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II. Neurophysiology and Perception > Center Surround (M1) > Flashcards

Flashcards in Center Surround (M1) Deck (24)

Where must a spot of light be shown on an OFF bipolar cell in order to get it to hyperpolarize?

center of its receptive field


What happens when an annulus of light is shown on an OFF bipolar cell?



What is the idea that if both center an surround of a bipolar cell is stimulated at the same time then the resulting response is the sum of the two?

center-surround antagonism


What is the center component in the center-surround antagonism due to? 1. What is the surround component due to? 2

1. direct input from photoreceptors
2. interaction between horizontal cells and either PRs or bipolars


What neurotransmitters do horizontal cells use onto photoreceptors? 1. What channels do these open and where do the ions flow? 2. What is this process called? 3

1. GABA and glycine
2. chloride into the neuron (hyperpolarize)
3. lateral inhibition


In the dark, if a PR is removed from its connection with horizontal cells would the PR be more depolarized or hyperpolarized?



What is the process when a neighboring photoreceptor is stimulated but not the one in question?

1. horizontal cell hyperpolarizes
2. LESS release of inhibitory compound (GABA) on PR in question
3. PR disinhibited and glutamate release increased
4. OFF bipolar further depolarizes
5. ON bipolar further hyperpolarize


What does the center-surround antagonism provide for?

enhanced edge that separates highlights and shadows


What does center-surround antagonism lead to in terms of our absolute sense of intensity?

makes it very poor


What is the idea that apparent brightness of an object is inversely related to the luminance of its surroundings called?

simultaneous contrast


What is the human visual system especially good at?

contrast detection


What is the idea that objects have a similar appearance regardless if viewed under bright or dim lighting conditions called?

lightness constancy


Where is the axon terminal of bipolar cells?

inner plexiform layer


What is the neurotransmitter released by bipolar cells? 1. When is this releases (depolarized or hyperpolarized)? 2. What is the release dependent on? 3

1. glutamate
2. depolarized
3. Ca2+


How many postsynaptic processes are along the active zone of a bipolar cell (and what are the cells in these positions)? 1. What is in the middle of these? 2. What is this arrangement called? 3

1. two (one amacrine and one ganglion cell)
2. ribbon
3. dyad synapse


What kind of receptors are found on retinal ganglion cell dendrites?

1. AMPA/kinate-type glutamate receptors
2. NMDA-type glutamate receptors


Is the synapse between bipolar cells and ganglion cells sign-conserving or sign-inverting?



Where are the dendrites of OFF RGC cells located? 1. ON RGC cells? 2

1. inner portion of IPL
2. outer portion of IPL


Do retinal ganglion cells have graded potentials or action potentials when depolarized?

action potentials


With increased depolarization, what happens to the retinal ganglion potentials?

increase in action potential spike frequency


What do extracellular recordings of RGCs detect? 1. What can they be used to monitor? 2

1. detect action potentials
2. light-induced changes in spiking frequency


What is the light-induced increase in activity of ON RGCs and ON-OFF RGCs primarily driven by? 1. In light, do the bipolar cells hyperpolarize or depolarize (and do they release more or less glutamate)? 2

1. ON bipolar cells
2. depolarize (more)


What is the light-induced decrease in activity of OFF RGCs and ON-OFF RGCs primarily driven by? 1. In light, do the bipolar cells hyperpolarize or depolarize (and do they release more or less glutamate)? 2

1. OFF bipolar cells
2. hyperpolarize (less)


What are the surround responses of RGCs driven by?

1. bipolar cells (mainly)
2. inhibitory input from amacrines