion is considered to come from spatial orientational interactions between orientation-tuned neurons in the primary visual cortex (V1), and tilt attraction is from higher-level effects of orientation processing in the visual information processing.Objectives: The present study focuses on visual spatial information processing and explores whether chronic AUD patients in abstinence period exhibited abnormal TI compared with healthy controls.Methods: The participants are 30 male volunteers (20–46 years old) divided into two groups: the study group consists of 15 clinically diagnosed AUD patients undergoing abstinence from alcohol, and the control group consists of 15 healthy volunteers. The TI consists of a center target surround with an annulus (both target and annulus are sinusoidal grating with spatial frequency = 2 cycles per degree). The visual angle between center and surround is a variable restricted to 0°, ±15°, ±30°, or ±75°. For measuring the TI, participants have to report whether the center target grating orientation tilted clockwise or counterclockwise from the internal vertical orientation by pressing corresponding keys on the computer keyboard. No feedback is provided regarding response correctness.Results: The results reveal significantly weaker tilt repulsion effect under surround orientation ±15° (p < 0.05) and higher lapse rate (attention limitation index) under all tested surround orientations (all ps < 0.05) in patients with chronic AUD compared with health controls.Conclusions: These results provide psychophysical evidence that visual perception of center-contextual stimuli is different between AUD and healthy control groups.

Moderate Alcohol Intake Changes Visual Perception by Enhancing V1 Inhibitory Surround Interactions.

Moderate alcohol consumption is considered to enhance the cortical GABA-ergic inhibitory system and it also variously affects visual perception. However, little behavioral evidence indicates changes of visual perception due to V1 modulated by alcohol intoxication. In this study, we investigated this issue by using center-surround tilt illusion (TI) as a probe of V1 inhibitory interactions, by taking into account possible higher-order effects. Participants conducted TI measures under sober, moderate alcohol intoxication, and placebo states. We found alcohol significantly increased repulsive TI effect and weakened orientation discrimination performance, which is consistent with the increase of lateral inhibition between orientation sensitive V1 neurons caused by alcohol intoxication. We also observed no visible changes in the data for global orientation processing but a presence of global attentional modulation. Thus, our results provide psychophysics evidence that alcohol changed V1 processing, which affects visual perception of contextual stimuli.

Curvature estimation and architecture of the Parthenon

Curvature in the Wundt–Hering illusion (the fan illusion) in the horizontal and vertical orientations is estimated for slightly concave and convex lines, as well as for straight lines. These estimates were compared with estimates of the curvature of imaginary (interpolated) lines through points that lie on the rays of a fan, as well as with estimates of the curvature of analogous lines when there is no image of a fan. It is shown that estimates of the curvature of the real lines and imaginary lines through the points where they intersect the fan are different and depend on the orientation of the stimuli. They also differ from the estimates obtained for the curvature of real and interpolated lines when there is no image of a fan. Two-dimensional projections of the Parthenon have convex horizontal and vertical lines, even though the temple is perceived as ideally rectilinear. The distortions of the curvature estimates that we found straighten convex lines in the architecture of the Parthenon, whose “curvature,” in our opinion, is generated by the Wundt–Hering illusion and the tilt illusion.