The visual system Flashcards
Connections from the retina to the LGN and Superior Colliculus are _____
Parallel
Connections from the LGN to the Cortex are _____
serial
What happens if the optic chiasm is cut?
Tunnel Vision
How is the LGN organized?
In layers (6)
From layers 1 to 6 of the LGN, describe the type of cells, present
1 - Magno (C) 2 - Magno (I) 3 - Parvo (I) 4 - Parvo (C) 5 - Parvo (I) 6 - Parvo (C)
Magno cells of the LGN are similar to _____ Ganglion cells and Parvo cells are similar to _____ RGCs
Magno = Parasol Parvo = Midget
What is the point of the LGN?
We don’t know (possible relay station)
Where do most optic neurons terminate?
In the 4C layer of the primary visual cortex
What are the 5 properties of V1?
Retinotopy Cortical magnification Ocular Dominance Orientation selectivity Direction selectivity
What is retinotopy?
The centre of V1 represents the centre of vision on the retina (recall images are flipped and reversed)
What is cortical magnification?
The neurons representing the fixation point are much more exaggerated than the periphery
True/False? V1 Cells respond best to bars of light
True (several simple cell RFs in a straight line connect to their respective LGN cell, which feeds into a single V1 cell, whose output is proportional to the amount of simple RGCs acviated)
True/False? If a V1 Cell doesn’t receive light at exactly the orientation it was optimized for it won’t fire
False (normal distribution)
True/False? All V1 cells have an optimal direction
False, some cells are nondirectional
Describe the organization of V1 cells
Columnar
Increasing depth reveals neurons representing the same field, whereas moving across reveals neurons whose RFs are shifted
