Kazuo Koga

Prismatic displacement of vision induces transient changes in the timing of eye-hand coordination

Eye-hand coordination was investigated during a task of finger pointing toward visual targets viewed through wedge prisms. Hand and eye latencies and movement times were identical during the control condition and at the end of prism exposure. A temporal reorganization of eye and hand movements was observed during the course of adaptation. During the earlier stage of prism exposure, the time gap between the end of the eye saccade and the onset of hand movement was increased from a control time of 23 to 68 msec. This suggests that a time-consuming process occurred during the early prism-exposure period. The evolution of this time gap was correlated with the evolution of pointing errors during the early stage of prism exposure, in such a way that both measures increased at the onset of prism exposure and decreased almost back to control values within about 10 trials. However, spatial error was not entirely corrected, even late in prism exposure when the temporal organization of eye and hand had returned to baseline. These data suggest that two different adaptive mechanisms were at work: a rather short-term mechanism, involved in normal coordination of spatially aligned eye and hand systems, and a long-term mechanism, responsible for remapping spatially misaligned systems. The former mechanism can be strategically employed to quickly optimize accuracy in a situation involving misalignment, but completely adaptive behavior must await the slower-acting latter mechanism to achieve longterm spatial alignment.

Culture in Vector-Averaged Gravity Under Clinostat Rotation Results in Apoptosis of Osteoblastic ROS 17/2.8 Cells

Space flight experiments and studies carried out in altered gravity environments have revealed that exposure to altered gravity conditions results in (mal)adaptation of cellular function. In the present study, we used a clinostat to generate a vector‐averaged gravity environment. We then evaluated the responses of osteoblast‐like ROS 17/2.8 cells subsequent to rotation at 50 revolutions per minute (rpm) for 6–24 h. We found that the cells started to detach from the substrate between 12 h and 24 h of rotation in clinostat but not in stationary cultures or after horizontal rotation (the latter serving as a motion control for turbulence, shear forces, and vibrations). At 24 h, 35% of clinorotated cells had detached and the cells underwent apoptotic death as evidenced by DNA fragmentation analysis, terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate‐biotin nick end labeling (TUNEL) staining, and flow cytometry with Annexin V staining. The apoptotic death was associated with perinuclear distribution of cell‐surface integrin β1 and disorganization of actin cytoskeleton. These results suggest that vector‐averaged gravity causes apoptosis of osteoblasts by altering the organization of the cytoskeleton. We hypothesize that apoptotic death of osteoblasts might play an important role in the pathogenesis of osteoporotic bone loss as observed in actual space flights.

Drifting and Blinking Compensation in Electro-oculography (EOG) Eye-gaze Interface

This paper describes an eye-gaze interface using a biological signal, electro-oculorgram (EOG). This interface enables a user to move a computer cursor on a graphical user interface using eye gaze movement alone. It will be useful as a communication aid for individuals with mobility handicaps. Although EOG is easily recordable, drifting and blinking problems must be solved to produce a reliable eye-gaze interface. Here we introduced a calibration method and a feedback control to overcome these problems.

Apparent body tilt and postural aftereffect

Apparent orientation of the body tilted laterally in the frontal plane was studied with the methods of absolute judgments in four experiments. In Experiment 1, 17 subjects, who maintained the normal adaptation of body to gravity, estimated their body tilts under the condition of seeing the gravitational vertical and under the condition of eliminating it. The results showed that (1) there was not a significant difference between the two conditions and (2) the small tilts of less than 45° were exactly estimated, whereas the large tilts of 45°–108° were overestimated. In Experiment 2,10 subjects estimated their body tilts under three velocities of a rotating chair on which each subject was placed. Although both body tilt and chair velocity were found to influence tilt estimation, the effect of body tilt was overwhelmingly greater than that of chair velocity. In Experiment 3, 11 subjects adapted their bodies to a 72° left tilt for 10 min and then estimated various body tilts around the adapting tilt. The estimations obtained under the 72° adaptation were lower than those obtained under the 0° adaptation, and this reduction was greater for the test tilt that was farther away from the adapting tilt. In Experiment 4, 11 subjects adjusted their own body tilts to designated angles. The results confirmed the outcomes of absolute estimation in Experiments 1-3. From these findings and past literature, the judgments of body tilt were considered to be subserved by a single sensory process that was based on the cutaneous and muscular proprioceptors, rather than the vestibular and joint proprioceptors.

Neural and humoral controlling mechanisms of cardiovascular functions in man under weightlessness simulated by water immersion.

To clarify how neural and humoral mechanisms operate to control cardiovascular functions in man under weightlessness, the response of sympathetic nerve activity was observed in healthy human subjects by means of microneurographic technique with the changes of several hemodynamic parameters and hormonal responses during thermoneural head-out water immersion. Muscle sympathetic nerve activity was markedly suppressed by head-out immersion, concomitantly with a reduction of the leg volume, an increase of the stroke volume and a reduction of total peripheral resistance. At the same time, plasma level of norepinephrine, vasopressive and antidiuretic hormones (ADH, aldosterone, renin activity, angiotensin I-II) were reduced, while vasodepressive and diuretic hormone (ANP) was markedly increased. The systemic blood pressure was maintained almost unchanged during head-out water immersion. The suppressive response of sympathetic nerve activity seemed to be age-dependent. This response was less prominent in the elderly than in young subjects. It is concluded that the suppressive response of muscle sympathetic activity plays an important role to maintain hemodynamic homeostasis under weightlessness to compensate for the cephalad fluid shift and the resultant increase of the stroke volume in cooperation with the hormonal responses.

Visual Information Processing in Augmented Reality: Some Aspects of Background Motion

We assessed discomfort, time and number of saccades for reading a text superimposed to a moving background. When background moved in the main directions of reading (left to right or top to bottom), discomfort was rated significantly lower than when background moved in the opposite directions. Neither time for reading nor number of saccades are affected by background motion. We therefore conclude that increased arousal might be responsible to cope with effects of background motion, resulting in an increased stress and rising discomfort when background moves opposite to main directions of reading. The findings suggest that reading in Augmented Reality for mobile use must be considered as a robust process. However, load may be increased and cause complaints in a prolonged reading task.

Integration of visual and vestibulo-tactile inputs affecting apparent self-motion around the line of sight

We investigated the effects of visual and vestibulo-tactile inputs on perceived self-motion. Each of 23 subjects was exposed to an optical pattern rotating around the roll axis (i.e., line of sight) while the chair, in which the subject was placed, was rotated back and forth between ±70° (i.e., large rolling) or between ±35° (i.e., small rolling) from the gravitational vertical. Each subject judged perceived velocity of self-motion under each of 16 combinations of pattern velocity and chair velocity. The main results were the following: (l) The mean estimation increased with pattern velocity, and it also increased with chair velocity; (2) to attain a constant perceived velocity of self-motion, pattern velocity was traded for chair velocity, and for the large rolling of the chair, visual inputs were more effective than vestibulotactile inputs, whereas for the small rolling, the inverse was true; (3) analyses of multiple regression, when applied to the mean estimations, showed that for both rollings of the chair, the visual component dominated over the vestibulo-tactile component, but for the small rolling of the chair, the difference in effectiveness between the two components was attenuated. We discuss these findings in terms of visual-vestibular interaction.

Perceived self-tilt in dynamic visual stimuli: evidence for suppression by vestibulo-tactile inputs.

Perception of self-tilt is affected by shearing force acting on the otolith organs in the ears, by pressure acting on the tactile receptors in the skin, and by visual pattern falling on the retinae. We examined how the vestibular, somatosensory, and visual inputs interact in judging self-tilt in roll. Each of fourteen observers, sitting in a chair and gazing at a rotation pattern in the frontal plane, was tilted to various angles and verbally judged to what extent his/her body was tilted. The independent variables examined were body tilt (0° to ±108°), and the rate (7.5° s−1, 15° s−1, and 30° s−1) and direction (CW and CCW) of the visual rotating pattern. We found that (i) the sensory scale for self-tilt is represented by a third-order polynomial lacking the quadratic component, (ii) perceived self-tilt for the CW (or CCW) rotation of the visual pattern is displaced CCW (or CW), (iii) the linear and cubic components of the equation increase with an increase in the rate of rotation of the visual pattern, and (iv) if the body is tilted in concord with the direction of vection, the velocity of visual pattern is effective, but when the body is tilted in conflict with the direction of vection, it is less effective. These findings are interpreted in terms of vestibular and somatosensory suppressions exerted on the effects of vection.

Visual Perception and Perceptual Processing in Real and Virtual Environments

We present a brief outline of the development of research in visual perception with the advent of new technologies up to New Media and virtual environments. There is a mutual inspiration and benefiting between fundamental and applied research and technological progress which should be utilized by the disciplines involved. Next, an overview of a conference, held in Nara (Japan) September 2001, is given of which different selections of articles are presented in the current special issues of the Swiss Journal of Psychology and of Japanese Psychological Research.

Perceived range, perceived velocity, and perceived duration of the body rotating in the frontal plane

We investigated perceived range, perceived velocity, and perceived duration of the body rotating in the frontal plane (in roll). Specifically, to examine how shear to the otoliths in the inner ears and tactile pressure to the trunk affect judgments of range and velocity, in two experiments, we manipulated rotating range (30°–160°), rotating velocity (1.8°/sec to 9.6°/sec), mean tilt of the body (−60°, 0°, and 60°), and exposure to the visual vertical. Thirty-three normal or blindfolded participants made verbal judgments of range, velocity, and duration for each combination of these factors. The exponents of the power functions fitted to these judgments were, as a first approximation, .94, .61, and .84 for range, velocity, and duration, respectively, and perceived velocity was proportional to the ratio of perceived range to perceived duration (r = .91). These results suggest that the vestibular and somatosensory inputs are effective on judgments of range, but less so on judgments of velocity, and that perceived velocity may be determined as a ratio of perceived range to perceived duration. In addition, we found that (1) when the range the body has traveled is constant, the perceived range increases as the objective velocity decreases (proprioceptive τ effect); (2) self-motion through the tilted roll sometimes enlarges perceived range and perceived duration but reduces perceived velocity; and (3) the exposure to the visual vertical reduces variability of judgments for range and velocity and also reduces perceived range and perceived velocity of self-motion within a small range through the vertical roll.