We analyzed vergence change by moving both the target and the subject toward depth direction simultaneously. It has been suggested that the command for vergence movement caused by depth-direction-head-movement and that caused by target movement are generated separately, then combined in the oculomotor system.

We studied the detection of the incongruence between the two eyes' retinal images from occlusion perception. We previously analyzed the evasion action caused by occlusion by using green-red equiluminance, which is processed by parvocellular cells. Here we analyzed this action by using yellow-blue equiluminance, which is said to be treated by koniocellular cells and parvocellular cells. We observed that there were the cases in which the subject could perceive incongruence by the occlusion and other cases in which the subject could not perceive it. Significant differences were not seen in all conditions. Because a difference was seen in an evasion action at the time of the rim occlusion gaze when we compare the result for the yellow-blue equiluminance with the green-red equiluminance, it is suggested that the response for each equiluminance is different. We were able to clarify the characteristic difference between parvocellular cells and koniocellular cells from an occlusion experiment.

To clarify the stereopsis disturbance in patients with Alzheimer's disease (AD), we analyzed binocular eye movement when subjects shifted their gaze between targets at different depths. Subjects are patients with Alzheimer's disease, Mluti-infarct dementia (MID), or Olivopontocerebellar atrophy (OPCA), and healthy controls. Targets are arranged in two ways: along the median plane and asymmetrically crossing the median plane, at distances from the eyes of 1000 mm and 300 mm. When the targets are switched at the onset of a beep, the subjects shifted their gaze to the lit target. The experiment is conducted in a dimly lit room whose structure is capable of providing good binocular cues for depth. In AD subjects, especially in the subjects whose symptoms are moderate (advanced stage), vergence is limited and the change in the convergence angle is small, unstable, and non-uniform. These results are different from those of other patients (MID) and OPCA) or healthy controls and suggest a disturbance of stereopsis in the parietal lobe where AD patients typically have dysfunctions.

Stereoscopic vision technology is applied in a wide range of fields, from 3D movies to medical care. Stereoscopic vision makes it possible to observe images in parallax between both eyes. However, parallax images cannot be used all the time due to a situation called “occlusion”, in which an object is hidden in the depths by another object. In this case, different images are projected on the right and left retina. Here, we propose a psychology experiment to elucidate the function of parvocellular cells in the LGN of the visual cortex of the brain using occlusion perception. As a new psychology experiment to clarify whether parvocellular cells in the LGN of the visual cortex, said to process chromatic and luminance information, can detect a disagreement between the retinal images produced by each eye, we measured convergence eye movement when gazing at the rim of a column under occlusion using an equiluminance random dot pattern. When eye movement prevented the disagreement of the retinal images caused by occlusion, we thought that convergence eye movement to move both eyes in front of the rim or divergence eye movement to move them behind the rim would occur. In other words, we thought that we could clarify whether there was parvocellular system process agreement or disagreement between the right and left retinal images under equiluminance. Therefore, we examined whether a system to detect disagreement between the retinal images exists in the brain when gazing at the rim of a column onto which an equiluminance random dot texture was mapped. Results suggested that the mechanism to avoid disagreement between the retinal images of the eyes caused by occlusion occurs in the parvocellular cells, which mainly process color information, as well as in the magnocellular cells, which process binocular disparity.

We develop a system for comprehensively evaluating the gaze motions of a person operating a small electronic device such as a PDA or tablet computer. When people operate small electronic devices, they hold the device in their hand and gaze at it. Their hand movements while holding the device are considered part of the movement involved in operating the device. Our measurement system uses a video camera image taken from behind the subject as a substitute for the view camera of an eye-tracking recorder. With our new system, it is also possible to measure the subject's gaze superimposed on the view image by directly inputting the display screen from a small electronic terminal or other display. We converted the subjects' head and hand movements into eye movements and we calculated the gaze from these values; we transformed the gaze coordinates into view image coordinates and superimposed each gaze on the view image. We examined this hand movement in relation to gaze movement by simultaneously measuring the gaze movement and hand movement. We evaluated the accuracy of the new system by conducting several experiments. We first performed an experiment testing gaze movement as the summation of head and eye movements, and then we performed an experiment to test the system's accuracy for measuring hand movements. From the result of experiments, less than approx. 6.1° accuracy was acquired in the horizontal 120° range and the perpendicular 90° range, and we found that the hand motions converted into the angle equivalent to gaze movement could be detected with approx. 1.2° accuracy for 5° and 10° hand movements. When the subjects' hand moved forward, the results were changed into the angle equivalent to gaze movement by converting the distance between the terminal and the subjects' eyes.

In this study, we first developed a simultaneous measurement system for accommodation and convergence eye movement and evaluated its precision. Then, using a stuffed animal as the target, whose depth should be relatively easy to perceive, we measured convergence eye movement and accommodation at the same time while a tablet displaying a 3D movie was moved in the depth direction. By adding the real 3D display depth movement to the movement of the 3D image, subjects showed convergence eye movement that corresponds appropriately to the dual change of parallax in the 3D movie and real display, even when a subject's convergence changed very little. Accommodation also changed appropriately according to the change in depth.

Three-dimensional (3D) movies have become very popular in movie theaters and for home viewing, To date, there has been no report of the effects of the continual vergence eye movement that occurs when viewing 3D movies from the beginning to the end. First, we analyzed the influence of viewing a 3D movie for several hours on vergence eye movement. At the same time, we investigated the influence of long viewing on the human body, using the Simulator Sickness Questionnaire (SSQ) and critical fusion frequency (CFF). It was suggested that the vergence stable time after saccade when viewing a long movie was influenced by the viewing time and that the vergence stable time after saccade depended on the content of the movie. Also the differences were seen in the SSQ and CFF between the movie's beginning and its ending when viewing a 3D movie.

We developed a device to measure gaze and hand movement in a natural setting such as while reading a book on a train or bus. We examined what kind of cooperation exists among the head, eye and hand movements while subjects were reading a book held in the hand.

The purpose of this study was to clarify whether viewers can perceive a digitally deteriorated image while pursuing a speedily moving digitally compressed image. We studied the perception characteristics of false contours among the various digital deteriorations for the four types of displays i.e. CRT, PDP, EL, LCD by changing the gradation levels and the speed of moving image as parameters. It is known that 8 bits is not high enough resolution for still images, and it is assumed that 8 bits is also not enough for an image moving at less than 5 deg/sec since the tracking accuracy of smooth pursuit eye movement (SPEM) is very high for a target moving at less than 5 deg/sec. Given these facts, we focused on images moving at more than 5 deg/sec. In our results, the images deteriorated by a false contour at a gradation level less than 32 were perceived by every subject at almost all velocities, from 5 degrees/sec to 30 degrees/sec, for all four types of displays we used. However, the perception rate drastically decreased when the gradation levels reached 64, with almost no subjects detecting deterioration for gradation levels more than 64 at any velocity. Compared to other displays, LCDs yielded relatively high recognition rates for gradation levels of 64, especially at lower velocities.

We measured eye movements at gaze points while subjects performed calculation tasks and examined the relationship between the eye movements and fatigue and/or internal state of a subject by tasks. It was suggested that fatigue and/or internal state of a subject affected eye movements at gaze points and that we could measure them using eye movements at gaze points in real time.

Over the last 10 years, tablets have spread to the point where we can now read electronic books (e-books) like paper books. There is a long history of studies of eye movement during reading. Remarkable results have been reported for reading experiments in which displayed letters are changed in conjunction with eye movement during reading. However, these studies were conducted in the 1970s, and it is difficult to judge the detailed descriptions of the experimental techniques and whether the display time was correctly controlled when changing letters. Here, we propose an experimental system to control the display information exactly, as well as the display time, and inspect the results of past reading research, with the aim of being at the forefront of reading research in the e-book era.

In a live 3D TV program, since a change and processing of an image is performed in real time, it is difficult to check depth perception in advance. From such a background, we made the trial 3D TV program where various visual effects were used and analyzed subject's vergence while viewing them.

With the advent of an aging society, the incidence of Alzheimer-type dementia (hereinafter referred to as AD for convenience) has drastically increased. Compared with classic cerebrovascular dementia, AD requires different therapeutic modalities. Despite such differences, it is difficult to establish a differential diagnosis of AD and cerebrovascular dementia. In the present paper, we analyze the neuropsychological symptoms and signs associated with AD, such as visual cognitive dysfunction, with particular attention to head and eye coordination. The subjects were allowed to gaze at targets disposed 1 m away and at a visual angle of 25 and 50 in order to compare healthy volunteers and patients with senile dementias such as multi-infarct dementia (MID). As a consequence, patients with AD presented clinical manifestations not seen in patients with other senile dementias; that is, (1) an increase in stepwise eye movement, (2) anisotropy in the velocity of right-directional and left-directional eye movements, (3) a decrease in the velocity of head movements (4) incomplete gaze, and (5) decreased head share.

We paid attention the amount of change for each resolution by specifying the gaze position of images, and measured accommodation and convergence eye movement when watching high-resolution images. Change of convergence angle and accommodation were like the actual depth composition in the image when images were presented in the high-resolution.

We investigated the function in the Lateral Geniculate Nucleus of avoidance behavior due to the inconsistency between binocular retinal images due to blue from vergence eye movement based on avoidance behavior caused by the inconsistency of binocular retinal images when watching the rim of a blue-yellow equiluminance column.

We investigated subjects' gaze movement when reading E-books and compared it with that when reading traditional paper books. By examining the eye motion associated with the reader encountering new lines and new pages during reading, we found that each new line was completed with one saccade in both E-books and paper books, but E-books and paper books differed in saccade patterns when the reader encountered a new page. In E-books, a regular eye movement such as steady gaze to the next page's start position was repeated. In contrast, in paper books, there is no regularity in eye movement during this transition. It was shown that reading behavior is variable and depends on the individual.

We measured head and eye movements while subjects viewed 4K high-definition images to clarify the influence of different viewing positions. Subjects viewed three images from nine viewing positions: three viewing distances x three viewing positions. Though heads rotated toward the center irrespective of viewing screen positions, they also tended to turn straight forward as the viewing distance became close to an image.

We can enjoy various video contents such as movies in several ways. In this report, we show the effects of content differences on physiological parameters such as eye movements and CFF. This time we confirmed the difference in responses that after watching a movie. In addition, a consistent change that can infer that due to a movie was also indicated. Our results showed that content differences affect the parameters. This suggests the possibility that the influence of movie contents on the viewer can be evaluated by physiological parameters.