Non-linear interaction of angular and translational vestibulo-ocular reflex during eccentric rotation in the monkey.
Eccentric sinusoidal rotation with the nose facing out or in leads to gain modulation of the vestibulo-ocular reflex (VOR), which is a result of an interaction between angular and translational VOR. There are conflicting reports with regard to the type of interaction. Combined angular and translational VOR during eccentric sinusoidal rotations over a wide range of target distances (12-180 cm), eccentricities (centric, 30 and 50 cm nose-out and nose-in eccentric) and frequencies (0.1-4 Hz) were studied in macaque monkeys trained to fixate earth-stationary light-emitting diode (LED) targets while binocular eye positions were measured using magnetic search coils. The monkeys were also exposed to sudden unpredictable position steps with peak accelerations of 500 degrees/s(2) using similar eccentricities and target distances. VOR gain enhancement during nose-out eccentric sinusoidal rotation was almost compensatory when the target was visible and was independent of stimulus frequency. Mean responses were still close to ideal when the target was extinguished; however, individual data showed increased variability. Sensitivities of the translational portion of the combined VOR were compensatory. These sensitivities were clearly reduced during nose-in eccentric sinusoidal rotation. Thus, especially for close targets at 4 Hz combined VOR was not compensatory, independent of target visibility. VOR elicited by sudden position steps showed a sequential response: (1) purely angular VOR (up to 40-45 ms); (2) additional translational VOR that was not modulated by target distance (45-65 ms); and (3) translational VOR weighted for target location (>65 ms). We conclude that angular and translational VOR have different latencies during transient accelerations and interact differently during agonistic (nose-out) and antagonistic stimulation (nose-in).
Fuhry
L
L
Institute of Physiology, Academy of Sciences of the Czech Republic, Praha. fuhry@lrz.uni-muenchen.de
Nedvidek
J
J
Haburcakova
C
C
Büttner
U
U
D000054:Acceleration; D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D001921:Brain / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology; D008253:Macaca mulatta / Q000502:physiology*; D017711:Nonlinear Dynamics; D010812:Physical Stimulation; D004856:Postural Balance / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D012399:Rotation; D014722:Vestibule, Labyrinth / Q000502:physiology*