Motion After Effect
Transcript: Waterfall Illusion By Cali Reis, Nikki Ambrose, Ellie Rice, Phillip Muscarella What is a motion after effect? The perceptual principle illustrated in our demo is the waterfall effect. This occurs after adapting to a particular motion environment when viewing a moving stimulus for 30 to 60 seconds and then viewing a stationary stimulus. As the moving stimulus sweeps across the retina, it activates directionally selective neurons in the cortex that respond to stimulus that is moving in a specific direction. http://www.michaelbach.de/ot/mot_adapt/ What did you see? • Adapted motion detectors are fatigued when staring at moving stimulus, allowing the detectors tuned to the opposite direction take over and activate allowing us to see motion in that opposite direction. Motion After Effect Occipital Lobe Motion Adaption Motion After Effects Damage! Why? Perceptual Principle In turn, the opposite direction neurons spike when a stationary stimulus is presented. When looking at a moving stimulus and then a stationary stimulus, it appears to move in the opposite direction, as neurons selective to opposite moving stimulus spike their activity. Neural excitability and motion adaptation is an explanation with this illusion. Temporal Lobe Stare at the blue dot, try not to blink often Why does this happen? Relevant Study A visual illusion experienced after viewing a moving stimulus for 30 - 60 seconds with stationary eyes, and then fixating a stationary stimulus. After the eyes have adapted to the moving stimulus, the stationary stimulus appears to move in the opposite direction as the original moving stimulus Areas involved in experience of motion aftereffects Cortical areas V1, middle temporal and V5 (also called MT) Typical V1 neurons respond to a particular orientation (edge or bar) moving in a particular direction. Typical MT neurons are velocity selective (speed and direction) - Tested the rate of fire of ganglion cells in a rabbits retina when experiencing motion pattern - There was a dramatic increase of activation in ganglion cells when first experiencing this motion pattern, lastly for 20 seconds - When motion stopped, firing rate decreased and the fatigue cells dropped below base line level gradually recovering taking about 30 seconds Relative cells in the surround become activated and produce the after effect that the motionless rings are moving Barlow and Hill 1963 Lesions to the medial temporal region can impair visual movement, and motion direction, which could possible result in an individual not able to detect the waterfall illusion. The medial temporal area projects to area MST, which neurons have large receptor fields and respond to complex motion patterns such as circular motion. Motion Aftereffect Dot Known as the Waterfall Illusion!