BioCog 3B Vision biological Flashcards
Basal visual functions
- colours, lines, angles
higher order visual functions
- what
- where
transduction
- conversion into electrical signals
- photoreceptors to ganglion cells
projection
- from sensory organ to the brain
hue
- colour
saturation
- grade to which a perceived colour has only one wavelength
2nd cranial nerve
- optic nerve
blind spot
- where the optic nerves meets the retina
- no rods not cones
fovea
- point of highest resolution
bipolar cells
- get signal from photoreceptors
- tranfer to ganglion cells
ganglion cells
- get signal from the bipolar cells
- merge into the optic nerve
receptive field
- region of space that induces a change of firing rate for certain neurons
- what the neuron “sees”
lamellae
- part of photoreceptors
- contain the photopigment
cones
- for colour
- red, green and blue
- made out of retinal and one of three opsins
rods
- for brightness
- made up of rod opsin and retinal = rhodopsin
brightness
= intensity
- coded by firing rate
ON cells
- fire more when there is more
- have their ON area in the center
OFF cells
- fire more when there is less
- have their OFF area in the center
Mach effect
- colour field edges appear lighter when a darker coulour is next to it or vice versa
- due to receptive fields, ON and OFF cells
rebound effect
- ganglion cells are stimulated / inhibited for a longer time
- stimulus seized
- ganglion cells fire temporarily less or more than
before
- creates afterimage
trichromatic coding
- red light activates the red cone and so on
opponent-process coding
- after trichromatic coding
- red-green and blue-yellow cell
- adds yellow
red-green ganglion cell
ON = red
- OFF = green
yellow-blue ganglion cell
- ON = yellow
- OFF = blue
simple cells
- get signals from single cells of LGN
- transfer to complex cells
complex cells
- get signals from simple cells
- make f.e. movement detection by combining receptive fields of simple cells
retinotopic organization
- an area of the visual field exactly corresponds with an area in the visual cortex
- for location detection
depth perception
- mainly by disparity of the eyes
striate cortex
= primary visual cortex
what
- ventral stream
- inferotemporal cortex
- colour, shape, pattern, faces
- 50% magnocellular
- 50% parvo and koniocellular
where
- dorsal stream
- prestriate cortex and posterior parietal cortex
- space, movement, coordination/tracking
- 95% magnocellular
V4
- for colour constancy
V8
- for colour vision
- colour imagination
- colour memory
cerebral achromatopsia
- no colour vision, imagination and memory
- from damage in V8
optic chiasm
- optic nerves switch sides
LGN
- lateral geniculate nuclei
- two of them
- 6 layers
layer 1 +2
- magnocellular
- shape, movement, depth
layer 3 - 6
- parvocellular
- colour and details
apperceptive agnosia
- inability to recognize objects
- inability to combine parts
propagnosia
- inability to recognize faces
face-inversion effect
- upside down face with reversed eyes and mouth
- > you dont find it weird
- turn that upside down
- > very weird
IP
- intraprietal sulcus
- in posterior parietal cortex
LIP + VIP
- attention and eye movement
VIP + MIP
- visual control of grasping and pointing
AIP
- graspin and manipulating with hands
CIP
- depth perception
V5
- movement perception
- extra thick and myelinate connections
akinetopsia
- inability perceive fluent movements
- from damage to V5
MST
- for optic flow
