Transaural linear vestibulo-ocular reflexes from a single utricle.
To clarify the directional sensitivity of a single utricle with respect to the transaural linear vestibulo-ocular reflex (L-VOR) we studied seven patients before and after vestibular neurectomy. Patients were seated upright in an electrically powered car running on a linear track. Transaural acceleration steps of 0.24 g were applied randomly to the left and right in the dark. The slow phase velocity of the L-VOR was measured from the average of the induced compensatory eye movements. L-VOR asymmetry was calculated as (R-L/R + L x 100) and is < 13% in normals. Before surgery, responses were mostly symmetrical. One week after surgery, however, all patients had diminished or absent responses with medial acceleration of the remaining utricle. Asymmetries averaged 65% after correction for spontaneous nystagmus. Our findings indicate that afferents for the L-VOR originate from the lateral region of the macula where hair cells with ipsilateral on-directions are located.
Lempert
T
T
MRC Human Movement and Balance Unit, National Hospital for Neurology and Neurosurgery, London, UK.
Gianna
C
C
Brookes
G
G
Bronstein
A M
AM
Gresty
M A
MA
D005123:Eye / Q000503:physiopathology*; D005133:Eye Movements / Q000502:physiology*; D006801:Humans; D008575:Meniere Disease / Q000503:physiopathology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*