What is Argos?
Genetically modified mice have been used in a great number of studies focusing on the investigation of the visual system function. Argos is a system that is devised to measure visual function in small research animals. This system measures both contrast sensitivity and visual acuity in mice and rats, which makes it possible to obtain data to help understand the visual function of these animals better. These results show that this type of system is useful for the evaluation of vision, providing very fast and highly reproducible results. Detailed information can be obtained (even on a daily basis) about what the mouse can actually see. Therefore, it would be possible to test potential treatments for visual illnesses, as the system enables us to compare, in a simple way, control animals with affected animals, and evaluate any residual vision or possible improvements through treatment.
The system consists of four computer monitors facing each other forming a cube. The outside of the system is covered with a carbon fiber casing and a CCD camera with an infrared light lamp that records a pedestal where mice are placed inside the cube. In addition, the Argos program has been developed with the purpose of displaying stimuli consisting of vertical black and white bars in motion. The software has been designed to display the visual stimuli on the monitors. It allows for an easy definition of stimuli characteristics, such as spatial and temporal frequency, time, contrast, etc.
How does it work?
Once the program Argos is executed, monitors turn grey, waiting for the user to set the parameters of the experiment and start it. Next, the mouse is placed on the platform inside the experimental cube and the cover is closed. The experimenter must choose the type of test to be performed Visual acuity or Contrast sensitivity test. Once the type of experiment has been selected, the experimenter observes the movement of the mouse on the control monitor. It is important to state that the system is blind, that is, the experimenter cannot see the stimuli that are being displayed. The only thing the experimenter can see on the operator monitor is the mouse on the platform. When the stimuli finish, the screens turn grey and the experimenter decides whether the mouse has performed an optomotoric movement or not. This movement is usually generated when the mouse stays still on the platform and moving the head slowly, approximately at the same speed as that of the stimulus, and towards the same direction. If the experimenter has seen the mouse’s movement, he should select the direction in which the mouse has moved. Once the direction button has been pressed, the program compares the decision taken with the direction of the stimulus and if they match, the coincidence-counter will increase. This process is repeated 10 times. When the 10 presentations of stimulus have finished, a certain percentage of correct answers is obtained. If this percentage is equal or greater than 80%, it means that the mouse has followed the stimuli during the displays, therefore seeing them. On the other hand, if this percentage is lower, this indicates that the mouse has not seen the stimuli.
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