Visual System Part 2 Flashcards
Lateral geniculate nucleus
takes information from retinal ganglions and send it to the visual cortex
may also send information to other parts of the brain: blindsight
Suprachiasmatic nucleus
regulates wake/dark cycle
sends information to pineal gland
Pretectum
controls pupil size
Superior colliculus
controls eye movements
Fixation points
area of interests the eyes move to
Saccades
rapid ballistic movements
smooth pursuit
following moving objects
vergence
distance adjustments
vestibular-ocular
adjustment for head movements
Eye tracking
identifies what eyes look at
How is eyetracking useful for neuroscience
allows a very precise motor movement
no body movement
can be performed with skull exposed
Optic chiasm
where nerves coss
What is the order for when light enters the eye
axons cross over in the optic chiasm to the lateral geniculate nuclei and then up to the primary visual cortex, then the secondary cortex, and finally the extrastriate cortex
where does information from the left visual field go?
the right thalamus and visual cortex
Where does information from upper visual field go?
to lower ventral parts of visual cortex
Where does information from central/foveal visual field go?
posterior visual cortex
How is the LGN organized?
in 6 layers
Magnocellular cells
Layer 1 and 2
Big and fast cells
mainly detects movement and is made up of mostly rods
Parvocellular cells
Layer 4-6
Small and slow cells
mainly detects colour, patterns,and detail and is made up of mostly cones
Koniocellular cells
in between layers and receives information from blue cones
Which layers are ipsilateral
1,4,6
Which layers are contralateral
2,3,5
What’s the point of LGN
its the first point where information from both eyes are combined
visual receptive fields grow at this point and thus they get the bigger pictures from all the fields
Visual radiation
band of tissues leaving the LGN and going to the visual cortex
How is the visual cortex divided
Primary cortex = V1 = striate cortex
Secondary cortex = V2 = Prestriate cortex
V2, V3, V4, V5/MT = extrastriate cortex
Primary visual cortex
25% of surface area devoted to the fovea
Receptive fields of cells in this area are larger than LGN and rectangular and organized into layers
Where do koniocellular, magnocellular, and parvocellular cells project to?
IVa and IVc
Simple V1 Cells
similar to LGN cells
can detect lines of a specific orientation in a specific location
Monocular
Complex V1 cells
can detect lines of a specific orientation in any location
binocular but one eye usually dominates
motion sensitive
Hypercomplex V1 cells
respond to lines in a particular orientation that end in a particular point in the receptive field
some respond to lines of a specific orientation
binocular but usually one eye dominates
V1 Columns
all the cells in one column have similar receptive field regions, orientations, and dominant eyes
Simple cells are on the surface while complex and hypercomplex cells are deeper within
What happens if you examine a row
The visual field and the orientation shifts systematically
eye dominance shifts as well
What measures colours
Blobs which are zones that cover many oriental columns and do not respond to orientation
located in layer 2,3 5,6
Module
Final level of organization within V1
contains columns of all orientation and a blob
How does the brain form these columns/modules?
Visual cortex organization depends on experience and is plastic
Critical period
changes that are often especially relevent for a particular stage in development
Ocular dominance
relative proportion of columns dominated by open eye
Scomata
area of poor acuity/detection in visual field
occurs after damage to retina, optic nerve, LGN, or V1
Personality scotoma
inability to perceive personality traits in themselves that are obvious to others
