The output neurons of the retina, the retinal ganglion cells, group together at ______.
the optic disk
____ are larger in the periphery of the retina..
What happens after the 2 optic nerves converge @ the optic chiasm?
half of the axons from each eye cross to the other side and continue on as the optic tract
What do rods mediate?
black/white; light/dark vision
What does activation of transducing cause?
activation of cGMP phosphodiesterase (PDE)
What coordinates head and eye movements? Where is this structure located?
the superior colliculus; on the dorsal surface of the midbrain
These are central regions of the hypercolumns where color information is deciphered.
These cells capture photons of light and convert them into an electrical signal.
What determines cortical wiring?
This is a .2mm wide region where acuity is the greatest.
The period of time when the connections can be altered by visual experience is called ____.
the critical period (or sensitive period)
What is the dorsal parallel pathway?
- from V1 dorsally --> parietal lobe
- spatial vision
- passes thru the thick stripe region of V2 and thru V5
What are binocular cells sensitive to?
Layers 1, 4, and 6 of the lateral geniculate nucleus (LGN) of the thalamus receive input from the ______.
What does the postsynaptic cell release to the presynaptic cell? When can the presynaptic cell take it up?
trophic factors; only when it's been recently active
_____ have donut-shaped receptive fields and come in on-center and off-center types.
Layers 3-6 of the lateral geniculate nucleus (LGN) of the thalamus receive inputs from the _____.
parvocellular ganglion cells
How many rods are in the human retina?
Category 4 ocular dominant cells are ____ driven.
equally (from both sides)
What do cones mediate?
What is hierarchical processing in the eye?
several cells with similar but spatially offset receptive fields converge on a higher order cell to create an altogether new type of receptive field
Beyond the lateral geniculate nucleus (LGN) of the thalamus, the axons fan out into the ______ to the visual cortex.
Receptive fields are larger in the ______ of the retina.
Each hypercolumn is divided into 2 parts, one half for each eye, called _____.
ocular dominance columns
What do complex cells do?
abstract for position
In the dark, the concentration of cGMP is ____, causing the nonselective cation channels to stay _____.
Layers 1 and 2 of the lateral geniculate nucleus (LGN) of the thalamus receive inputs from the _____.
magnocellular ganglion cells
What are the features of the parvocellular ganglion cells.?
object vision- color, form, detail high acuity --> fine detail small receptive fields not responsive to motion color vision (input from cones) layers 3-6 of the LGN
What are the 2 primary parallel pathways through the ascending visual system?
- the dorsal pathway
- the ventral pathway
What are the features of the magnocellular ganglion cells.?
spatial vision- motion and depth low acuity (crude) large receptive fields responsive to motion no color vision (input from rods) layers 1 and 2 of the LGN