Signal processing in first- and second-order vestibular neurons.

This symposium was held in Anaheim California, on February 8, 2010, at the 33rd annual Midwinter Meeting of the Association for Research in Otolaryngology (ARO). The meeting program and abstracts are published online (http://aro.org/abstracts/abstracts.html). Organized by Jay Goldberg and Kenna Peusner, the symposium was directed toward clinicians who want to bridge the gap between basic science and treating patients for vestibular disorders, vestibular neuroscientists using structural and functional approaches to understand the labyrinth and its central pathways at the system, cellular, and molecular levels, and auditory neuroscientists intrigued by the similarities and differences in signal processing in the two systems. This special issue contains those presentations on signal processing in second-order vestibular neurons and their connections. The articles underwent peer-review for this special issue. We would like to thank the Journal of Vestibular Research for the production of this special issue devoted to the symposium. The vestibular system demonstrates a remarkable plasticity in response to changing environmental demands [9] and to recover function after pathologies affecting the peripheral vestibular receptors on one side [16]. Second-order vestibular neurons are characterized by a high degree of plasticity in their connections with first-order vestibular neurons and nonlabyrinthine inputs (for review, see [20]). As demonstrated in this symposium, recent research has been directed toward defining synaptic transmission and ionic conductances involved in signal processing from the vestibular periphery to the first brain centers located in the vestibular nuclei. The experiments utilize multiple structural and functional approaches performed on intact animals, isolated vestibular circuits in culture, or brain slice preparations. The article by Beraneck and Straka entitled “Vestibular Signal Processing by Separate Sets of Neuronal Filters” reviews recent research on detecting static head position and head motion by the peripheral vestibular receptors and the activation of specific receptor areas by high or low frequency movements during locomotion. Vestibular nerve afferents convey the different dynamics of head motion in a wide range of frequencies to second–order vestibular neurons, which are equipped dynamically to process the signals [18]. From the firing patterns generated by second-order vestibular nuclei neurons, the authors propose that there are two different populations of vestibular nuclei neurons that process high or low frequency signals within two separate pathways [19]. Tonic-firing vestibular nuclei neurons process low frequency signals, and are well-suited for synaptic integration, whereas phasic-firing vestibular nuclei neurons process high frequency signals and are designed to detect events. This dual system may underlie the ability of the brain to distinguish between tilt and linear translation, or self-induced motion and passive body movements (for review, see [1]). Finally, differences in the dynamic properties between frog and mammalian vestibular nuclei neurons are discussed in relation to species-specific locomotor patterns.