Red and green defocus curves and duochrome test in different age groups / Curvas de desenfoque rojo y verde y prueba de duocromo en diferentes grupos de edad

Purpose: To compare the eye defocus curves (DCs) obtained with stimuli on red, green, and white backgrounds and to investigate the applicability of the duochrome test (DT) in different age groups. Methods: 12 elderly (ELD: 59.3 ± 3.9 years) and 8 young (YG: 22.1 ± 1.1 years) subjects were recruited. An optometric assessment with the DT was carried out to obtain the subjective refraction at distance. DCs at distance on green, white, and red backgrounds were measured and the following parameters were deduced: dioptric difference between red-green, green-white, red-white focal positions (minima of the DCs), best corrected visual acuity (BCVA), and widths of the DCs for red, green, and white. Results: The DC difference between the green-white focal positions (mean ± standard deviation) was -0.12±0.17 diopters (D) (ELD, p = 0.012) and -0.11±0.12 D (YG, p = 0.039), while the red-white difference was not statistically significant. The DC red-green difference was 0.20±0.16 D (ELD, p = 0.002) and 0.18±0.18 D (YG, p = 0.008). The ELD BCVA with green background was significantly worse than BCVA with red (p = 0.007) and white (p = 0.007). The mean value of the DC's width in ELD for green (1.01±0.36 D) was higher than for red (0.77±0.21 D) and for white (0.84±0.35 D), but with no statistical significance. Conclusion: Both age groups showed a slight focusing preference for red when using white light. Moreover, ELD showed a worse BCVA with a green compared to a red background. Despite these results deduced by DC analyses, these aspects do not compromise the possibility of using the DT in clinical practice both in the young and in the elderly. Furthermore, the difference of about 0.20 D between red-green DC in both groups confirms the clinical appropriateness of the widespread use of 0.25 D step as the standard minimum difference in power between correcting lenses.(AU)

Assessing the role of visual dysfunctions in the association between visual symptomatology and the use of digital devices / Evaluación del papel de las disfunciones visuales en la asociación entre la sintomatología visual y el uso de dispositivos digitales

Purpose: To evaluate the association between visual symptoms and use of digital devices considering the presence of visual dysfunctions. Methods: An optometric examination was conducted in a clinical sample of 346 patients to diagnose any type of visual anomaly. Visual symptoms were collected using the validated SQVD questionnaire. A threshold of 6 hours per day was used to quantify the effects of digital device usage and patients were divided into two groups: under and above of 35 years old. A multivariate logistic regression was employed to investigate the association between digital device use and symptoms, with visual dysfunctions considered as a confounding variable. Crude and the adjusted odds ratio (OR) were calculated for each variable. Results: 57.02 % of the subjects reported visual symptoms, and 65.02% exhibited some form of visual dysfunction. For patients under 35 years old, an association was found between having visual symptoms and digital device use (OR = 2.10, p = 0.01). However, after adjusting for visual dysfunctions, this association disappeared (OR = 1.44, p = 0.27) and the association was instead between symptoms and refractive dysfunction (OR = 6.52, p < 0.001), accommodative (OR = 10.47, p < 0.001), binocular (OR = 6.68, p < 0.001) and accommodative plus binocular dysfunctions (OR = 46.84, p < 0.001). Among patients over 35 years old, no association was found between symptoms and the use of digital devices (OR = 1.27, p = 0.49) but there was an association between symptoms and refractive dysfunction (OR = 3.54, p = 0.001). Conclusions: Visual symptoms are not dependent on the duration of digital device use but rather on the presence of any type of visual dysfunction: refractive, accommodative and/or binocular one, which should be diagnosed.(AU)

Investigating the impact of asymmetric macular sensitivity on visual acuity chart reading in choroideraemia.

INTRODUCTION: Degeneration in choroideraemia, unlike typical centripetal photoreceptor degenerations, is centred temporal to the fovea. Once the fovea is affected, the nasal visual field (temporal retina) is relatively spared, and the preferred retinal locus shifts temporally. Therefore, when reading left to right, only the right eye reads into a scotoma. We investigate how this unique property affects the ability to read an eye chart. METHODS: Standard- and low-luminance visual acuity (VA) for right and left eyes were measured with the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart. Letters in each line were labelled by column position. The numbers of letter errors for each position across the whole chart were summed to produce total column error scores for each participant. Macular sensitivity was assessed using microperimetry. Central sensitivity asymmetry was determined by the temporal-versus-nasal central macular difference and subsequently correlated to a weighted ETDRS column error score. Healthy volunteers and participants with X-linked retinitis pigmentosa GTPase regulator associated retinitis pigmentosa (RPGR-RP) were used as controls. RESULTS: Thirty-nine choroideraemia participants (median age 44.9 years [IQR 35.7-53.5]), 23 RPGR-RP participants (median age 30.8 years [IQR 26.5-40.5]) and 35 healthy controls (median age 23.8 years [IQR 20.3-29.0]) were examined. In choroideraemia, standard VA in the right eye showed significantly greater ETDRS column errors on the temporal side compared with the nasal side (p = 0.002). This significantly correlated with greater asymmetry in temporal-versus-nasal central macular sensitivity (p = 0.04). No significant patterns in ETDRS column errors or central macular sensitivity were seen in the choroideraemia left eyes, nor in RPGR-RP and control eyes. CONCLUSION: Difficulty in tracking across lines during ETDRS VA testing may cause excess errors independent of true VA. VA assessment with single-letter optotype systems may be more suitable, particularly for patients with choroideraemia, and potentially other retinal diseases with asymmetric central macular sensitivity or large central scotomas including geographic atrophy.

An Improved SSVEP-based Brain-Computer Interface with Low Contrast Visual Stimulation and its Application in UAV Control.

Efficient communication and regulation are crucial for advancing brain-computer interfaces (BCIs), with the steady-state visual evoked potential (SSVEP) paradigm demonstrating high accuracy and information transfer rates. However, the conventional SSVEP paradigm encounters challenges related to visual occlusion and fatigue. In this study, we propose an improved SSVEP paradigm that addresses these issues by lowering the contrast of visual stimuli. visual stimulation. The improved paradigms outperform the traditional paradigm in the experiments, significantly reducing the visual stimulation of the SSVEP paradigm. Furthermore, we apply this enhanced paradigm to a BCI navigation system, enabling two-dimensional navigation of Unmanned Aerial Vehicles (UAVs) through a first-person perspective. Experimental results indicate the enhanced SSVEP-based BCI system's accuracy in performing navigation and search tasks. Our findings highlight the feasibility of the enhanced SSVEP paradigm in mitigating visual occlusion and fatigue issues, presenting a more intuitive and natural approach for BCIs to control external equipment.

Investigating the role of flight phase and task difficulty on low-time pilot performance, gaze dynamics and subjective situation awareness during simulated flight.

Gaze behaviour has been used as a proxy for information processing capabilities that underlie complex skill performance in real-world domains such as aviation. These processes are highly influenced by task requirements, expertise and can provide insight into situation awareness (SA). Little research has been done to examine the extent to which gaze behaviour, task performance and SA are impacted by various task manipulations within the confines of early-stage skill development. Accordingly, the current study aimed to understand the impact of task difficulty on landing performance, gaze behaviour and SA across different phases of flight. Twenty-four low-time (<300 hours) pilots completed simulated landing scenarios under visual flight rules conditions. Traditional gaze metrics, entropybased metrics, and blink rate provided meaningful insight about the extent to which information processing is modulated by flight phase and task difficulty. The results also suggested that gaze behavior changes compensated for increased task demands and minimized the impact on task performance. Dynamic gaze analyses were shown to be a robust measure of task difficulty and pilot flight hours. Recommendations for the effective implementation of gaze behaviour metrics and their utility in examining information processing changes are discussed.

The role of extrinsic and intrinsic factors in perceptual filling-in of the blind-spot with variegated color and texture stimuli.

Vision scientists dedicated their efforts to unraveling the mechanism of filling-in at the blind-spot (BS) through numerous psychophysical experiments. The prevalent interpretation, emphasizing active filling-in, has spurred extensive research endeavors. In a parallel vein, a pertinent study highlighted the predominance of the nasal Visual Field (VF) over the temporal one and postulated the role of the Cortical Magnification Factor (CMF) in explaining the asymmetry of filling-in. In this study, we first replicated this experiment and then conducted BS-specific psychophysical experiments employing various bi-colored and bi-textured (patterned) stimuli. We observed that nasal dominance is not persistent in the context of the spread of perception for BS filling-in. We posit that the visual information processing priority index (VIPPI), comprising the CMF (an intrinsic factor unaffected by stimulus characteristics) and relative luminance (an extrinsic factor dependent on stimulus characteristics), governs the spread of perception for filling-in in case of diverse neighborhoods of the BS.

Mechanisms of visual working memory processing task-irrelevant information retrieved from visual long-term memory.

Visual working memory (VWM) can selectively filter task-irrelevant information from incoming visual stimuli. However, whether a similar filtering process applies to task-irrelevant information retrieved from visual long-term memory (VLTM) remains elusive. We assume a "resource-limited retrieval mechanism" in VWM in charge of the retrieval of irrelevant VLTM information. To make a comprehensive understanding of this mechanism, we conducted three experiments using both a VLTM learning task and a VWM task combined with pupillometry. The presence of a significant pupil light response (PLR) served as empirical evidence that VLTM information can indeed make its way into VWM. Notably, task-relevant VLTM information induced a sustained PLR, contrasting with the transient PLR observed for task-irrelevant VLTM information. Importantly, the transience of the PLR occurred under conditions of low VWM load, but this effect was absent under conditions of high load. Collectively, these results show that task-irrelevant VLTM information can enter VWM and then fade away only under conditions of low VWM load. This dynamic underscores the resource-limited retrieval mechanism within VWM, exerting control over the entry of VLTM information.

Silent threat of isolated sphenoid sinus tuberculosis resulting in blindness and ophthalmoplegia.

A diabetic woman in her fifties presented with a sudden onset of failing vision and diplopia involving the right eye for two days, along with fever and headache. Radiological investigations revealed right sphenoid sinusitis along with inflammation around the right orbital apex and optic nerve. Functional endoscopic sinus surgery, with orbital and optic nerve decompression improved the ocular movements, but not the visual acuity. Histopathology was suggestive of a granulomatous inflammatory lesion, and high-resolution computed tommography (HRCT) of the thorax revealed lung lesions suggestive of an old tubercular infection, and antitubercular treatment (ATT) was then initiated.At the end of two months of ATT, there was complete resolution of ophthalmoplegia, relative afferent pupillary defect, direct and consensual light reflex however, failure of improvement in her visual acuity, indicated damage to the optic nerve.Extrapulmonary tuberculosis involving an isolated sphenoid sinus is rare and elusive. Prompt radiological investigations, followed by orbital decompression and ATT, provide the best possible outcomes.

Successful treatment of cortical visual impairment in children using anti-amblyopia treatment despite the absence of amblyopia: a case report.

BACKGROUND: Cortical visual impairment (CVI) is a verifiable visual dysfunction that cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment. Given the limited knowledge on the most effective interventions for visual impairment resulting from CVI, this case report provides valuable insights into an example of successful implementation of anti-amblyopia therapy in a patient with CVI. CASE PRESENTATION: This case report presents a 5-year-old girl with CVI secondary to hypoxic-ischemic injury, resulting in visual impairment, dyspraxia, and abnormal visual evoked potential testing. The girl did not suffer from amblyopia, there was no evidence of relevant refractive errors or strabismus, so visual pathway damage was the cause of her visual deficit. Nevertheless, the patient underwent anti-amblyopia therapy and showed significant improvement in visual acuity after 12 months of treatment. The improvement, resulting from visual stimulation, was due to a good functional recovery by a better usage of the damaged visual pathways. The therapy included prescribing corrective glasses and implementing secondary occlusion of the better eye for 4 months, which was protracted for another 4 months, leading to further improvements in visual acuity. CONCLUSIONS: The case report shows that addressing even minor refractive errors and implementing anti-amblyopia therapy can significantly improve vision in children with CVI, even without co-existing amblyopia. It also highlights the importance of early intervention and multidisciplinary rehabilitation in children with CVI, focusing on motor and cognitive skills. Additionally, it emphasizes the need for further research to establish evidence-based practice standards for improving vision in children with CVI.

Visual Inspection with Acetic Acid Positivity in Screening and Early Detection of Cervical Dysplasia in Africa, 2023: A Meta-Analysis.

Background: Visual Inspection with Acetic acid (VIA) is the best feasible method of screening and early detecting for cervical dysplasia for resource limited settings like Africa. There is no study that can represent Africa on VIA positivity. Therefore, this metaanalysis was planned to verify the best available articles to pool the visual inspection with acetic acid positivity in screening and early detection of cervical dysplasia in Africa. Methods: The Cochrane Library, Web of Science, PubMed, Scopus, free Google database search engines, Google Scholar, and Science Direct databases were used to conduct a true search of this research article. STATA version 14.0 was used to do the metaanalysis. This meta-analysis was registered in PROSPERO database under the identity pf CRD42023392197. Result: This meta-analysis analyzed data from 21,066 women who had VIA examination to estimate the pooled VIA positivity in Africa. The overall pooled effect estimate of VIA positivity in Africa was 11.93 (95%CI: 11.48-12.37). Age <16 year during first intercourse 2.58(95%CI: 1.53-3.62), lifetime sexual partner ≥2 3.92(95%CI: 2.05-5.78) and HIV positivity 2.92(95%CI: 1.72-4.12) were the significant variables which influence VIA positivity. Conclusion: Overall pooled effect estimate of VIA positivity in Africa was high compared to other continents. The main factors that affect VIA positivity are age at first sexual contact being under 16 years old, the number of lifetime sexual partners being at least two, and HIV positivity. Therefore, the WHO's goal of creating Africa free of cervical cancer is still one that requires significant effort.

The mechanism of human color vision and potential implanted devices for artificial color vision.

Vision plays a major role in perceiving external stimuli and information in our daily lives. The neural mechanism of color vision is complicated, involving the co-ordinated functions of a variety of cells, such as retinal cells and lateral geniculate nucleus cells, as well as multiple levels of the visual cortex. In this work, we reviewed the history of experimental and theoretical studies on this issue, from the fundamental functions of the individual cells of the visual system to the coding in the transmission of neural signals and sophisticated brain processes at different levels. We discuss various hypotheses, models, and theories related to the color vision mechanism and present some suggestions for developing novel implanted devices that may help restore color vision in visually impaired people or introduce artificial color vision to those who need it.

LUMINA: Linguistic unified multimodal Indonesian natural audio-visual dataset.

The LUMINA (Linguistic Unified Multimodal Indonesian Natural Audio-Visual) Dataset is a carefully curated constrained audio-visual dataset designed to support research in the field of speech perception. Spoken exclusively in Indonesian, LUMINA contains high-quality audio-visual recordings featuring 14 native speakers, including 9 males and 5 females. Each speaker contributes approximately 1,000 sentences, producing a rich and diverse data collection. The recorded videos focus on facial recordings, capturing essential visual cues and expressions that accompany speech. This extensive dataset provides a valuable resource for understanding how humans perceive and process spoken language, paving the way for speech recognition and synthesis technology advancements.

Childhood craniopharyngioma: a retrospective study of children followed in Hôpital Universitaire de Bruxelles.

Introduction: Craniopharyngiomas (CPs) are benign brain tumors accounting for 5 - 11% of intracranial tumors in children. These tumors often recur and can cause severe morbidity. Postoperative radiotherapy efficiently controls and prevents progression and recurrence. Despite advancements in neurosurgery, endocrinological, visual, and neuropsychological complications are common and significantly lower the quality of life of patients. Methods: We performed a retrospective study, including all patients younger than sixteen diagnosed with CP between July 1989 and August 2022 and followed up in Hôpital Universitaire de Bruxelles. Results: Nineteen children with CP were included, with median age of 7 years at first symptoms and 7.5 at diagnosis. Common symptoms at diagnosis were increased intracranial pressure (63%), visual impairment (47%), growth failure (26%), polyuria/polydipsia (16%), and weight gain (10.5%). As clinical signs at diagnosis, growth failure was observed in 11/18 patients, starting with a median lag of 1 year and 4 months before diagnosis. On ophthalmological examination, 27% of patients had papillary edema and 79% had visual impairment. When visual disturbances were found, the average preoperative volume was higher (p=0.039). Only 6/19 patients had gross total surgical resection. After the first neurosurgery, 83% experienced tumor recurrence or progression at a median time of 22 months. Eleven patients (73%) underwent postsurgical radiotherapy. At diagnosis, growth hormone deficiency (GHD) was the most frequent endocrine deficit (8/17) and one year post surgery, AVP deficiency was the most frequent deficit (14/17). Obesity was present in 13% of patients at diagnosis, and in 40% six months after surgery. There was no significant change in body mass index over time (p=0.273) after the first six months post-surgery. Conclusion: CP is a challenging brain tumor that requires multimodal therapy and lifelong multidisciplinary follow-up including hormonal substitution therapy. Early recognition of symptoms is crucial for prompt surgical management. The management of long-term sequelae and morbidity are crucial parts of the clinical path of the patients. The results of this study highlight the fundamental importance of carrying out a complete assessment (ophthalmological, endocrinological, neurocognitive) at the time of diagnosis and during follow-up so that patients can benefit from the best possible care.

Compliance with spectacle wear among learners with hearing impairment in Ghana.

Background: Hearing-impaired learners with refractive problems require correction because poor vision hinders their development and educational pursuits. Objectives: To determine the level of compliance with spectacle wear in learners with hearing impairment in Ghana. Method: A descriptive cross-sectional study design was used to investigate the level of compliance with spectacle wear in hearing-impaired learners with uncorrected refractive errors (URE). The participants were from six schools for the hearing impaired, comprising three schools from each sector (Northern and Southern) of Ghana. Results: Of the 1914 learners screened, 69 (3.61% CI: 2.82-4.54%) had URE. Sixty-two (89.9%) learners with URE had myopia (-0.50 Dioptre Sphere (DS) to -2.00DS), and 7 (10.1%) had hyperopia (+2.00DS to +10.00DS). There were more females (53.6%) with URE than males, and their ages ranged from 8 to 35 years, with a mean of 17.35 ± 5.19 years. Many (56.5%) learners complied with spectacle wear after 3 months of reassessment, with females being more compliant than males, but the difference was not significant (p = 0.544). Learners who complied well with the spectacle wear were those with moderate visual impairment (VI), followed by mild VI, while those with no VI were the least compliant. A significant difference was observed between spectacle compliance and presenting VI (p = 0.023). Conclusion: The spectacle wear compliance level was high compared to a previous study (33.7%) in Ghana. Contribution: This study highlights the importance of addressing URE among learners with hearing impairment in Ghana and Africa.

Ophthalmologic findings in abusive head trauma.

A leading cause of death and disability in infancy is abusive head trauma (AHT) and there are common clinical signs that help to establish this diagnosis. Children diagnosed with AHT can have many ophthalmologic findings, including retinal hemorrhages, retinoschisis, subconjunctival hemorrhages, corneal injury, and globe rupture. If any such injuries are suspected, an ophthalmologic consultation, with indirect ophthalmoscopy, should be completed. In addition to a complete physical exam, a thorough history imaging, and lab work, should be obtained to investigate the etiology of ophthalmic pathology including accidental and systemic causes. In general, studies show that retinal hemorrhages that are multilayered, too numerous to count, and located from the posterior pole to the ora serrata are highly suspicious for abusive head trauma.

Parsing evoked and induced gamma response differences in Autism: A visual evoked potential study.

OBJECTIVE: Electroencephalography (EEG) measures of visual evoked potentials (VEPs) provide a targeted approach for investigating neural circuit dynamics. This study separately analyses phase-locked (evoked) and non-phase-locked (induced) gamma responses within the VEP to comprehensively investigate circuit differences in autism. METHODS: We analyzed VEP data from 237 autistic and 114 typically developing (TD) children aged 6-11, collected through the Autism Biomarkers Consortium for Clinical Trials (ABC-CT). Evoked and induced gamma (30-90 Hz) responses were separately quantified using a wavelet-based time-frequency analysis, and group differences were evaluated using a permutation-based clustering procedure. RESULTS: Autistic children exhibited reduced evoked gamma power but increased induced gamma power compared to TD peers. Group differences in induced responses showed the most prominent effect size and remained statistically significant after excluding outliers. CONCLUSIONS: Our study corroborates recent research indicating diminished evoked gamma responses in children with autism. Additionally, we observed a pronounced increase in induced power. Building upon existing ABC-CT findings, these results highlight the potential to detect variations in gamma-related neural activity, despite the absence of significant group differences in time-domain VEP components. SIGNIFICANCE: The contrasting patterns of decreased evoked and increased induced gamma activity in autistic children suggest that a combination of different EEG metrics may provide a clearer characterization of autism-related circuitry than individual markers alone.

Long-term results of Ahmed glaucoma valve implantation with/without intravitreal anti-VEGF injection in neovascular glaucoma patients.

PURPOSE: This study aimed to evaluate the efficacy of Ahmed glaucoma valve (AGV) implantation with or without anti-VEGF injections in neovascular glaucoma patients. MATERIALS AND METHODS: This single-center retrospective study assessed NVG patients who underwent AGV implantation with or without anti-VEGF injections. Demographic and clinical data, including ocular findings, intraocular pressure (IOP), visual acuity, and glaucoma medication count, were recorded preoperatively and postoperatively at one day, one month, and one year. The study included 35 patients. Group 1 consisted of 23 patients who received anti-VEGF injections before AGV surgery. Group 2, with 12 patients, had no anti-VEGF injections prior to surgery. Successful surgery was defined as IOP values between 6 and 21mmHg. The primary outcome was a 30% or more reduction in IOP. RESULTS: The groups displayed no significant difference in their demographic or clinical profiles (P>0.05). The visual acuity before and one year after surgery did not differ significantly between the groups. However, IOP values significantly decreased by the end of the one-year follow-up for both groups. No significant differences were found between the groups regarding visual acuity, IOP, or the number of medications during the one-year follow-up (P>0.05). Success rates were 95.7% for Group 1 and 91.7% for Group 2. No significant difference in complications between the groups was observed (P>0.05). CONCLUSION: Anti-VEGF injections prior to AGV implantation did not significantly impact visual acuity, IOP values, or medication count during the one-year follow-up.

Allometry and ecology shape eye size evolution in spiders.

Eye size affects many aspects of visual function, but eyes are costly to grow and maintain. The allometry of eyes can provide insight into this trade-off, but this has mainly been explored in species that have two eyes of equal size. By contrast, animals possessing larger visual systems can exhibit variable eye sizes within individuals. Spiders have up to four pairs of eyes whose sizes vary dramatically, but their ontogenetic, static, and evolutionary allometry has not yet been studied in a comparative context. We report variable dynamics in eye size across 1,098 individuals in 39 species and 8 families, indicating selective pressures and constraints driving the evolution of different eye pairs and lineages. Supplementing our sampling with a recently published phylogenetically comprehensive dataset, we confirmed these findings across more than 400 species; found that ecological factors such as visual hunting, web building, and circadian activity correlate with eye diameter; and identified significant allometric shifts across spider phylogeny using an unbiased approach, many of which coincide with visual hunting strategies. The modular nature of the spider visual system provides additional degrees of freedom and is apparent in the strong correlations between maximum/minimum investment and interocular variance and three key ecological factors. Our analyses suggest an antagonistic relationship between the anterior and posterior eye pairs. These findings shed light on the relationship between spider visual systems and their diverse ecologies and how spiders exploit their modular visual systems to balance selective pressures and optical and energetic constraints.

Short-latency preference for faces in primate superior colliculus depends on visual cortex.

Face processing is fundamental to primates and has been extensively studied in higher-order visual cortex. Here, we report that visual neurons in the midbrain superior colliculus (SC) of macaque monkeys display a preference for images of faces. This preference emerges within 40 ms of stimulus onset-well before "face patches" in visual cortex-and, at the population level, can be used to distinguish faces from other visual objects with accuracies of ∼80%. This short-latency face preference in SC depends on signals routed through early visual cortex because inactivating the lateral geniculate nucleus, the key relay from retina to cortex, virtually eliminates visual responses in SC, including face-related activity. These results reveal an unexpected circuit in the primate visual system for rapidly detecting faces in the periphery, complementing the higher-order areas needed for recognizing individual faces.

Rare incompatible stimuli evoke visual mismatch negativity in a flanker task.

In the flanker task, the behavioral performance for incompatible stimuli is worse in the mostly compatible (rare) condition than in the equiprobable condition. Furthermore, incompatible stimuli evoke visual mismatch negativity (VMMN) when comparing the rare and equiprobable conditions. Compatible and incompatible stimuli differ in terms of their shape and type. This study aimed to examine whether VMMN evoked by rare incompatible stimuli were associated with the shape or type of the stimulus. In a modified version of the flanker task, stimuli were manipulated by two shapes (typical or peculiar) and two types (compatible or incompatible): typical compatible stimuli (< < < < < and > > > > >), typical incompatible stimuli (> > < > > and < < > < <), peculiar compatible stimuli (+ < < < + and + > > > +), and peculiar incompatible stimuli (+ > < > + and + < > < +). In the rare condition, typical incompatible, peculiar compatible, and peculiar incompatible stimuli were presented with a probability of 10%, whereas all the stimuli were presented equally in the equiprobable condition. Right posterior negativity from 200 to 250 ms was significantly more negative in the rare condition than in the equiprobable condition for typical and peculiar incompatible stimuli; however, this difference was not observed for peculiar compatible stimuli. VMMN was significantly more negative for typical and peculiar incompatible stimuli than for peculiar compatible stimuli, and was not significantly different between typical and peculiar incompatible stimuli. These findings suggest that VMMN for incompatible stimuli is associated with the type rather than the shape of the stimulus.