Saccades, pupil response and blink abnormalities in Huntington's disease patients during free viewing.

OBJECTIVE: Video-based eye tracking was used to investigate saccade, pupil, and blink abnormalities among patients with Huntington's disease (HD) who watched sequences of short videos. HD, an autosomal dominant neurodegenerative disorder resulting from a CAG mutation on chromosome 4, produces motor and cognitive impairments including slow or irregular eye movements, which have been studied using structured tasks. METHODS: To explore how HD affects eye movements under instruction free conditions, we assessed 22 HD patients and their age matched controls in a 10-minute video-based free viewing task. RESULTS: Patients with HD experienced a significant reduction in saccade exploration rate following video clip transitions, an increase in pupil reactions to luminance changes after clip transitions, and a significant higher blink rate throughout the task compared to the control group. CONCLUSIONS: These results show that HD has a significant impact on how patients visually explore and respond to their environment under unconstrained and ecologically natural conditions. SIGNIFICANCE: Eye tracking in HD patients revealed saccadic, pupil, and blink abnormalities in early HD patients, suggestive of brain circuitry abnormalities that probably involve brain stem deficits. Further research should explore the impact of these changes on the quality of life of the patients affected by the disease.

Decrease in reaction time for volleyball athletes during saccadic eye movement task: A preliminary study with evoked potentials.

AIM: This preliminary study investigated the differences in event-related potential and reaction time under two groups (athletes vs. non-athletes). MATERIAL AND METHODS: The P300 was analyzed for Fz, Cz, and Pz electrodes in thirty-one healthy volunteers divided into two groups (volleyball athletes and non-athletes). In addition, the participants performed a saccadic eye movement task to measure reaction time. RESULTS: The EEG analysis showed that the athletes, in comparison to the no-athletes, have differences in the P300 in the frontal area (p = 0.021). In relation to reaction time, the results show lower reaction time for athletes (p = 0.001). CONCLUSIONS: The volleyball athletes may present a greater allocation of attention during the execution of the inhibition task, since they have a lower reaction time for responses when compared to non-athletes.

Vestibular evaluation with video head impulse test in pediatric cochlear implant patients.

BACKGROUND: The cochlear implant (CI) is effective for rehabilitating patients with severe to profound sensorineural hearing loss. However, its placement and use have been associated with various complications, such as those affecting the vestibular system. The objective of this study was to compare vestibular function using the video head impulse test (vHIT) in pediatric patients before and after CI placement. METHODS: A descriptive and retrospective study was conducted. The outcomes of 11 pediatric patients of both sexes with a history of profound hearing loss were evaluated. The results of vestibular-ocular reflex (VOR) gain, saccades, asymmetry, Pérez Rey (PR) index, and VOR/saccade ratio for both ears obtained by the vHIT test before and after CI placement were compared. RESULTS: Of the 11 patients evaluated, the VOR gain showed that 81.8% had normal function, 18.2% had hypofunction, and no patients had hyperfunction before implantation. No statistically significant differences were found when compared with post-implant off and post-implant on conditions (p > 0.05). The extracted variables, asymmetry, PR index, and the VOR/saccades ratio also showed no statistically significant differences between the pre- and post-implant conditions, whether off or on. CONCLUSIONS: The vestibular function of pediatric patients did not show significant changes before and after CI placement. The vHIT test is a valuable tool for assessing vestibular function and could be considered a criterion for surgical and rehabilitation decisions in patients undergoing CI placement.

INTRODUCCIÓN: El implante coclear es un dispositivo eficaz para la rehabilitación de pacientes con hipoacusia neurosensorial severa a profunda. Sin embargo, su colocación y uso se ha asociado a diversas complicaciones, entre ellas a nivel del sistema vestibular. El objetivo del presente estudio fue comparar la función vestibular mediante la prueba de videoimpulso cefálico (vHIT) de pacientes pediátricos antes y después de la colocación del implante coclear. MÉTODOS: Se llevó a cabo un estudio descriptivo y retrospectivo. Se evaluaron los resultados de 11 pacientes pediátricos de ambos sexos con antecedente de hipoacusia profunda. Se compararon los resultados de ganancia del VOR, sacadas, asimetría, índice PR así como la relación VOR/sacadas para ambos oídos obtenidos mediante la prueba vHIT antes y después de la colocación del implante coclear. RESULTADOS: De los 11 pacientes evaluados, la ganancia del VOR mostró que el 81.8% tenía normofunción, 18.2% hipofunción y ningún paciente hiperfunción antes del implante. Al compararlo con la ganancia post implante apagado y post implante encendido no se encontraron diferencias estadísticamente significativas (p > 0.05). Las variables sacadas, asimetría, índice PR así como la relación VOR/sacadas tampoco mostraron diferencias estadísticamente significativas entre las condiciones pre y pos implante ya sea apagado o encendido. CONCLUSIONES: La función vestibular de pacientes pediátricos no mostró cambios significativos previo y posterior a la colocación del implante coclear. La prueba vHIT es una herramienta útil que permite evaluar la función vestibular y que podría considerarse como criterio para tomar decisiones quirúrgicas en pacientes que se encuentran en protocolo para implante coclear.

Saccadic movements during an exploratory visual search task in patients with glaucomatous visual field loss.

PURPOSE: To evaluate the saccadic movements of patients with visual field loss due to primary open-angle glaucoma. METHODS: Thirteen patients with good visual acuity (0.2 logMAR or better) (seven patients with primary open-angle glaucoma 65 ± 13 years) and six controls (51 ± 6 years) yielded a comprehensive ophthalmological examination, including Humphrey Visual Field tests (SITA-Standard 24-2), and performed a monocular, exploratory digital visual search task that quantifies the duration for finding the number "4" on a random array of digits distributed on the screen. After individual adjustments of the angle and distance positioning, the screen was spatially matched with the 24-2 visual field, and divided into five areas for analysis. During the task, saccades were simultaneously recorded in the same eye with a video-based eye tracker. RESULTS: The patients with primary open-angle glaucoma showed a significantly higher number of saccades/screen (median ± interquartile range, 59.00 ± 29.00 vs. 32.50 ± 19.75 saccades (p=0.027) and visual search time per screen (38.50 ± 60.14 vs. 23.75 ± 8.90 seconds (p=0.035) than the controls did. Although the univariate analysis indicated a significant correlation with visual field mean deviation (coefficient=26.19 (p=0.02), only the visual search time/screen was significantly associated with the number of saccades/screen in the multivariate regression model (coefficient=0.55 (p<0.001). Overall, no significant correlation was observed between the sectorial number of saccades and the sensitivity of the five visual field areas. CONCLUSIONS: The patients with primary open-angle glaucoma show impaired search performance and showed a higher number of saccades needed to find stimuli when performing the exploratory visual task.

Differences between hemispheres and in saccade latency regarding volleyball athletes and non-athletes during saccadic eye movements: an analysis using EEG.

BACKGROUND: The saccadic eye movement is responsible for providing focus to a visual object of interest to the retina. In sports like volleyball, identifying relevant targets quickly is essential to a masterful performance. The training improves cortical regions underlying saccadic action, enabling more automated processing in athletes. OBJECTIVE: We investigated changes in the latency during the saccadic eye movement and the absolute theta power on the frontal and prefrontal cortices during the execution of the saccadic eye movement task in volleyball athletes and non-athletes. We hypothesized that the saccade latency and theta power would be lower due to training and perceptual-cognitive enhancement in volleyball players. METHODS: We recruited 30 healthy volunteers: 15 volleyball athletes (11 men and 4 women; mean age: 15.08 ± 1.06 years) and 15 non-athletes (5 men and 10 women; mean age: 18.00 ± 1.46 years). All tasks were performed simultaneously with electroencephalography signal recording. RESULTS: The latency of the saccadic eye movement presented a significant difference between the groups; a shorter time was observed among the athletes, associated with the players' superiority in terms of attention level. During the experiment, the athletes observed a decrease in absolute theta power compared to non-athletes on the electrodes of each frontal and prefrontal area. CONCLUSION: In the present study, we observed the behavior of reaction time and absolute theta power in athletes and non-athletes during a saccadic movement task. Our findings corroborate the premise of cognitive improvement, mainly due to the reduction of saccadic latency and lower beta power, validating the neural efficiency hypothesis.

ANTECEDENTES: O movimento ocular sacádico é responsável por dar foco a um objeto visual de interesse para a retina. Em esportes como o vôlei, identificar alvos relevantes o mais rápido possível é essencial para se ter um desempenho magistral. O treinamento melhora as regiões corticais subjacentes à ação sacádica, e permite um processamento mais automatizado em atletas. OBJETIVO: Investigamos as mudanças na latência durante o movimento ocular sacádico e a potência teta absoluta nos córtices frontal e pré-frontal durante a execução da tarefa de movimento ocular sacádico em atletas e não atletas de voleibol. Nossa hipótese é a de que a latência sacádica e a potência teta seriam menores em atletas devido ao treinamento e ao aprimoramento perceptivo-cognitivo em jogadores de voleibol. MéTODOS: Ao todo, 30 voluntários saudáveis foram recrutados para este estudo: 15 atletas de voleibol (11 homens e 4 mulheres; idade média: 15,08 ± 1,06 anos) e 15 não atletas (5 homens e 10 mulheres; idade média: 18,00 ± 1,46 anos). Todas as tarefas foram realizadas simultaneamente com o registro do sinal eletroencefalográfico. RESULTADOS: O resultado da latência do movimento ocular sacádico apresentou diferença significativa entre os grupos, sendo observado menor tempo entre os atletas, associado à superioridade dos jogadores em termos de nível de atenção. Durante o experimento, nos eletrodos de cada área frontal e pré-frontal, observou-se uma diminuição na potência teta absoluta nos atletas em comparação aos não atletas. CONCLUSãO: Neste estudo, observou-se o comportamento do tempo de reação e da potência teta absoluta em atletas e não atletas durante uma tarefa de movimento sacádico. Nossos achados corroboram a premissa de melhora cognitiva, principalmente pela redução da latência sacádica e menor potência beta, o que valida a hipótese de eficiência neural.

[Effects of postural control upon anti-saccade error rate in older people]. / Efectos del control postural en la tasa de error anti-sacádico en personas mayores.

BACKGROUND: The anti-saccadic (AS) error-rate is used to diagnose neurological disorders. The natural aging process could generate difficulty in carrying out parallel neural processes of conscious motor inhibition and eye movement. Therefore, if balance control is imposed on an elderly person in biped positions during an AS movement, an increase in the AS error-rate is expected. OBJECTIVE: To study the effects of postural control on the AS error-rate in older people. METHODS: An intra and intergroup comparison was made of AS error-rate in an experimental group of older people (PM) and another control group of young people (PJ). For this, blocks of AS and pro-saccadic movements (control) were used randomly in four different postures: (1)sitting (SENT), (2)standing normally (NORMAL), (3)feet together (REDUC), and (4)feet in line (TANDEM). RESULTS: The PM group, compared to the PJ group, showed a progressive increase in the AS error-rate from the sitting position to all standing positions, with the maximum AS error-rate in more complex vertical postures. In contrast, the PJ group did not present significative variability of this AS error-rate in all positions. CONCLUSIONS: It is confirmed that the aging process is associated with an increase in the AS error-rate. This study reveals for the first time a significant increase in the AS error-rate when control of body balance is required for PM, implying a decrease in the multiple processing capacity in PM for the execution of complex and parallel tasks.

Modelling the eye movements of dyslexic children during reading as a continuous time random walk.

The study of eye movements during reading is considered a valuable tool for understanding the underlying cognitive processes and for its ability to detect alterations that could be associated with neurocognitive deficiencies or visual conditions. During reading, the gaze moves from one position to the next on the text performing a saccade-fixation sequence. This dynamics resembles processes usually described as continuous time random walk, where the jumps are the saccadic movements and waiting times are the duration of fixations. The time between jumps (intersaccadic time) consists of stochastic waiting time and flight time, which is a function of the jump length (the amplitude of the saccade). This motivates the present proposal of a model of eye movements during reading in the framework of the intermittent random walk but considering the time between jumps as a combined stochastic-deterministic process. The parameters used in this model were obtained from records of eye movements of children with dyslexia and typically developed for children performing a reading task. The jump lengths arise from the characteristics of the selected text. The time required for the flights was obtained based on a previously proposed model. Synthetic signals were generated and compared with actual eye movement signals in a complexity-entropy plane.

Microsaccades are directed toward the midpoint between targets in a variably cued attention task.

Reliable, noninvasive biomarkers that reveal the internal state of a subject are an invaluable tool for neurological diagnoses. Small fixational eye movements, called microsaccades, are a candidate biomarker thought to reflect a subject's focus of attention [Z. M. Hafed, J. J. Clark, VisionRes. 42, 2533-2545 (2002); R. Engbert, R. Kliegl, VisionRes. 43, 1035-1045 (2003)]. The linkage between the direction of microsaccades and attention has mainly been demonstrated using explicit and unambiguous attentional cues. However, the natural world is seldom predictable and rarely provides unambiguous information. Thus, a useful biomarker must be robust to such changes in environmental statistics. To determine how well microsaccades reveal visual-spatial attention across behavioral contexts, we analyzed these fixational eye movements in monkeys performing a conventional change detection task. The task included two stimulus locations and variable cue validities across blocks of trials. Subjects were adept at the task, showing precise and graded modulations of visual attention for subtle target changes and performing better and faster when the cue was more reliable [J. P. Mayo, J. H. R. Maunsell, J. Neurosci. 36, 5353 (2016)]. However, over tens of thousands of microsaccades, we found no difference in microsaccade direction between cued locations when cue variability was high nor between hit and miss trials. Instead, microsaccades were made toward the midpoint of the two target locations, not toward individual targets. Our results suggest that the direction of microsaccades should be interpreted with caution and may not be a reliable measure of covert spatial attention in more complex viewing conditions.

Cortical maps as a fundamental neural substrate for visual representation.

Visual perception is the product of serial hierarchical processing, parallel processing, and remapping on a dynamic network involving several topographically organized cortical visual areas. Here, we will focus on the topographical organization of cortical areas and the different kinds of visual maps found in the primate brain. We will interpret our findings in light of a broader representational framework for perception. Based on neurophysiological data, our results do not support the notion that vision can be explained by a strict representational model, where the objective visual world is faithfully represented in our brain. On the contrary, we find strong evidence that vision is an active and constructive process from the very initial stages taking place in the eye and from the very initial stages of our development. A constructive interplay between perceptual and motor systems (e.g., during saccadic eye movements) is actively learnt from early infancy and ultimately provides our fluid stable visual perception of the world.

Ocular findings from otoneurological examinations in children with and without dyslexia: a systematic review with meta-analysis.

OBJECTIVE: To investigate ocular movements measures of vectoelectro-nystagmography and video-nystagmography in dyslexic children and compare with measures of typical children. METHODS: A systematic review of observational studies comparing the ocular movements differences between dyslexic and typical children with no publication date or language restriction. The literature survey included the bibliographic databases MEDLINE, ScienceDirect, Scopus, Web of Science, SciELO, Lilacs and CENTRAL. Gray literature databases were also searched, including: OpenGrey.eu, DissOnline.de, The New York Academy of Medicine and WorldCat. The meta-analysis was performed using software RevMan 5.3 (Cochran Collaboration). RESULTS: A total of 2375 articles were found of which 113 fell within the inclusion criteria. Among these, 52 were duplicates (found in more than one research source), and 45 articles were selected for reading in full. Thirteen (13) articles were included for analysis and discussion. Meta-analysis showed statistical differences between the two groups for the total number of saccades and duration of fixation. CONCLUSION: The study revealed that children with dyslexia have longer duration of fixation and fewer saccades during ocular movements on vectoelectro-nystagmography and video-nystagmography when compared to children without dyslexia.

Saccadic eye movement performance reduces visual manipulation influence and center of pressure displacements in older fallers.

This study examined changes in postural control and gaze performance of faller and non-faller older adults under conditions of visual tasks and optical flow manipulations. Fifteen older non-fallers (69.8 years, ± 3.2) and fifteen older fallers (71.1 years, ± 6.4) stood on a force platform inside a moving room wearing an eye tracker. Four tasks were performed: gaze fixation; predictable saccades; unpredictable saccades; and free-viewing. The stimuli appeared at a frequency of 1.1 Hz during conditions of predictable and unpredictable saccades. Sixteen trials were divided into two blocks. In the first block, the room remained stationary. In the second block, the room oscillated, without the participant's awareness, with a 0.6 cm amplitude and 0.2 Hz frequency. Results showed postural sway attenuation in older fallers during the saccadic tasks compared to gaze fixation and free-viewing tasks, in both stationary and moving room conditions. Both groups showed increased center of pressure (CoP) magnitude during the moving room condition and CoP displacements strongly coupled to the room's movement. The influence of the moving room on the postural sway was reduced during the saccadic tasks for both older groups. Older fallers exhibited higher variability compared to older non-fallers. Gaze behavior differences between groups were dependent on the goals of the visual tasks. Therefore, CoP displacements of older adults are reduced during saccadic tasks regardless of their falling history. However, postural and gaze performance of older fallers suggests increased deterioration of postural and oculomotor control which may be used as a predictor of fall risk.

Trunk and head displacements stabilized to perform both horizontal and vertical saccadic eye movements.

Vision is crucial for humans to interact with their surrounding environment, and postural sway is reduced to allow short eye movements. However, the extent of subtle changes in postural control for horizontal and vertical eye movements remains unclear. The goal of this study was to investigate the effects of vertical and horizontal eye movements on head and trunk control in young adults. Fifteen healthy adults (23.4 ± 4.7 years) stood upright in three conditions for 60 s: fixation, horizontal, and vertical guided eye movements. In fixation, participants had to fixate on a stationary target. In both the horizontal and vertical eye movements, the target was presented with a frequency of 0.5 Hz and a visual angle of 11°. Eye displacement was monitored using a SMI eye tracker (ETG2.0) and trunk and head sway were monitored using infrared markers (Optotrak 3020, NDI). The mean sway amplitude was lower in both directions for eye movements and lowest in the vertical direction compared to the fixation condition. The sway area was also lower in vertical eye movement than in the fixation condition. We also found that the sway reduction was greater at head than at trunk level. The median frequency sway in the anterior-posterior direction was higher in both eye movements than in fixation. Based upon these results, we suggest that to perform short eye movements, postural sway is more strongly controlled at the head level than at the trunk and in vertical eye movements than in horizontal movements.

Corrective Saccades in Unilateral and Bilateral Vestibular Hypofunction During Slow Rotation Expressed by Visually Enhanced VOR and VOR Suppression: Role of the Cerebellum.

In clinical practice, the head impulse test paradigm (HIMP) and the suppression head impulse paradigm (SHIMP) stimulate high-frequency head movements so that the visual system is temporarily suppressed. The two tests could also be useful tools for vestibular assessment at low frequencies: VVOR (visually enhanced vestibulo-ocular reflex) and VORS (vestibulo-ocular reflex suppression). The aim of this study is to analyze the eye movements typically found during VVOR and VORS testing in patients with unilateral and bilateral vestibular hypofunction. Twenty patients with unilateral vestibular hypofunction, three patients with bilateral vestibular hypofunction, and ten patients with normal vestibular function (control group) were analyzed through VVOR and VORS testing with an Otometrics ICS Impulse system. During the VVOR test, patients with unilateral vestibular hypofunction exhibited corrective saccades to the same direction of the nystagmus fast phase toward the healthy side when the head rotates toward the affected side, while patients with bilateral vestibular hypofunction exhibited corrective saccades to the opposite side of head movements to each side. During the VORS test, patients with unilateral vestibular hypofunction seem to exhibit larger corrective saccades to the healthy side when the head was moved to this side, while patients with bilateral vestibular hypofunction did not exhibit corrective saccades during head movements to either side. Our data suggest that the VVOR and VORS tests yield the same diagnostic information as the HIMP and SHIMP tests in unilateral and bilateral vestibular hypofunction, and can contribute to the diagnosis of a peripheral vestibular loss as well as the affected side.

Eye vergence responses in children with and without reading difficulties during a word detection task.

Vergence eye movements are movements of both eyes in opposite directions. Vergence is known to have a role in binocular vision. However recent studies link vergence eye movements also to attention and attention disorders. As attention may be involved in dyslexia, it is sensible to guess that the presence of reading difficulties can be associated with specific patterns in vergence responses. Data from school children performing a word-reading task have been analysed. In the task, children had to distinguish words from non-words (scrambled words or row of X's), while their eye positions were recorded. Our findings show that after stimulus presentation eyes briefly converge. These vergence responses depend on the stimulus type and age of the child, and are different for children with reading difficulties. Our findings support the idea of a role of attention in word reading and offer an explanation of altered attention in dyslexia.

Dorsolateral prefrontal cortex hyperactivity during inhibitory control in children with ADHD in the antisaccade task.

Children with ADHD show significant deficits in response inhibition. A leading hypothesis suggests prefrontal hypoactivation as a possible cause, though, there is conflicting evidence. We tested the hypoactivation hypothesis by analyzing the response inhibition process within the oculomotor system. Twenty-two children diagnosed with ADHD and twenty control (CTRL) children performed the antisaccade task while undergoing an fMRI study with concurrent eye tracking. This task included a preparatory stage that cued a prosaccade (toward a stimuli) or an antisaccade (away from a stimuli) without an actual presentation of a peripheral target. This allowed testing inhibitory control without the confounding activation from an actual response. The ADHD group showed longer reaction times and more antisaccade direction errors. While both groups showed activations in saccade network areas, the ADHD showed significant hyperactivation in the dorsolateral prefrontal cortex during the preparatory stage. No other areas in the saccade network had significant activation differences between groups. Further ADHD group analysis OFF and ON stimulant medication did not show drug-related activation differences. However, they showed a significant correlation between the difference in OFF/ON preparatory activation in the precuneus, and a decrease in the number of antisaccade errors. These results do not support the hypoactivity hypothesis as an inhibitory control deficit general explanation, but instead suggest less efficiency during the inhibitory period of the antisaccade task in children. Our findings contrast with previous results in ADHD adults showing decreased preparatory antisaccade activity, suggesting a significant age-dependent maturation effect associated to the inhibitory response in the oculomotor system.

Emotional faces modulate eye movement control on an antisaccade task.

The ability to modulate automatic responses, in order to favor voluntary actions is crucial for cognition and behavior, and this is particularly difficult when dealing with highly salient stimuli as emotional faces. The aim of this study was to evaluate the effects of angry faces on cortical activity during preparation of saccadic inhibition and voluntary reorientation of attention. Behavioral performance, eye movements and presaccadic event-related potentials were evaluated as 30 participants performed an antisaccadic task with neutral and angry faces presented in the peripheral visual field. Two components of the presaccadic activity were measured: positive presaccadic slope and spike potential. Results showed lower accuracy in the presence of angry faces than neutral ones. Saccade onset latency was longer for angry faces than for neutral ones on the prosaccadic trials, but the opposite result occurred on the antisaccadic trials. Finally, higher spike potential amplitudes were observed for the angry faces than the neutral ones. These results suggest that potentially threatening stimuli like angry facial expressions require greater effort to achieve inhibitory control and voluntary reorientation of attention.

Profile and neuropsychological differences in adolescent students with and without dyslexia / Perfil y diferencias neuropsicológicas en alumnos adolescentes con y sin dislexia

Abstract Dyslexia is a problem of increasing prevalence in school-age students. The latest experiences in the application of neuropsychology to education are interesting because they allow for the evaluation of different neuropsychological variables to obtain a better understanding of the learning processes of students in this population for specific subsequent interventions. The purpose of this study was to explore the following neuropsychological variables related to reading in adolescent students with and without dyslexia. The sample consisted of 60 students between 13 and 15 years of age, 30 with dyslexia and 30 without. The King Devick test was used to assess the saccadic eye movements, specifically the fast and automated denomination of digits; the Harris laterality test was used to evaluate functional laterality, and the ENFEN test for executive functions. The results revealed significant differences between the two groups. Students with dyslexia scored lower on the three neuropsychological skills assessed. These findings suggest that students with dyslexia may manifest poorer performance in those neuropsychological skills that are key to reader development.

Resumen La dislexia es un problema que cada vez afecta más al alumnado en edad escolar. Las últimas experiencias de aplicación de la neuropsicología al ámbito educativo resultan interesantes porque van a permitir evaluar distintas variables neuropsicológicas con el objeto de comprender mejor los procesos de aprendizaje del alumnado para plantear posteriormente intervenciones específicas en esta población. El propósito de este estudio fue explorar variables neuropsicológicas relacionadas con la lectura y escritura en estudiantes con y sin dislexia. La muestra estuvo compuesta por 60 estudiantes de entre 13 y 15 años, 30 con dislexia y treinta sin dislexia. La prueba King Devick fue utilizada para valorar los movimientos oculares sacádicos, la prueba de la lateralidad de Harris para evaluar la lateralidad y la prueba ENFEN para las funciones ejecutivas. Los resultados revelaron diferencias significativas entre los dos grupos. Los estudiantes con dislexia obtuvieron puntuaciones más bajas en las tres habilidades neuropsicológicas evaluadas. Estos hallazgos sugieren que los niños con dislexia podrían manifestar un peor desempeño en habilidades neuropsicológicas que son clave para el desarrollo lector y escritor.

Models for saccadic motion and postsaccadic oscillations.

In a recent letter [S. Bouzat et al., Phys. Rev. Lett. 120, 178101 (2018)10.1103/PhysRevLett.120.178101], a mathematical model for eyeball and pupil motion was developed allowing for the understanding of the postsaccadic oscillations (PSO) as inertial effects. The model assumes that the inner part of the iris, which defines the pupil, moves driven by inertial forces induced by the eyeball rotation, in addition to viscous and elastic forces. Among other achievements, the model correctly reproduces eye-tracking experiments concerning PSO profiles and their dependence on the saccade size. In this paper we propose various extensions of the mentioned model, we provide analytical solutions, and we perform an exhaustive analysis of the dynamics. In particular, we consider a more general time dependence for the eyeball velocity enabling the description of saccades with vanishing initial acceleration. Moreover, we give the analytical solution in terms of hypergeometric functions for the constant parameter version of the model and we provide particular expressions for some cases of interest. We also introduce a new version of the model with inhomogeneous viscosity that can improve the fitting of the experimental results. Our analysis of the solutions explores the dependence of the PSO profiles on the system parameters for varying saccade sizes. We show that the PSO emerge in critical-like ways when parameters such as the elasticity of the iris, the global eyeball velocity, or the saccade size vary. Moreover, we find that the PSO profiles with the first overshoot smaller than the second one, which are usually observed in experiments, can be associated to parameter regions close to criticality.

Determinación y cuantificación de subpoblaciones de linfocitos T y células natural killer en sangre periférica de individuos sanos por citometría de flujo / Detection and quantification of T-cell subpopulations and NK cells in peripheral blood from healthy individuals

Resumen Introducción: La determinación de las diferentes subpoblaciones de los linfocitos T en las diversas patologías y el monitoreo postratamiento ayuda a que el médico tome decisiones terapéuticas teniendo como referencia la cinética de los linfocitos T localizados en sangre periférica. Métodos: Se realizó la estandarización de un perfil de moléculas de superficie para la caracterización de subpoblaciones de linfocitos T: naïve, activados y de memoria, así como las células natural killer o asesinas naturales (CD3− CD56+) en sangre periférica de individuos clínicamente sanos. Resultados: Se identificaron las subpoblaciones de linfocitos: naïve (CD3+, CD4+ o CD8+, CD45RA+, CD62L+, CCR7+), activados (CD3+, CD4+ o CD8+, CD45RA+ o CD45RO+, CD69+ y/o CRTAM+), efectores (CD3+, CD4+ o CD8+, CD45RA+, CD62L−, CCR7−), de memoria central (CD3+, CD4+ o CD8+, CD45RO+, CD62L+, CCR7+) y de memoria efectora (CD3+, CD4+ o CD8+, CD45RO+, CD62L−, CCR7−) en las poblaciones de linfocitos T CD4+ y CD8+. Se integraron los datos obtenidos con estadística descriptiva (valores mínimos, valores máximos, media, mediana). Conclusiones: Este panel será de gran utilidad para monitorear pacientes en quienes se requiera valorar el estado inmunológico desde el punto de vista celular. Particularmente, puede apoyar en el seguimiento de los pacientes en los que se requiera evaluar la reconstitución inmunológica (componente celular de estirpe T).

Abstract Background: The knowledge of the participation of different subpopulations of T lymphocytes in various pathologies helps to make therapeutic decisions, having as reference the presence of the different subpopulations of the T lymphocytes associated with the disease. Methods: A profile standardization of surface molecules for the characterization of subpopulations of T cells was conducted: naïve, activated and memory, as well as natural killer (CD3− CD56+) cells in peripheral blood of clinically healthy individuals. Results: Naïve (CD3+, CD4+ or CD8+, CD45RA+, CD62L+, CCR7+), activated (CD3+, CD4+ or CD8+, CD45RA+ or CD45RO+, CD69+ and/or CRTAM+), effectors (CD3+, CD4+ o CD8+, CD45RA+, CD62L−, CCR7−), central memory (CD3+, CD4+ o CD8+, CD45RO+, CD62L+, CCR7+), memory effectors (CD3+, CD4+ or CD8+, CD62RO+, CD62L−, CCR7−) subpopulations were analyzed by flow cytometry. Descriptive statistics parameters were calculated (minimum values, maximum values, mean values, median). Conclusions: This panel can be very useful for monitoring patients in whom the immunological status from a cellular perspective is needed. Particularly, it can support the follow-up of patients who require an immunological reconstitution (T-cell component) evaluation.

Postural Control Complexity and Fatigue in Minimally Affected Individuals with Multiple Sclerosis.

This study investigated changes in postural control complexity in people with multiple sclerosis (PwMS) before and after a fatigue protocol. Thirteen minimally affected PwMS (1.53 ± 1.03- Expanded Disability Status Scale) and 12 non-MS controls. Postural test included quiet stance on a force platform under two visual conditions (saccades and fixation) before and after a fatigue protocol. Postural complexity was assessed through the multiscale entropy. A three-way ANOVA showed a main effect of fatigue in the medial-lateral direction (p <0.007), with fatigue protocol reducing postural complexity in both groups. No differences were found between groups or visual conditions. Minimally affected PwMS demonstrated similar postural complexity compared with non-MS controls under both visual tasks and showed similar decrements in postural complexity as a result of fatigue.