Vestibular Precision at the Level of Perception, Eye Movements, Posture, and Neurons – PubMed
Figure 1:
Noise in vestibular behavior is added at different levels of processing, leading to imprecision in neurons, the VOR, perception, and posture. A: Illustration of precision and accuracy. Dots represent responses of the nervous system, which ideally would fall on the ideal value (dotted black line). Cyan dots illustrate an example of a system with high accuracy, i.e., the mean of the dots is near the ideal, and high precision, i.e., scatter of the dots is relatively low. Green dots illustrate an example of a system with low accuracy, i.e., the mean of the dots is far from ideal, and high precision, i.e., the scatter of the dots is relatively low. Purple dots illustrate an example of a system with high accuracy, i.e., the mean of the dots is near the ideal, and low precision, i.e., the scatter of the dots is relatively high. B: Noise is added to vestibular transduction at various levels of processing. C: Neuronal responses (reproduced from Jamali et al. 2013) show that when a repeated stimulus is presented, the firing rate response varies across repetitions. These variations usually follow a Gaussian distribution (red) and imprecision can be characterized by the standard deviation (red arrow) across the responses from a particular stimulus. D: The response of the vestibulo-ocular reflex varies trial-to-trial (grey) to stereotyped rotations of the head about the earth-vertical yaw axis. The dashed black line shows the ideal response, i.e., a gain of 1. The solid black line shows the mean response, and the blue arrow shows the inaccuracy of the mean response relative to the ideal. The red Gaussian distribution describes the trial-to-trial variability and the red arrow shows the standard deviation across trials (i.e., imprecision). Motor processes also add noise that affect the VOR. E: Example of a perceptual subjective visual vertical task in which subjects align a bar with perceived vertical with different body tilt angles. Subjects exhibit trial-to-trial variability across repeated trials (imprecision, red arrow), as well as well-known accuracy errors (blue arrow). Perceptual processes may also add noise that affect perception, and perception also receives non-vestibular sensory information. F: During stance, body tilt angle (black line) relative to gravity continuously deviates from perfectly upright, and sensory feedback, including vestibular feedback, is used to control muscles to stabilize the posture. Postural imprecision is described by the red Gaussian distribution and the red arrow shows the standard deviation across time. Motor processes, non-vestibular sensory noise, and feedback all contribute to postural imprecision.
