Name: Calibration of Mouse Eye Movements
Uploaded: 2023-06-23T13:40:00
Description: Watch this Scientific Journal Video about Calibration of Mouse Eye Movements at JoVE.com

calibration of mouse eye movements

Evaluating Optokinetic Reflex Responses in Mice: A New High-Precision Protocol

In response to visual stimuli in the environment, our eyes move to shift our gaze, stabilize retinal images, track moving targets, or align the foveae of two eyes with targets located at different distances from the observer, which are vital to proper vision1,2. Oculomotor behaviors have been widely used as attractive models of sensorimotor integration to understand the neural circuits in health and disease, at least partly because of the simplicity of the oculomotor system3. Controlled by three pairs of extraocular muscles, the eye rotates in the socket primarily around three corresponding axes: elevation and depression along the transverse axis, adduction and abduction along the vertical axis, and intorsion and extorsion along the anteroposterior axis1,2. Such a simple system allows researchers to evaluate the oculomotor behaviors of mice easily and accurately in a lab environment.
One prime oculomotor behavior is the optokinetic reflex (OKR). This involuntary eye movement is triggered by slow drifts or slips of images on the retina and serves to stabilize retinal images as an animal&#39;s head or its surroundings move2,4. The OKR, as a behavioral paradigm, is interesting to researchers for several reasons. First, it can be stimulated reliably and quantified accurately5,6. Second, the procedures of quantifying this behavior are relatively simple and standardized and can be applied to evaluate the visual functions of a large cohort of animals7. Third, this innate behavior is highly plastic5,8,9. Its amplitude can be potentiated when repetitive retinal slips occur for a long time5,8,9, or when its working partner vestibular ocular reflex (VOR), another mechanism of stabilizing retinal images triggered by vestibular input2, is impaired5. These experimental paradigms of OKR potentiation empower researchers to unveil the circuit basis underlying oculomotor learning.
Two non-invasive methods have primarily been used to evaluate the OKR in previous studies: (1) video-oculography combined with a physical drum7,10,11,12,13 or (2) arbitrary determination of head turns combined with a virtual drum6,14,15,16. Although their applications have made fruitful discoveries in understanding the molecular and circuit mechanisms of oculomotor plasticity, these two methods each have some drawbacks which limit their powers in quantitatively examining the properties of the OKR. First, physical drums, with printed patterns of black and white stripes or dots, do not allow easy and quick changes of visual patterns, which largely restricts the measurement of the dependence of the OKR on certain visual features, such as spatial frequency, direction, and contrast of moving gratings8,17. Instead, tests of the selectivity of the OKR to these visual features can benefit from computerized visual stimulation, in which visual features can be conveniently modified from trial to trial. In this way, researchers can systematically examine the OKR behavior in the multi-dimensional visual parameter space. Moreover, the second method of the OKR assay reports only the thresholds of visual parameters that trigger discernible OKRs, but not the amplitudes of eye or head movements6, 14,15,16. The lack of quantitative power thus prevents analyzing the shape of tuning curves and the preferred visual features, or detecting subtle differences between individual mice in normal and pathological conditions. To overcome the above limitations, video-oculography and computerized virtual visual stimulation had been combined to assay the OKR behavior in recent studies5,17,18,19,20. However, these previously published studies did not provide enough technical details or step-by-step instructions, and consequently it is still challenging for researchers to establish such an OKR test for their own research.
Here, we present a protocol to precisely quantify the visual feature selectivity of OKR behavior under photopic or scotopic conditions with the combination of video-oculography and computerized virtual visual stimulation. Mice are head-fixed to avoid the eye movement evoked by vestibular stimulation. A high-speed camera is used to record the ocular movements from mice viewing moving gratings with changing visual parameters. The physical size of the eyeballs of individual mice is calibrated to ensure the accuracy of deriving the angle of eye movements21. This quantitative method allows comparing OKR behavior between animals of different ages or genetic backgrounds, or monitoring its change caused by pharmacological treatments or visual-motor learning.

Author Spotlight: An Accurate and Quantitative Approach to Study Visual Feature Selectivity of the Optokinetic Reflex in Mice 

Cuantificación de la selectividad de las características visuales del reflejo optocinético en ratones

We're interested in the capacity of retinal system in health and disease mouse model. Currently, we are using optokinetic reflex or OKR insured, which is our involuntary eye movement that serves to stabilize retinal images to understand how the retinal system contributes to the adaptive plasticity in retinal innate behaviors. OKR model studies have advanced our understanding of innate behavior plasticity by demonstrating that prolonged retinal stimulation or impaired by similar ocular reflex can increase the behavior amplitude.And by investigating the underlying molecular synaptic and secretory mechanisms. We combined video oculargraphy and computerized virtual visual stimulation to precisely quantify the OKR behavior invokes by truncating with freely changing parameters. This procedure is relatively simple and can be standardized to accommodate large scale studies.Our protocol accurately analyzes to include shapes and prefer visual features, detects subtle differences in normal and pathological conditions, and also can monitor changes in OKR due to pharmacological treatments or visual motor learning. The high precision and the quantitative power make it possible to compare repetitive OKR measurements of the same eyes in longitudinal studies and their different pharmacological treatments or under neurosurpreterations. It also provides opportunities to study the neurosurpres and the circuit mechanisms of OKR plasticity.

Watch this Scientific Journal Video about Calibration of Mouse Eye Movements at JoVE.com

Calibration of Mouse Eye Movements  

Calibración de los movimientos oculares del ratón

Después de configurar el tambor virtual y la oculografía de video, fije la cabeza del animal en un escenario personalizado. Ajuste la inclinación de la cabeza para que los ojos izquierdo y derecho estén nivelados y las esquinas nasales y temporales de los ojos estén alineadas horizontalmente. Traslade el escenario con el animal de cabeza fija al centro del recinto formado por los tres monitores.Abra el software de seguimiento ocular y haga clic en Ejecución libre. A continuación, haga clic en el botón Ejecutar para encender la cámara. Ajusta la posición del ojo derecho hasta que aparezca en el centro del video.Gire el brazo de la cámara hacia el extremo izquierdo. A continuación, mueva manualmente la posición del ojo derecho del animal en el plano horizontal perpendicular al eje óptico con un ajuste fino de la etapa de traslación 2D hasta que la reflexión de la córnea X esté en el centro horizontal de la imagen. Ahora gire el brazo de la cámara hacia el otro extremo, y si el reflejo de la córnea X se aleja del centro de la imagen, mueva el ojo derecho a lo largo del eje óptico con el ajuste fino hasta que el reflejo de la córnea X llegue al centro.Repita varias veces hasta que el reflejo de la córnea X permanezca en el centro cuando el brazo de la cámara se balancee hacia la izquierda y hacia la derecha. Haga clic en el botón Calibración y luego en el botón Ejecutar. Encienda el LED de reflexión de la córnea Y y grabe su posición en el video.A continuación, cambie al LED de reflexión de la córnea X y registre su posición. Para medir el radio de rotación de la pupila, gire el brazo de la cámara hacia el extremo izquierdo. Grabe las posiciones de la pupila y el reflejo de la córnea X en el vídeo haciendo clic con el botón derecho del ratón y, a continuación, gire el brazo de la cámara hacia el extremo derecho.Graba las posiciones de la pupila y el reflejo de la córnea X en el vídeo. A partir de los valores registrados, calcule el radio de rotación de la pupila, Rp, utilizando esta fórmula. Para desarrollar la relación entre la rotación de la pupila y el diámetro de la pupila, ajuste la luminancia de los monitores de 0 a 160 candelas por metro cuadrado para controlar el tamaño de la pupila y registre el diámetro de la pupila para cada valor de luminancia.Para cada valor de luminancia, mida el radio de rotación de la pupila de 8 a 10 veces y registre el diámetro de la pupila. A continuación, utilice la regresión lineal para analizar la relación entre el radio de rotación de la pupila, Rp y el diámetro de la pupila, y para derivar la pendiente y la intersección del modelo lineal.

Research

JoVE Journal

Neuroscience

Calibration of Mouse Eye Movements

Quantification of Visual Feature Selectivity of the Optokinetic Reflex in Mice

The optokinetic reflex (OKR) is an essential innate eye movement that is triggered by the global motion of the visual environment and serves to stabilize ...

Investigación

Neurociencias

Implantation of a Head Bar on Top of the Mouse Skull

Implantación de una barra de cabeza en la parte superior del cráneo del ratón

Recording Eye Movements of the Optokinetic Reflex (OKR)

Registro de los movimientos oculares del reflejo optocinético (OKR)