COGS 101A Lecture Notes - Visual Field, Lateral Geniculate Nucleus, Occipital Lobe
● Action potentials are all the same voltage, having more excitation only changes the
frequency that a neuron fires
● Neural Circuits
○ Groups of neurons interconnected and will fire together as result of stimulation
■ Simples level neuron > receptor
○ Convergence
■ Multiple neurons synapse onto a single neuron
● Can be excitatory and inhibitory
■ Rods
● 120:1 ganglion cells
● More responsive to same amount of light; more sensitive
● Rods sum their response
● Lower acuity
● In periphery
● Not in fovea (mostly)
■ Cones
● 6:1
● Fovea = 1:1
● Less sensitive, high acuity
● Cones everywhere
○ Lateral inhibition
■ Lateral plexus inhibits transmitted laterally across neural circuits
● Allows us to detect features, less cells being activated = more
activity
■ Can be thought of as a specific type of neural convergence
■ Limulus (horseshoe crab)
■ Horizontal cells
● Between rods and cones and bipolar
■ Amacrine cells
● Between bipolar and ganglion cells
■ Illusions
● Hermann Grid: seeing spots at intersections
○ More lateral inhibition to intersection than from the ones
between two black squares
● Simultaneous contrast: areas of difference in brightness
○ more lateral inhibition from white square making middle
square seem darker and v.v.
■ Wrong!
● White’s illusion, same color but with different color background
look lighter or darker
● Receptive fields
○ Receptive field of a particular neuron = area of receptors on retina that affects the
neuron/ganglion’s firing
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Document Summary
Action potentials are all the same voltage, having more excitation only changes the frequency that a neuron fires. Groups of neurons interconnected and will fire together as result of stimulation. Multiple neurons synapse onto a single neuron. More responsive to same amount of light; more sensitive. Lateral plexus inhibits transmitted laterally across neural circuits. Allows us to detect features, less cells being activated = more activity. Can be thought of as a specific type of neural convergence. More lateral inhibition to intersection than from the ones between two black squares. Simultaneous contrast: areas of difference in brightness. More lateral inhibition from white square making middle square seem darker and v. v. White"s illusion, same color but with different color background look lighter or darker. Receptive field of a particular neuron = area of receptors on retina that affects the neuron/ganglion"s firing. What info is transmitted from a single ganglion cell.
