Plasticity of the human otolith-ocular reflex.
The eye movement response to earth vertical axis rotation in the dark, a semicircular canal stimulus, can be altered by prior exposure to combined visual-vestibular stimuli. Such plasticity of the vestibulo-ocular reflex has not been described for earth horizontal axis rotation, a dynamic otolith stimulus. Twenty normal human subjects underwent one of two types of adaptation paradigms designed either to attenuate or enhance the gain of the semicircular canal-ocular reflex prior to undergoing otolith-ocular reflex testing with horizontal axis rotation. The adaptation paradigm paired a 0.2 Hz sinusoidal rotation about a vertical axis with a 0.2 Hz optokinetic stripe pattern that was deliberately mismatched in peak velocity. Pre- and post-adaptation horizontal axis rotations were at 60 degrees/s in the dark and produced a modulation in the slow component velocity of nystagmus having a frequency of 0.17 Hz due to putative stimulation of the otolith organs. Results showed that the magnitude of this modulation component response was altered in a manner similar to the alteration in semicircular canal-ocular responses. These results suggest that physiologic alteration of the vestibulo-ocular reflex using deliberately mismatched visual and semicircular canal stimuli induces changes in both canal-ocular and otolith-ocular responses. We postulate, therefore, that central nervous system pathways responsible for controlling the gains of canal-ocular and otolith-ocular reflexes are shared.
Wall
C
C
Department of Otology and Laryngology, Harvard Medical School, Boston, MA.
Smith
T R
TR
Furman
J M
JM
D000222:Adaptation, Physiological; D000328:Adult; D003624:Darkness; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009041:Motion Sickness / Q000503:physiopathology; D009760:Nystagmus, Physiologic / Q000502:physiology; D010775:Photic Stimulation; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D012399:Rotation; D012665:Semicircular Canals / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology