Masae Yokota

Eye movement inhibits the facilitation of perceptual filling-in

When a small figure is presented in human peripheral vision, it becomes invisible and invaded by surrounding texture, within a few seconds. This visual illusion is called perceptual filling-in. Time to filling-in (filling-in time) is varied by the properties of small figure, surround texture and some experimental conditions. In our preliminary study (Yokota, IEEE/IC-EMBS 2005), we found that incomplete fixation distributes filling-in time. Furthermore, that we can see nothing by restraining eye movement artificially is well known. Therefore, we can consider that filling-in time is influenced by eye movement. Although it has been recently reported that eye movement influences the filling-in occurrence (Martinez-Conde, Neuron 2006), the relation between eye movement and the filling-in time has rarely been reported. For this study, we measured the filling-in time for three subjects, for four surrounding textures, with simultaneous recording of eye movement. The results show that the filling-in time correlates to the standard deviation of the power of the eye distance from the fixation point. Furthermore, we found relatively strong correlation between the filling-in time and the power of high frequency component 50–200 (Hz) in the eye movement, though the correlation of the power of low frequency component 10–50 (Hz) is not so high. Thus we suppose that filling-in is inhibited by small involuntary eye movement.

The effect of spatio-temporal frequency of dynamic texture on perceptual filling-in

Humans do not see scotomas shaded by the optical disk and blood vessels on retina. Texture of surrounding scotomas fills in to occupy the scotoma area. Similarly, when viewing a monochromatic figure surrounding dynamic textured background in monocular peripheral vision, background texture appears to fill into the figure. To investigate spatial and temporal frequency characteristics of the filling-in process, we measured time to filling-in when a gray figure surrounding dynamic random-dot texture with limited bandwidth of spatiotemporal frequency was presented in peripheral vision of subjects. Based on subject reports, a model of filling-in mechanism is proposed. The model is represented by the spatial and temporal perceptual power of dynamic texture. Model validity is verified by applying measured data to the model.

Relationship between Eye Movement and Facilitation of Perceptual Filling-in

For a few seconds, under certain circumstances, a subject perceives a filling-in target as filled by its surrounding texture when a small area (filling-in target) with different texture from its surroundings is presented to the person’s peripheral vision. This illusion is perceptual filling-in.

A hypothesis of perceptual filling-in process for spatio-temporal frequency of dynamic textures

Perceptual filling-in is a famous visual illusion. We have proposed a hypothesis of the filling-in process to address the phenomenon when a small homogeneous area (filling-in target), which is surrounded by spatio-temporal frequency limited random-dot dynamic textures, is presented to an observers peripheral vision. This hypothesis introduces perceptual power, which is distinguishability of the small area from the surrounding dynamic texture. Beyond a brief transient, perceptual power decreases from initial values according to texture movement from the beginning of motion of the surrounding texture. As perceptual power falls to a certain level, the small area is filled with the surrounding dynamic texture and is perceived to disappear. According to this hypothesis, we reported estimation of the time course of perceptual power at EBMS-BMES2002. However, that study ignored transient characteristics by which the surrounding texture starts to move. This study estimates the time course of perceptual power while considering the initial transient. First, we estimated visual sensitivity for spatio-temporal frequency in peripheral vision by an experiment. Second, the time to filling-in was measured for various spatio-temporal frequencies of the surrounding texture. These results were applied to the filling-in process hypothesis. As a result, we inferred that perceptual power decreases with spatio-temporal sensitivity of vision.

Involuntary Eye Movement during Fixation Depends on Spatio-Temporal Frequency of Stimuli

Our eyes oscillate small and rapidly, even while we gaze at something. Visual objects become to fade and we can see nothing, if involuntary eye movement is eliminated temporarily. Involuntary eye movement is essential to acquire visual information. As preliminary experiment, we have been recorded eye movement when filling-in, one of famous visual illusions, occurs in our peripheral vision (EMBEC2008). These experiments suggested that eye movement depends on the attributes of visual stimuli. In this study, we focus on spatiotemporal frequency as an attribute of visual stimuli in order to understand spatio-temporal frequency property in the pathway of human vision. In this study, we measured eye movement during fixation when 16 random-dot dynamic textures that have various frequency bands in spatially and temporally, are presented to the subjects as visual stimuli. The result shows that eye movement depends on both spatial and temporal frequencies of visual stimuli. The eye movement includes higher frequency components, in other words, higher velocity components, when visual stimulus has higher spatial frequency and/or higher temporal frequency.

The relation between eye movement and filling-in time

When a small area is presented in peripheral vision, it becomes invisible and invaded by surrounding texture within a few seconds. This visual illusion is called perceptual filling-in. Investigation on filling-in characteristics contributes to understand human visual information processing mechanism.

Spatio-temporal frequency characteristics of perceptual filling-in

When a small object surrounded by a dynamic texture is presented in human peripheral vision, the object is perceived to fade and disappear within a few seconds, under certain conditions. This phenomenon is called perceptual filling-in. Characteristics of filling-in for various kinds of surrounding textures is important to understand the manner of information processing in human vision, because filling-in has been considered that it greatly contributes to capturing external visual information efficiently. From this point of view, we have proposed a model of the filling-in process to address the phenomenon when a small homogeneous area (filling-in target), which is surrounded by spatio-temporal frequency limited random-dot dynamic textures, is presented to an observers peripheral vision (Proc. IC-EMBS2003). This study reports measurement of time to filling-in for various surrounding dynamic textures that have different spatio-temporal frequency. Applying these results to the proposed model, we estimate the time course of distinguishability of the target from surround (perceptual power). The estimate indicates that if spatial frequency of dynamic textures is low, lower spatio-temporal sensitivity decreases perceptual power more rapidly. However, the opposite property appears if spatial frequency is high.

Influence of Spatio-Temporal Frequency of Dynamic Textures on Fixational Eye Movement in Central and Peripheral Vision

Our eyes move slightly and rapidly, even while we gaze at an object. If fixational eye movement is inhibited, visual objects begin to fade until we ultimately cannot see them at all. Involuntary fixational eye movement is essential for the acquisition of visual information, as neurons become inactive when exposed to continuous homogeneous visual stimuli. Involuntary fixational eye movement is believed to be generated by random neural activation. In this study, we focused on the other role of eye movement. It is supposed that fixational eye movement is affected by perception of a visual stimulus. Thus, involuntary fixational eye movement might be controlled by perception. We measured subjects’ fixational eye movement while dynamic textures with limited spatio-temporal frequency were presented to their central or peripheral visual field. Results indicated that recorded fixational eye movements are influenced by the spatio-temporal frequency sensitivity of vision. The higher frequency component of the fixational eye movement in both central and in peripheral vision increases when the dynamic texture of a stimulus has a spatio-temporal frequency of a higher visual sensitivity.

Influence of Small Eye Movement on Perceptual Filling-in Time

When a small area that has a different texture from its surroundings is presented to a subjects peripheral vision, that person perceives that the area is filled by its surrounding texture. It disappears within a few seconds under certain circumstances. This illusion is called filling-in. The filling-in time depends on textural properties, the areas size, the eccentricity with which the small area is projected, and so on. Filling-in characteristics must be elucidated to understand the mode of information processing in human vision because filling-in has been considered to contribute greatly to capturing external visual information. Facilitation of filling-in is generally evaluated using the filling-in time. Furthermore, it is well-known that we can see nothing by restraining eye movement artificially. Eye movement is important to acquire visual information. Therefore, we can suppose that facilitation of filling-in is influenced by eye movement. Although it has been recently indicated that eye movement influences the filling-in time while measuring time to filling-in, the relationship between eye movement and the filling-in time has rarely been reported. In this study, we measured the filling-in time, with simultaneous recording of eye movement. Results showed that the filling-in time correlates moderately or weakly with eye movement, under the condition that complete fixation is achieved.

Model of Ca/sup 2+/ concentration controlled by sarcoplasmic reticulum of skeletal muscle, using the state transition

[Ca/sup 2+/] in a muscle cell is controlled by the sarcoplasmic reticulum (SR) that releases Ca/sup 2+/ through the channels, takes up Ca/sup 2+/ by the pumps on the SR membrane, and stores up Ca/sup 2+/ with Ca/sup 2+/ binding protein called calsequestrin (CS). This report proposed a model that represents [Ca/sup 2+/] in a muscle cell controlled by the SR using a state transition probability model in which one state means that protein in the SR is binding ligands, and the other is releasing them. The proposed model consists of 4 modules: calsequestrin, voltage dependent Ca/sup 2+/ release channels, Ca/sup 2+/ induced Ca/sup 2+/ release channels, and Ca/sup 2+/ pumps. Estimating the amount of Ca/sup 2+/ both released and pumped up with the model, it was indicated that [Ca/sup 2+/] rapidly increases from the static state as soon as nerve impulses arrive at a muscle. We further reveal that the fact that Ca/sup 2+/ pumps are located apart from Ca/sup 2+/ release channels has an important influence on generating a Ca/sup 2+/ spike signal.