The Illusion Of Afterimage
When playing “would you rather” with my flat mate, we both agreed that out of all the senses, we would rather not lose vision. We agreed that vision is the most fundamental sense in relaying information from our environment. Our eyes contain more than half of the sensory receptors in the human body (Tortora and Derrickson, 2008), so we receive a huge source of information through our visual pathway. This essay will discuss the visual pathway and the neural adaptations that occur when we perceive the illusion of afterimage.
When light enters the eye, it is the job of the cornea and the lens to focus the light onto the photoreceptors of the retina to produce a focussed image. The photoreceptors on the retina include rods and cones. The rods contain …show more content…
The motion aftereffect is another example of neural adaptation as neurons coding for a particular movement (ie clockwise) reduce their response with exposure. The exposure of clockwise motion to these neurons reduces their baseline activity, and once the stimulus stops, the cells that code for the opposite movement (ie anticlockwise) have a higher response compared to the fatigued cells, so an anticlockwise motion is seen. In the lab, we performed an experiment in which our subject watched a rotating wheel for 20 seconds, and then we paused the image. After the image stopped rotating, our subject saw the wheel move in the opposite direction for approximately 10 seconds. We repeated the experiment with our subject having one eye open and one eye closed, and then swapping when the wheel stopped spinning. Unlike the colour after image experiment, our subject saw the wheel rotate (in the opposite direction) in the eye that was closed. This is evidence that motion is processed in the brain and there is some inter-ocular transfer (IOT). The IOT is due to the involvement of binocular visual neurons that respond to stimulation of either eye (Blake et al, 1981). If these neurons get fatigued, both eyes will experience the motion aftereffect
When light enters the eye, it is the job of the cornea and the lens to focus the light onto the photoreceptors of the retina to produce a focussed image. The photoreceptors on the retina include rods and cones. The rods contain …show more content…
The motion aftereffect is another example of neural adaptation as neurons coding for a particular movement (ie clockwise) reduce their response with exposure. The exposure of clockwise motion to these neurons reduces their baseline activity, and once the stimulus stops, the cells that code for the opposite movement (ie anticlockwise) have a higher response compared to the fatigued cells, so an anticlockwise motion is seen. In the lab, we performed an experiment in which our subject watched a rotating wheel for 20 seconds, and then we paused the image. After the image stopped rotating, our subject saw the wheel move in the opposite direction for approximately 10 seconds. We repeated the experiment with our subject having one eye open and one eye closed, and then swapping when the wheel stopped spinning. Unlike the colour after image experiment, our subject saw the wheel rotate (in the opposite direction) in the eye that was closed. This is evidence that motion is processed in the brain and there is some inter-ocular transfer (IOT). The IOT is due to the involvement of binocular visual neurons that respond to stimulation of either eye (Blake et al, 1981). If these neurons get fatigued, both eyes will experience the motion aftereffect