QUIZ 4: VISION STUDY GUIDEWill consist of multiple choice, fill in the blank, matching and short answer questions.1. Know qualities of light, i.e. that it is measured according to wavelength, that opsins absorb a photon.Qualities of light:- Reflected (color visible), refracted (bent), or absorbed by an object.- Measured by wavelength on electromagnetic spectrum 400-700 nanometerso Lower wavelengths=blue/purple hueso Higher wavelengths=red/orange hues- Consists of photons that are absorbed by opsin (protein that detects wavelength) and captured by chromophore stored in visual pigments. 2. Know the parts of the eye and their function.- Cornea=protective layer that produces tears when scratched.- Aqueous Humor=fluid filled chamber before the lens.- Iris and pupil=iris is the colored portion and the pupil is the dark center in which both help regulate the amount of light that enters by functioning as the focus of camera lens.- Lens=refracts and focuses light on the retina for accurate representation.- Vitreous Humor=fluid filled chamber in the retina for further refraction- Retina=back of the eyeball that contains photoreceptors.3. Know the components of a photoreceptor. Know how different opsins are distributed, and how they determine what each photoreceptor detects.Photoreceptor: detects visual information- Inner segment=produces visual pigments, neurotransmitters, proteins, and other cellular machinery.- Outer segment=stores visual pigments that consist of an opsin and chromophore.o Rhodopsin detects amount of light to perceive shape/contrast.o Three different types of opsins that detect short, medium, and long wavelengths to perceive color4. What are rods cones, and in what type of conditions are they most effective? Know the three types of cones and the wavelengths/colors they respond to along with how they are distributed across the retina.Rods:- Detect amount of light to perceive shape/contrast.- Most active in scotopic (low light) conditions in which the environment is dimand dark.- Mainly distributed in periphery of retina.Cones:- Detects color with three different opsins.o S-cones=short wavelengths (blue)o M-cones=middle wavelengths (green)o L-cones=long wavelengths (red)- Mainly distributed in the fovea of the retina.- Mostly active in photopic (daylight) conditions.- Higher distribution of M & L cones in fovea (red & green).- Higher distribution of S-comes in periphery (blue).5. Be able to differentiate between the inner and outer segments of photoreceptors. - Inner segment=produces visual pigments, neurotransmitters, proteins, and other cellular machinery.- Outer segment=stores visual pigments that consist of an opsin and chromophore.6. Be able to label a graph of the cells in the retina (Change Blindness Powerpoint, Slide 3).7. Know the pathway optic information travels to and in the brain, including structures and when information crosses to the other hemisphere.1. photoreceptors—2. Horizontal (synapse) & bipolar cells—3. Amacrine (synapse) & ganglion cells—4. optic nerve (optic disk)—5. Optic chiasm (half crosses over to contra lateral side)—6. Optic tract—7. Superior colliculus (movement and blindsight) & Lateral Geniculate Nucleus of Thalamus (relays info. To cortex)—8. Striate cortex (primary visual cortex V1).8. What is the blind spot/optic disc and what is a unique feature of this area?Area where the ganglion axons merge into the optic nerve and exit the retina to the brain which causes a blind spot.9. Read and be able to answer questions regarding the flicker technique. Know how we typically detect change and why the flicker technique results in change blindness. Change blindness:- What is it? The inability to detect changes to an object or scene.- Implications? Very large changes can be made to a picture without observers noticing them.- How is it tested? Experiments show two visual scenes with some kind of brief disruption in visual continuity (flicker technique).- Disruption? Film cut in motion picture sequence, eye blink, eye cascade, a brief flicker.Flicker Technique:- How does this cause change blindness? Typically, a change is detected by local motion signals since its easy to detect movement in the superior colliculus. The disturbance (flicker) causes overload in processing change detection, so the brain is forced to scan each item of the picture until it detects the change. Important changes get detected easier and faster than small changes due to the brain’s higher order processing. 10. What are the monocular and binocular cues involved in depth perception? Describe them.- Binocular cues= the visual fields of both eyes overlap so field of view is decreased but gain better depth perception.o Convergence=the difference between images seen in each eye due to the angle each eye is viewing the object.o Retinal Disparity=each eye sees a slightly different image and the brain combines information from the two images to create perception of object.- Monocular cues=the visual fields of both eyes remain separate so field of viewincreases but limits depth perception. o Texture=greater detail in closer objects.o Linear perspective=property of parallel lines converging allow the relative distance between two parts of an object. o Interposition (occlusion)=overlapping objects are seen as closer while objects that are partially obstructed are seen as farther
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