Optokinetic reflex in chickens (Gallus gallus domesticus)

Abstract: Optokinetic reflex in chickens Vision is the most important sense for many birds. Birds use their vision for many different tasks like finding food, spotting potential mates and predators. They also use this very important sense to navigate and move through the environment, and this is interpreted by the visual system as self-motion. The visual system divides properties of the environment into different spatial frequencies ranging from low to high. Low spatial frequencies represent coarse details, while high frequencies represent fine details. Another important property is the contrast of an image. There are different types of contrast an image with different light levels and intensities can contain. We focused on black and white contrast as well as contrast between red and green colours. In this study we investigated the contrast sensitivity and spatial acuity of chickens by measuring a reflex birds have to moving patterns. This reflex is called the optokinetic reflex. When the bird looks at a moving pattern, the optokinetic reflex will turn the head to follow in the same direction as the motion of the pattern, with interruptions of fast head movements in the opposite direction interspersed throughout the behaviour. In order to measure the optokinetic reflex, we used an experimental setup that consisted of four large LCD monitors that could present a wide range of contrasts and spatial frequencies for large moving black and white patterns and large moving red and green patterns. The results we got from testing the optokinetic reflex showed us that the chicken spatial acuity is above 2 cycles/degree for black and white patterns, which corresponds to fine spatial detail. For comparison humans have much higher spatial acuity compared to this value. We also could see that the lowest contrast the chickens could see for black and white patterns was between 7 and 12%. This threshold occurred at 1 cycles/degree. The results we got from testing red and green large moving patterns showed us that chickens cannot perform an optokinetic reflex in response to this colour pattern. Compared to other studies done on black and white moving patterns we can say that results vary a lot. However, our results correspond quite well to one of the two studies done on the same subject. The results gained from the tests on colour patterns suggests that the neural pathway involved in large moving patterns is not entirely colour blind. Even though the chickens did not show any optokinetic reflex, they could still slowly follow the motion of the pattern. Advisors: Mindaugas Mitkus and Almut Kelber Master’s Degree Project in Biology, 30 credits, 2016 Department of Biology, Lund University