空間識と可塑性（何が変わるか）

Abstract

The vestibulo-ocular reflex (VOR) generates smooth eye movements that are compensatory for head movements to ensure gaze stabilization during head rotation. The VOR, which consists of semicircular-ocular reflex (ScOR) and otolith-ocular reflex (OOR), is adaptively controlled to correct VOR performance when visual-vestibular mismatch arises during head movement. Most studies have investigated horizontal ScOR gain adaptation after exposure to enhanced, reduced, or direction-reversed visual surround motion produced either by optical devices or by coupling altered visual surround motion with head movement in such a way as to reduce or eliminate retinal image slip during head movement. In natural head movement, not only the ScOR, but also the OOR must be used to keep the line of sight stationary in space. It remains unclear how human subjects combine input from the semicircular canals and otolith organs to establish spatial orientation. To investigate the synergy of the ScOR and the OOR, we examine the plasticity of the OOR using visual-vestibular interaction and the effect of adaptive plasticity in the OOR upon ScOR. We demonstrated a reason-ably consistent effect of adaptation of OOR sensitivity on the ScOR using a visual magnification paradigm. Our data suggest that the OOR and the ScOR partly share common neural pathways in such a way that a change in the synaptic efficacy of one pathway is accompanied by a change in the other. Recent data have also suggested the existence of a convergent neuron that receives input from both the semicircular canals and otolith organs in the cat. The role of a neural store that receives input from both the semicircular canals and the otolith organs to maintain a spatial orientation is discussed.