visual processing in the brain Flashcards
1
Q
what does the brain want to know from visual information
A
- conscious experience of our environment involves knowing; what things are,
- the retinogeniculate pathway is largely responsible for conscious visual experience.
2
Q
visual input to the PVC
A
- majority of ganglion cell axons go back to the PVC
3
Q
contralateral arrangement
A
signals from one side of the visual field are processed by the opposite side of the brain.
4
Q
retinotopic organization of the primary visual cortex
A
- extracellular animal studies
retinotopic organization - cells close together get input from same region of the retina
- where an object is important for vision
- cortical magnification: more cortical cells devoted to the fovea than periphery
5
Q
functional organization of PVC
A
- visual cortex: 6 layers based on visible anatomical differences
- input to layer 2/3 and 4 from the LGN
cortical column modules - process information in small region of space
- but their tile the entire visual field
blobs- - color
interblobs - orientation, motion, depth
6
Q
specialized visual areas that revive input vial the PVC
A
- modular organization: each area has neurons with receptive fields that tile the visual field
modules have slightly different function, focusing on a particular aspect of the visual scene
7
Q
hierarchal feed forward model
A
- neurons responses become more specific
- although lots of feedback and interconnection
8
Q
the two-streams hypothesis of visual processing in the brain
A
- Dorsal and ventral stream:
- the ventral stream computed a detailed map of the world from visual input
- the dorsal ‘action’ stream transforms incoming visual information for action.
- also referred to as the ‘where’ and ‘what’ pathway
- the independence of the two streams had been overemphasized.
9
Q
colour processing pathway
A
- wavelength sensitivity in the retina. speech sensitivity of L, M and S cones.
- congenital color blindness
- circulate center-surround cone opponent receptive fields in the retinal ganglion cells.
- functional segregation evident in different layers of the LGN
10
Q
R-G opponent ganglion cell
A
- excited by red light
- inhibited by green light
- (also have G-r)
11
Q
Y-B opponent ganglion cell
A
- excited by yellow light
- inhibited by blue light
12
Q
areas responsive to color
A
- area V4 is highly responsive to color, subsequent work has shown that V4 is also responsibe to changes in shape and curvature
- damage to corresponding region in human cortex causes color blindness.
- achromatopisa
13
Q
motion processing pathway
A
- retinal ganglion cells and LGN neurons respond to moving stimuli but
- stimulus could be moving in any direction
- stimulus could even just be turning off and on
- although Mangnocelluar neurons are particularly responsive to motion.
SO cells in V1 are orientation selective: respond to moving bars or edges with specific orientation
14
Q
MT neurons influence the perception of movement
A
- the medial temporal-temporal (MT) area in the monkey has neurons with large receptive fields that are direction selective
- damage to the MT in the monkey reduces the ability to judge movement
- stimulation of individual neurons in MT biases perceived direction of motion
- motion selective neurons show adaptation.
15
Q
MST integrates local motion
A
- the media-superior-temporal (MSt) area in the monkey has neurons that are
- sensitive to optic flow (movement of the world cause by self motion)
- responsive to complex movement
- associated with the perception of biological motion.
