Neuro-otology Unit, Division of Brain Sciences, Imperial College London, Charing Cross Hospital, London, UK.
PLoS One. 2013 May 9;8(5):e61862. doi: 10.1371/journal.pone.0061862. Print 2013.
Little is known about the vestibulo-perceptual (VP) system, particularly after a unilateral vestibular lesion. We investigated vestibulo-ocular (VO) and VP function in 25 patients with vestibular neuritis (VN) acutely (2 days after onset) and after compensation (recovery phase, 10 weeks). Since the effect of VN on reflex and perceptual function may differ at threshold and supra-threshold acceleration levels, we used two stimulus intensities, acceleration steps of 0.5°/s(2) and velocity steps of 90°/s (acceleration 180°/s(2)). We hypothesised that the vestibular lesion or the compensatory processes could dissociate VO and VP function, particularly if the acute vertiginous sensation interferes with the perceptual tasks. Both in acute and recovery phases, VO and VP thresholds increased, particularly during ipsilesional rotations. In signal detection theory this indicates that signals from the healthy and affected side are still fused, but result in asymmetric thresholds due to a lesion-induced bias. The normal pattern whereby VP thresholds are higher than VO thresholds was preserved, indicating that any 'perceptual noise' added by the vertigo does not disrupt the cognitive decision-making processes inherent to the perceptual task. Overall, the parallel findings in VO and VP thresholds imply little or no additional cortical processing and suggest that vestibular thresholds essentially reflect the sensitivity of the fused peripheral receptors. In contrast, a significant VO-VP dissociation for supra-threshold stimuli was found. Acutely, time constants and duration of the VO and VP responses were reduced - asymmetrically for VO, as expected, but surprisingly symmetrical for perception. At recovery, VP responses normalised but VO responses remained shortened and asymmetric. Thus, unlike threshold data, supra-threshold responses show considerable VO-VP dissociation indicative of additional, higher-order processing of vestibular signals. We provide evidence of perceptual processes (ultimately cortical) participating in vestibular compensation, suppressing asymmetry acutely in unilateral vestibular lesions.
关于前庭感知（VP）系统，人们知之甚少，尤其是在单侧前庭病变之后。我们在 25 例前庭神经炎（VN）患者中进行了研究，分别在急性期（发病后 2 天）和恢复期（10 周）对前庭眼动（VO）和 VP 功能进行了研究。由于 VN 对反射和知觉功能的影响可能在阈下和超阈加速度水平上有所不同，因此我们使用了两种刺激强度，加速度为 0.5°/s² 和速度为 90°/s（加速度为 180°/s²）。我们假设，前庭病变或代偿过程可能会分离 VO 和 VP 功能，尤其是在急性眩晕感干扰知觉任务时。在急性期和恢复期，VO 和 VP 阈值均升高，尤其是在同侧旋转时。在信号检测理论中，这表明来自健康侧和病变侧的信号仍在融合，但由于病变引起的偏差导致不对称阈值。VP 阈值高于 VO 阈值的正常模式得以保留，表明任何由眩晕引起的“知觉噪声”都不会破坏知觉任务固有的认知决策过程。总的来说，VO 和 VP 阈值的平行发现表明，几乎没有或没有额外的皮质处理，并且暗示前庭阈值本质上反映了融合的外周感受器的敏感性。相比之下，在超阈值刺激下发现了显著的 VO-VP 分离。急性期，VO 和 VP 反应的时间常数和持续时间缩短 - 如预期的那样，VO 反应不对称，但令人惊讶的是，感知反应却是对称的。在恢复期，VP 反应正常化，但 VO 反应仍然缩短且不对称。因此，与阈值数据不同，超阈值反应显示出相当大的 VO-VP 分离，表明对前庭信号进行了额外的高级处理。我们提供了知觉过程（最终是皮质）参与前庭代偿的证据，在单侧前庭病变中急性抑制了不对称性。
