Ch 3. The Visual Brain Flashcards
Nasal Vs. Temporal retina
Fibres from the nasal retina cross to the other side of the brain
Fibres from the temporal retinal stay on the same side of the brain
3 ganglion cells and they’re layers in the LGN
- Parasol (M–>magnocellular)
- Midgit (P–>parvocellular)
- bistratified (B/Y–>koniocellular)
3 things that the LGN does
Retinotopic Maps
Functional Specialization
Center-Surround Receptive Fields
info from eyes to V1 stops at 2 possible places
LGN (later geniculate nucleus) superior colliculus (old sys)
S. Colliculus
orients eye movements, gets 10% of ganglions, site of multisens integration
Hubel and Wisel found what?
- cells don’t respond to sports of light
- respond to bars on light (in V1)
Simple cells
like a single orientation
column orietntaiton
Adjacent columns change preference in an orderly fashion
1 millimeter across the cortex represents entire range of orientation
Pathway: Parasol
parasol–>LGN Magno(flicker)–>MT (motion)–>parietal cortex(motion, motor)–>Dorsal where
Pathway: Midgit
LGN (parvo, R/G detail)–>blob–>V4(colour/form)–>inferotemportal cortex(object recognition)–>Ventral What
Pathway: Bistratified
Bistratified–>LGN knit (B/Y–>blobs–>V4(colour/form)–>inferotemportal cortex(object recognition)–>Ventral What
Patient D.F
Ventral path damage, agnosia, could reach and do tasks okay
Optic Ataxia
- Difficulty with reaching and grasping objects
- have trouble acting on things, only visually guided, close eyes and is fine
V4
colour/curature, Ventral, Loss=Achromatopsia
Achromatopsia
V4 colour damage
IT
inferotemporal cortex, shapes, ventral, Loss=agnoisa (prosopagnosia FFA)
MT
motion perception,dorsal, moving objects, dif direction responses, Loss=Akinetopsia
Akinetopsia
inability to perceive motion
IPS
intraparietal sulcus, dorsal, visually guided reaches & grasps, eye movements, Loss=optic ataxia
Distributed coding
population coding: one cell is ambiguous but if you look at multiple cells, different response patterns of activity can uniquely define 90degrees across multiple cells.
hypercomplex cells
A neuron in the visual cortex that responds to the presence of a line segment with a particular orientation that ends at a particular point within the cell’s receptive field.
Organization of V1 (5)
- retniotopic maps
- cortical magnification
- oreintation selectivity and column
- colours
- occular dominance colums
