Psych 160 - Lectures 7-9

Front 1

What are the 2 main reasons we have an inverted retina?

Back 1

Because the retina takes more energy than the brain by restoring membrane potentials, and because photoreceptors have blood supplies from behind and in front of the eye

Front 2

Which photoreceptors process one photon at a time, and many photons at a time? Wavelengths?

Back 2

Rods (large receptive fields) - one, cones (small receptive fields) - many: L, M, S

Front 3

What do bipolar cells do in the eye?

Back 3

Transmit signals from the photoreceptor to the ganglion

Front 4

What are the 3 issues in vision?

Back 4

Inverse problem - 2D vision in a 3D world; Compression problem - there is more visual input to the retina than can be transmitted to the brain (many photoreceptors, few axons on the optic nerve); vision is constructive, i.e. it sometimes fills in for itself

Front 5

T/F: The large range of light requires processing within the retina to convert intensity signals to contrast signals – i.e., emphasize differences in light intensity, not absolute intensity.

Back 5

True

Front 6

Why do some ganglion cells that have ‘melanopsin’ and respond to absolute light intensity?

Back 6

Usually for circadian rhythms

Front 7

Which bipolar cells work in light through ionotropic receptors?

Back 7

On cells

Front 8

Which bipolar cells work in the dark through metabotropic receptors?

Back 8

Off cells

Front 9

What are the vertical and horizontal organizational pathways in the eye?

Back 9

Vertical: photoreceptor - bipolar call - ganglion. Horizontal: photoreceptor - horizontal cell - bipolar cell

Front 10

Horizontal cells and amacrine cells are key for...

Back 10

Lateral inhibition

Front 11

T/F: Bipolar cells (and consequently ganglion cells) responsive to light/dark within a small region of the visual field are inhibited by cells responsive to light/dark within an adjacent region of the visual field.

Back 11

True

Front 12

T/F: The loss of acuity of an inverted retina is partially compensated by the lack of obscuring fibers and blood vessels over the fovea – the most sensitive portion of the retina.

Back 12

True

Front 13

What are the two functions of center/surround organization?

Back 13

To act as a spatial filter (emphasizing edges_ and a temporal filter (emphasizing motion)

Front 14

What is the part of the on center off surround cell that is "off" called?

Back 14

The annulus

Front 15

T/F: The precise wavelength of photon is lost once it stimulates photoreceptor. The photoreceptor uses an intensity code, not wavelength code. So there is an inherent ambiguity.

Back 15

True

Front 16

What does the herring opponent process theory say?

Back 16

That we never see reddish-green or yellowish-blue light, but we see after-images

Front 17

What are the dorsal and ventral LGNs (lateral geniculate nuclei) for?

Back 17

Dorsal - form, color, motion. Ventral - light intensity/pupil dilation

Front 18

T/F: Upper visual field projects to lower brain. Lower visual field projects to upper brain.

Back 18

True

Front 19

If the optic chiasm itself is damaged, then one suffers a _ _. This means that both the left and right temporal visual field (the outer part of the each visual field) is blind. Subjects see only the nasal part of the visual field.

Back 19

Bitemporal hemianopia

Front 20

Experiencing visual hallucinations in scotomas or hemianopsias is called...

Back 20

Charles Bonnet Syndrome

Front 21

8: What are the 3 types of cells in V1 and V2?

Back 21

Simple, complex, and end-stopped (all respond best to edges, end-stopped must have particular length)

Front 22

T/F: V1 - note also that layer 4 is monocular – ocular dominance columns, while layers 2-3 are binocular.

Back 22

True

Front 23

Lesion in right hemisphere V4 – achromotopsic patient.

Back 23

Disrupted color identification in visual field quadrant that was appropriate for the location of the lesion.

Front 24

Dorsal pathway examples?

Back 24

Zihl study with akinetopsia patient