RESUMEN
The origin of depth in Panum's limiting case is unclear at present, so we investigated the depth perception mechanism using a triangle type of Panum's stimulus with a slant effect and clear criterion. Experiment 1 explored whether participants can correctly perceive fixation and nonfixation features using the fixation point and quick representation of stimuli, then examined whether participants' depth judgments supported double fusion or single fusion. The results of Experiment 1 showed that participants could correctly perceive the depth of fixation and nonfixation features. That is, it supported double fusion. In Experiment 2, we examined whether the depth perceived by observers comes from depth contrast. The results of Experiment 2 showed that the depth of the two features perceived after binocular fusion did not originate from the depth contrast. The findings suggest that the depth perception mechanism of Panum's limiting case is more likely to be double fusion.
Asunto(s)
Percepción de Profundidad , Modelos Neurológicos , Disparidad Visual , Percepción de Profundidad/fisiología , Disparidad Visual/fisiología , Humanos , Fijación Ocular/fisiología , Estimulación Luminosa , Reproducibilidad de los Resultados , Masculino , Femenino , Adulto Joven , Adulto , Análisis de Varianza , Sensibilidad de Contraste/fisiologíaRESUMEN
The literature has long emphasized the role of higher cortical structures in endogenous orienting. Based on evolutionary explanation and previous data, we explored the possibility that lower monocular channels may also have a functional role in endogenous orienting of attention. Sensitive behavioral manipulation was used to probe the contribution of monocularly segregated regions in a simple cue - target detection task. A central spatially informative cue, and its ensuing target, were presented to the same or different eyes at varying cue-target intervals. Results indicated that the onset of endogenous orienting was apparent earlier when the cue and target were presented to the same eye. The data provides converging evidence for the notion that endogenous facilitation is modulated by monocular portions of the visual stream. This, in turn, suggests that higher cortical mechanisms are not exclusively responsible for endogenous orienting, and that a dynamic interaction between higher and lower neural levels, might be involved.
Asunto(s)
Atención , Orientación , Visión Monocular , Señales (Psicología) , Femenino , Humanos , Masculino , Estimulación Luminosa , Psicofísica , Tiempo de Reacción , Percepción Visual , Adulto JovenRESUMEN
The literature has long emphasized the role of the cerebral cortex in executive functions. Recently, however, several researchers have suggested that subcortical areas might also be involved in executive functions. The current study explored the possibility that subcortical mechanisms have a functional role in adaptive resolution of Stroop interference. We asked 20 participants to complete a cued task-switching Stroop task with variable cue-target intervals (CTI). Using a stereoscope, we manipulated which eye was shown the relevant dimension and which was shown the irrelevant dimension. This technique allowed us to examine the involvement of monocularly segregated - subcortical - regions of the visual processing stream. The interference effect was modulated by this eye-of-origin manipulation in the 0 CTI condition. This finding provides a novel indication for the notion that subcortical regions have a functional role in the resolution of Stroop interference. This indication suggests that cortical regions are not solely involved and that a dynamic interaction between cortical and subcortical regions is involved in executive functions.
Asunto(s)
Corteza Cerebral/fisiología , Señales (Psicología) , Función Ejecutiva/fisiología , Test de Stroop , Adulto , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
Gradients of absolute binocular disparity across a slanted surface are often considered the basis for stereoscopic slant perception. However, perceived stereo slant around a vertical axis is usually slow and significantly under-estimated for isolated surfaces. Perceived slant is enhanced when surrounding surfaces provide a relative disparity gradient or depth step at the edges of the slanted surface, and also in the presence of monocular occlusion regions (sidebands). Here we investigate how different kinds of depth information at surface edges enhance stereo slant about a vertical axis. In Experiment 1, perceived slant decreased with increasing surface width, suggesting that the relative disparity between the left and right edges was used to judge slant. Adding monocular sidebands increased perceived slant for all surface widths. In Experiment 2, observers matched the slant of surfaces that were isolated or had a context of either monocular or binocular sidebands in the frontal plane. Both types of sidebands significantly increased perceived slant, but the effect was greater with binocular sidebands. These results were replicated in a second paradigm in which observers matched the depth of two probe dots positioned in front of slanted surfaces (Experiment 3). A large bias occurred for the surface without sidebands, yet this bias was reduced when monocular sidebands were present, and was nearly eliminated with binocular sidebands. Our results provide evidence for the importance of edges in stereo slant perception, and show that depth from monocular occlusion geometry and binocular disparity may interact to resolve complex 3D scenes.