Keeping our balance—a tale of two systems: Our vestibular system reflects evolution from sea to land November 11, 2016 The transition from being sea creatures to living on land, even if it happened over 300 million years ago, seems to have left its traces on the way we keep our balance today. "It's a discovery that is likely to be controversial," says Kathy Cullen, the senior researcher on a paper on the subject that was published recently in Nature Communications. She has been working on this problem for over a decade with her colleague Maurice Chacron who also teaches in McGill's Department of Physiology. "What we've found is that there are two sensory channels that transmit information to the brain about how we move around in the world using fundamentally different approaches. No one has ever demonstrated anything of the kind before," says Cullen. "But what is even more exciting to us is that we believe that the different ways that each of these channels sends information to the brain is a legacy of the differences between needing to navigate in water and in air." http://medicalxpress.com/news/2016-11-balancea-tale-vestibular-evolution-sea.html
http://www.nature.com/articles/ncomms13229 Self-motion evokes precise spike timing in the primate vestibular system: Abstract The accurate representation of self-motion requires the efficient processing of sensory input by the vestibular system. Conventional wisdom is that vestibular information is exclusively transmitted through changes in firing rate, yet under this assumption vestibular neurons display relatively poor detection and information transmission. Here, we carry out an analysis of the system’s coding capabilities by recording neuronal responses to repeated presentations of naturalistic stimuli. We find that afferents with greater intrinsic variability reliably discriminate between different stimulus waveforms through differential patterns of precise (∼6 ms) spike timing, while those with minimal intrinsic variability do not. A simple mathematical model provides an explanation for this result. Postsynaptic central neurons also demonstrate precise spike timing, suggesting that higher brain areas also represent self-motion using temporally precise firing. These findings demonstrate that two distinct sensory channels represent vestibular information: one using rate coding and the other that takes advantage of precise spike timing.
