Adaptive plasticity in the naso-occipital linear vestibulo-ocular reflex

This study was intended to test the adaptive plasticity of the vestibulo-ocular reflex before and after either a midsagittal or parasagittal incision in the brainstem. Eye movements were measured with the electromagnetic search coil technique during the vestibulo-ocular reflex (VORD) in the dark, the optokinetic reflex (OKN), and the visuo-vestibular adaptive training procedure. Two types of visual-vestibular combined stimulation were applied by means of low frequency stimuli (0.05 to 0.10 Hz). In order to increase or decrease the VORD gain, the optokinetic drum was oscillated either 180∘ out-of-phase or in-phase with the vestibular stimulus turntable. This “training” procedure was applied for 4 hours. Initial measurements of the VORD were normal with a mean gain value of 0.92 ± 0.08. After 4 hours of “training” with the out-of-phase condition (180∘), VORD gain reached mean values of 1.33 ± 0.11 (n = 6 cats). In the in-phase combination, the mean VORD gain decreased from 1.0 to 0.63 ± 0.02 (n = 2 cats). No significant change of VORD phase was found in any of the cats. Midsagittal or parasagittal pontomedullary brainstem incisions were performed in 4 cats. Recovery of the VOR was tested on the 2nd, 7th, and 30th day after operation. After the 30th day, recovery of the VORD gain stabilized at about 66% of the initial preoperative value. At this stage of the recovery, the optokinetic response (OKN) of the midsagittal-Iesioned cats was practically normal: in the parasagittal-Jesioned cats, the postoperative OKN responses were asymmetric. After stabilization of recovery, lesioned cats were trained with the same adaptation procedure. Although the direct effect of the visuo-vestibular combined stimulation during the training was still operative in all lesioned cats, the adaptive plasticity was completely abolished by the lesions. These results suggest that the commissural brainstem network may play a crucial role in the acquisition of the forced VOR adaptation.

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The Aging Vestibulo-Ocular Reflex (VOR) and Adaptive Plasticity

Acta Oto-Laryngologica ◽

10.3109/00016489109131406 ◽

1991 ◽

Vol 111 (sup481) ◽

pp. 297-300 ◽

Cited By ~ 13

Author(s):

Gary D. Paige

Keyword(s):

Adaptive Plasticity ◽

Ocular Reflex ◽

Vestibulo Ocular Reflex

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The squirrel monkey vestibulo-ocular reflex and adaptive plasticity in yaw, pitch, and roll

Experimental Brain Research ◽

10.1007/bf00228506 ◽

1991 ◽

Vol 87 (1) ◽

Cited By ~ 35

Author(s):

S. Bello ◽

G.D. Paige ◽

S.M. Highstein

Keyword(s):

Squirrel Monkey ◽

Adaptive Plasticity ◽

Ocular Reflex ◽

Vestibulo Ocular Reflex

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Vestibular Neurophysiology

Otolaryngology ◽

10.1177/019459988409200112 ◽

1984 ◽

Vol 92 (1) ◽

pp. 55-58 ◽

Cited By ~ 7

Author(s):

Hugh O. Barber

Keyword(s):

Vestibular System ◽

Low Frequency ◽

The Elderly ◽

Adaptive Plasticity ◽

Ocular Reflex ◽

Visual Stabilization ◽

Vestibulo Ocular Reflex ◽

Bedside Tests ◽

Eye Velocity ◽

Simple Bedside

An important function of the vestibular system is to secure visual stabilization during head movement, and at low-frequency movements the optokinetic and pursuit systems collaborate to this end. Oscillopsia results when eye velocity fails to match head velocity. Simple bedside tests to identify oscillopsia and impaired cancellation of the vestibulo-ocular reflex (VOR) are described. Adaptive plasticity, directed to the goal of maintenance of foveation despite marked changes in the external (e.g., reversed visual surround) or internal (e.g., after labyrinthectomy) environment, is an important attribute of the vestibular system. The flocculus and some of its connections are essential to this function. Reduction of floccular efficiency, as in the elderly, might be an important cause of defective adaptation to a vestibular lesion, such as labyrinthectomy.

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