Biomedical subjects

Kaori Iwata

Publications and source records attributed to Kaori Iwata.

3 recordsLinked to original sources

PubMed2004

Vestibulo-ocular reflex and gravity in fish.

An otolith organ on ground behave as a detector of both gravity and linear acceleration, and play an important role in controlling posture and eye movement for tilt of the head or translational motion. On the other hand, a gravitational acceleration ingredient to an otolith organ disappears in microgravity environment. However, linear acceleration can be received by otolith organ and produce a sensation that is different from that on Earth. It is suggested that in microgravity signal from the otolith organ may cause abnormality of posture control and eye movement. We examined function of otolith organ in goldfish revealed from analysis of eye movement induced by linear acceleration. We analyzed vertical eye movements from video images frame by frame. In normal fish, leftward lateral acceleration induced downward eye rotation in the left eye and upward eye rotation in the right eye. Acceleration from caudal to rostra1 evoked downward eye rotation in both eyes. When the direction of acceleration was shifted 15 degrees left, the responses in the left eye disappeared. These results suggested that otolith organs in each side transmitted different signals.

Acceleration↗

PubMed2004

Eye movements of goldfish depending on the relationship between acceleration vector and otolith organ.

Prior experiments demonstrated that the acceleration deviating 15 degrees to the right (left) from the longitudinal body axis could not produce vertical eye movement in left (right) eye of the goldfish. From these results, we expected that vertical eye movement of goldfish for the acceleration perpendicular to the longitudinal body axis might different between right and left eye. However, in this experiments, there were no clear difference in magnitude of vertical eye movements for the acceleration shifted 15 degrees around the left-right body axis. On the other hand, the response of right eye was larger than that of left eye for the acceleration applied from left to right of the body. These results suggest that stimulation from medial to lateral and lateral to medial of the otolith organ has different effect on vertical eye movement in each eye of goldfish.

Acceleration↗

PubMed2003

Function of otolith organ in goldfish revealed from analysis of eye movement induced by acceleration.

An otolith organ on ground behave as a detector of both gravity and linear acceleration, and play an important role in controlling posture and eye movement for tilt of the head or translational motion. On the other hand, a gravitational acceleration ingredient to an otolith organ disappears in microgravity environment. However, linear acceleration can be received by otolith organ and produce a sensation that is different from that on Earth. It is suggested that in microgravity signal from the otolith organ may cause abnormality of posture control and eye movement. Therefore, the central nervous system may re-interprets all output from the otolith organ to indicate linear motion. A study of eye movement has been done a lot as one of a reflection related to an otolith organ system. In this study, we examined function of otolith organ in goldfish revealed from analysis of eye movement induced by linear acceleration or the tilt of body. We analyzed both torsional and vertical eye movements from video images frame by frame. For tilting stimulation, torsional eye movements induced by head down was larger than that induced by head up for larger tilt angle than 30 degrees. In the case of linear acceleration below 0.4 G, however, no clear differences were observed in both torsional and vertical eye movement. These results suggest that body tilt and linear acceleration may not be with equivalent stimulation to cause eye movement on the ground.

Acceleration↗