Visual system 2 Flashcards
(62 cards)
where does info from the optic nerve travel to?
Optic nerve → Optic chiasm → Optic tract → LGN (Thalamus)
what is the optic chiasm?
The part of the brain where nasal retinal fibres cross over, ensuring visual fields are processed in the contralateral hemisphere.
what happens to nasal retinal fibres at optic chiasm?
Nasal retinal fibres from the right eye cross over to the left optic tract at the optic chiasm
Nasal retinal fibres from the left eye cross over to the right optic tract at the optic chiasm
what are nasal retinal fibres?
They cross over at the optic chiasm and project to the opposite (contralateral) hemisphere of the brain.
This ensures that visual information from the right visual field is processed in the left hemisphere and vice versa.
What happens to temporal retinal fibres at the optic chiasm?
Temporal retinal fibres remain on the same side
Temporal retinal fibres from the right eye travel to the right optic tract
Temporal retinal fibres from the left eye travel to the left optic tract
What brain structure receives visual information after the optic chiasm?
The lateral geniculate nucleus (LGN) in the thalamus.
do retinal ganglion cells and lGN cells respond to motion?
not direction selective and don’t respond to motion
What does the spatiotemporal pattern of light on the retina help detect? and what carries this out
The spatiotemporal pattern of light on the retina helps detect motion. When the same pattern is seen in different places on the retina, milliseconds apart, the brain interprets this as movement
. This process is carried out by neurons in the visual cortex, not by ganglion cells.
What cells send motion information to the LGN?
Magnocellular retinal ganglion cells send their output to layers 1 and 2 of LGN
what info is carried in magnocellular layers of the LGN?
Motion information is carried in the magnocellular layers of the LGN
are magnocellular cells or parvocellular cells bigger?
Magnocellular cells in LGN are much larger than the parvocellular cells
what layers of LGN are magnocellular cells in?
layers 1 and 2 of LGN
what is the difference between magnocellular and parvocellular cells?
Magnocellular cells are fast, large, and good at detecting motion.
Parvocellular cells are smaller, slower, and good at detecting fine details and color
where are magnocellular and parvocellular cells located in the eye
M= peripheral retina
P= central retina
where do parvocellular cells send their output?
layers 3, 4, 5 and 6 of LGN
what information do parvocellular cells carry?
Colour and form information is carried in the parvocellular layers of the LGN
What are the LGN cells that are responsible for colour processing?
Parvocellular cells → Red-green colour processing.
Koniocellular cells → Blue colour processing.
Magnocellular cells → No colour processing, only motion and depth.
where does information for the LGN travel to?
optic radiations
visual cortex
where in the brain does visual info first enter?
occipital cortex in visual brain area V1 (also known as primary visual cortex)
what is area V1 responsible for?
V1 is responsible for processing low level visual information, and passing it on to higher levels of the visual system in the brain for further processing
how many layers does area V1 have?
6
which layer does information from LGN arrive in area V1
layer 4 which is sub divided to 4A, 4B, 4Cα and 4Cβ
What types of processing occur in V1?
There is parallel processing of information in the visual cortex
Different features such as shape and colour are processed separately at the same time
Where do magnocellular and parvocellular cells send their axons in V1?
Magnocellular LGN cells send their output to neurons in sub-layer 4Cα of V1.
Parvocellular LGN neurons send their output to neurons in sub-layer 4Cβ
