6.7

• This theory hypothesized that each of the three classes of cells encoded two complementary color perceptions. One class of color-coding cells signaled red by changing its activity in one direction (e.g., hyperpolarization) and signaled red’s complementary color, green, by changing its activity in the other direction (e.g., depolarization). Another class of color-coding cells was hypothesized to signal blue and its complement, yellow, in the same opponent fashion; and a class of brightness-coding cells was hypothesized to similarly signal both black and white.

  Opponent-Process Theory
• Complementary colors are pairs of colors (e.g., green light and red light) that produce white or gray when combined in equal measure.
• What is red's complement color?

  Green
• What is blue's complement color?

  Yellow
• True or False, component and Opponent color-coding mechanisms coexist in our visual systems.

  True
• Dragonflies have how many photopigments?

  10
• Color constancy refers to the fact that the perceived color of an object is not a simple function of the wavelengths reflected by it.
• Color constancy is the tendency for an object to stay the same color despite major changes in the wavelengths of light that it reflects.
• This theory states that color of an object is determined by its reflectance—the proportion of light of different wavelengths that a surface reflects.

  Retinex Theory of Color Vision
• This is an area of cortex that receives most of its input from the visual relay nuclei of the thalamus which is located in the posterior region of the occipital lobes, much of it hidden from view in the longitudinal fissure.

  Primary Visual Cortex
• This receives most of their input from the primary visual cortex.

  Secondary Visual Cortex
• Most areas of secondary visual cortex are located in two general regions: in the prestriate cortex and in the inferotemporal cortex.
• Prestriate Cortex is the band of tissue in the occipital lobe that surrounds the primary visual cortex.
• Inferotemporal Cortex is the cortex of the inferior temporal lobe.
• This receive input from areas of secondary visual cortex as well as from the secondary areas of other sensory systems which is located in several parts of the cerebral cortex, but the largest single area is in the posterior parietal cortex.

  Visual Association Cortex
• This is damage to an area of the primary visual cortex. An area of blindness in the corresponding area of the contralateral visual field of both eyes.

  Scotoma
• This test is usually given to Neurological patients with suspected damage to the primary visual cortex.

  Perimetry Test
• True or False, many patients with scotomas are not consciously aware of their deficits.

  True
• This is a factor that contributes to this lack of awareness of patients with scotoma.

  Completion
• This is sometimes displayed by patients with scotomas resulting from damage to primary visual cortex. It is the ability to respond to visual stimuli in a scotoma with no conscious awareness of them.

  Blindsight