Linear transmission of neural information between afferent neurons and vestibular nuclei

초록

Galvanic vestibular stimulation (GVS) is widely used in vestibular research, but the ambiguity of its effects on the central nervous system still remains. Especially, it has not thoroughly studied how the neural information by GVS is transmitted when it is combined with those by the kinematic stimuli related with angular or linear head movements. Traditionally, the neural information of vestibular reflexes between afferent neurons and those in the vestibular nuclei (VN) has been believed to be linearly transmitted. Many studies have supported this view showing the relation between stimulation and the neuronal firing rates related with head or eye velocity. However, this view is challenged by the efficient neural representation in the central nervous system. According to Massot et al. (2012), the central vestibular neurons nonlinearly respond to high frequency head rotation while the responses to low frequency head rotation was linearly maintained in both the afferent and the VN neurons. Here, we investigated the linear transmission of neural information beTtween the afferent neurons and VN, using a combined stimulus with head rotation and galvanic vestibular stimulation (GVS). Twenty six (15 regular and 11 irregular units) responses from twenty healthy guinea pigs were used for this study. Following anesthesia, the animal’s head was fixed in a stereotaxic apparatus, and loaded on top of a horizontally combined stimulus of GVS and horizontal head rotation. Two comparisons between the firing rates of single kinetic and a combined stimulus with GVS demonstrated that the linear transmission of neural information was maintained from the afferent neurons to the VN.