Illusory Perception Research Articles

Multisensory integration and motor resonance in the primary motor cortex

Humans are endowed with a motor system that resonates to speech sounds, but whether concurrent visual information from lip movements can improve speech perception at a motor level through multisensory integration mechanisms remains unknown. Therefore, the aim of the study was to explore behavioral and neurophysiological correlates of multisensory influences on motor resonance in speech perception. Motor-evoked potentials (MEPs), by single pulse transcranial magnetic stimulation (TMS) applied over the left lip muscle (orbicularis oris) representation in the primary motor cortex, were recorded in healthy participants during the presentation of syllables in unimodal (visual or auditory) or multisensory (audio-visual) congruent or incongruent conditions. At the behavioral level, subjects showed better syllable identification in the congruent audio-visual condition as compared to the unimodal conditions, hence showing a multisensory enhancement effect. Accordingly, at the neurophysiological level, increased MEPs amplitudes were found in the congruent audio-visual condition, as compared to the unimodal ones. Incongruent audio-visual syllables resulting in illusory percepts did not increase corticospinal excitability, which in fact was comparable to that induced by the real perception of the same syllable. In conclusion, seeing and hearing congruent bilabial syllables increases the excitability of the lip representation in the primary motor cortex, hence documenting that multisensory integration can facilitate speech processing by influencing motor resonance. These findings highlight the modulation role of multisensory processing showing that it can boost speech perception and that multisensory interactions occur not only within higher-order regions, but also within primary motor areas, as shown by corticospinal excitability changes.

Evidence for a Causal Dissociation of the McGurk Effect and Congruent Audiovisual Speech Perception via TMS to the Left pSTS.

Congruent visual speech improves speech perception accuracy, particularly in noisy environments. Conversely, mismatched visual speech can alter what is heard, leading to an illusory percept that differs from the auditory and visual components, known as the McGurk effect. While prior transcranial magnetic stimulation (TMS) and neuroimaging studies have identified the left posterior superior temporal sulcus (pSTS) as a causal region involved in the generation of the McGurk effect, it remains unclear whether this region is critical only for this illusion or also for the more general benefits of congruent visual speech (e.g., increased accuracy and faster reaction times). Indeed, recent correlative research suggests that the benefits of congruent visual speech and the McGurk effect rely on largely independent mechanisms. To better understand how these different features of audiovisual integration are causally generated by the left pSTS, we used single-pulse TMS to temporarily disrupt processing within this region while subjects were presented with either congruent or incongruent (McGurk) audiovisual combinations. Consistent with past research, we observed that TMS to the left pSTS reduced the strength of the McGurk effect. Importantly, however, left pSTS stimulation had no effect on the positive benefits of congruent audiovisual speech (increased accuracy and faster reaction times), demonstrating a causal dissociation between the two processes. Our results are consistent with models proposing that the pSTS is but one of multiple critical areas supporting audiovisual speech interactions. Moreover, these data add to a growing body of evidence suggesting that the McGurk effect is an imperfect surrogate measure for more general and ecologically valid audiovisual speech behaviors.

High segregation and diminished global integration in large-scale brain functional networks enhances the perceptual binding of cross-modal stimuli.

Speech perception requires the binding of spatiotemporally disjoint auditory-visual cues. The corresponding brain network-level information processing can be characterized by two complementary mechanisms: functional segregation which refers to the localization of processing in either isolated or distributed modules across the brain, and integration which pertains to cooperation among relevant functional modules. Here, we demonstrate using functional magnetic resonance imaging recordings that subjective perceptual experience of multisensory speech stimuli, real and illusory, are represented in differential states of segregation-integration. We controlled the inter-subject variability of illusory/cross-modal perception parametrically, by introducing temporal lags in the incongruent auditory-visual articulations of speech sounds within the McGurk paradigm. The states of segregation-integration balance were captured using two alternative computational approaches. First, the module responsible for cross-modal binding of sensory signals defined as the perceptual binding network (PBN) was identified using standardized parametric statistical approaches and their temporal correlations with all other brain areas were computed. With increasing illusory perception, the majority of the nodes of PBN showed decreased cooperation with the rest of the brain, reflecting states of high segregation but reduced global integration. Second, using graph theoretic measures, the altered patterns of segregation-integration were cross-validated.

Perceptual Training as Means to Assess the Effect of Alpha Frequency on Temporal Binding Window.

For decades, it has been shown that alpha frequency is related to temporal binding window, and currently, such is the mainstream viewpoint [Noguchi, Y. Individual differences in beta frequency correlate with the audio-visual fusion illusion. Psychophysiology, 59, e14041, 2022; Gray, M. J., & Emmanouil, T. A. Individual alpha frequency increases during a task but is unchanged by alpha-band flicker. Psychophysiology, 57, e13480, 2020; Hirst, R. J., McGovern, D. P., Setti, A., Shams, L., & Newell, F. N. What you see is what you hear: Twenty years of research using the sound-induced flash illusion. Neuroscience & Biobehavioral Reviews, 118, 759-774, 2020; Keil, J. Double flash illusions: Current findings and future directions. Frontiers in Neuroscience, 14, 298, 2020; Migliorati, D., Zappasodi, F., Perrucci, M. G., Donno, B., Northoff, G., Romei, V., & Costantini, M. Individual alpha frequency predicts perceived visuotactile simultaneity. Journal of Cognitive Neuroscience, 32, 1-11, 2020; Keil, J., & Senkowski, D. Individual alpha frequency relates to the sound-induced flash illusion. Multisensory Research, 30, 565-578, 2017; Minami, S., & Amano, K. Illusory jitter perceived at the frequency of alpha oscillations. Current Biology, 27, 2344-2351, 2017; Cecere, R., Rees, G., & Romei, V. Individual differences in alpha frequency drive crossmodal illusory perception. Current Biology, 25, 231-235, 2015]. However, recently, this stance has been challenged [Buergers, S., & Noppeney, U. The role of alpha oscillations in temporal binding within and across the senses. Nature Human Behaviour, 6, 732-742, 2022]. Moreover, both stances appear to have their limitations regarding the reliability of results. Therefore, it is of paramount importance to develop new methodology to gain more reliable results. Perceptual training seems to be such a method that also offers significant practical implications.

Illusory percepts of curvilinear self-motion when moving through crowds.

Self-motion generates optic flow, a pattern of expanding visual motion. Heading estimation from optic flow analysis is accurate in rigid environments, but it becomes challenging when other human walkers introduce independent motion to the scene. Previous studies showed that heading perception is surprisingly accurate when moving through a crowd of walkers but revealed strong heading biases when either articulation or translation of biological motion were presented in isolation. We hypothesized that these biases resulted from misperceiving the self-motion as curvilinear. Such errors might manifest as opposite biases depending on whether the observer perceived the crowd motion as indication of his/her self-translation or self-rotation. Our study investigated the link between heading biases and illusory path perception. Participants assessed heading and path perception while observing optic flow stimuli with varying walker movements. Self-motion perception was accurate during natural locomotion (articulation and translation), but significant heading biases occurred when walkers only articulated or translated. In this case, participants often reported a curved path of travel. Heading error and curvature pointed in opposite directions. On average, participants perceived the walker motion as evidence for viewpoint rotation leading to curvilinear path percepts.

E-governance as a new public administration paradigm: a rhetoric or reality?

This study was motivated by the need to shift from the illusory perception of longing for e-Governance to be declared a new paradigm of Public Administration. Public Administration is said to be static, but yet dynamic. Implying that the dynamics of Public Administration can incorporate electronic governance (e-Governance) to improve matters of governance, public service delivery, accountability and transparency in public affairs. However, even with an incongruous adoption and implementation of Information and Communication Technologies (ICTs) within the South African government, this study shed light on the empirical and systematic evidence and analytical distinction between e-Governance and public administration. The analysis suggests that the complexity and implication of e-Governance via the use of ICTs may enhance government efficacy. Still, it cannot be entirely trusted in maintaining administration and government-businesses-citizens interaction partly due to its rapid technological changes and the various conditions of its implementation within different nations including South Africa. With the aid of qualitative research methods, which heavily relied on secondary data gathered from scholarly journals, academic books, trusted databases and websites, this study reveal that there is scant evidence to support research in incorporating e-Governance as a new paradigm of Public Administration due to the imbalance, network failures, inadequate ICTs infrastructure to govern in a democratic manner which include all citizens. This study concludes that e-Governance is already analysed from a public administration dynamic and complementary perspective implying that it is an analytically and structurally incomplete reform to take its full form as a new Public Administration paradigm due to its rapid technological changes.

The illusory perception of distinctiveness in familiar faces.

An illusion of distinctiveness for faces is described that manifests as a positive association between perceived familiarity and perceived distinctiveness. This association seems partly rooted in intrinsic facial characteristics but is boosted by actual exposure to faces. Such illusion could impede research on familiar faces where distinctiveness is manipulated or controlled and researchers will need to find ways around it.

Illusory optical defocus generated by shaded surface texture

The human visual system is tasked with the problem of extracting information about the world from images that contain a conflated mixture of environmental sources and optical artifacts generated by the focal properties of our eyes. In most contexts, our brains manage to distinguish these sources, but this is not always the case. Recent work showed that shading gradients generated by smooth three-dimensional (3D) surfaces can elicit strong illusory percepts of optical defocus1,2 - the perception of illusory blur is only eliminated when the surface appears attached to self-occluding contours3, surface discontinuities1, or sharp specular reflections1,2, which all generate sharp ('high spatial frequency') image structure. This suggests that it should also be possible to eliminate the illusory blur elicited by shaded surfaces by altering the surface geometry to include small-scale surface relief, which would also generate high-frequency image structure. We report the surprising result here that this manipulation fails to eliminate the perception of blur; the fine texture fails to perceptually 'bind' to the low-frequency image structure when there is a sufficient gap between the spatial scales of the fine and coarse surface structure. These findings suggest that discontinuous 'gaps' in the spatial scale of textures are a segmentation cue the visual system uses to extract multiple causes of image structure.

Variation of corticospinal excitability during kinesthetic illusion induced by musculotendinous vibration.

Despite being studied for more than 50 years, the neurophysiological mechanisms underlying vibration (VIB)-induced kinesthetic illusions are still unclear. The aim of this study was to investigate how corticospinal excitability tested by transcranial magnetic stimulation (TMS) is modulated during VIB-induced illusions. Twenty healthy adults received vibration over wrist flexor muscles (80 Hz, 1 mm, 10 s). TMS was applied over the primary motor cortex representation of wrist extensors at 120% of resting motor threshold in four random conditions (10 trials/condition): baseline (without VIB), 1 s, 5 s, and 10 s after VIB onset. Means of motor-evoked potential (MEP) amplitudes and latencies were calculated. Statistical analysis found a significant effect of conditions (stimulation timings) on MEP amplitudes (P = 0.035). Paired-comparisons demonstrated lower corticospinal excitability during VIB at 1 s compared with 5 s (P = 0.025) and 10 s (P = 0.003), although none of them differed from baseline values. Results suggest a time-specific modulation of corticospinal excitability in muscles antagonistic to those vibrated, i.e., muscles involved in the perceived movement. An early decrease of excitability was observed at 1 s followed by a stabilization of values near baseline at subsequent time points. At 1 s, the illusion is not yet perceived or not strong enough to upregulate corticospinal networks coherent with the proprioceptive input. Spinal mechanisms, such as reciprocal inhibition, could also contribute to lower the corticospinal drive of nonvibrated muscles in short period before the illusion emerges. Our results suggest that neuromodulatory effects of VIB are likely time-dependent, and that future work is needed to further investigate underlying mechanisms.NEW & NOTEWORTHY The modulation of corticospinal excitability when perceiving a vibration (VIB)-induced kinesthetic illusion evolves dynamically over time. This modulation might be linked to the delayed occurrence and progressive increase in strength of the illusory perception in the first seconds after VIB start. Different spinal/cortical mechanisms could be at play during VIB, depending on the tested muscle, presence/absence of an illusion, and the specific timing at which corticospinal drive is tested pre/post VIB.

Unravelling brain connectivity patterns in body dysmorphic disorder during decision-making on visual illusions: A graph theoretical approach

Body dysmorphic disorder (BDD) is characterized by an excessive preoccupation with perceived defects in physical appearance, and is associated with compulsive checking. Visual illusions are illusory or distorted subjective perceptions of visual stimuli, which are induced by specific visual cues or contexts. While previous research has investigated visual processing in BDD, the decision-making processes involved in visual illusion processing remain unknown. The current study addressed this gap by investigating the brain connectivity patterns of BDD patients during decision-making about visual illusions. Thirty-six adults - 18 BDD (9 female) and 18 healthy controls (10 female) - viewed 39 visual illusions while their EEG was recorded. For each image, participants were asked to indicate (1) whether they perceived the illusory features of the images; and (2) their degree of confidence in their response. Our results did not uncover group-level differences in susceptibility to visual illusions, supporting the idea that higher-order differences, as opposed to lower-level visual impairments, can account for the visual processing differences that have previously been reported in BDD. However, the BDD group had lower confidence ratings when they reported illusory percepts, reflecting increased feelings of doubt. At the neural level, individuals with BDD showed greater theta band connectivity while making decisions about the visual illusions, likely reflecting higher intolerance to uncertainty and thus increased performance monitoring. Finally, control participants showed increased left-to-right and front-to-back directed connectivity in the alpha band, which may suggest more efficient top-down modulation of sensory areas in control participants compared to individuals with BDD. Overall, our findings are consistent with the idea that higher-order disruptions in BDD are associated with increased performance monitoring during decision-making, which may be related to constant mental rechecking of responses.

The switching glare illusion: Appearance and disappearance of glare effect due to figure-ground reversal.

The glare illusion is an illusory perception of brightness enhancement and self-luminosity from a glare pattern, which consists of a central white area and surrounding areas with radial darkening luminance gradients. Here, we report a phenomenon we call "the switching glare illusion." In this phenomenon, observers experience perceptual alternation in which the glare effect repeatedly appears and disappears or attenuates when the multiple glare patterns are arranged in a grid pattern. This perceptual alternation is caused by a figure-ground reversal in the grid pattern. Since such a phenomenon has not been reported for a single glare pattern, this is caused by arranging multiple glare patterns in a grid. This new finding is worthy for further studies for understanding the mechanisms underlying the glare effect and brightness perception.

Moral Common Sense: Examining the False Consensus Effect of Morality in Japan

Researchers have continually studied the classical false consensus effect (FCE) and documented its robustness across specific contexts. Under the influence of the FCE, people create an illusory perception of others around them and maintain this perception, believing that own opinion serves as “common sense.” Because shared morality plays an important role in group contexts, people’s (illusory) perceptions about how much their morality is shared should be clarified. Therefore, the present study investigated the presence of the FCE in the domain of morality based on the Moral Foundations Theory (MFT). The pilot study required participants to rank the five moral foundations according to their perceived level of importance and estimate others’ perceived importance of the same five foundations. The Purity foundation of the MFT was not sufficient to identify Japanese values on religion and cleanliness. Thus, the main study supplemented the pilot study with the Purity Orientation–Pollution Avoidance Scale (POPA). The importance given to the moral foundations among participants in the main study was measured using both the Moral Foundations Questionnaire (MFQ) and the POPA. The results from both studies showed that the FCE occurs in the moral domain among Japanese individuals. Furthermore, the use of the POPA in addition to the MFQ can benefit future research on morality in cultures that are not Western, educated, industrialized, rich, and democratic such as Japan. The present research will contribute significantly to further understanding the role of morality in group contexts.

Dexamphetamine widens temporal and spatial binding windows in healthy participants.

The pathophysiology of psychosis is complex, but a better understanding of stimulus binding windows (BWs) could help to improve our knowledge base. Previous studies have shown that dopamine release is associated with psychosis and widened BWs. We can probe BW mechanisms using drugs of specific interest to psychosis. Therefore, we were interested in understanding how manipulation of the dopamine or catecholamine systems affect psychosis and BWs. We aimed to investigate the effect of dexamphetamine, as a dopamine-releasing stimulant, on the BWs in a unimodal illusion: the tactile funneling illusion (TFI). We conducted a randomized, double-blind, counterbalanced placebo-controlled crossover study to investigate funnelling and errors of localization. We administered dexamphetamine (0.45 mg/kg) to 46 participants. We manipulated 5 spatial (5-1 cm) and 3 temporal (0, 500 and 750 ms) conditions in the TFI. We found that dexamphetamine increased funnelling illusion (p = 0.009) and increased the error of localization in a delay-dependent manner (p = 0.03). We also found that dexamphetamine significantly increased the error of localization at 500 ms temporal separation and 4 cm spatial separation (p interaction = 0.009; p 500ms|4cm v. baseline = 0.01). Although amphetamine-induced models of psychosis are a useful approach to understanding the physiology of psychosis related to dopamine hyperactivity, dexamphetamine is equally effective at releasing noradrenaline and dopamine, and, therefore, we were unable to tease apart the effects of the 2 systems on BWs in our study. We found that dexamphetamine increases illusory perception on the unimodal TFI in healthy participants, which suggests that dopamine or other catecholamines have a role in increasing tactile spatial and temporal BWs.

Investigating the parameters affecting spectro-temporal integration in pitch

Previous research has shown that a virtual pitch percept of the fundamental frequency (F0) can be extracted from a sequence of non-overlapping, harmonically related tones in the presence of background noise. We have established that the F0 percept is strongest for low numbered harmonics and absent when only high-numbered harmonics (>10) are presented as well as when the tones are inharmonically related. The present series of experiments explores the effect of dichotic presentation, notched noise, and varying degrees of inharmonicity on this virtual pitch percept. F0 difference limens (F0DLs) for synchronous and sequentially presented components in noise were measured in normal-hearing participants. For the dichotic conditions, each ear received a random subset of components to investigate if this percept was dependent on peripheral interactions. The inharmonic conditions varied the extent of spectral jitter on each of the components (by 10%, 20%, and 30%) to understand if F0DLs worsened with increasing amounts of jitter. Finally, the notched noise conditions investigated whether background noise within the harmonic frequencies was essential for the F0 percept. Preliminary results indicate that the virtual pitch can be perceived dichotically and the characteristics of the background noise and harmonic relations play key roles in this illusory percept.

Resting-state neural correlates of visual Gestalt experience.

Subjective perceptual experience is influenced not only by bottom-up sensory information and experience-based top-down processes, but also by an individual's current brain state. Specifically, a previous study found increased prestimulus insula and intraparietal sulcus (IPS) activity before participants perceived an illusory Gestalt (global) compared with the non-illusory (local) interpretation of a bistable stimulus. That study provided only a snapshot of the brain state that favors the illusory interpretation. In the current study, we tested whether areas that differentiate between the illusory and non-illusory perception, immediately before stimulus onset, are also associated with an individual's general tendency to perceive it, which remains stable over time. We examined individual differences in task-free functional connectivity of insula and IPS and related them to differences in the individuals' duration of the two stimulus interpretations. We found stronger connectivity of the IPS with areas of the default mode and visual networks to be associated with shorter local perceptual phases, i.e. a faster switch to an illusory percept, and an opposite effect for insula connectivity with the early visual cortex. Our findings suggest an important role of IPS and insula interactions with nodes of key intrinsic networks in forming a perceptual tendency toward illusory Gestalt perception.

Magnetoencephalography recordings reveal the neural mechanisms of auditory contributions to improved visual detection

Sounds enhance the detection of visual stimuli while concurrently biasing an observer’s decisions. To investigate the neural mechanisms that underlie such multisensory interactions, we decoded time-resolved Signal Detection Theory sensitivity and criterion parameters from magneto-encephalographic recordings of participants that performed a visual detection task. We found that sounds improved visual detection sensitivity by enhancing the accumulation and maintenance of perceptual evidence over time. Meanwhile, criterion decoding analyses revealed that sounds induced brain activity patterns that resembled the patterns evoked by an actual visual stimulus. These two complementary mechanisms of audiovisual interplay differed in terms of their automaticity: Whereas the sound-induced enhancement in visual sensitivity depended on participants being actively engaged in a detection task, we found that sounds activated the visual cortex irrespective of task demands, potentially inducing visual illusory percepts. These results challenge the classical assumption that sound-induced increases in false alarms exclusively correspond to decision-level biases.

No common factor for illusory percepts, but a link between pareidolia and delusion tendency: A test of predictive coding theory.

Predictive coding theory is an influential view of perception and cognition. It proposes that subjective experience of the sensory information results from a comparison between the sensory input and the top-down prediction about this input, the latter being critical for shaping the final perceptual outcome. The theory is able to explain a wide range of phenomena extending from sensory experiences such as visual illusions to complex pathological states such as hallucinations and psychosis. In the current study we aimed at testing the proposed connection between different phenomena explained by the predictive coding theory by measuring the manifestation of top-down predictions at progressing levels of complexity, starting from bistable visual illusions (alternating subjective experience of the same sensory input) and pareidolias (alternative meaningful interpretation of the sensory input) to self-reports of hallucinations and delusional ideations in everyday life. Examining the correlation structure of these measures in 82 adult healthy subjects revealed a positive association between pareidolia proneness and a tendency for delusional ideations, yet without any relationship to bistable illusions. These results show that only a subset of the phenomena that are explained by the predictive coding theory can be attributed to one common underlying factor. Our findings thus support the hierarchical view of predictive processing with independent top-down effects at the sensory and cognitive levels.

CHILDREN’S ADDICTION ON THE DIGITAL WORLD: REASONS AND POSSIBLE SOLUTIONS

% of children and young people all over the world are offi cially diagnosed with addiction. To identify the reasons of the children’s gadgets addiction this research was conducted as a part of the educational activities of the Family, Women, and Children Affairs Committee and the Committee on Education and Science of the public organization “The sovereign course” with participation of teachers and psychologists: Frolova O.S., Fakhrieva O.N., Konoshenko K.N. The research surveys and interviews were conducted with  groups: students of a general education school aged from  to  and their families (parents, siblings and immediate family members). In a secondary school, an observation was made among th and th graders for  months in order to identify adolescents’ dependence on phones. Based on the results of all types of research, the problem of addiction to gadgets and its reasons were identifi ed, and steps to overcome this addiction were developed. Parents’ awareness of the illusory perception of the reasons for children’s gadget addiction and the ways how to solve this problem. The necessity to show to a child a cause-and-effect relationship of the gadget addiction and the idea that it is their growth point which is important to let them live a real life. The lack of quality relationships in families has led to teenagers’ smartphone addiction. () If a family realizes their goals, traditions and there are healthy relationships between parents and good quality time together, children do not go into gadgets. () Children’s gadget addiction is formed by parents focusing on their career, not giving necessary attention to their children. In order to treat their children’s addiction to gadgets parents should () support the interests of the kids, help them fi nd answers to any questions, and () to take into account the child’s individuality and strengths.

Using illusions to understand hallucinations: differences in perceptual performances on illusory figures may underscore specific visuoperceptual impairments in Parkinson's disease.

Visual hallucinations are prevalent, potentially disabling symptoms of Parkinson's Disease. Multiple impairments in bottom-up sensory processing and top-down perceptual modulation are implicated in the pathophysiology of these phenomena. In healthy individuals, visual illusions are elicited by illusory figures through parametric manipulations of geometrical configurations, contrast, color, or spatial relationships between stimuli. These illusory percepts provide insight on the physiologic processes subserving conscious and unconscious perception. In this exploratory, cross-sectional, controlled study, perceptual performance on illusory figures was assessed on 11 PD patients with hallucinations, 10 non-hallucinating PD patients, and 10 age-matched healthy individuals. In order to characterize potential neural substrates of perceptual performances, patients' brain metabolic patterns on FDG PET were also analyzed. Illusions relying on attentional modulation and global perception were attenuated in PD patients without hallucinations. This pattern was no longer recognizable in hallucinating patients. Conversely, illusory effects normally counteracted by figure to background segregation and overlapping figures recognition were enhanced in PD patients with hallucinations. FDG PET findings further suggest that perceptual differences between PD patients might be linked to abnormal top-down perceptual modulation.

Illusory perception of visual patterns in pure noise is associated with COVID-19 conspiracy beliefs.

Just as perceptual heuristics can lead to visual illusions, cognitive heuristics can lead to biased judgements, such as "illusory pattern perception" (i.e., seeing patterns in unrelated events). Here we further investigated the common underlying mechanism behind irrational beliefs and illusory pattern perception in visual images. For trials in which no object was present in the noise, we found that the tendency to report seeing an object was positively correlated with the endorsement of both COVID-19 specific conspiracy theories and paranormal beliefs. The present results suggest that the cognitive bias to see meaningful connections in noise can have an impact on socio-political cognition as well as on perceptual decision making.