PS 222 Exam 2 review questions and
verified answers already passed
After incoming light is transduced, neural signals are transmitted through the circuit. - answer
✔✔-what happens after incoming light is transduced?
Combination of center and surround influences on the bipolar cells determines the strength of
the signals that the bipolar cells send to the RGC. - answer ✔✔-determines the strength of the
signals that the bipolar cells send to the RGC.
Combination of center and surround influences on the bipolar cells determines the strength of
the signals that the bipolar cells send to the RGC. - answer ✔✔-This determines the firing rate
of the RGC as it sends action potentials into the optic nerve.
a balance of the excitatory signals sent by center photoreceptors and the inhibitory signals sent
by horizontal cells. - answer ✔✔-RGCs' response reflects
lateral inhibition - answer ✔✔-Refers to the inhibitory signals sent by horizontal cells, which
modify the responses of photoreceptors and provide a way in which neural activity in one part
of the circuit can influence neural activity in adjacent parts of the circuit.
which modify the responses of photoreceptors and provide a way in which neural activity in one
part of the circuit can influence neural activity in adjacent parts of the circuit. - answer ✔✔-
function of horizontal cells
,In this circuit underlying an on-center receptive field, signals from cones in the surround tend to
reduce the responses of the bipolar cells, whereas signals from the cone in the center tend to
strengthen bipolar cell responses.
The RGC response is based on the signals it receives from the bipolar cells and therefore
depends on the balance between the signals from cones in the center and surround. - answer
✔✔-how does RGC response depend on the center and the surround?
edge enhancement - answer ✔✔-Process by which the visual system makes edges as visible as
possible, facilitating perception of where one object or surface ends in the retinal image and
another begins.
lateral inhibition - answer ✔✔-inhibition works to sharpen boundaries to enhance the process
of edge enhancement
RGCs with center-surround receptive fields that exhibit lateral inhibition (spot detectors) make
edge enhancement happen. - answer ✔✔-what makes edge enhancement happen?
FIGURE 2.29
Part (a): Each strip in the illustration at top is uniform in intensity across its width, as indicated
by the "Physical intensity" graph at bottom. But, each appears to be lighter at the right and
darker at the left, as indicated by the "Perceived intensity" graph. The edges where the strips
meet are perceptually enhanced by an illusory increase in contrast at the edge—the apparently
darkest part of the strip on the left is next to the apparently lightest part of the strip on the
right. (You can verify that the individual strips are, in fact, of uniform intensity. Just look at each
one separately by masking off the strips on either side of it with pieces of paper.)
Part (b): The enlargement at top shows Mach bands in this Ellsworth Kelly painting (Spectrum
II). Each strip of color appears to vary in brightness from left to right, yet each is a uniform color
and intensity throughout. - answer ✔✔-what do mach bands demonstrate?
FIGURE 2.30
, This enlargement of a small part of the retinal image of the strips in Figure 2.29 also includes
the on-center receptive fields (RFs) of four RGCs near an edge between two strips. The
differences in the responses of the RGCs lead to edge enhancement.
The visual system is accomplishing something useful through this failure of accurate vision. In
this case, edges are enhanced in order to improve our ability to see shapes (the individual
strips). In the chapters ahead, we'll encounter other illusions that lead to similar insights about
how the visual system optimizes our ability to see "what is where." - answer ✔✔-how do
center-surround receptive fields do lateral inhibition?
trichromatic theory - answer ✔✔-Explanation of color vision based on the coding of three
primary colors: red, green, and blue.
Trichromatic Theory: Explanation of color vision based on the coding of three primary colors:
red, green, and blue.
The color we see is determined by the relative responses of the different cone types. - answer
✔✔-how does the trichromaatic theory explain color vision?
Can explain different types of color blindness
Limitations:
- Cannot explain color afterimages (Red-green; blue-yellow) - answer ✔✔-what can the
trichromatic theory explain? What can it not explain?
We know that color mixing is a property of the cones in the retina. Light of different
wavelengths stimulates the three different types of cone receptors in different ways, and the
ratio of the activity of these creates our impression of different colors. RANGE FRACANATION
Subtractive color mixing absorbs the light waves that we see as red, blue or yellow. When all
visible wavelengths are absorbed, we see black. In the case of our vision, with less light, we
see black.
Additive color mixing reflect the light waves that we see as red, blue and green. When all
verified answers already passed
After incoming light is transduced, neural signals are transmitted through the circuit. - answer
✔✔-what happens after incoming light is transduced?
Combination of center and surround influences on the bipolar cells determines the strength of
the signals that the bipolar cells send to the RGC. - answer ✔✔-determines the strength of the
signals that the bipolar cells send to the RGC.
Combination of center and surround influences on the bipolar cells determines the strength of
the signals that the bipolar cells send to the RGC. - answer ✔✔-This determines the firing rate
of the RGC as it sends action potentials into the optic nerve.
a balance of the excitatory signals sent by center photoreceptors and the inhibitory signals sent
by horizontal cells. - answer ✔✔-RGCs' response reflects
lateral inhibition - answer ✔✔-Refers to the inhibitory signals sent by horizontal cells, which
modify the responses of photoreceptors and provide a way in which neural activity in one part
of the circuit can influence neural activity in adjacent parts of the circuit.
which modify the responses of photoreceptors and provide a way in which neural activity in one
part of the circuit can influence neural activity in adjacent parts of the circuit. - answer ✔✔-
function of horizontal cells
,In this circuit underlying an on-center receptive field, signals from cones in the surround tend to
reduce the responses of the bipolar cells, whereas signals from the cone in the center tend to
strengthen bipolar cell responses.
The RGC response is based on the signals it receives from the bipolar cells and therefore
depends on the balance between the signals from cones in the center and surround. - answer
✔✔-how does RGC response depend on the center and the surround?
edge enhancement - answer ✔✔-Process by which the visual system makes edges as visible as
possible, facilitating perception of where one object or surface ends in the retinal image and
another begins.
lateral inhibition - answer ✔✔-inhibition works to sharpen boundaries to enhance the process
of edge enhancement
RGCs with center-surround receptive fields that exhibit lateral inhibition (spot detectors) make
edge enhancement happen. - answer ✔✔-what makes edge enhancement happen?
FIGURE 2.29
Part (a): Each strip in the illustration at top is uniform in intensity across its width, as indicated
by the "Physical intensity" graph at bottom. But, each appears to be lighter at the right and
darker at the left, as indicated by the "Perceived intensity" graph. The edges where the strips
meet are perceptually enhanced by an illusory increase in contrast at the edge—the apparently
darkest part of the strip on the left is next to the apparently lightest part of the strip on the
right. (You can verify that the individual strips are, in fact, of uniform intensity. Just look at each
one separately by masking off the strips on either side of it with pieces of paper.)
Part (b): The enlargement at top shows Mach bands in this Ellsworth Kelly painting (Spectrum
II). Each strip of color appears to vary in brightness from left to right, yet each is a uniform color
and intensity throughout. - answer ✔✔-what do mach bands demonstrate?
FIGURE 2.30
, This enlargement of a small part of the retinal image of the strips in Figure 2.29 also includes
the on-center receptive fields (RFs) of four RGCs near an edge between two strips. The
differences in the responses of the RGCs lead to edge enhancement.
The visual system is accomplishing something useful through this failure of accurate vision. In
this case, edges are enhanced in order to improve our ability to see shapes (the individual
strips). In the chapters ahead, we'll encounter other illusions that lead to similar insights about
how the visual system optimizes our ability to see "what is where." - answer ✔✔-how do
center-surround receptive fields do lateral inhibition?
trichromatic theory - answer ✔✔-Explanation of color vision based on the coding of three
primary colors: red, green, and blue.
Trichromatic Theory: Explanation of color vision based on the coding of three primary colors:
red, green, and blue.
The color we see is determined by the relative responses of the different cone types. - answer
✔✔-how does the trichromaatic theory explain color vision?
Can explain different types of color blindness
Limitations:
- Cannot explain color afterimages (Red-green; blue-yellow) - answer ✔✔-what can the
trichromatic theory explain? What can it not explain?
We know that color mixing is a property of the cones in the retina. Light of different
wavelengths stimulates the three different types of cone receptors in different ways, and the
ratio of the activity of these creates our impression of different colors. RANGE FRACANATION
Subtractive color mixing absorbs the light waves that we see as red, blue or yellow. When all
visible wavelengths are absorbed, we see black. In the case of our vision, with less light, we
see black.
Additive color mixing reflect the light waves that we see as red, blue and green. When all
