4.2 The visual system Flashcards
Sclera
1 White outer surface of eye
Cornea
2 the clear layer that covers the front portion of the eye - focus
Pupil
3 regulates the amount of light that enters by changing its size
Iris
4 a round muscle that adjusts the size of the pupil - colour
Lens
5 a clear structure that focuses light onto the back of the eye (accommodation - change of shape)
Retina
6 lines the inner surface of the back of the eye and consists of specialized receptors that absorb light and send signals related to the properties of light to the brain
Optic nerve
7 a dense bundle of fibres that connect to the brain - track ganglion cell activity (photoreceptor info)
Optic disc
blind spot
Rods
sensitive under low light levels - black, grey
(1:10, ganglion cells : rods)
Cones
sensitive to diff wavelengths of light that we perceive as colour - located arround fovea
(1:1, ganglion cells : cones)
Fovea
central region of retina
Dark adaptation
is the process by which the rods and cones become increasingly sensitive to light under low levels of illumination = more rod activity
Trichromatic theory
maintains that colour vision is determined by three different cone types that are sensitive to short, medium, and long wavelengths of light (Blue, green, red)
Opponent-process theory
states that we perceive colour in terms of opposing pairs: red to green, yellow to blue, and white to black
Optic chiasm
the point at which the optic nerves cross at the midline of the brain
Feature detection cells
cells in the visual cortex that respond selectively to simple and specific aspects of a stimulus, such as angles and edges
Ventral stream
a neural circuit for vision that extends from the visual cortex to the lower part of the temporal lobe - object recognition
Dorsal stream
a neural circuit for vision that extends from the visual cortex to the parietal lobe - interaction w object
Prospopagnosia
the ability to perceive objects as having constant shape, size, and colour despite changes in perspective
Binocular depth cues
distances cues that are based on the differing perspectives of both eyes
Convergence
Depth cue - eye muscles contract so both eyes focus on same object
Retinal disparity (aka binocular)
Depth cue - the difference in relative position of an object as seen by both eyes, which provides information to the brain about depth
Monocular cues
are depth cues that we can perceive with only one eye
Pictorial depth cues
used by painters - texutre, linear perspective, etc
Stereoscopic vision
overlapping visual fields - humans
