Comparison of Head Thrust Test With Head Autorotation Test Reveals That the Vestibulo-ocular Reflex Is Enhanced During Voluntary Head Movements

Abstract

When comparison of half-cycle gains is used to identify the lesion side, self-generated predictable head movement paradigms, such as HART and active HTT, are less accurate than passive HTT in the characterization of UVD, in part because preprogramming can augment the VOR during voluntary head movements.

The Interaction of Pre-programmed Eye Movements With the Vestibulo-Ocular Reflex

“…We also found that despite a relatively low gain, eye movements show a strong correlation to head movement, as demonstrated by a high R 2 (0.98 ± 0.01). During active-only movements, compensatory eye movements had a similarly high R 2 (0.97 ± 0.03) but a significantly higher gain (−0.83 ± 0.13; p < 0.001) and shorter latency (1.3 ms ± 1.6; p < 0.001) as would be expected with PPEM and as previously noted by others (Della Santina et al, 2002 ; Shanidze et al, 2010a ). Thus, despite the goal of stabilizing gaze, gaze moved at approximately 30% of head velocity during passive-only movements but only 17% of head velocity during active-only head movements.…”

Restoration of 3D vestibular sensation in rhesus monkeys using a multichannel vestibular prosthesis

“…This is similar to observations in animals with a single normal labyrinth after contralateral labyrinthectomy (Sadeghi et al, 2007) and in humans after unilateral labyrinthectomy (Della Santina et al, 2002) or unilateral treatment with intratympanic gentamicin (Carey et al, 2002). However, asymmetry was typically greater in the prosthetic case than in our unilaterally gentamicin-treated monkeys, probably because (1) rhesus monkeys appeared to suffer only modest degradation of VOR responses after unilateral gentamicin treatment, and (2) withdrawal of MVP excitation to encode inhibitory head rotations probably cannot down-modulate afferent firing rates below a floor of spontaneous natural activity, whereas a single normal labyrinth can (e.g., via down-modulation of hair cell neurotransmitter release).…”

The Role of Predictability in Saccadic Eye Responses in the Suppression Head Impulse Test of Horizontal Semicircular Canal Function

“…This suggests that this time delay of the saccadic response is mainly depending on the (non-conditioned) predictability of the impulse. This relation between the predictability and the latency delay of the saccadic responses has been previously reported in head rotation based tests with a measured delay of 15 ms of eye responses as an effect of predictability ( 16 ). In the present study, we further presented the forced predictability as a mechanism that can influence the time latency of the saccadic responses.…”