Chapter 9: Vision Flashcards
What is a topographic map?
a spatially organized neural representation of the external world
What do Muller cells do?
help transmit light through neurons to the photoreceptors
What range of vision can humans see?
380nm-760nm
What wavelengths/colours correspond with small, medium and large cones in most mammals? How do humans differ?
Blue: 419nm - Human: 426nm
Green: 531nm - Human: 530nm
Red: 559nm - Human: 552 or 557
What type of light is below 400nm and what kind of animal can see it?
Ultraviolet light: butterflies and honeybees
What type of light is above 700nm and what kind of animal can see it?
Infrared (night vision): snakes
What is Myopia? What can it be caused by?
nearsightedness; a longer eyeball or curvature of the cornea; could be from too much strain (reading etc) or not enough bright light as a child (too much time indoors)
What is Hyperopia? What is it caused by?
it is farsightedness; caused by a shorter eyeball or a lense that is too flat
What is Presbyopia and what is it caused by?
oldsightedness; caused by the hardening of the lense so it can’t contract to view closer objects
What are some properties of rods and what wavelength are they most sensitive to?
specialized for functioning at low light, more numerous, longer and cylindrical;for 496nm
What are some properties of cones and what is the least common type of cone? What wavelength are they maximally responsive to?
specialized for colour and high visual acuity, responsive to bright light and fine detail; blue cones; 560nm
What are the 6 types of cells in the retina?
1) Retinal ganglion cell
2) Amacrine cell
3) Bipolar cell
4) Horizontal cell
5) Cone
6) Rod
What is a horizontal cell’s function?
to link the photoreceptors with bipolar cells
What is an amacrine cell’s function?
to link bipolar cells with RGC
What is a retinal ganglion cell? What are two categories of these cells?
a cell with axons that give rise to the optic nerve the transmit information from the photoreceptors to the brain; M cells and P cells
What are characteristics of magnocellular cells? Where do they project to in the LGN and striate?
larger and receive information from rods; sensitive to moving stimulus; project to layers 1-2 in LGN and bottom part of striate
What are characteristics of parvocellular cells? Where do they project to in the LGN and striate?
smaller and receive information from cones; sensitive to forms and colour; layers 3-6 in LGN and top part of striate
Where does the Geniculostriate system pathway go? What type of axons are in this pathway?
retina –> lateral geniculate nucleus (in thalamus) –> layer IV of the visual cortex; all the P axons and some M axons; 90% of RGCs in here
Where does the Tectopulvinar system pathway go? What type of axons are in this pathway?
retina –> superior collicus (in tectum) –> pulvinar (thalamus) –> parietal and temporal visual areas; the remaining M axons
Where does the Retinohypothalamic tract go and what is it’s function? What cells form it?
it is formed by photo-retinal ganglion cells (pRGCs) which are RGC that absorb blue wavelength (460-480nm); it goes from the pRGCsto the suprachaismatic nucleus; it allows light to entrain the SCN’s rhythmic activity and contracts the pupil in response to light
Where is the Dorsal Stream? What is it’s main function? What area of the visual cortex is crucial to it?
from area V1 to the parietal lobe; guides movements relative to objects; area V5
Where is the Ventral Stream? What is it’s main function? What area of the visual cortex is crucial to it?
from area V1 to the temporal lobe; object identification and perceiving related movements; area V4
What does ipsilateral mean? What layers in the thalamus do these neurons go to?
same side eye; layers 2, 3 & 5
What does contralateral mean? What layers in the thalamus do these neurons go to?
opposite side eye; layers 1, 4 & 6