Massive splenic infarction secondary to exacerbation of chronic pancreatitis - Initial diagnosis with digestive ultrasound.

Splenic infarction is a rare complication present in 7% of pancreatic inflammatory pathologies. This is justified by the close anatomical relationship between the pancreas and the splenic hilum. Although CT is considered the technique of choice for the diagnosis of this type of complications, the growing use of ultrasound in many digestive units, due to its accessibility and safety for patients, allows for early diagnosis and targeted treatment to prevent further complications. Splenectomy is reserved for cases where complications such as splenic abscess, spleen rupture, haemoperitoneum or persistent pain are present.

Adherence to patient blood management strategy in patients with gastrointestinal bleeding: a prospective nationwide multicenter study.

INTRODUCTION: Patient blood management (PBM) adherence in clinical practice is unclear. This real-world practice study assessed the management of patients with gastrointestinal (GI) bleeding after the implementation of the PBM strategy. METHODS: This was a nationwide multicenter and prospective study involving consecutive adults with GI bleeding between March 2019 and March 2021. Patients were examined according to hemoglobin (Hb) level at admission (<7 g/dl, n = 93; 7-8 g/dl, n = 47; 8-9 g/dl, n = 61; and >9 g/dl, n = 249). Study outcomes measures were morbidity and mortality during hospitalization and at 3- and 6-month follow-up. Appropriate anemia or iron deficiency management was considered when adherence to PBM policy was higher than 75%. RESULTS: A total of 450 patients (57.6% men, median age: 74 years, interquartile range: 63-82) were included. Overall, 55.1% and 59.3% of patients received transfusion and iron supplementation, respectively. The rates of appropriate transfusion and iron supplementation adherence were 90.9% (range: 86.9-93.5%, P = 0.109) and 81.8% (range: 78.5-85.1%, P = 0.041), depending on Hb level, respectively. No associations were observed between adherence to the PBM strategy and length of stay (P = 0.263) or risk of further bleeding (P = 0.742). Patients who were transfused [hazard ratio (HR): 0.79, 95% confidence interval (CI): 0.27-0.85] and iron supplemented (HR: 0.91, 95% CI: 0.38-1.41), however, appropriately achieved a lower risk of death. Age (HR: 1.12, 95% CI: 1.12-1.25) and further bleeding (HR: 39.08, 95% CI: 4.01-181.24) were poor prognostic factors. No serious adverse events were reported. CONCLUSIONS: In this nationwide study, there is a high level of adherence and safety of PBM for the treatment of GI bleeding. Adherence to the PBM strategy improved outcomes in patients with GI bleeding.

Do patients with inflammatory bowel disease really know what other immune-mediated inflammatory diseases they are diagnosed with?

BACKGROUND AND AIMS: The association of inflammatory bowel disease (IBD) with other immune-mediated inflammatory diseases (IMIDs) in the same patient is well known. We aimed to evaluate the degree of knowledge that patients with IBD have regarding the coexistence of other IMIDs and to analyze the factors associated with the concordance between self-reported and confirmed medical information. METHODS: Patients with IBD at a tertiary hospital answered a questionnaire on the presence of 54 IMIDs (self-reported diagnosis), and their IMID diagnosis was confirmed in their medical records (reference diagnosis). Agreement between the self-reported IMID and the IMID according to medical records was evaluated. The association between concordance and different predictors was evaluated using logistic regression models. RESULTS: A total of 1,620 patients were included. Six hundred and twenty-six (39%) patients were diagnosed with at least one IMID, and 177 (11%) with two or more. Overall agreement between patients´ self-report and medical records was k:0.61. When we grouped IMIDs according to affected organs or systems, agreement on rheumatic IMIDs was moderate (k:0.58), whereas agreement on cutaneous (k:0.66), endocrine (k: 0.74) and ocular (k:0.73) IMIDs was substantial. Among patients who had IMIDs, the factor associated with greater concordance was female gender, while lower concordance was associated with a lower educational level and the fact that the IMID had been diagnosed at the same time or later than IBD. CONCLUSION: The knowledge that patients with IBD have regarding the coexistence of other IMIDs is poor, especially in rheumatic IMIDs.

Reliability and robustness of a novel preclinical torsional wave-based device for stiffness evaluation.

In this work, we present a novel preclinical device utilizing Torsional Wave Elastography (TWE). It comprises a rotational actuator element and a piezoceramic receiver ring circumferentially aligned. Both allow the transmission of shear waves that interact with the tissue before being received. Our main objective is to demonstrate and characterize the reliability, robustness, and accuracy of the device for characterizing the stiffness of elastic materials and soft tissues. Experimental tests are performed using two sets of tissue mimicking phantoms. The first set consists of calibrated CIRS gels with known stiffness value, while the second test uses non-calibrated manufactured phantoms. Our experimental observations show that the proposed device consistently and repeatably quantifies the stiffness of elastic materials with high accuracy. Furthermore, comparison with established techniques demonstrates a very high correlation (> 95%), supporting the potential medical application of this technology. The results obtained pave the way for a cross-sectional study aiming to investigate the correlation between gestational age and cervical elastic properties during pregnancy.

Assessment of visual fatigue in SSVEP-based brain-computer interface: a comprehensive study.

Fatigue deteriorates the performance of a brain-computer interface (BCI) system; thus, reliable detection of fatigue is the first step to counter this problem. The fatigue evaluated by means of electroencephalographic (EEG) signals has been studied in many research projects, but widely different results have been reported. Moreover, there is scant research when considering the fatigue on steady-state visually evoked potential (SSVEP)-based BCI. Therefore, nowadays, fatigue detection is not a completely solved topic. In the current work, the issues found in the literature that led to the differences in the results are identified and saved by performing a new experiment on an SSVEP-based BCI system. The experiment was long enough to produce fatigue in the users, and different SSVEP stimulation ranges were used. Additionally, the EEG features commonly reported in the literature (EEG rhythms powers, SNR, etc.) were calculated as well as newly proposed features (spectral features and Lempel-Ziv complexity). The analysis was carried out on O1, Oz and O2 channels. This work found a tendency of displacement from high-frequency rhythms to low-frequency ones, and thus, better EEG features should present a similar behaviour. Then, the 'relative power' of EEG rhythms, the rates (θ + α)/ß, α/ß and θ/ß, some spectral features (central and mean frequencies, asymmetry and kurtosis coefficients, etc.) and Lempel-Ziv complexity are proposed as reliable EEG features for fatigue detection. Hence, this set of features may be used to construct a more trustworthy fatigue index.

Torsade de pointes secondary to long QT syndrome after intragastric balloon placement. A rare but severe complication.

The obesity pandemic is becoming one of the most prevalent diseases nowadays. There is a wide spectrum of treatment, ranging from hygienic-dietary measures to bariatric surgery. Endoscopic intragastric balloon placement is becoming increasingly more frequent, due to its technical simplicity, safety and short-term success(1). Although complications are rare some can be severe, so pre-endoscopic evaluation must be carried out carefully. A 43-year-old woman with a history of grade I obesity (BMI 32.7) had an Orbera® intragastric balloon implanted successfully. After the procedure she presented frequent nausea and vomiting, partially controlled with antiemetics. She attended the Emergency Department(ED) with a persistent emetic syndrome - oral intolerance and short-term loss of consciousness(syncope), for which she was admitted. Lab tests showed metabolic alkalosis with severe hypokalemia(K+ 1.8mmol/L), so fluid therapy was initiated for hydroelectrolytic replacement. During the patient's stay in the ED, two episodes of polymorphic ventricular tachychardia "Torsades de Pointes" (PVT-TDP) occurred, leading to cardiac arrest and requiring electrical cardioversion to restore sinus rhythm, in addition to a temporary pacemaker placement. Telemetry showed a corrected QT interval of >500ms, compatible with Long QT Syndrome(LQTS). Once the patient was hemodynamically stabilized a gastroscopy was performed. The intragastric balloon located in the fundus was removed using an extraction kit, puncturing and aspirating 500ml of saline solution, and extracting the collapsed balloon without any complications. The patient achieved an adequate oral intake afterwards, and no recurrence of emetic episodes were noticed. Previous ECGs revealed a prolonged QT interval and a genetic study confirmed a congenital type 1 LQTS. Treatment was initiated with beta-blockers and a bicameral automatic defibrillator was implanted in order to prevent recurrences. Intragastric balloon placement is generally a safe procedure, serious complications present in 0.70% of cases(2). It is essential to have a proper pre-endoscopic evaluation, including patient's medical history and comorbidities. Episodes of PVT-TDP may present precipitated by certain medications (eg. metoclopramide) or hydroelectrolytic imbalances (eg, hypokalemia)(3). A standardized evaluation of ECG before intragastric balloon placement may be useful to prevent these rare but serious complications.

Biases in the spectral amplitude distribution of a natural scene modulate horizontal size perception.

Introduction: Visual perception is a complex process that involves the analysis of different spatial and temporal features of the visual environment. One critical aspect of this process is adaptation, which allows the visual system to adjust its sensitivity to specific features based on the context of the environment. Numerous theories highlight the significance of the visual scene and its spectral properties in perceptual and adaptation mechanisms. For example, size perception is known to be influenced by the spatial frequency content of the visual scene. Nonetheless, several inquiries still exist, including how specific spectral properties of the scene play a role in size perception and adaptation mechanisms. Methods: In this study, we explore aftereffects on size perception following adaptation to a natural scene with a biased spectral amplitude distribution. Twenty participants had to manually estimate the horizontal size of a projected rectangle after adaptation to three visually biased conditions: vertical-biased, non-biased, and horizontal-biased. Size adaptation aftereffects were quantified by comparing the perceptual responses from the non-biased condition with the vertical- and horizontal-biased conditions. Results: We found size perception shifts which were contingent upon the specific orientation and spatial frequency distribution inherent in the amplitude spectra of the adaptation stimuli. Particularly, adaptation to vertical-biased produced a horizontal enlargement, while adaptation to horizontal-biased generated a decrease in the horizontal size perception of the rectangle. On average, size perception was modulated by 5-6%. Discussion: These findings provide supporting evidence for the hypothesis that the neural mechanisms responsible for processing spatial frequency channels are involved in the encoding and perception of size information. The implications for neural mechanisms underlying spatial frequency and size information encoding are discussed.

Evaluating the impact of COVID-19 pandemic-related home confinement on the refractive error of school-aged children in Germany: a cross-sectional study based on data from 414 eye care professional centres.

OBJECTIVE: This study aimed at evaluating refractive changes in German school-aged children before and after the COVID-19 pandemic. DESIGN: Cross-sectional study. SETTING: 414 eye care professional centres from Germany. PARTICIPANTS: Refractive data from 59 926 German children aged 6-15 years were examined over a 7-year period (2015-2021). PRIMARY AND SECONDARY OUTCOME MEASURES: Spherical equivalent refraction was assessed as a function of year, age and gender. The refractive values concerning 2020 and 2021 were compared with those assigned to prior years (2015-2019). RESULTS: The refractive data associated with 2020 and 2021 showed a myopic refractive shift of approximately -0.20D compared with the 2015-2019 range. The refractive change was statistically considerable in the 6 to 11-year range (p<0.05), while from 12 to 15 years was negligible (p≥0.10). Percentage of myopes was also impacted in 2021 (p=0.002), but not in 2020 (p=0.25). From 6 to 11 years, the percentage of myopes in 2021 increased significantly by 6.02% compared with the 2015-2019 range (p≤0.04). The highest percentage increase occurred at 8 and 10 years of age, showing a rise of 7.42% (p=0.002) and 6.62% (p=0.005), respectively. From 12 to 15 years, there was no significant increase in the percentage of myopes in 2021 (p≥0.09). Percentage of myopes in 2020 was not influenced at any age (p≥0.06). CONCLUSION: Disruption of normal lifestyle due to pandemic-related home confinement appears to lead to a myopic refractive shift in children aged 6-11 years in Germany. The greater effect observed at younger ages seems to emphasise the importance of refractive development in this age group.

Prediction of refractive error and its progression: a machine learning-based algorithm.

OBJECTIVE: Myopia is the refractive error that shows the highest prevalence for younger ages in Southeast Asia and its projection over the next decades indicates that this situation will worsen. Nowadays, several management solutions are being applied to help fight its onset and development, nonetheless, the applications of these techniques depend on a clear and reliable assessment of risk to develop myopia. METHODS AND ANALYSIS: In this study, population-based data of Chinese children were used to develop a machine learning-based algorithm that enables the risk assessment of myopia's onset and development. Cross-sectional data of 12 780 kids together with longitudinal data of 226 kids containing age, gender, biometry and refractive parameters were used for the development of the models. RESULTS: A combination of support vector regression and Gaussian process regression resulted in the best performing algorithm. The Pearson correlation coefficient between prediction and measured data was 0.77, whereas the bias was -0.05 D and the limits of agreement was 0.85 D (95% CI: -0.91 to 0.80D). DISCUSSION: The developed algorithm uses accessible inputs to provide an estimate of refractive development and may serve as guide for the eye care professional to help determine the individual best strategy for management of myopia.

The influence of action on perception spans different effectors.

Perception and action are fundamental processes that characterize our life and our possibility to modify the world around us. Several pieces of evidence have shown an intimate and reciprocal interaction between perception and action, leading us to believe that these processes rely on a common set of representations. The present review focuses on one particular aspect of this interaction: the influence of action on perception from a motor effector perspective during two phases, action planning and the phase following execution of the action. The movements performed by eyes, hands, and legs have a different impact on object and space perception; studies that use different approaches and paradigms have formed an interesting general picture that demonstrates the existence of an action effect on perception, before as well as after its execution. Although the mechanisms of this effect are still being debated, different studies have demonstrated that most of the time this effect pragmatically shapes and primes perception of relevant features of the object or environment which calls for action; at other times it improves our perception through motor experience and learning. Finally, a future perspective is provided, in which we suggest that these mechanisms can be exploited to increase trust in artificial intelligence systems that are able to interact with humans.

Nutritional Analysis of the Spanish Population: A New Approach Using Public Data on Consumption.

Official population consumption data are frequently used to characterize the diet of countries; however, this information may not always be representative of reality. This study analyses the food consumption of the Spanish population by reconstructing the whole food chain. The results have been compared with the data provided by the National Consumption Panel to which the food losses/waste reported in the literature along the distribution chain have been added. The difference between them allowed a new calculation of the estimated food consumption that was subjected to a dietary-nutritional analysis. Most of the foods were consumed more than those officially reported (range of 5-50%). The unhealthy ratios of consumed foods and recommended servings were: meat products (Rcr = 3.6), fruits and legumes (Rcr = 0.5), and nuts (Rcr = 0.14). Caloric intake surpasses needs. The results were consistent with the data on the prevalence of overweight and obesity in Spain, as well as with the prevalence of associated diseases. To make a judgment about the quality of a country's diet, it is necessary to have reliable data on food consumption, as well as energy and nutrient intake. This study encourages other authors to implement this method to verify and quantify the possible difference between official and real consumption data.

Horizontal target size perturbations during grasping movements are described by subsequent size perception and saccade amplitude.

Perception and action are essential in our day-to-day interactions with the environment. Despite the dual-stream theory of action and perception, it is now accepted that action and perception processes interact with each other. However, little is known about the impact of unpredicted changes of target size during grasping actions on perception. We assessed whether size perception and saccade amplitude were affected before and after grasping a target that changed its horizontal size during the action execution under the presence or absence of tactile feedback. We have tested twenty-one participants in 4 blocks of 30 trials. Blocks were divided into two experimental tactile feedback paradigms: tactile and non-tactile. Trials consisted of 3 sequential phases: pre-grasping size perception, grasping, and post-grasping size perception. During pre- and post-phases, participants executed a saccade towards a horizontal bar and performed a manual size estimation of the bar size. During grasping phase, participants were asked to execute a saccade towards the bar and to make a grasping action towards the screen. While grasping, 3 horizontal size perturbation conditions were applied: non-perturbation, shortening, and lengthening. 30% of the trials presented perturbation, meaning a symmetrically shortened or lengthened by 33% of the original size. Participants' hand and eye positions were assessed by a motion capture system and a mobile eye-tracker, respectively. After grasping, in both tactile and non-tactile feedback paradigms, size estimation was significantly reduced in lengthening (p = 0.002) and non-perturbation (p<0.001), whereas shortening did not induce significant adjustments (p = 0.86). After grasping, saccade amplitude became significantly longer in shortening (p<0.001) and significantly shorter in lengthening (p<0.001). Non-perturbation condition did not display adjustments (p = 0.95). Tactile feedback did not generate changes in the collected perceptual responses, but horizontal size perturbations did so, suggesting that all relevant target information used in the movement can be extracted from the post-action target perception.

Anal squamous cell carcinoma in HIV patients with HPV-16 condylomas: a serious complication in immunocompromised patients.

Human papillomavirus (HPV) infection is one of the most frequent sexually transmitted infections in the world, with great importance due to its oncogenic potential. Both the risk of infection and the development of neoplasia are increased in people with human immunodeficiency virus (HIV) infection, so HPV vaccination should be recommended in these patients.

LMS parameters, percentile, and Z-score growth curves for axial length in Chinese schoolchildren in Wuhan.

Understanding the ocular structural changes are fundamental to defining strategies for myopia prevention and management. This study aimed to establish age-gender specific normative LMS parameters for axial length to generate percentile and Z-score growth curves in a population of Chinese schoolchildren. A total of 14,760 individuals aged 6 to 15 years from Wuhan, central China, contributed to this study. The LMS method was used for the calculation of LMS parameters and the generation of percentile and Z-score growth curves for axial length. Growth curves derived from the LMS parameters were compared with those originally calculated. Axial elongation was age- and percentile-dependent. The highest elongation rate occurred at the 98th percentile in the range 6 to 9 years, being up to 1.46 mm in boys and 1.42 mm in girls. The largest differences between original and newly generated growth curves were detected at the 98th percentile at age 15; 0.78 mm (females) and 0.63 mm (males). Multinomial logistic regression and receiver operating characteristic analyses revealed Z-scores as a good predictor for estimating high myopia development. The axial length growth curves presented in this study provide a technically solid instrument that depicts the best description of physiological eye growth for Chinese schoolchildren aged 6 to 15 years.

Adherence to endoscopic surveillance for advanced lesions and colorectal cancer in inflammatory bowel disease: an AEG and GETECCU collaborative cohort study.

BACKGROUND AND AIMS: Patients with colonic inflammatory bowel disease (IBD) have a high risk of colorectal cancer (CRC). Current guidelines recommend endoscopic surveillance, yet epidemiological studies show poor compliance. The aims of our study were to analyse adherence to endoscopic surveillance, its impact on advanced colorectal lesions, and risk factors of non-adherence. METHODS: A retrospective multicentre study of IBD patients with criteria for CRC surveillance, diagnosed between 2005 and 2008 and followed up to 2020, was performed. Following European guidelines, patients were stratified into risk groups and adherence was considered when surveillance was performed according to the recommendations (±1 year). Cox-proportional regression analyses were used to compare the risk of lesions. p-values below 0.05 were considered significant. RESULTS: A total of 1031 patients (732 ulcerative colitis, 259 Crohn's disease and 40 indeterminate colitis; mean age of 36 ± 15 years) were recruited from 25 Spanish centres. Endoscopic screening was performed in 86% of cases. Adherence to guidelines was 27% (95% confidence interval, CI = 24-29). Advanced lesions and CRC were detected in 38 (4%) and 7 (0.7%) patients respectively. Adherence was associated with increased detection of advanced lesions (HR = 3.59; 95% CI = 1.3-10.1; p = 0.016). Risk of delay or non-performance of endoscopic follow-up was higher as risk groups increased (OR = 3.524; 95% CI = 2.462-5.044; p < 0.001 and OR = 4.291; 95%CI = 2.409-7.644; p < 0.001 for intermediate- and high- vs low-risk groups). CONCLUSIONS: Adherence to endoscopic surveillance allows earlier detection of advanced lesions but is low. Groups at higher risk of CRC are associated with lower adherence.

Longitudinal analysis of axial length growth in a German cohort of healthy children and adolescents.

PURPOSE: To generate continuous growth curves for axial length (AL) in German children. We hypothesise that percentile curves of AL can be used as a predictive measure of myopia. METHODS: In this longitudinal and cross-sectional LIFE Child Study, children's non-cycloplegic refraction data was collected using the Zeiss i.Profiler plus while AL was measured using the Haag-Streit Lenstar. Reference growth curves were estimated as a continuous non-parametric function of age. RESULTS: Data from 4511 visits of 1965 participants (1021 boys and 944 girls) between 3 and 18 years of age were analysed. For all ages and percentiles, the estimated AL was higher in boys than girls. AL differences between boys and girls were most pronounced in the 98th percentile at 3 years of age, being 0.93 mm longer eyes in boys. This difference decreased to 0.21 mm at 18 years of age. While the lower percentiles of AL reach their final value around age 13, the 50th percentile was still increasing by 0.05 mm per year until the end of the observation period. While, in general, children with longer eyes are more likely to develop myopia, this relationship is weaker between the ages of 5 and 8. CONCLUSION: The LIFE Child Study data provides European AL data. In both Germany and China, AL has comparable growth rates when the baseline ALs are compared as percentiles. Thus, percentile curves of AL can be used as a predictive measure for the likelihood of developing as well as the progression of myopia.

Accommodation responses following contrast adaptation.

The current study explored the effects of contrast adaptation on the accommodation response (AR), using low- and high-pass filtered video clips as stimuli. Ten young myopic (mean ± standard deviation: -2.91 ± 1.36D) and 10 near emmetropic subjects (-0.19 ± 0.14D) participated in the study. The AR was monitored under monocular viewing conditions using an eccentric infrared photorefractor. A 2-stage procedure was used: (1) the minimum spatial frequency content necessary to produce a proper individual AR; and (2) the AR was compared before and after adaptation to low-pass (s = -0.5), control (s = 0) and high-pass (s = +0.5) filtered videos. We found that (1) the average threshold Sinc-blur of both myopes and emmetropes necessary to evoke accommodation was (mean ± standard deviation) λ = 7.40 ± 4.05 cpd. Myopes required a higher Sinc blur (average, 10.00 ± 4.05 cpd) compared to emmetropes (average, 4.80 ± 1.60 cpd). (2) Adaptation to low-pass filtered videos increased the AR by 0.41 ± 0.33D in the myopic group and reduced it in the emmetropic group by 0.31 ± 0.25D. Adaptation to high pass-filtered videos induced similar changes in both refractive groups (an increase of 0.41 ± 0.40D and 0.46 ± 0.29D for myopes and emmetropes, respectively). Our measurements show that the human AR can be modified by spatial frequency selective contrast adaptation although these were short-term effects. The perhaps most striking finding was that adaptation to low pass filtered videos had opposite effects on the AR in emmetropes and myopes. It remains to be studied whether these differences were a consequence of myopia or a contributing factor in myopia development.

Multisensory Stimulation and EEG Recording Below the Hair-Line: A New Paradigm on Brain Computer Interfaces.

To test the feasibility of implementing multisensory (auditory and visual) stimulation in combination with electrodes placed on non-hair positions to design more efficient and comfortable Brain-computer interfaces (BCI). Fifteen volunteers participated in the experiments. They were stimulated by visual, auditory and multisensory stimuli set at 37, 38, 39 and 40Hz and at different phases (0°, 90°, 180° and 270°). The electroencephalogram (EEG) was measured from Oz, T7, T8, Tp9 and Tp10 positions. To evaluate the amplitude of the visual and auditory evoked potentials, the signal-to-noise ratio (SNR) was used and the accuracy of detection was calculated using canonical correlation analysis. Additionally, the volunteers were asked about the discomfort of each kind of stimulus. The multisensory stimulation allows for attaining higher SNR on every electrode. Non-hair (Tp9 and Tp10) positions attained SNR and accuracy similar to the ones obtained from occipital positions on visual stimulation. No significant difference was found on the discomfort produced by each kind of stimulation. The results demonstrated that multisensory stimulation can help in obtaining high amplitude steady-state evoked responses with a similar discomfort level. Then, it is possible to design a more efficient and comfortable hybrid-BCI based on multisensory stimulation and electrodes on non-hair positions. The current article proposes a new paradigm for hybrid-BCI based on steady-state evoked potentials measured from the area behind-the-ears and elicited by multisensory stimulation, thus, allowing subjects to achieve similar performance to the one achieved by visual-occipital BCI, but measuring the EEG on a more comfortable electrode location.

Assessment of high-frequency steady-state visual evoked potentials from below-the-hairline areas for a brain-computer interface based on Depth-of-Field.

BACKGROUND AND OBJECTIVE: Recently, a promising Brain-Computer Interface based on Steady-State Visual Evoked Potential (SSVEP-BCI) was proposed, which composed of two stimuli presented together in the center of the subject's field of view, but at different depth planes (Depth-of-Field setup). Thus, users were easily able to select one of them by shifting their eye focus. However, in that work, EEG signals were collected through electrodes placed on occipital and parietal regions (hair-covered areas), which demanded a long preparation time. Also, that work used low-frequency stimuli, which can produce visual fatigue and increase the risk of photosensitive epileptic seizures. In order to improve the practicality and visual comfort, this work proposes a BCI based on Depth-of-Field using the high-frequency SSVEP response measured from below-the-hairline areas (behind-the-ears). METHODS: Two high-frequency stimuli (31 Hz and 32 Hz) were used in a Depth-of-Field setup to study the SSVEP response from behind-the-ears (TP9 and TP10). Multivariate Spectral F-test (MSFT) method was used to verify the elicited response. Afterwards, a BCI was proposed to command a mobile robot in a virtual reality environment. The commands were recognized through Temporally Local Multivariate Synchronization Index (TMSI) method. RESULTS: The data analysis reveal that the focused stimuli elicit distinguishable SSVEP response when measured from hairless areas, in spite of the fact that the non-focused stimulus is also present in the field of view. Also, our BCI shows a satisfactory result, reaching average accuracy of 91.6% and Information Transfer Rate (ITR) of 5.3 bits/min. CONCLUSION: These findings contribute to the development of more safe and practical BCI.

Effect of spatial filtering on accommodation.

The purpose of this study was to develop and test a new method that uses natural images to investigate the influence of their spatial frequency content on the accommodation response (AR). Furthermore, the minimum spatial frequency content was determined that was necessary to induce an AR. Blur of the images was manipulated digitally in the Fourier domain by filtering with a Sinc function. Fourteen young subjects participated in the experiment. A 2-step procedure was used: (1) verifying that a high amount of Sinc-blur does not evoke accommodation, (2) increasing the width of the Sinc-blur filter in logarithmic steps until an AR was evoked. AR was continuously monitored using eccentric infrared photorefraction at 60 Hz sampling rate under monocular viewing conditions. Under condition (1), Sinc-blur of λ = 1 cpd did not evoke accommodation, while under condition (2) an average (mean ±â€¯standard deviation) Sinc-blur of λ = 5.57 ±â€¯4.67 cpd (median: 4 cpd, interquartile range: 2-7 cpd) evoked accommodation. Dividing the subjects into myopes and emmetropes revealed that the myopic group required higher amounts of λ (higher spatial frequencies) to stimulate their accommodation (mean λ = 9.33 ±â€¯4.99 cpd, for myopes; and mean λ = 2.75 ±â€¯0.97 cpd, for emmetropes). Our results support the notion that the AR is most effectively stimulated at mid-spatial frequencies and that myopes may require higher spatial frequencies to elicit a comparable AR.