TY - GEN A1 - Knorr, Alexander G. A1 - Gravot, Céline M. A1 - Gordy, Clayton A1 - Glasauer, Stefan A1 - Straka, Hans T1 - I spy with my little eye: a simple behavioral assay to test color sensitivity on digital displays T2 - Biology Open Y1 - 2018 U6 - https://doi.org/10.1242/bio.035725 SN - 2046-6390 VL - 7 IS - 10 ER - TY - GEN A1 - Kutz, Dieter F. A1 - Kolb, Florian P. A1 - Glasauer, Stefan A1 - Straka, Hans T1 - Somatosensory Influence on Platform-Induced Translational Vestibulo-Ocular Reflex in Vertical Direction in Humans T2 - Frontiers in Neurology N2 - The vestibulo-ocular reflex (VOR) consists of two components, the rotational VOR (rVOR) elicited by semicircular canal signals and the translational VOR (tVOR) elicited by otolith signals. Given the relevant role of the vertical tVOR in human walking, this study aimed at measuring the time delay of eye movements in relation to whole-body vertical translations in natural standing position. Twenty (13 females and 7 males) healthy, young subjects (mean 25 years) stood upright on a motor-driven platform and were exposed to sinusoidal movements while fixating a LED, positioned at a distance of 50 cm in front of the eyes. The platform motion induced a vertical translation of 2.6 cm that provoked counteracting eye movements similar to self-paced walking. The time differences between platform and eye movements indicated that the subject's timing of the extraocular motor reaction depended on stimulus frequency and number of repetitions. At low stimulus frequencies (<0.8 Hz) and small numbers of repetitions (<3), eye movements were phase advanced or in synchrony with platform movements. At higher stimulus frequencies or continuous stimulation, eye movements were phase lagged by ~40 ms. Interestingly, the timing of eye movements depended on the initial platform inclination. Starting with both feet in dorsiflexion, eye movements preceded platform movements by 137 ms, whereas starting with both feet in plantar flexion eye movement precession was only 19 ms. This suggests a remarkable influence of foot proprioceptive signals on the timing of eye movements, indicating that the dynamics of the vertical tVOR is controlled by somatosensory signals. Y1 - 2020 U6 - https://doi.org/10.3389/fneur.2020.00332 SN - 1664-2295 VL - 11 SP - 1 EP - 10 ER - TY - GEN A1 - Glasauer, Stefan A1 - Straka, Hans T1 - Low Gain Values of the Vestibulo-Ocular Reflex Can Optimize Retinal Image Slip T2 - Frontiers in Neurology N2 - The angular vestibulo-ocular reflex (aVOR) stabilizes retinal images by counter-rotating the eyes during head rotations. Perfect compensatory movements would thus rotate the eyes exactly opposite to the head, that is, eyes vs. head would exhibit a unity gain. However, in many species, but also in elderly humans or patients with a history of vestibular damage, the aVOR is far from compensatory with gains that are in part considerably lower than unity. The reason for this apparent suboptimality is unknown. Here, we propose that low VOR gain values reflect an optimal adaptation to sensory and motor signal variability. According to this hypothesis, gaze stabilization mechanisms that aim at minimizing the overall retinal image slip must consider the effects of (1) sensory and motor noise and (2) dynamic constraints of peripheral and central nervous processing. We demonstrate that a computational model for optimizing retinal image slip in the presence of such constraints of signal processing in fact predicts gain values smaller than unity. We further show specifically for tadpoles of the clawed toad, Xenopus laevis with particularly low gain values that previously reported VOR gains quantitatively correspond to the observed variability of eye movements and thus constitute an optimal adaptation mechanism. We thus hypothesize that lower VOR gain values in elderly human subjects or recovered patients with a history of vestibular damage may be the sign of an optimization given higher noise levels rather than a direct consequence of the damage, such as an inability of executing fast compensatory eye movements. Y1 - 2022 U6 - https://doi.org/10.3389/fneur.2022.897293 SN - 1664-2295 VL - 13 ER - TY - GEN A1 - Glasauer, Stefan A1 - Straka, Hans T1 - Ear pins down evolution of thermoregulation T2 - Nature N2 - An analysis of fossil specimens of the inner ear helps to refine the timeframe of a key transition in vertebrate evolution — when our mammal-like ancestors began to regulate and maintain a high body temperature. Y1 - 2022 U6 - https://doi.org/10.1038/d41586-022-01943-1 IS - 607 SP - 661 EP - 662 ER - TY - GEN A1 - Glasauer, Stefan A1 - Straka, Hans T1 - Optimality of the vestibulo-ocular reflex T2 - Abstracts NWG Meeting Göttingen 2021 Y1 - 2021 UR - https://www.nwg-goettingen.de/2021/module/posterliste/supMat.asp?nr=T17-11 VL - 2021 ER - TY - GEN A1 - Glasauer, Stefan A1 - Straka, Hans T1 - Der Beginn der Warmblütigkeit T2 - Spektrum der Wissenschaft Y1 - 2023 UR - https://www.spektrum.de/magazin/evolution-der-beginn-der-warmbluetigkeit/2085762 SN - 0170-2971 IS - 2 SP - 30 EP - 31 ER - TY - GEN A1 - Knorr, Alexander G. A1 - Gravot, Céline M. A1 - Glasauer, Stefan A1 - Straka, Hans T1 - Image motion with color contrast suffices to elicit an optokinetic reflex in Xenopus laevis tadpoles T2 - Scientific Reports N2 - The optokinetic reflex is a closed-loop gaze-stabilizing ocular motor reaction that minimizes residual retinal image slip during vestibulo-ocular reflexes. In experimental isolation, the reflex is usually activated by motion of an achromatic large-field visual background with strong influence of radiance contrast on visual motion estimation and behavioral performance. The presence of color in natural environments, however, suggests that chromatic cues of visual scenes provide additional parameters for image motion detection. Here, we employed Xenopus laevis tadpoles to study the influence of color cues on the performance of the optokinetic reflex and multi-unit optic nerve discharge during motion of a large-field visual scene. Even though the amplitude of the optokinetic reflex decreases with smaller radiance contrast, considerable residual eye movements persist at the ‘point of equiluminance’ of the colored stimuli. Given the color motion preferences of individual optic nerve fibers, the underlying computation potentially originates in retinal circuits. Differential retinal ganglion cell projections and associated ocular motor signal transformation might further reinforce the color dependency in conceptual correspondence with head/body optomotor signaling. Optokinetic reflex performance under natural light conditions is accordingly influenced by radiance contrast as well as by the color composition of the moving visual scene. Y1 - 2021 U6 - https://doi.org/10.1038/s41598-021-87835-2 SN - 2045-2322 VL - 11 ER -