N165 Quiz 2; Unit 2a

the entire area or field of view that can be seen when an eye is fixed straight at a point on space.

• vertical meridian- line dividing the field of view into left/right halves
• horizontal meridian- line dividing field of view into top and bottom halves

• 'half the visual field'
• typically refers to left and right halves only 
• not top/bottom

• 'one quarter or quadrant of the visual field'
• defined by the quadrant created by the vertical and horizontal meridian lines

the transparent dome-shaped anterior portion of the outer covering of the eye

• situated behind the iris of the eye
• it focuses light entering the eye onto the retina

the white part of the eye that, with the cornea, forms the protective outer covering of the eye

• the colored portion of the eye
• a muscular diaphragm that controls the size of the pupil, which in turn controls the amount of light that enters the eye

• the hole located in the center of the iris of the eye that allows light to strike the retina
• it appears black because light rays entering the pupil are either absorbed by tissues inside the eye

• the back of the eyeball
• considered a part of the brain
• where light hits the photoreceptive cells and visual information begins being processed

• the part of the retina, where vision is most acute and color vision is best
• cone photoreceptors are most prevalent here

• the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the axons of the retinal ganglion cells exit the retina and form the optic nerve
• because there are no photoreceptor cells to detect light on the optic disc, the corresponding part of the field of vision is invisible
• some process in our brains "fills-in" the blind spot with estimates of expected visual info based on surrounding detail and information from the other eye, so we do not normally perceive the blind spot

• cells that line the back of the retina and have parts that change shape when they are hit with a photon, allowing them to detect light in a certain part of the visual field
• the overall function of the photoreceptor cell is to convert the light energy of the photon into a form of energy communicable to the nervous system and readily usable to the organism
• this conversion is called signal transduction
• humans have two main types: rods and cones
• there are three different subtypes of cones

• photoreceptor cells that are located outside the fovea
• they are highly sensitive to light and thus are responsible for low-light (scotopic) vision, like under starlight
• rods also contribute to visual motion detection, but have poor visual acuity
• they also do not differentiate between colors

• photoreceptor cells that are concentrated in the fovea, but also more sparsely extend into the periphery
• they are responsible for high acuity vision, but take more photons of light to activate (good for daytime - photopic - vision)
• there are three types, each most responsible to different wavelengths of light (long (L), middle (M), and short (S)- wavelength cones, corresponding to maximal absorption of red, green, and blue light, respectively)
• the combination of inputs from different cone types though opponent processing produces for color vision

• light-sensitive protein molecules involved in the sensing and response to light in a variety of organisms by undergoing a structural change when they absorb light.
• this structural change opens ion channels, which causes a change in the graded potential (ion flow) of the photoreceptive (in other words, causes the photoreceptor cell to signal that light has been detected)

• a type of photosensitive pigment protein found in photoreceptors
• ex. rhodopsin in rods and photopsin in cones
• (3 types are in cones, making up the L,M,
• and S cone types), and melanopsin in the melanopsin-containing retinal ganglion
• cells. Also called intrinsically photosensitive retinal ganglion cells

• cells in the retina that receive input from modulatory neurons (which get input from photoreceptor cells) and transmit the information down the optic nerve to the brain
• primary types of retinal ganglion cells are the midget cells (parvocellular pathway), parasol cells (magnocellular pathway), and small bi-stratified cells (koniocellular pathway)

• color is processed in 3 different opponency channels created by specific writing together of cone photoreceptors and retinal ganglion cells:
• red (L cone) vs green (M cone)
• blue (S cone) vs yellow (L + M cone)
• dark vs bright (red/L + green/M + blue/S) --> comparison produces luminance

• composed of the axons of the retinal ganglion cells that leave the retina and head back towards the optic chiasm in the brain, taking with them visual information
• this nerve is the reason humans have a blind spot, because no photoreceptive cells exists where the optic nerve exits the eye

• a visual processing stream that pools over fewer receptors
• the cells involved (midget retinal ganglion cells) have a sustained response and are involved in processing color, fine details, textures, and depth.

a visual processing stream that pools over many receptors, whose retinal ganglion cells (parasol retinal ganglion cells) fire in bursts and are useful for detecting motion

a visual processing stream that gets S-cone input only (from small bi-stratified cells), processing low acuity visual information, and innervating V1 and extrastriate cortex

• are a recently discovered type of retinal ganglion cell that can directly absorb light.
• They contain the photopigment melanopsin (related to melanin), which allows them to function like the photoreceptors that transduce light for the rod and cone retinal ganglion cells.
• These ganglion cells have a very large dendritic tree, which contributes to the role of these cells in signaling gross changes in light intensity.
• This information is sent to subcortical structures and is thought to be used in circadian rhythms and pupil constriction.

where the optic nerves cross in the brain, allowing information from the left visual field (from both eyes) and right visual field (from both eyes) to be separated and directed to the appropriate contralateral hemisphere

a part of the brain involved in relaying sensory information from sensory organs to processing areas of the cerebral cortex

a part of the thalamus where the visual processing stream from the LGN to primary visual cortex

nerve pathway along the visual processing stream from the LGN to primary visual cortex

refers to the first location in cortex that receives inputs from the peripheral sensory receptors- in this case, the retina

• The first area in the brain where visual information is processed at a low level.
• Visual information flows into here from the retina and flows to higher levels of visual processing (V2, V3, etc.) that do increasingly complex visual processing.
• V1 is also called striate cortex due to the visible stripe of inputs from retina to layer 4 of V1.