Cerebellum-mediated trainability of eye and head movements for dynamic gazing

Abstract

ObjectiveTo investigate whether gaze stabilization exercises (GSEs) improve eye and head movements and whether low-frequency cerebellar repetitive transcranial magnetic stimulation (rTMS) inhibits GSE trainability.Methods25 healthy adults (real rTMS, n = 12; sham rTMS, n = 13) were recruited. Real or sham rTMS was performed for 15 min (1 Hz, 900 stimulations). The center of the butterfly coil was set 1 cm below the inion in the real rTMS. Following stimulation, 10 trials of 1 min of a GSE were conducted at 1 min intervals. In the GSE, the subjects were instructed to stand upright and horizontally rotate their heads according to a beeping sound corresponding to 2 Hz and with a gaze point ahead of them. Electrooculograms were used to estimate the horizontal gaze direction of the right eye, and gyroscopic measurements were performed to estimate the horizontal head angular velocity during the GSE trials. The percentage change from the first trial of motion range of the eye and head was calculated for each measurement. The percent change of the eye/head range ratio was calculated to assess the synchronous changes of the eye and head movements as the exercise increased.ResultsBayesian two-way analysis of variance showed that cerebellar rTMS affected the eye motion range and eye/head range ratio. A post hoc comparison (Bayesian t-test) showed evidence that the eye motion range and eye/head range ratio were reduced in the fifth, sixth, and seventh trials compared with the first trial sham stimulation condition.ConclusionsGSEs can modulate eye movements with respect to head movements, and the cerebellum may be associated with eye–head coordination trainability for dynamic gazing during head movements.

Cerebellar Repetitive Transcranial Magnetic Stimulation and Noisy Galvanic Vestibular Stimulation Change Vestibulospinal Function

“…The participants were instructed to lie down on a bed in the prone position. Because previous studies have shown that the figure-of-eight coil could stimulate the cerebellum (Haarmeier and Kammer, 2010;Popa et al, 2010;Tremblay et al, 2016), a magnetic stimulator (MagPro compact, MagVenture, Denmark) was used to deliver TMS to the cerebellum with a butterfly coil (MC-B70, MagVenture, Denmark) (Matsugi et al, 2019). The center of the coil's junction was set at a distance 1 cm below the inion to stimulate the central region of the cerebellum (Zangemeister and Nagel, 2001;Nagel and Zangemeister, 2003;Jayasekeran et al, 2011;Hardwick et al, 2014;van Dun et al, 2017); prior research has demonstrated that stimulation from this position can modulate vestibular and ocular motor functions (Zangemeister and Nagel, 2001;Nagel and Zangemeister, 2003;Jenkinson and Miall, 2010).…”

“…As previous studies have observed that an upward current applied to the cerebellum can effectively stimulate this region (Ugawa et al, 1995;Hiraoka et al, 2010;Matsugi et al, 2013), the coil was oriented such that the current therein was directed downward to deliver the upward current to the brain (van Dun et al, 2017). TMS intensity was set to 50% of the maximum stimulator output: the same setting as those employed by previous studies investigating cerebellar and vestibular functions (Zangemeister and Nagel, 2001; Nagel and Zangemeister, 2003;Haarmeier and Kammer, 2010;Jenkinson and Miall, 2010;van Dun et al, 2017;Matsugi et al, 2019). Because a 1-Hz crTMS reduces motor function and motor adaptation (Miall and Christensen, 2004;Jenkinson and Miall, 2010) the inter-stimulus interval was set at 1 s, and 900 pulses were applied (Fierro et al, 2007;Popa et al, 2010;Matsugi et al, 2019).…”

“…TMS intensity was set to 50% of the maximum stimulator output: the same setting as those employed by previous studies investigating cerebellar and vestibular functions (Zangemeister and Nagel, 2001; Nagel and Zangemeister, 2003;Haarmeier and Kammer, 2010;Jenkinson and Miall, 2010;van Dun et al, 2017;Matsugi et al, 2019). Because a 1-Hz crTMS reduces motor function and motor adaptation (Miall and Christensen, 2004;Jenkinson and Miall, 2010) the inter-stimulus interval was set at 1 s, and 900 pulses were applied (Fierro et al, 2007;Popa et al, 2010;Matsugi et al, 2019). In the stimulation condition, electrical field stimulation of the brain structures was performed with SimNIBS software (version 2.1.1) using default head models, biological tissue conductivity values included in the software, and the aforementioned parameters of the TMS using a butterfly coil (shown in Figure 2) (Thielscher et al, 2015).…”

“…Furthermore, the cerebellum is involved in the plasticity of vestibular reflex excitability, because crTMS modulates the effect of intervention for increased vestibulo-ocular movement for dynamic gaze (Matsugi et al, 2019). Deep cerebellar nuclei and Purkinje fibers in the cerebellar gray matter project to the vestibular nucleus.…”

Cerebellar Transcranial Magnetic Stimulation Reduces the Silent Period on Hand Muscle Electromyography During Force Control

“…Transcranial magnetic stimulation (TMS) is often used for assessing motor control associated with the primary motor cortex (M1) [1]. Repetitive [2,3], paired-pulse [4], and single-pulse TMS enables the probing of neural circuit function in M1 [1]. Single-pulse TMS induces a silent period (SP) on electromyography (EMG) in hand muscles during the slight voluntary muscle contraction that follows motor-evoked potentials (MEPs) [5,6].…”