February 5th, 2020 
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Find a Youtube video or similar source with an interesting visual illusion. Provide the link for your peers to also be able to watch the illusion. Based on your understanding of the visual system, describe which neurologic processes (such as lateral inhibition or opponent process color vision) might explain this illusion.
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SPINNING BALLERINA ILLUSION
To understand exactly what is going on in this clip, one must understand sensation vs. perception. Sensation is described as the cells in the nervous system specialized to detect stimuli from the environment (Carlson & Birkett, 2017, p. 166). Perception refers to how the conscious experiences and interprets the info from the senses. This involves the neurons in the central nervous system.
Optical illusions use light, patterns, and color that can be misleading to the brain. The information that is gathered by the eye is then processed by the brain that may make one perceive it as reality, but it really does not match what the eye sees.
In this optical illusion, there is a spinning dancer. One may see her turning in one direction and others may see her turning in the other direction. If a person concentrates enough, they may even have the ability to make her switch directions while spinning. About twelve years ago, this illusion was incorrectly labeled as a personality test. This dancer is just a silhouette and therefore, the brain must fill in the rest. This does not show whether someone is left or right brain dominant, but more so what their visual preference is.
This optical illusion looks at the brain’s perception of spatial location. The retina helps us see images when we move our heads, contributing to depth perception. This is done by the use of stereoscopic vision and is extremely important when it comes to the guidance of fine movements done by the hands and fingers. The striate cortex has neurons that are mostly binocular. These neurons respond to retinal disparity. When looking at a three-dimensional scene, each eye sees it differently. Due to the presence of retinal disparity, there are differences in the distance of objects from the observer (Carlson & Birkett, 2017, p. 195). Looking at the perception of orientation and movement in the striate cortex, one is able to see that the neurons seem to respond best to a line that is in a particular position. To make the optical illusion more clear to the observer, white edges are often placed around the silhouette or details are given to the dancer’s body.
This optical illusion takes advantage of the striate cortex and extrastriate cortex mainly to deceive the brain and its perception of the direction of the ballerina. If akinetopsia, damage to area V5 in the extrastriate cortex happened, then one would not be able to perceive movement.
References
Carlson, N. R., & Birkett, M. A. (2017). Physiology of Behavior, 12th Edition. Boston, Massachusetts: Pearson.
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