Superposition violations in the compensatory eye movement system

PURPOSE. Compensatory eye movements (CEM) maintain a stable image on the retina by minimizing retinal slip. The optokinetic reflex (OKR) and vestibulo-ocular reflex (VOR) compensate for low and high velocity stimuli, respectively. The OKR system is known to be highly nonlinear. The VOR is generally modeled as a linear system and assumed to satisfy the superposition and homogeneity principles. To probe CEM violation of the superposition principle, we recorded eye movement responses in C57BL/6 mice to sum of sine (SoS) stimulation, a combination of multiple nonharmonic inputs. METHODS. We tested the VOR, OKR, WOR (visually enhanced VOR), and SVOR (suppressed VOR). We used stimuli containing 0.6 Hz, 0.8 Hz, 1.0 Hz, and 1.9 Hz. Power spectra of SoS stimuli did not yield distortion products. Gains and delays of SoS and single sine (SS) responses were compared to yield relative gains and delays. RESULTS. We find the superposition principle is violated primarily in the OKR, VOR, and SVOR conditions. In OKR, we observed relative gain suppression of the lower SoS stimulus frequency component irrespective of the absolute frequency. Conversely, SVOR and VOR results showed gain enhancement of the lower frequency component and overall decrease in lead. Visually enhanced VOR results showed trends for overall gain suppression and delay decrease. CONCLUSIONS. Compensatory eye movements arguably depend on predictive signals. These results may reflect better prediction for SS stimuli. Natural CEM system stimulation generally involves complex frequency spectra. Use of SoS stimuli is a step toward unravelling the signals that really drive CEM and the predictive algorithms they depend on

A Neuroanatomically Grounded Optimal Control Model of the Compensatory Eye Movement System in Mice

We present a working model of the compensatory eye movement system in mice. We challenge the model with a data set of eye movements in mice (n =34) recorded in 4 different sinusoidal stimulus conditions with 36 different combinations of frequency (0.1–3.2 Hz) and amplitude (0.5–8°) in each condition. The conditions included vestibular stimulation in the dark (vestibular-ocular reflex, VOR), optokinetic stimulation (optokinetic reflex, OKR), and two combined visual/vestibular conditions (the visual-vestibular ocular reflex, vVOR, and visual suppression of the VOR, sVOR). The model successfully reproduced the eye movements in all conditions, except for minor failures to predict phase when gain was very low. Most importantly, it could explain the interaction of VOR and OKR when the two reflexes are activated simultaneously during vVOR stimulation. In addition to our own data, we also reproduced the behavior of the compensatory eye movement system found in the existing literature. These include its response to sum-of-sines stimuli, its response after lesions of the nucleus prepositus hypoglossi or the flocculus, characteristics of VOR adaptation, and characteristics of drift in the dark. Our model is based on ideas of state prediction and forward modeling that have been widely used in the study of motor control. However, it represents one of the first quantitative efforts to simulate the full range of behaviors of a specific system. The model has two separate processing loops, one for vestibular stimulation and one for visual stimulation. Importantly, state prediction in the visual processing loop depends on a forward model of residual ret

Queer Victims: Reports of Violence by LGBTQI Survivors Result in Violent Assaults by Police

abstract: LGBTQI people are often victimized by law enforcement and these victimizations often are related to victimizations of domestic violence and hate violence. Because reporting a victimization to the police leads to contact with police, a part of the research question involved herein looked at whether or not reporting a victimization to the police also increases the rate of police violence. Through secondary data analysis, this study investigated the correlation between reporting domestic violence and hate violence to the police, and subsequent victimizations by the police in the form of police violence. Additionally through secondary data analysis, this study investigated whether or not this correlation is stronger with transgender women and people of color. All data analyzed in this study was collected in Tucson, Arizona through the Wingspan Anti-Violence Project (WAVP). All data was analyzed with the permission of the data owner, the National Coalition of Anti-Violence Programs (NCAVP) (see Appendix IV), and with IRB approval from the Arizona State University Office of Research Integrity and Assurance (see Appendix III). The findings demonstrated a positive correlation between the rate of LGBTQI people reporting violent crimes to the police and the rate of police violence against LGBTQI survivors of domestic violence and hate violence. The results further demonstrated the rate of police violence associated with reporting domestic violence or hate violence is greatest for transgender women and people of color.Dissertation/ThesisMasters Thesis Social Work 201