Unilateral Vestibular Loss Impairs External Space Representation

Abstract

The vestibular system is responsible for a wide range of postural and oculomotor functions and maintains an internal, updated representation of the position and movement of the head in space. In this study, we assessed whether unilateral vestibular loss affects external space representation. Patients with Menière's disease and healthy participants were instructed to point to memorized targets in near (peripersonal) and far (extrapersonal) spaces in the absence or presence of a visual background. These individuals were also required to estimate their body pointing direction. Menière's disease patients were tested before unilateral vestibular neurotomy and during the recovery period (one week and one month after the operation), and healthy participants were tested at similar times. Unilateral vestibular loss impaired the representation of both the external space and the body pointing direction: in the dark, the configuration of perceived targets was shifted toward the lesioned side and compressed toward the contralesioned hemifield, with higher pointing error in the near space. Performance varied according to the time elapsed after neurotomy: deficits were stronger during the early stages, while gradual compensation occurred subsequently. These findings provide the first demonstration of the critical role of vestibular signals in the representation of external space and of body pointing direction in the early stages after unilateral vestibular loss.

Vestibular contribution to three-dimensional dynamic (allocentric) and two-dimensional static (egocentric) spatial memory

“…Likewise neurological patients with a spatial hemineglect, which involves the vestibular cortex, have both object-based allocentric and body-centered egocentric impairment of spatial awareness [5]. Similar findings were seen in patients after an acute unilateral vestibular loss [6].…”

The development of a new questionnaire for cognitive complaints in vertigo: the Neuropsychological Vertigo Inventory (NVI)

“…A second explanation is that spatial perception (or navigational abilities) might be truly altered in patients with vestibular disorders [22,24,[63][64][65], but that the impairment could be rapidly compensated, or reduced through vestibular rehabilitation [66]. Furthermore, spatial perception may be more difficult to self-evaluate because of the temporary characteristic of their affection in vertigo.…”

Does vestibular input affect body posture alterations?

“…By regulating the skeletal muscle tone, the central vestibular system pathways, mainly the lateral vestibulospinal tract, play an important role in the correct postural muscle activity and maintaining correct body posture [6][7][8][9]. The vestibulospinal tract which is the neural tract starting primarily in lateral vestibular nucleus, partly in the inferior vestibular nucleus and the medial vestibular nucleus runs in front of and ends in the anterior part of the spinal cord where motor representation is located [7,33].…”

“…The sensory processes (vision, tactile, vestibular system), movement and body image are integrated for controlling overall body posture and spinal alignment The integration of external, proprioceptive and interoceptive stimuli generate in the central nervous system, a coherent picture of the various parts of the body, the body as a whole and the body's interaction to the environment [6][7][8][9]. In recent years, there has been an increasing interest in the role of vestibular system on controlling the body posture [7][8][9]. According to imaging studies by Pfeiffer et al, cortex activity during vestibular stimulation, identified in complex regions of cerebral cortex, coincides with cortical representation for vision, movement, somatosensation, and proprioception [8].…”

“…The correlation between visual and motion perception is crucial element of effective activation of postural stability [7,8]. It should be emphasized that, the vestibular system supports balance, postural control, and mobility [6][7][8][9].…”