The neuroanatomical basis of oculomotor disorders: the dual motor control of extraocular muscles and its possible role in proprioception

Büttner‐Ennever, Jean A.; Horn, Anja K.E.

doi:10.1097/00019052-200202000-00007

Cited by 39 publications

(26 citation statements)

References 76 publications

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“…Thus they may participate in a proprioceptive system important for setting and stabilising the alignment of the eye. 46 However, due to slower conduction and execution time the motor responses mediated by this system could be expected to occur at longer latencies as the responses in the current study.…”

Section: Proprioceptive Reflexes Of the Extraocular Musclesmentioning

confidence: 64%

Short latency responses in the averaged electro-oculogram elicited by vibrational impulse stimuli applied to the skull: could they reflect vestibulo-ocular reflex function?

Jombik¹

2005

Journal of Neurology, Neurosurgery & Psychiatry

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Objectives: To investigate whether vibrational impulse stimuli applied to the skull can be used to evoke the vestibulo-ocular reflex (VOR) and detect vestibular lesions. Methods: Twenty four patients with unilateral vestibular loss (UVD), five with bilateral vestibular loss, two with ocular palsies, and 10 healthy subjects participated. Vibrations of the skull were induced with head taps and with a single period of 160 Hz tone burst on the inion, vertex, and the mastoids while the patients viewed a distant target. Several patients were also examined while viewing a near target, with eccentric gaze and in tilted postures. Responses were recorded by EOG. Results: Responses occurred between 5 ms and 20 ms and seemed to be compensatory to the second phase of the sine wave of vibration impulse and were greatly diminished/absent in patients with bilateral VD and ocular palsies. The patients with UVD had asymmetrical responses in the vertical EOG with stimuli applied on the inion and vertex, with enhancement of the response amplitude on the side of vestibular loss and/or diminution on the healthy side. The asymmetry ratios between the healthy subjects and patients with UVD, and among patients with UVD were statistically significant. Some gaze and positional influences could be demonstrated consistent with otolithic reflexes. Conclusion: If the asymmetric responses to skull vibration in UVD result from passive oscillatory movements of the orbital tissues they may reflect the otolith mediated sustained skew torsion. Conversely, if generated by active eye movements, their likely origin is a phasic VOR. B oth primary otolithic and canal afferents of a monkey can be activated by vibration. The lowest phase locking thresholds have been determined at 270 to 280 dB and median values in the most sensitive frequency range (200-400 Hz) at 220 to 240 dB of gravitational acceleration.1 It is still not clear whether activation of vestibular receptors by vibration has the same mechanical basis as the response to more physiological head movements. Mechanical factors are not the only determinants of response dynamics since vestibular nerve fibres can show a frequency dependent increase in gain greater than that predicted for the mechanics of sensory end organs. The mechanics of the otolithic membrane can be approximated by a damped second-order system with a resonant frequency of the order of 50-500 Hz. Thus, in contrast to the cupula-endolymph system in which the upper frequency limit is set below 60 Hz, the otolithic membrane is much better suited for transmission of bone vibrations in the audio frequency range. Conversely, canal neurones tend to be more irregular than otolith neurones, and hence might be expected to have lower vibration thresholds.

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Section: Proprioceptive Reflexes Of the Extraocular Musclesmentioning

confidence: 64%

Short latency responses in the averaged electro-oculogram elicited by vibrational impulse stimuli applied to the skull: could they reflect vestibulo-ocular reflex function?

Jombik¹

2005

Journal of Neurology, Neurosurgery & Psychiatry

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“…They may be the principal source of proprioceptive feedback from extraocular muscles (19,20), although as with muscle spindles, this has been disputed (21).…”

Section: Extraocular Muscle Receptorsmentioning

confidence: 99%

“…Based mainly on animal studies, Buttner-Ennever et al (20,23) have suggested that each layer of the extraocular muscles has its own type of sensory receptor to generate afferent signals, with the orbital layer utilizing muscle spindles and the global layer relying on palisade endings. These investigators also suggest that sensory signals from palisade endings form part of a proprioceptive feedback network that modulates the non-twitch motor neurons that innervate the slow non-twitch extraocular muscles fibers.…”

Section: Experimental Studiesmentioning

confidence: 99%

Proprioception in Extraocular Muscles

Weir¹

2006

Journal of Neuro-Ophthalmology

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Human extraocular muscles are richly endowed with sensory receptors. The precise role of afferent signals derived from these proprioceptors in ocular motor control and spatial localization has been the subject of considerable debate for more than a century. Laboratory-based and clinical studies have increasingly suggested that proprioceptive signals from extraocular muscles influence visuomotor behavior.

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“…From palisade endings in extraocular muscle. 4 Although the precise function of these putative proprioceptive endings is a topic of debate, and the particular pathways by which they might influence the neural integrator not completely specified, the general proposition that information about muscle state is important for accurate eye-velocity commands seems very plausible. A fault in the proprioceptive input to the neural integrator might well produce nystagmus, and indeed modulation of proprioceptive input has been suggested as an explanation for the beneficial effects of horizontal rectus tenotomy on EON.…”

Section: Underlying Neuroanatomymentioning

confidence: 99%