Optical Illusions

1. Figure/Ground Ambiguity

Higher cortical processing is involved in when a person identifies a figure in a figure/ground ambiguous drawing. This is because the brain recovers stored information about the figure that is identified. When the eye sends the visual information to the brain, it attempts to distinguishes the figure that is being seen from the background. Hence, we know that vision is not solely determined by an image formed from the retina. When looking at the vase/profile picture, higher cortical information is processed because the viewer is presented with two valid interpretations but can only see one when viewing the image for the first time. When processing such an image, the information may pass through the visual cortex, specifically into the ventral stream where object recognition may be formed. The ventral stream works hand-in-hand with the medial temporal lobe where long term memories are stored

2. Color Afterimage

Color Afterimage is caused by the photoreceptors in the retina, specifically the cones and some rods. In this case, the cones are over stimulated and lose sensitivity. When one looks away from the image, the surrounding cones that were not stimulated send strong signals to the brain, while the adapted ones send a very little information to the brain. The signals send by the surrounding cells, send the opposite information to the brain, and this is how the brain interprets it.

3. Rotating Snake Illusion

The illusions are result of fast and slow changes of neuronal representation of contrast (luminance) over time (Backus & Oruc, 2004). The illusion appears in the peripheral vision therefore the illusion’s strength depends on the luminance of the background. The illusion of rotation is strongest for 50% grey; color and contrast is what ultimately causes this phenomena.

Photoreceptors have a large influence in this case; specifically retinal cells (ganglion cells) that send axons through the optic nerve to work with...