Inhibitory mechanisms in visual motion perception
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2024
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11/05/2023
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Universidad Complutense de Madrid
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Abstract
El mundo estimular que nos rodea está en constante cambio, donde múltiples objetos del entorno cambian de posición, luminancia y color. Estos objetos, además, se pueden mover sobre fondos estáticos, en movimiento, con la misma o diferente velocidad, en sentido opuesto, etc. Nuestro Sistema Visual tiene la habilidad para segregar la figura del fondo y de este modo extrae información acerca de los objetos en entornos tan complejos. Entender cómo el ser humano procesa el movimiento es uno de los problemas más importantes y sofisticados de la percepción visual (ver Nishida, 2011). Las características funcionales delos mecanismos subyacentes no se conocen completamente, en particular, se desconoce el papel de los mecanismos inhibitorios en la percepción del movimiento. Es por ello que el objetivo principal de esta Tesis es la caracterización psicofísica de las propiedades funcionales de dos mecanismos implicados de la percepción visual del movimiento. Tradicionalmente se ha propuesto que el ser humano utiliza mecanismos antagónicos centro-periferia para segregar la figura del fondo (Lappin & Tadin, 2004; Tadin et al.,2019). El funcionamiento normal de estos mecanismos hace que objetos en movimiento de alto contraste y gran tamaño sean percibidos con dificultad (Derrington & Goddard, 1989).Sin embargo, en bajo contraste, cuanto mayor es el tamaño del objeto, más fácil es detectar su movimiento (Tadin et al., 2003). Para explicar estos resultados se asume que en estos mecanismos, cuando el estímulo tiene gran tamaño y alto contraste, la región periférica suprime o inhibe la activación del centro, y para bajo contraste facilita la activación del centro. Se han encontrado los mismos resultados analizando la respuesta de neuronas con campos receptores antagónicos centro-periferia presentes en el área medio temporal (MT)de la corteza visual (Pack, Hunter & Born, 2005) y en el área temporal medial superior(MST) (Eifuku & Wurtz, 1998). La forma de estos campos receptores no está completamente caracterizada, aunque estudios recientes sugirieren una configuración espacial elongada en la dirección del movimiento (Serrano-Pedraza, Hogg & Read, 2011),coincidiendo con evidencias fisiológicas (Xiao et al., 1997)...
The world around us is constantly changing, with multiple objects in the environment changing position, luminance, and color. These objects can also move on static or in motion backgrounds, with the same or different speed, in opposite direction, etc. Our Visual System can segregate figures from the background and thus extract information about objects in complex environments. Understanding how humans process motion is one of the most relevant and sophisticated problems in visual perception (see review of Nishida, 2011). The functional characteristics of the underlying mechanisms are not completely known, in particular, the role of the inhibitory mechanisms in motion perception. Therefore, the main goal of this Thesis is the psychophysical characterization of the functional properties of two inhibitory mechanisms involved in visual motion perception. It has traditionally been proposed that the antagonistic center-surround mechanisms are implicated in the segregation of the figure from the background (Lappin & Tadin, 2004;Tadin et al., 2019). The normal functioning of these mechanisms causes difficulties in perceiving large moving objects at high contrast (Derrington & Goddard, 1989). However, at low contrast, the larger the size of the object, the easier it is to detect its motion (Tadin etal., 2003). To explain these results, it is assumed that in these mechanisms, when the stimulus is large and has high contrast, the peripheral region suppresses or inhibits the activation of the center, and for low contrast, it facilitates the activation of the center. The same results have been found by analyzing the response of neurons with antagonistic center-surround receptive fields present in the medial temporal (MT) area of the visual cortex (Pack, Hunter & Born, 2005) and in the medial superior temporal (MST) area (Eifuku & Wurtz, 1998). The shape of these receptive fields is not fully characterized, although recent studies suggest an elongated spatial configuration in the direction of movement (Serrano-Pedraza, Hogg & Read, 2011), in agreement with physiological evidence (Xiao et al., 1997)...
The world around us is constantly changing, with multiple objects in the environment changing position, luminance, and color. These objects can also move on static or in motion backgrounds, with the same or different speed, in opposite direction, etc. Our Visual System can segregate figures from the background and thus extract information about objects in complex environments. Understanding how humans process motion is one of the most relevant and sophisticated problems in visual perception (see review of Nishida, 2011). The functional characteristics of the underlying mechanisms are not completely known, in particular, the role of the inhibitory mechanisms in motion perception. Therefore, the main goal of this Thesis is the psychophysical characterization of the functional properties of two inhibitory mechanisms involved in visual motion perception. It has traditionally been proposed that the antagonistic center-surround mechanisms are implicated in the segregation of the figure from the background (Lappin & Tadin, 2004;Tadin et al., 2019). The normal functioning of these mechanisms causes difficulties in perceiving large moving objects at high contrast (Derrington & Goddard, 1989). However, at low contrast, the larger the size of the object, the easier it is to detect its motion (Tadin etal., 2003). To explain these results, it is assumed that in these mechanisms, when the stimulus is large and has high contrast, the peripheral region suppresses or inhibits the activation of the center, and for low contrast, it facilitates the activation of the center. The same results have been found by analyzing the response of neurons with antagonistic center-surround receptive fields present in the medial temporal (MT) area of the visual cortex (Pack, Hunter & Born, 2005) and in the medial superior temporal (MST) area (Eifuku & Wurtz, 1998). The shape of these receptive fields is not fully characterized, although recent studies suggest an elongated spatial configuration in the direction of movement (Serrano-Pedraza, Hogg & Read, 2011), in agreement with physiological evidence (Xiao et al., 1997)...
Description
Tesis inédita de la Universidad Complutense de Madrid, Facultad de Psicología, leída el 11-05-2023. Tesis formato europeo (Compendio de artículos)