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

Valutazione delle risposte riflesse optocinetiche nei topi: un nuovo protocollo ad alta precisione

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.

Autore in primo piano: un approccio accurato e quantitativo per studiare la selettività delle caratteristiche visive del riflesso optocinetico nei topi 

Quantificazione della selettività delle caratteristiche visive del riflesso optocinetico nei topi

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  

Calibrazione dei movimenti oculari del mouse

Dopo aver impostato il tamburo virtuale e l'oculografia video, fissa la testa dell'animale su un palco personalizzato. Regolare l'inclinazione della testa in modo che gli occhi sinistro e destro siano livellati e gli angoli nasali e temporali degli occhi siano allineati orizzontalmente. Trasferisci il palco con l'animale fissato alla testa al centro del recinto formato dai tre monitor.Apri il software di tracciamento oculare e fai clic su Esecuzione libera. Quindi, fare clic sul pulsante Esegui per accendere la fotocamera. Regola la posizione dell'occhio destro finché non appare al centro del video.Ruotare il braccio della fotocamera all'estremità sinistra. Quindi, spostare manualmente la posizione dell'occhio destro dell'animale sul piano orizzontale perpendicolare all'asse ottico con regolazione fine dello stadio di traslazione 2D fino a quando il riflesso X-corneale non si trova al centro orizzontale dell'immagine. Ora ruota il braccio della fotocamera all'altra estremità e, se il riflesso corneale X si allontana dal centro dell'immagine, sposta l'occhio destro lungo l'asse ottico con la regolazione fine finché il riflesso corneale X non arriva al centro.Ripeti più volte fino a quando il riflesso X-corneale rimane al centro quando il braccio della fotocamera oscilla a sinistra e a destra. Fare clic sul pulsante Calibrazione e quindi sul pulsante Esegui. Accendi il LED di riflessione corneale Y e registra la sua posizione sul video.Quindi, passare al LED di riflessione corneale X e registrarne la posizione. Per misurare il raggio di rotazione della pupilla, ruotare il braccio della fotocamera verso l'estremità sinistra. Registra le posizioni della pupilla e del riflesso della cornea X sul video facendo clic con il pulsante destro del mouse, quindi ruota il braccio della fotocamera all'estremità destra.Registra le posizioni della pupilla e il riflesso della cornea X sul video. Sulla base dei valori registrati, calcolare il raggio di rotazione della pupilla, Rp, utilizzando questa formula. Per sviluppare la relazione tra la rotazione della pupilla e il diametro della pupilla, regolare la luminanza dei monitor da 0 a 160 candele per metro quadrato per controllare la dimensione della pupilla e registrare il diametro della pupilla per ogni valore di luminanza.Per ogni valore di luminanza, misurare il raggio di rotazione della pupilla da 8 a 10 volte e registrare il diametro della pupilla. Quindi, utilizzare la regressione lineare per analizzare la relazione tra il raggio di rotazione della pupilla, Rp e il diametro della pupilla e per derivare la pendenza e l'intercetta del modello lineare.

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 ...