retina to cortex Flashcards
lateral geniculate nucleus
- located in the thalamus
- has 6 layers
optic chiasm
where the nerves from each eye meet
LGN layers 1 & 2
magnocellular layers from m ganglion cells
layer 3-6 of LGN
parvocellular layers from p ganglion cells
- process shape and color
contralateral layers
- receive information from opposite eye
- 1,4,6
ipsilateral layers
- receive from the same side eye
- 2, 3, 5
koniocellular layers
involved in specialized color input from k ganglion cells
two visual pathways
- dorsal
- ventral
dorsal pathway
where/how pathway which does spatial and motion information
ventral
- what pathway
- object recognition, color
Primary visual cortex (V1)
- aka striate cortex
- has 200 millio cells
- where circular receptive fields turn into striped ones
retinotopic mapping
relative placement of where things are in the visual cortex
cortical magnification
makes it so that objects in the middle of our field of view will occupy a larger part of the cortex than the peripheral
- more neurons process in center than in the peripheral
visual crowding
objects in peripheral have much lower resolution than those in central vision so its hard to detect things in our peripheral that are cluttered
types of neurons in V1
- simple cells
- complex cells
simple cells
respond bets to bars of light or dark and have a particular oritnetation preference and location preference
complex cells
respond to bars of light or dark with a orientation preference but dont need a specific location
- good for moving bar
- usually bigger field
David Hubel and Torsten Wiesel
- discovered striped receptive fields while playong with a cat
end stopped
some cells in V1 also have a preference for length.
the preferred length will be the whole receptive field and when it gets longer it decreases
V1 columns
- columns with preferred orientations
- columns for each eye
selective adaptation
a technique where we can selectively deactivate groups of neurons through adaptation by presenting a stimulus for an extended perior of time
- ex: titled bars
comparing visual areas by
- the tupes and distributions of neurons in that area
- other areas they connect to
- properties which they are tuned to
- retinotopic map
dorsal stream
diffuse–> m-ganglion–> magnocellular layer –> v1 –> v2 –> MT –> parietal cortex
ventral pathway
midget –> p ganglion –> parvocellular layer –> V1 –> V2 –> V4 –> inferotemporal
- object regocnition
visual agnosia
inability to recognise objects by their shape despite having normal vision and IQ
manual estimation
using the distance between index and thumb to estimate the size of an object they can see
grasp calibration
adjust the distance between thumb and index as you reach to grasp it
optic apraxia
affects the dorsall stream
- couldnt grasp to pick it up but can esrimate its size
V4
processes color, edges and curvatures
- contour selective
inferotemporal cortex
processes objects, faces and places
3 parts of the inferotemporal cortex
- fusiform face area
- parahippocampal place area: places and layouts
- extrastriate body: full body and parts
grandmother cell hypothesis
- thought that we have specific neurons for indentifying specific people
- more likely distributed coding: combinations
