Abstracts of the last publications
Perez Zapata, L.; Solé-Puig, M.; Aznar-Casanova; J.A. and Hans Supèr (2014). Evidence for a role of corrective eye movements during gaze fixation in saccade planning. European Journal of Neuroscience, first online, 1–7. doi:10.1111/ejn.12777
Abstract:
In a three-dimensional (3D) world most saccades are made towards visual targets that are located at different distances. We previously demonstrated that gaze shifts within 3D space consist of two stages: a target saccade followed by a corrective saccade during gaze fixation that directs the eyes to the physical target location. We proposed that, by accurately positioning the eyes on the visual object, the visual system maintains an orderly representation of the visual world. In this study we used a double saccade experiment to assess the function of corrective saccades in humans. We found that, when a corrective eye movement occurred during fixation on the first target point, the direction of the second saccade towards the next target point was accurate. When a corrective saccade was absent, a directional error of the second target saccade was observed. This finding, which cannot be explained by current models of eye movement control, supports the idea of a two-step model in saccade programming. We suggest that the motor system sends a corollary discharge when programming a corrective saccade for maintaining an orderly representation of the visual world. In conclusion, our results indicate that corrective saccades have a role in programming target saccades within 3D space.
Keywords: corollary discharge, corrective eye movement, efferent copy, human, oculomotor, saccadic eye movement
Solé Puig M, Puigcerver L, Aznar-Casanova JA, Supèr H (2013) Difference in Visual Processing Assessed by Eye Vergence Movements. PLoS ONE 8(9): e72041. doi:10.1371/journal.pone.0072041
Abstract:
Orienting visual attention is closely linked to the oculomotor system. For example, a shift of attention is usually followed by a saccadic eye movement and can be revealed by micro saccades. Recently we reported a novel role of another type of eye movement, namely eye vergence, in orienting visual attention. Shifts in visuospatial attention are characterized by the response modulation to a selected target. However, unlike (micro-) saccades, eye vergence movements do not carry spatial information (except for depth) and are thus not specific to a particular visual location. To further understand the role of eye vergence in visual attention, we tested subjects with different perceptual styles.
Perceptual style refers to the characteristic way individuals perceive environmental stimuli, and is characterized by a spatial difference (local vs. global) in perceptual processing. We tested field independent (local; FI) and field dependent (global; FD) observers in a cue/no-cue task and a matching task. We found that FI observers responded faster and had stronger modulation in eye vergence in both tasks than FD subjects. The results may suggest that eye vergence modulation may relate to the trade-off between the size of spatial region covered by attention and the processing efficiency of sensory information. Alternatively, vergence modulation may have a role in the switch in cortical state to prepare the visual system for new incoming sensory Information. In conclusion, vergence eye movements may be added to the growing list of functions of fixational eye movements in visual perception. However, further studies are needed to elucidate its role.
Quevedo, L.; Aznar-Casanova, J.A; Merindano, D.; Cardona, G. and Solé-Fortó, J. (2012). A novel computer software for the evaluation of dynamic visual acuity. Journal of Optometry, http://dx.doi.org/10.1016/j.optom.2012.05.003
Abstract:
Purpose: Dynamic visual acuity (DVA) is defined as the ability to discriminate fine details in a moving target. Albeit a growing interest in DVA, there is a lack of standardized, validated instrumentation and procedures for the assessment of this visual function parameter. The aim of the present study was to analyze qualitative construct validity and test---retest reliability of a novel, computer-assisted instrument (DinVA 3.0) for the measurement of DVA.
Methods: Two different experiments are presented, involving the participation of 33 subjects. The first experiment aimed at testing qualitative construct validity of the DinVA 3.0 by comparing the outcome of a series of trials consisting in different speeds, contrasts and trajectories of the target stimuli with those reported in the literature. The second experiment assessed test---retest reliability by repeating a series of trials at three different time intervals, at maximum target stimuli contrast and either high or low speed configurations.
Results: The results of the first experiment gave support to the qualitative construct validity of DinVA 3.0, as the DVA scores were found to be modulated by the speed of the moving target (high speeds yielded lower DVA), contrast (high contrast resulted in better DVA) and trajectory (DVA was better at horizontal rather than oblique trajectories). Test---retest reliability was found to be good, with a small insignificant trend towards improvement with learning.
Keywords: Dynamic visual acuity; Ocular movements; Sports vision; Visual function.
Solé Puig M, Pérez Zapata L, Aznar-Casanova JA, Supèr H (2013) A Role of Eye Vergence in Covert Attention. PLoS ONE 8(1): e52955. doi: 10.1371/journal.pone. 0052955.
Abstract:
Covert spatial attention produces biases in perceptual and neural responses in the absence of overt orienting movements. The neural mechanism that gives rise to these effects is poorly understood. Here we report the relation between Fixational Eye movements, namely eye vergence, and covert attention. Visual stimuli modulate the angle of eye vergence as a function of their ability to capture attention. This illustrates the relation between eye vergence and bottom-up attention. In visual and auditory cue/no-cue paradigms, the angle of vergence is greater in the cue condition than in the no-cue condition. This shows a top-down attention component. In conclusion, observations reveal a close link between covert attention and modulation in eye vergence during eye fixation. Our study suggests a basis for the use of eye vergence as a tool for measuring attention and may provide new insights into attention and perceptual disorders
Keywords: Dynamic visual acuity, cognitive skills, ocular movements, performance in sports, sports vision.
Amador Campos, JA; Aznar Casanova, JA; Moreno Sánchez, M.; Medina, A.; Ortiz Guerra, JJ (2013). Psychometric Properties of a Test for ADHD Based on Binocular Rivalry. The Spanish Journal of Psychology, 16, (e-20) pag. 1-8.
Abstract:
The psychometric properties of a Binocular Rivalry (BR)-based test on a group of 159 participants (57 with attention deficit hyperactivity disorder, ADHD) aged between 6 and 15 years are presented. Two factors, which explained 56.82% of the variance, were obtained by exploratory factor analysis: (a) Alternations and Duration of exclusive dominances, and (b) Decision time. Reliability was excellent (Cronbach’s a = .834 and .884). The ADHD group showed fewer alternations and longer duration of dominances and decision time than the control group. Correlations between measures of BR, IQ, working memory, and processing speed of the WISC-IV, and ADHD symptoms, assessed by parents and teachers, ranged between low and medium.
Keywords: attention deficit hyperactivity disorder, visual attention, automatic inhibition, binocular rivalry, psychometric profiles.
Aznar Casanova, J.A.; Amador Campos, J.A.; Sanchez, M. & Supèr H. (2013). Onset time of binocular rivalry and duration of inter-dominance periods as psychophysical markers of ADHD. Perception, 42(1): 16-27.
Abstract:
Abstract. Attention deficit hyperactivity disorder (ADHD) is one of the main neurobiological disorders in young children. Despite its prevalence, current diagnosis is debated. In this study we tested whether measures of binocular rivalry (BR) can contribute to the diagnosis of ADHD. BR is a phenomenon that is produced when two different images are presented to the two eyes simultaneously. Under these conditions the image presented to one eye competes with that presented to the other eye in seeking to achieve perceptual dominance. This competition is resolved through the activation of a given percept coupled with the suppression of the percept that had predominated until that point. We assume that the difficulty with inhibiting responses of ADHD children also affects their ability to inhibit the dominant image in a BR context. We analyzed the time to rivalry onset and the inter-dominance periods as measures of the temporal cost of resolving how long it takes for the brain to select (or suppress) one percept over the other. Our results show that the time to onset of rivalry (the first dominance) was longer in the clinical groups (ADHD-C and ADHD-I) than in the control group. As regards the interdominance periods, these were longer in the ADHD-C group than among controls, with the shortest period corresponding to the ADHD-I group. This study shows that BR can be used as a tool to develop a behavioral indicator of ADHD.
Keywords: attention deficit hyperactivity disorder (ADHD), binocular rivalry, inhibition mechanism, suppression/fusion mechanism, visual attention
Amador Campos, J.A.; Aznar Casanova, J.A.; Ortíz, J.J.; Moreno, M. & Medina, A. (2013). Assessing Attention Deficit by Binocular Rivalry. Journal of Attention Disorders, Journal of Attention Disorders, 1087054713482686, first published on April 8, 2013 as doi:10.1177/1087054713482686
Abstract:
Objective: To determine whether the frequency and duration of the periods of suppression of a percept in a binocular rivalry (BR) task can be used to distinguish between participants with ADHD and controls.
Method: A total of 122 participants (6-15 years) were assigned to three groups: ADHD-Combined (ADHD-C), ADHD-Predominantly Inattentive (ADHD-I), and controls. They each performed a BR task and two measures were recorded: alternation rate and duration of exclusive dominance periods.
Results: ADHD-C group presented fewer alternations and showed greater variability than did the control group; results for the ADHD-I group being intermediate between the two. The duration of dominance periods showed a differential profile: In control group, it remained stable over time, whereas in the clinical groups, it decreased logarithmically as the task progressed.
Conclusion: The differences between groups in relation to the BR indicators can be attributed to the activity of involuntary inhibition. (J. of Att. Dis. 2013; XX(X) 1-XX).
Keywords: attention deficit hyperactivity disorder, visual attention, binocular rivalry, automatic inhibition, eye movement
Pérez Zapata, L., Aznar-Casanova, J.A., Supèr, H., (2013). Two stages of programming eye gaze shifts in 3-D space, Vision Research, 86: 15-26. doi:
http://dx.doi.org/10.1016/j.visres.2013.04.005
Abstract:
Accurate saccadic and vergence eye movements towards selected visual targets are fundamental to perceive the 3-D environment. Despite this importance, shifts in eye gaze are not always perfect given that they are frequently followed by small corrective eye movements. The oculomotor system receives distinct information from various visual cues that may cause incongruity in the planning of a gaze shift. To test this idea, we analyzed eye movements in humans performing a saccade task in a 3-D setting. We show that saccades and vergence movements towards peripheral targets are guided by monocular (perceptual) cues. Approximately 200 ms after the start of fixation at the perceived target, a fixational saccade corrected the eye positions to the physical target location. Our findings suggest that shifts in eye gaze occur in two phases; a large eye movement toward the perceived target location followed by a corrective saccade that directs the eyes to the physical target location
Aznar-Casanova; J.A. y Moreno-Sánchez, M. (2011). "Neurocomputacion en el Sistema Visual Humano". Editorial Académica Española (LAP LAMBERT Academic Publishing GmbH & Co. KG.) ISBN 978-3-8443-3879-9.
Descipción:
Esta monografía representa el enfoque de la Neurociencia Computacional, que trata de integrar de modo coherente, en un modelo explicativo, los hallazgos convergentes provenientes de la Neurofisiología, la Psicofísica y la Inteligencia Artificial (aplicada a la visión), procurando mantener la plausibilidad biológica. Es decir, que el modelo sea una explicación cabal de la visión en los sistemas visuales de los seres vivos y no sólo una serie de algoritmos computacionales que pretenden como objetivo lograr la máxima eficiencia en el procesamiento de información icónica.
Probablemente, en las especies vivas, a lo largo de la evolución y mediante ese potente mecanismo que es la selección natural, se han ensayado diferentes sistemas de procesamiento visual, por lo que, a través de la escala filogenética, los sistemas visuales han experimentado un progresivo refinamiento de todos sus sistemas sensoriales a lo largo de grandes periodos temporales. Quizá, por ello, el algoritmo mas eficiente sea el biológico sometido al test de la vida mediante la lucha por la supervivencia de las especies.
Desde el enfoque neurocomputacional, aquí adoptado, se defiende la tesis de David Marr, según la cual si algún aspecto dl procesamiento visual puede explicarse mediante procesamiento de abajo-a-arriba, ó de bajo nivel, no hay por qué apelar al procesamiento guiado conceptualmente, ó de alto nivel. En otras palabras, que los conocimientos previamente adquiridos a través de nuestra experiencia con el mundo apenas son utilizados en las primeras etapas del procesamiento visual. Y ello implica que el cerebro visual debe tener una estructura modular, a saber, que las funciones visuales se hallan repartidas en módulos cerebrales, independientes unos de otros, operando en paralelo. Pero también, implica que la imagen (tal como suele entenderse este concepto) desaparece una vez que la información que han captado las células foto-receptoras de la retina empaquetan, en el haz de fibras del nervio óptico (axones de la células ganglionares), la distribución espaciotemporal de la energía luminosa, la cual contiene jugosa información de lo que hay ahí fuera, en el mundo exterior. A partir de su salida por el punto ciego, la tasa de impulsos bio-eléctricos por unidad de tiempo recodifica, en el dominio frecuencial, la información que llevaba la imagen, sin pérdida de detalles. El procesamiento en este dominio es mucho más rápido que el que puede ocurrir en el dominio espacial y, además, facilita el principal trabajo del sistema visual: el filtrado de detalles que distribuirán la información en múltiples escalas y resoluciones espaciales que operan a modo de lente zoom. Así, diferentes representaciones espectrales representan la información de la imagen, ya sea atenuando o excluyendo cierta información “irrelevante” para el perceptor”, ya sea realzando (bordes, contrastes, etc.) o rellenando (filling in) información de la imagen. No obstante, estas representaciones visuales multiescala, no trasparentes para el que percibe, son susceptibles de ser trasformadas, de nuevo, al dominio espacial, del cual somos conscientes. Así, a partir de la comprensión de las primeras etapas de la visión, se pone de manifiesto la idea original de D. Marr de que la visión es, esencialmente calculo, operaciones aplicadas a representaciones, que transforman sucesivamente la imagen que captó la retina, es decir: neuro-computación. Sin olvidar, que en el llamado ‘procesamiento visual tardío’ se añadirá un plus de información a la generada en la etapa de procesamiento inicial o temprano, también referida como ‘etapa de bajo nivel’.
Aznar-Casanova, J.A.; Keil, S.K.; Moreno, M. and Supèr, H. (2011). Differential intrinsic bias of the 3-D perceptual environment and its role in shape constancy. Experimental Brain Research, 215(1): 35-43.
Abstract:
In a three-dimensional (3-D) environment, sensory information is projected on a 2-D retina with the consequence that the visual system needs space information for accurately reconstructing the visual world. However, the 3-D environment is not accurately represented in the brain; in particular, the perception of distances in depth is imprecise. It has been argued that the visual system has an intrinsic bias of visual space where targets located on the ground floor are perceived on an implicit elevated surface. We studied how such an intrinsic bias of visual space affects shape constancy. We found that the projected shape of a semicircle can be explained taking into account a differential implicit slant surface. The depth/width ratio, which is a measure for the shape of the stimulus, is overestimated for angular declination smaller than *60 , while it is underestimated for larger angular declinations. Our results are important for explaining shape constancy and may be important for understanding some perceptual illusions.
Keywords: Visual space; Perceptual space; Shape constancy; Geometrical slant; Object recognition.
Torrents, A.; Lupón, N.; Cardona, G. and Aznar-Casanova; J.A. (in 2011). Visual mechanisms governing the perception of auto-stereograms. Journal of Clinical and Experimental Optometry, Article first published online : 24 OCT 2011, DOI: 10.1111/j.1444-0938.2011.00664.x
Abstract:
BACKGROUND
Single Image Random Dot Stereograms (SIRDS) have been employed to study diverse visual parameters and skills. The aim of this study was to identify the main optometric factors involved in the perception of SIRDS, as well as to obtain a discriminant model to categorize our participants in terms of their skill in perceiving SIRDS.
METHODS
Response time was determined in order to assess the ability of a total of 69 participants to perceive the hidden 3D shape in an auto-stereogram presented under controlled conditions, whereupon three skill level groups were defined. The same participants were administered a battery of optometric tests to evaluate various aspects of accommodation and convergence, as well as stereopsis and phoria. Linear discriminant analysis, which served to examine the relationship between response times and the evaluated visual parameters and skills, provided a set of discriminant functions (or model), thus allowing for the categorization of participants according to their skill to perceive SIRDS.
RESULTS
Two discriminant functions were obtained, which allowed for an overall predictive accuracy of 66.67% (p = 0.024), with a higher predictive accuracy for groups 1 (78.26%) and 2 (75.86%) than for group 3 (35.29%). Stereoacuity, negative relative convergence, phoria at near and, to a lesser extent, AC/A ratio were found to be the most relevant discriminant variables, although between-group statistically significant differences were only disclosed for stereoacuity (p = 0.001) and negative relative convergence (p = 0.003).
CONCLUSION
The ability to perceive SIRDS was found to be related to many visual parameters and skills, including, but not limited to, stereoacuity and negative relative convergence. However, it is uncertain whether SIRDS may be considered a useful tool in clinical practice.
Keywords: Accommodation and Convergence; Auto-stereogram; Binocular vision; SIRDS (Single Image Random Dot Stereogram); Stereoacuity.
Torrents, A.; Aznar-Casanova, J.A. and Cardona, G. (2011). The influence of background on the precision of 3D depth judgment tasks in a real environment. Perceptual and Motor Skills, 113 (3): 793-802.
Abstract:
Nowadays, little is known about the effect of curved backgrounds against which the target stimulus is presented on precision in stereoacuity. One experiment was conducted in order to analyze the influence of stimulus orientation and 3D background configuration on stereoscopic vision. Participants were instructed to perform 3D visual alignment tasks on a modified version of the Howard-Dolman apparatus, whereupon precision in depth perception for different curved backgrounds (flat, black, concave and convex) was evaluated. In addition, we examined the influence of stimulus orientation (0, 45 and 90 degrees) on precision. Our findings revealed an underestimation in the perceived depth in all background configurations, disclosing highest and lowest precision outcomes for convex and concave backgrounds, respectively. In addition, a statistically significant interaction of background and orientation was encountered. It may be concluded that, in a real environment, background local depth cues are integrated with target stimuli to contribute to depth perception.
Keywords: Depth perception; Figure-Background relationship; Stereoacuity; Visual Psychophysics; Perception of the orientation.
Quevedo, Ll.; Aznar-Casanova, J.A.; Merindano, D. Solé, J. and Cardona, G. (2011). Comparative study of dynamic visual acuity between elite and sub-elite water-polo players and sedentary students. Research Quarterly for Exercise and Sport (USA), 82 (4):644-651.
Abstract:
In this study, we examined differences in dynamic visual acuity between elite and subelite water polo players and sedentary students. To measure dynamic visual acuity binocularly, we asked participants to indicate the orientation of a broken ring, similar to the Landolt C, which increased in size as it moved across a computer screen. Two different speeds, three possible trajectories, and two different levels of contrast were evaluated. There were statistically significant differences between elite players and sedentary for each combination of speed, contrast, and trajectory. Elite players achieved better dynamic visual acuity scores, and results also improved for some combinations of speed, contrast, and trajectory. Comparison between elite and subelite groups failed to reveal any difference.
Keywords: Dynamic visual acuity, cognitive skills, ocular movements, performance in sports, sports vision.
Aznar-Casanova, J.A.; Torro-Alves, N. and Fukusima, S.S. (2010). How much older do you get when a wrinkle appears on your face? Modifying age estimates by number of wrinkles. Aging, Neuropsychology and Cognition. 14, 2-16.
Abstract:
The present study investigated the influence of wrinkles on facial age judgments. In Experiment 1, preadolescents, young adults, and middle-aged adults made categorical age judgments for male and female faces. The qualitative (type of wrinkle) and quantitative (density of wrinkles and depth of furrows) contributions of wrinkles were analyzed. Results indicated that the greater the number of wrinkles and the depth of furrows, the older a face was rated. The roles of the gender of the face and the age of the participants were discussed. In Experiment 2, participants performed relative age judgments by comparing pairs of faces. Results revealed that the number of wrinkles had more influence on the perceived facial age than the type of wrinkle. A MDS analysis showed the main dimensions on which participants based their judgments, namely, the number of wrinkles and the depth of furrows. We conclude that the quantitative component is more likely to increase perceived facial age. Nevertheless, other variables, such as the gender of the face and the age of the participants, also seem to be involved in the age estimation process.
Keywords: Age estimates; Face perception; Psychophysics; Visual perception; Multidimensional scaling.
Quevedo, L. y Aznar-Casanova, JA., Merindano, D. y Solé, J. (2010). Una tarea para evaluar la Agudeza Visual Dinámica y una valoración de la estabilidad de sus mediciones. Psicológica, 31, 109-128.
Abstract:
Apenas existen instrumentos de medición adecuados de la capacidad para discriminar estímulos en movimiento, cuya aplicación resulte fácil y cuyas valoraciones sean estables a través del tiempo. También se constata la ausencia de un paradigma de evaluación que se muestre sensible ante aquellos factores que, en estudios previos, han sido relacionados con la visión dinámica. En consecuencia, nos proponemos como objetivo diseñar una tarea que permita la valoración de la agudeza visual dinámica (AVD), definida como la capacidad de discriminar detalles en condiciones de movimiento relativo entre sujeto y objeto. Para ello, hemos realizado dos estudios psicofísicos. El primero muestra que la AVD resulta modulada por tres factores: velocidad, contraste y trayectoria del estímulo móvil, interaccionando significativamente los dos primeros. En el segundo estudio, hemos averiguado la correlación entre la AVD obtenida por los sujetos en tres momentos separados, al menos, una semana (t1 y t2) y entre, al menos, dos semanas (t2 y t3). Estas oscilaron entre 0,78-0,92, para una velocidad de 14,1º/seg. y entre 0,72-0,85 para una velocidad de 1,4º/seg. Finalmente, comparamos las valoraciones de AVD en esos tres momentos, no encontrando diferencias significativas en el factor temporal. Concluimos que, nuestra tarea constituye una herramienta objetiva, y de fácil aplicación tanto clínica como experimental, muy útil para valorar la AVD.
Keywords: Percepción del movimiento, Agudeza visual dinámica, Percepción de la velocidad, Psicofísica visual.
Alves, N. T., Aznar-Casanova, J. A. and Fukusima, S. S.(2009). Patterns of brain asymmetry in the perception of positive and negative facial expressions. Laterality: Asymmetries of Body, Brain and Cognition,14:3,256 — 272
Abstract:
The divided visual field technique was used to investigate the pattern of brain asymmetry in the perception of positive/approach and negative/withdrawal facial expressions. A total of 80 undergraduate students (65 female, 15 male) were distributed in five experimental groups in order to investigate separately the perception of expressions of happiness, surprise, fear, sadness, and the neutral face. In each trial a target and a distractor expression were presented simultaneously in a computer screen for 150 ms and participants had to determine the side (left or
right) on which the target expression was presented. Results indicated that expressions of happiness and fear were identified faster when presented in the left visual field, suggesting an advantage of the right hemisphere in the perception of these expressions. Fewer judgement errors and faster reaction times were also observed for the matching condition in which emotional faces were presented in the left visual field and neutral faces in the right visual field. Other results indicated that positive expressions (happiness and surprise) were perceived faster and more accurately than negative ones (sadness and fear). Main results tend to support the right hemisphere hypothesis, which predicts a better performance of the right hemisphere to perceive emotions, as opposed to the approachwithdrawal hypothesis.
Keywords: Visual percepción; Hemispheric asymmetry; Facial expressions; Emotion from faces; Laterality; Approachwithdrawal hypothesis.
Aznar-Casanova,J.A.; Da Silva, J.A.; Ribeiro-Filho, N.P. y Santillán, J.E. (2009). ¿Es el espacio visualmente percibido un espacio métrico? Estudios de Psicología, 30 (3), 345-371
Abstract:
The study addresses several questions about measuring visually perceived space. Special attention is paid to measuring perceived egocentric distance (from observer to object) and perceived exocentric distance (between objects or parts of the same object). In addition, we briefly review theories, nature of depth cues, types of perceived distance information, and the environments in which distances are estimated. From the latter we conclude that the relationship between perceived and physical distance does not reflect just a simple geometrical transformation, but rather depends on (i) the environment in which subjective distance estimates were made, and (ii) the specific combination of depth cues available in this environment.
Keywords: Depth perception, visual space, spatial vision, distance perception, visual psychophysics, geometry of visual space.
Nuñez-Peña, M.I. and Aznar-Casanova, J.A. 2009). Mental rotation of mirrored letters: Evidence from event-related brain potentials. Brain and Cognition, 69(180-187).
Abstract:
Event-related brain potentials (ERPs) were recorded while participants (n = 13) were presented with mirrored and normal letters at different orientations and were asked to make mirror-normal letter discriminations. As it has been suggested that a mental rotation out of the plane might be necessary to decide on mirrored letters, we wanted to determine whether this rotation occurs after the plane rotation in mirror rotated letters. The results showed that mirrored letters in the upright position elicited a negative-going waveform over the right hemisphere in the 400–500 ms window. A similar negativity was also present in mirrored letters at 30, 60, and 90, but in these cases it was delayed. Moreover, the well-known orientation effect on the amplitude of the rotation-related negativity was also found, although it was more evident for normal than for mirrored letters. These results indicate that the processing of mirrored letters differs from that of normal letters, and suggest that a rotation out of the plane after the plane rotation may be involved in the processing of mirror rotated letters.
Keywords: Event-related brain potentials; Mental rotation; Cognition; Rotation-related negativity; Dynamic rotation; Perceived rotation.
Núñez-Peña, M. I. y Aznar-Casanova, J. A. (2009) Rotación mental: Cómo la mente rota las imágenes hasta colocarlas en su posición normal. Ciencia Cognitiva: Revista Electrónica de Divulgación, 3 (2), 58-61.
Abstract:
Algunas investigaciones han demostrado que cuando se nos presenta un objeto rotado lo giramos mentalmente hasta colocarlo en su posición habitual. En nuestro laboratorio hemos comprobado que si este objeto es una letra que se presenta en su versión simétrica (su imagen en un espejo), primero la rotamos mentalmente hasta colocarla en posición vertical, y luego, la volvemos a rotar fuera del plano para colocarla en su posición normal. Los resultados de este experimento pueden ser útiles no sólo para incrementar nuestro conocimiento sobre el proceso de rotación mental, sino también para favorecer una mayor comprensión del origen de los errores de escritura de los pacientes con dislexia, un trastorno en el que se confunde la escritura de letras simétricas como la ‘p’ y la ‘q’.
Keywords: Event-related brain potentials; Mental rotation; Cognition; Rotation-related negativity; Dynamic rotation; Perceived rotation
Aznar-Casanova, J.A.; Matsushima, E.H.; Pérez-Zapata, L.; Ribeiro-Filh0, N.P. and Da Silva, J.A. (2008). Interaction between egocentric and exocentric frames of reference as assessed by perceptual constancy parameters. Cognitive Studies, 15 (1), 1-16.
Abstract:
Distance from a stimulus, stimulus size and orientation with respect to the observer are relevant metric properties of visual space. However, whether and how these metrics are related to each other is not well known. Some studies have shown that estimates of egocentric distances are usually more accurate than judgments of exocentric distances, suggesting that there is dissociation between ‘localization’ judgments and ‘size’ judgments. Other investigations have revealed that the orientation of the stimulus influences the accuracy of size estimations. To better understand the relationships between these metric properties of visual space, we conducted an experiment to compare size perception as a function of orientation from viewer egocentric and exocentric frames of reference (FoR). Observers were instructed to draw two circles on a screen by clicking with a mouse when the screen was positioned on either the frontoparallel plane or the ground plane. From an egocentric FoR, egocentric distance and direction were processed asymmetrically, as knowledge of the particular combination of both size and orientation was always needed to compute visual direction. However, in terms of the accuracy of size estimates (S0/S) from an exocentric FoR, size and orientation were independent for all conditions. Therefore, the orientation did not need to be computed in order to compute the size. Regarding exocentric direction or orientation (α0/α), size and orientation were only dependent when the two points were presented successively. In conclusion, these findings suggest that orientation and distance always interact and that distance, visual direction or orientation require an egocentric cue.
Keywords: Metrics of visual space, exocentric distances and orientations, frames of reference, depth perception, binocular vision.
Aznar-Casanova, J.A.; Matsushima, E.H.; Da Silva, J.A. and Ribeiro-Filho, N.P. (2008). Can exocentric direction be dissociated from its exocentric distance in virtual environments? Perception and Psychophysics, 70(3), 541-550.
Abstract:
We conducted two psychophysical experiments to investigate the relationship between processing mechanisms for exocentric distance and direction. In the first experiment, the task was to discriminate exocentric distances. In the second one, the task was to discriminate exocentric directions. The individual effects of distance and direction on each task were dissociated by analyzing their corresponding psychophysical functions. Under stereoscopicviewing conditions, distance judgments of exocentric intervals were not affected by exocentric direction. However, direction judgments were influenced by the distance between the pair of stimuli. Therefore, the mechanism processing exocentric direction is dependent on exocentric distance, but the mechanism processing exocentric distance does not require exocentric direction measures. As a result, we suggest that exocentric distance and direction are hierarchically processed, with distance preceding direction. Alternatively, and more probably, a necessary condition for pprocessing the exocentric direction between two stimuli may be to know the location of each of them.
Keywords: Visual psychophysics; binocular vision; depth perception; distance perception; orientation perception.
Aznar-Casanova, J.A.; Torrents, A. and Alves, N. T. (2008). The role of the vertical disparities in the Oblique Effect. Psychology & Neuroscience, 1(2), 85-98.
Abstract:
A great deal of studies using different visual tasks (e.g., Vernier acuity tasks, tilt illusion, crowding, etc) have revealed that our perception is strongly influenced by the orientation of the stimulus. Most studies have investigated visual acuity in two-dimensional visual spaces (2D) but little is known about the effect of line orientation in depth perception (3D). In one experiment, Vernier Acuity (VA) in frontoparallel (2D) and medial (3D) planes was investigated. We used a virtual reality setup inducing inter-ocular disparities to simulate a 3D visual space, and a common computer screen to present stimuli in the frontal plane. In the experiment, by using the method of constant stimuli, the observer compared VA in the 2D and 3D visual spaces as a function of the stimulus orientation. Results showed that only judgments in the 3D condition were affected by the well-known ‘oblique effect’, and some impairment in stereoacuity (lines in depth plane) in comparison to 2D acuity (lines in frontal plane) was observed. We attributed the cause for such deterioration in stereoacuity to changes in vertical disparities. Keywords: binocular vision, depth perception, stereoacuity, vernier acuity.
Keywords: Binocular vision, Vertical disparities, Oblique effect, Stereopsis, Visual psychophysics, Stereoacuity.
Torro-Alves, N.; Fukusima, S.S.; Aznar-Casanova, J.A.(2008). Models of brain asymmetry in emotional processing. Psychology & Neuroscience 1(1): 63-66.
Abstract:
Two models of brain asymmetry in emotional processing were reviewed: the right hemisphere and the valence hypotheses. The first states a dominant role for the right hemisphere in emotional processing, whereas the second assumes that the left hemisphere is dominant
for positive emotions and the right hemisphere for negative ones. Different methods, such as the divided visual field technique, have
supported both hypotheses. The amygdala and the prefrontal cortex are presented as important structures involved on brain asymmetry
in emotional processing. The paper ends pointing out new perspectives for the study of the neural subtrates of different components of emotions. Keywords: brain asymmetry, right hemisphere hypothesis, valence hypothesis.
Keywords: Emotion recognition, emotion from faces, brain asymmetry, right hemisphere hypothesis, valence hypothesis.
Pitarque, A.; Algarabel, S. y Aznar-Casanova, J.A. (2007). Familiaridad y recuerdo en el reconocimiento de rostros ficticios: implicaciones para los modelos de reconocimiento. Psicothema, 19, 4, 565-571.
Abstract:
Siguiendo el paradigma experimental de “recordar-saber” (Gardiner, 1988; Tulving, 1985) los sujetos llevaron a cabo una tarea de reconocimiento de rostros ficticios, en la que manipulamos en tres condiciones entresujetos el tipo de cambio acaecido en los rostros entre las fases de estudio y reconocimiento (operacionalizado éste mediante la inclusión o no arrugas en los mismos: sin cambio, con cambio sencillo, o con doble cambio). Nuestros objetivos eran analizar si con dicho procedimiento maximizábamos los juicios de familiaridad y si así los resultados se acomodaban mejor a las predicciones de los modelos duales de reconocimiento o las modelos de detección de señales. En general nuestros resultados tienden a apoyar este último punto de vista, aunque se discute la capacidad predictiva de dichos modelos en relación a las demandas implicadas en la tarea a realizar (mejor ajuste ante tareas más basadas en la familariadad, peor ante tareas más inclinadas hacia la recolección).
Keywords: visual perception, memoria, reconocimiento, recolección, familiaridad, modelos de reconocimiento, reconocimiento de rostros.
J.A. Aznar-Casanova, J.A.; Matsushima, E.H.; Ribeiro-Filho, N.P. & Da Silva, J.A (2006). One-dimensional and Multi-dimensional studies of the exocentric distance estimates in frontoparallel plane, virtual space, and outdoors open field. The Spanish Journal of Psychology, 9 (2), 273-284.
Abstract:
The aim of this study is twofold: on the one hand, to determine how visual space, as assessed by exocentric distance estimates, is related to physical space. On the other hand, to determine the structure of visual space as assessed by exocentric distance estimates. Visual space was measured in three environments: (a) points located in a 2-D frontoparallel plane, covering a range of distances of 20 cm; (b) stakes placed in a 3-D virtual space (range ≈ 330 mm); and (c) stakes in a 3-D outdoors open field (range = 45 m). Observers made matching judgments of distances between all possible pairs of stimuli, obtained from 16 stimuli (in a regular squared 4 × 4 matrix). Two parameters from Stevens’ power law informed us about the distortion of visual space: its exponent and its coefficient of determination (R2). The results showed a ranking of the magnitude of the distortions found in each experimental environment, and also provided information about the efficacy of available visual cues of spatial layout. Furthermore, our data are in agreement with previous findings showing systematic perceptual errors, such as the further the stimuli, the larger the distortion of the area subtended by perceived distances between stimuli. Additionally, we measured the magnitude of distortion of visual space relative to physical space by a parameter of multidimensional scaling analyses, the RMSE. From these results, the magnitude of such distortions can be ranked, and the utility or efficacy of the available visual cues informing about the space layout can also be inferred.
Keywords: visual space perception, depth perception, monocular and binocular vision, multidimensional scaling, stereopsis, visual psychophysics, exocentric space.
>Da Silva, J.A; Matsushima, E.H.; Aznar-Casanova, J.A. & Ribeiro-Filho, N.P.(2006). Distance perception in a natural outdoor setting: is there a developmental trend to overconstancy?. The Spanish Journal of Psychology, 9 (2), 285-294.
Abstract:
The main purpose of the present study was to investigate whether in natural environment, using very large physical distances, there is a trend to overconstancy for distance estimates during development. One hundred and twenty-nine children aged 5 to 13 years old and twenty-one adults (in a control group), participated as observers. The observer’s task was to bisect egocentric distances, ranging from 1.0 to 296.0 m, presented in a large open field. The analyses focused on two parameters, constant errors and variable errors, such as measuring accuracy and precision, respectively. A third analysis focused on the developmental pattern of shifts in constancy as a function
of age and range of distances. Constant error analysis showed that there are two relevant parameters for accuracy, age, and range of distances. For short distances, there are three developmental stages: 5-7 years, when children have unstable responses, 7-11, underconstancy, and 13 to adulthood, when accuracy is reached. For large distances, there is a two-stage development: 5-11 years, with severe underconstancy, and beyond this age, with mild underconstancy. Variable errors analyses indicate that precision is noted for 7 year-old children, independently
of the range of distances. The constancy analyses indicated that there is a shift from constancy (or slightly overconstancy) to underconstancy as a function of physical distance for all age groups. The age difference is noted in the magnitude of underconstancy that occurs in larger distances, where adults presented lower levels of underconstancy than children. The present data were interpreted as due to a developmental change in cognitive processing rather than to changes in visual space perception.
Keywords: Visual perception, space perception, perceptual development, psychophysics, egocentric distance.
Artigas, AA; Aznar-Casanova, JA and Chamizo, V.D. (2005). Effects of absolute proximity and generalization gradient in humans when manipulating the spatial location of landmarks. International Journal of Comparative Psychology. 18, 225-239.
Abstract:
In two experiments in a virtual pool the participants were trained to find a hidden platform placed in a specific position in relation to one (Experiment 1) or two (Experiment 2) objects; then, all the participants received a test trial, without the platform, and the time spent in the segment where the platform should have been was measured. In Experiment 1, groups differed in the distance between the landmark and the hidden platform. Test results showed that the control acquired by the landmark was different depending on its relative distance from the platform: Closer landmarks acquired a better control than distant ones. In Experiment 2, two objects, B and F, were simultaneously present during acquisition. Object B was just above the hidden platform (i.e., a beacon for the platform) while object F was above the edge of the pool (i.e., a frame of reference). On the test, the spatial location of B in relation to F was manipulated in the different groups and a generalization gradient was found: Participants spent more time in the segment where B was when B was in front of F (training position), and this time decreased symmetrically with distance of B from F. The two experiments provide convergent evidence of spatial learning effects in a virtual task with humans.
Keywords: Spatial navigation, Virtual environments, spatial learning, visual perception, learning based on landmarks.
Nuñez-Peña, MI; Aznar-Casanova, J.A.; Linares, D.; Corral, M.J. Escera, C. (2005). Effects of dynamic rotation on event-related brain potentials. Cognitive Brain Research, 24, 307-316.
Abstract:
Event-related potentials were recorded during a mental rotation task. Subjects were shown pairs of letter-like shapes and were asked to make a parity judgment. The shape on the left was always in its canonical position and the shape on the right could either be in its canonical position or be a mirror image. Two variables were manipulated for the shape on the right. First, it could appear at different orientations (50º,100º or 150º); second, it could be presented in a stationary position, in a dynamic congruent direction (the shape slowly rotating toward its normal upright position) or in a dynamic incongruent direction (the shape slowly rotating in the opposite direction to its normal upright position). Orientation- and direction-dependent modulations of a negative slow wave were found. For orientation, the typical amplitude effect
over parietal sites was found, the amplitude becoming more negative as the rotational angle increased. For direction, the amplitude of the negative slow wave was larger for stationary and dynamic incongruent trials than for dynamic congruent trials at 1008 and 1508. This result suggests that presentation of a stimulus in a dynamic congruent direction facilitates the mental rotation process. At 508, differences between
dynamic incongruent trials and both stationary and dynamic congruent trials were found, suggesting that the incongruent movement elicits an obstructing effect over the mental rotation process. In summary, the present experiment provides new evidence in support of the idea that the amplitude modulation over the parietal cortex is a psychophysiological marker of the mental rotation process.
Keywords: Event-related brain potentials; Mental rotation; Cognition; Rotation-related negativity; Dynamic rotation; Perceived rotation.
Aznar-Casanova, J.A.; Quevedo, L. y Sinnett, S. (2005). The Effects of Drift and Displacement Motion on Dynamic Visual Acuity. Psicológica, 26(1): 75-92.
Abstract:
Dynamic Visual Acuity (DVA) can be measured from two types of equivalently considered movement referred to as drifting-motion and displacement-motion. Displacement motion can be best described as the horizontal displacement of a stimulus, thus implying pursuit eye movements, and involves moving the stimulus from the fixation point of gaze towards the periphery. The drifting motion of a Gabor patch, for example, avoids pursuit eye movements, since the gaze is fixed in a point of the patch. Our data shows that in both types of movement visual acuity (VA), expressed in terms of spatial frequency, diminished as the velocity of the target increased. However, the slope of the regression equation indicated that this impairment is more than two-fold in the case of drifting-motion when compared to displacement motion. As the greater impairment took place when pursuit eye movements did not exist, our data suggests that these two types of motions correct differently for retinal slip. Retinal slip appears to be less efficiently compensated for in the case of drifting motion having adverse consequences on VA, while retinal slip has a higher tolerance in the case of displacement motion exhibited by the performance in VA.
Keywords: Dynamic Visual Acuity, drifting motion, displacement motion, Visual perception, motion perception
Chamizo, V.D.; Aznar-Casanova, J.A.; Artigas, A.A. (2003). Human Overshadowing in a Virtual pool: Simple guidance is a good competitor against locale learning. Learning and Motivation, 56 (2): 173-184.
Abstract:
In four experiments a new virtual preparation for humans of the Morris water task (VMWT) was used. Psychology students were trained to locate a platform (either visible or invisible) in the presence of four landmarks (A, B, C, D), spaced at equal intervals around the edge of the pool. At the end of training one test trial was given in the presence of one or several landmarks, without the platform, and the time the students spent in the platform quadrant was registered. Experiment 1 used an invisible platform. It was designed to see how much the students had learned either of the whole set of four landmarks or of some subset of it when searching for the platform on test. When tested with four or two landmarks (either relatively near or far from the platform), the students performance was equivalent and significantly better than that obtained with one landmark only (either relatively near or far from the platform). In Experiment 2, for Group Experimental, the platform was visible, while for Group Control, it was invisible. On the test trial, a clear overshadowing effect was found: the Overshadowing group spent significantly less time in the platform quadrant than the Control group. A third group, Group Experimental-Slow, was subsequently added to eliminate an alternative explanation of spatial overshadowing in terms of differential experience with the landmarks during training. Finally, Experiments 3 and 4 were conducted to control for generalization decrement. The data are discussed within the growing body of evidence that suggests that the general laws of learning apply to many species, both in the spatial and temporal domains.
Keywords: Spatial navigation, Virtual environments, spatial learning, visual perception, learning based on landmarks.