A system to measure the Optokinetic and Optomotor response in mice.
BACKGROUND
Visually evoked compensatory head movements (Optomotor responses) or eye movements (Optokinetic responses) are extensively used in experimental mouse models for developmental defects, pathological conditions, and testing the efficacy of therapeutic manipulations.


METHODS
We present an automated system to measure Optomotor and Optokinetic responses under identical stimulation conditions, enabling a direct comparison of the two reflexes. A semi-automated calibration procedure and a commercial eye tracker are used to record angular eye velocity in the restrained animal. Novel video tracking algorithms determine the location of the mouse head in real time and allow repositioning of the stimulus relative to the mouse head.


RESULTS
Optomotor and Optokinetic responses yield comparable results with respect to determining visual acuity in mice. Our new head tracking algorithms enable a far more accurate analysis of head angle determination, and reveal individual head retractions, analogous to saccadic eye movements observed during Optokinetic Nystagmus.


METHODS
To our knowledge this is the first apparatus allowing the direct comparison of Optomotor and Optokinetic responses in mice. Our tracking algorithms, which allow an objective determination of head movements are a significant increment over existing systems which rely on subjective human observation. The increased accuracy of the novel algorithms increases the robustness of automated Optomotor response determinations and reveals novel aspects of this reflex.


CONCLUSIONS
We provide the blueprints for inexpensive hardware, and release open source software for our system, and describe an accurate and accessible method for Optomotor and Optokinetic response determination in mice.
Retinal Circuit Development & Genetics Unit, Neurobiology Neurodegeneration & Repair Laboratory, National Eye Institute, National Institute of Health, Bethesda, MD, USA. Electronic address: friedrich@openetho.com.
Friedrich
F
Kretschmer
Retinal Circuit Development & Genetics Unit, Neurobiology Neurodegeneration & Repair Laboratory, National Eye Institute, National Institute of Health, Bethesda, MD, USA.
Szilard
S
Sajgo
Retinal Circuit Development & Genetics Unit, Neurobiology Neurodegeneration & Repair Laboratory, National Eye Institute, National Institute of Health, Bethesda, MD, USA.
Viola
V
Kretschmer
Retinal Circuit Development & Genetics Unit, Neurobiology Neurodegeneration & Repair Laboratory, National Eye Institute, National Institute of Health, Bethesda, MD, USA. Electronic address: tudor.badea@nih.gov.
Tudor C
TC
Badea
D000465:Algorithms; D000818:Animals; D002138:Calibration; D004867:Equipment Design; D053483:Eye Movement Measurements / Q000295:instrumentation*; D005133:Eye Movements; D006257:Head; D019416:Head Movements; D008810:Mice, Inbred C57BL; D010363:Pattern Recognition, Automated; D010775:Photic Stimulation / Q000295:instrumentation / Q000379:methods*; D012018:Reflex; D012149:Restraint, Physical / Q000295:instrumentation / Q000379:methods; D012984:Software; D014741:Video Recording / Q000295:instrumentation / Q000379:methods; D014792:Visual Acuity
Behavior; Eye movements; Head movements; Mouse; Optokinetic reflex; Optomotor response; Retina; Video tracking visual field; Vision