Passive eye movements induced by electromagnetic force (EMF) in rats.

Yue Yu,David S Sandlin,Alberto A Arteaga,Tian-Wen Chen,Susan Warren,Jerome Allison,Chun-Ming Zhang,Paul May,Jun Huang,Hong Zhu,Shao-Xun Wang,Wu Zhou,Yang Ou

doi:10.24272/j.issn.2095-8137.2019.024

Abstract

Accurate information on eye position in the orbit is available from visual feedback, efference copy of the oculomotor commands and proprioceptive signals from the extraocular muscles (EOM). Whereas visual feedback and oculomotor commands have been extensively studied, central processing of EOM proprioceptive signals remains to be elucidated. A challenge to the field is to develop an approach to induce passive eye movements without physically contacting the eyes. A novel method was developed to generate passive eye movements in rats. A small rare-earth magnet disk (0.7 mm diameter, 0.5 mm thickness) was attached to the surface of a rat’s eyeball. A metal rod (5 mm diameter) wrapped with an electromagnetic (EM) coil was placed near the magnet (8–15 mm). By passing currents to the EM coil, electromagnetic force (EMF) was generated and acted upon the magnet and induced passive eye movements. The EMF induced well-defined passive eye movements, whose directions were dependent on current polarity and amplitudes and peak velocities were dependent on current intensity and duration. Peak velocities of the EMF-induced eye movements were linearly related to amplitudes, exhibiting main sequence relationships similar to that of saccades in awake rats and eye movements induced by electrical microstimulation of the abducens nucleus in anesthetized rats. Histological examination showed that repetitive EMF stimulations did not appear to result in damages in the EOM fibers. These results validated the EMF approach as a novel tool to investigate EOM proprioceptive signals and their roles in visual localization and gaze control.

Highlights

An important issue in modeling visual localization and gaze control is to determine whether the central nervous system (CNS) obtains eye position information in the orbit via efference copy of ocular motor commands or proprioception signals from the extraocular muscles (EOM) or the orbital connective tissues
Based on the assumption that the trigeminal nerves carry eye proprioceptive information to the brain (Porter et al, 1983), these results suggested that eye proprioception signal is not necessary for visual localization and gaze control because efference copy of the oculomotor motor commands is sufficient to implement these tasks
We described a novel approach, which employs electromagnetic force (EMF) to induce passive eye movements in rats

Summary

INTRODUCTION

An important issue in modeling visual localization and gaze control is to determine whether the central nervous system (CNS) obtains eye position information in the orbit via efference copy (or corollary discharge) of ocular motor commands or proprioception signals from the extraocular muscles (EOM) or the orbital connective tissues. Based on the assumption that the trigeminal nerves carry eye proprioceptive information to the brain (Porter et al, 1983), these results suggested that eye proprioception signal is not necessary for visual localization and gaze control because efference copy of the oculomotor motor commands is sufficient to implement these tasks. The third method is to perturb the proprioceptive representation by vibrating the extraocular muscle tendon or electrically stimulating extraocular muscles (Han & Lennerstrand, 1999) These approaches suffer from the fact they may disrupt ongoing behaviors and create other sensory or motor signals. It can be used to determine the roles of eye position proprioceptive signals in visual localization and gaze control

MATERIALS AND METHODS

Surgical procedures

RESULTS