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

マウスの視運動反射反応の評価:新しい高精度プロトコル

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.

著者スポットライト:マウスの視運動反射の視覚特徴選択性を研究するための正確で定量的なアプローチ 

マウスにおける視運動性反射の視覚特徴選択性の定量化

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  

マウスの眼球運動のキャリブレーション

バーチャルドラムとビデオ眼球撮影を設定したら、動物の頭をカスタマイズされたステージに固定します。左右の目が水平になり、目尻と側頭が水平になるように頭の傾きを調整します。頭部を固定した動物を乗せたステージを、3台のモニターで形成された囲いの中央に移します。アイトラッキングソフトウェアを開き、「フリーラン」をクリックします。次に、[実行]ボタンをクリックしてカメラの電源を入れます。右目の位置を、ビデオの中央に表示されるまで調整します。カメラアームを左端に回転させます。次に、X角膜反射が画像の水平中心になるまで、2D並進段階を微調整しながら、光軸に垂直な水平面上の動物の右目の位置を手動で移動させます。次に、カメラアームをもう一方の端に回転させ、X角膜の反射が画像の中心から遠ざかる場合は、X角膜の反射が中央に来るまで微調整で右目を光軸に沿って動かします。カメラアームを左右に振ったときにX角膜の反射が中央にとどまるまで、数回繰り返します。[キャリブレーション]ボタンをクリックしてから、[実行]ボタンをクリックします。Y角膜反射LEDを点灯し、その位置をビデオに記録します。次に、X角膜反射LEDに切り替えて、その位置を記録します。瞳孔の回転半径を測定するには、カメラアームを左端に回転させます。マウスを右クリックして、瞳孔と角膜X線の反射の位置をビデオに記録し、カメラアームを右端に回転させます。瞳孔の位置と角膜X線の反射をビデオに記録します。記録された値に基づいて、この式を使用して瞳孔の回転半径 Rp を計算します。瞳孔の回転と瞳孔径の関係を開発するには、モニターの輝度を平方メートルあたり0〜160カンデラに調整して瞳孔サイズを制御し、輝度値ごとに瞳孔径を記録します。輝度値ごとに、瞳孔の回転半径を8〜10倍に測定し、瞳孔の直径を記録します。次に、線形回帰を使用して、瞳孔回転半径、Rp、および瞳孔径の関係を解析し、線形モデルの傾きと切片を導出します。

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 ...