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psych 120B > Visual pathway & Spatial vision > Flashcards

Visual pathway & Spatial vision Flashcards

1
Q

Cornea

A

the first tissue that light will encounter is the cornea, it is transparent meaning it is made of a highly ordered arrangement of fibers and contains no blood vessels or blood which would absorb light

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2
Q

Ciliary muscles

A

responsible for stretching and compressing the zonules of zinn

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3
Q

Zonules of zinn

A

responsible for changing the lens to intake the light

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4
Q

Iris

A

the colored part of the eye , consisting of a muscular diaphragm surrounding the pupil and regulating the light entering the eye by expanding and contracting the pupil

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5
Q

Fovea

A

A small pit located near the center of the macula and containing the highest concentration of cones and no rods. It is the portion of the retina that produces the highest visual acuity and serves as the point of fixation

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6
Q

How images are projected onto the retina

A

REVERSED TO RIGHT -> LEFT AND UPSIDE DOWN!!

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7
Q

photoreceptors

A

light sensitive receptor in retina

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8
Q

Rods

A

a photoreceptor specialized for night vision

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9
Q

Cones

A

a photoreceptor specialized for daylight vision, fine visual acuity and color

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10
Q

Bipolar cells

A

Bipolar cells are the ones spoken about in class when discussing convergence and are primarily thought of as the connection between rods/cones and ganglion cells- furthermore they are distinct as midget/ non midget cells where the former receive information from a single cone rather than multiple receptors.

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11
Q

Horizontal cells

A

Squeezed between rods/cones and bipolar cells these cells are important for creation of center-surround receptive fields

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12
Q

Visual angle

A

the angle that would be formed by lines going from the top and bottom of a cycle on the page, passing through the center of the lens and ending on the retina

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13
Q

Fovea

A

~2º diameter of central vision; no rods, only cones; 1% retina but ~50% of visual cortex!!!

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14
Q

Para-fovea

A

area immediately surrounding fovea (~4-5º around the center)

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15
Q

Periphery

A

the area beyond fovea

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16
Q

Blind spot

A

location of optic nerve that leaves the retina about 3 degrees diameter.

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17
Q

Eccentricity

A

the distance between the retinal image and the fovea many functions depend on the eccentricity of the stimulus, such a acuity, color, and motion

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18
Q

Distribution of rods and cones in terms of retinal location

A

Rods are in the periphery and cones are primarily in the fovea

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19
Q

Pupil size

A

the diameter of the pupil can vary by about a factor of 4; pupil size accounts for only a small part of the visual system’s overall ability to adapt to light/dark conditions

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20
Q

Photopigment regeneration

A

Second mechanism for achieving a large sensitivity range is provided by the way photopigments are used up and replaced in receptor cells

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21
Q

Dim Lighting

A

As the overall light level inc the number of photons starts to overwhelm the system: photopigment molecules can’t be regenerated fast enough to detect all the photons hitting the photoreceptors ties into opposite neurons

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22
Q

Difference between rods and cones

A

responses to different wavelengths (cones can detect different colors [S,M,L]; rods only have one kind of photopigment called rhodopsin)
In their distribution across retina (rods in periphery, cones in fovea)

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23
Q

Retinal ganglion cells

A

These cells are responsible for telling the brain what the eye sees; this is accomplished through two pathways: the M absorb information from multiple converging bipolar cells whereas those in the P pathway synapse with single bipolar cells which lead to individuals cones and less information.

24
Q

Visual acuity

A

the smallest spatial detail that can be resolved at 100% contrast

25
Q

Difference in acuity between foveal and peripheral vision

A

Rods and cones in the periphery are packed together less tightly than in the fovea and her many receptors converge on each ganglion cell making acuity much poorer in the periphery than the fovea!

26
Q

The acuity-sensitivity trade-off

A

Cones have higher acuity because of their ability to see detail and color whereas rods are more sensitive as they can see in the dark, recover faster in the dark and allow you to see movement in dim lighting (this may have evo psych implications)

27
Q

Sine-wave gratings

A

a grating with a sinusoidal luminance profile as shown in figure

28
Q

Sensitivity of retinal ganglion cells to:

A

responds (ON to light on-center and OFF to dark on-center) greatly to 0 degrees (upward sine wave) and 180 degrees (downward sine wave). Flat line response at 90 degrees and 270 degrees (responding to half light/dark in center).

29
Q

phase

A

the relative position of a grating

30
Q

spatial frequencies

A

the number of grating cycles (i.e., dark and bright bars) in given unit of a space.

31
Q

Lateral Geniculate Nuclei (LGN)

A

a structure in the thalamus, part of the midbrain, that receives input from the retinal ganglion cells and has input and output connections to the visual cortex.

32
Q

Topographical mapping

A

the orderly mapping of the world in the lateral geniculate nucleus and the visual cortex

33
Q

Magnocellular layers

A

either of the bottom tow neuron-containing layers of the lateral geniculate nucleus, the cells of which are physically larger than those in the top four layers.

34
Q

Parvocellular layers

A

any of the top fou neuron-containing layers of the lateral geniculate nucleus, the cells of which are physically larger than those in the top four layers

35
Q

Primary visual cortex (V1)

A

the area of the cerebral cortex of the brain that receives direct inputs from the lateral geniculate nucleus, as well as feedback from other brain areas, named because it has white stripes.

36
Q

Topographical mapping

A

Adjacent things are adjacent. Systematic mapping of visual field. It is not just a bigger version of the LGN. A major and complex transformation fo visual information takes place in the striate cortex.

37
Q

Cortical magnification factor

A

Foveal representations are ‘expanded’ relative to peripheral representations. The amount of cortical area devoted to a specific region

38
Q

Receptive field

A

The region in space in which stimuli will activate a neuron.

39
Q

Cells in V1

A

a cortical neuron whose receptive field has clearly defined excitatory and inhibitory regions

40
Q

Simple cells

A

Respond to edges/bars of specific orientations • This is a different receptive field structure than the center/surround structure of cells in LGN - orientation

  •   spatial frequency (related to scale)
  •   phase sensitive
41
Q

Complex cells

A

Orientation specific (like simple cells). But, they are most active when the oriented stimuli is moving. Some cells respond to motion in any direction, some respond to motion only in very specific directions -  orientation

  •   spatial frequency
  •   phase insensitive
  • motion direction
42
Q

End-stopped cells

A

Like complex cells but respond to lines of only a certain length - Orientation specific

  • Motion specific
  • Length specific
  • corners
  • motion direction
43
Q

V1 Organization

A

The cortex is organized into ‘columns’ that represent specific values of a feature. A column is a vertical arrangement of neurons. Neurons within a single column tend to have similar receptive fields and similar orientation preference.

44
Q

location columns

A

Columns of neurons that all have their receptive field on roughly the same location on the retina. Run perpendicular to the cortex

45
Q

orientation columns

A

Column of cells that all prefer the same orientation

• Aligned perpendicular to cortex (like location columns

46
Q

ocular dominance columns

A

property of receptive fields of striate cortex neurons by which they demonstrate a preference, responding somewhat more rapidly when a stimulus is presented in one eye than when it is presented in the other.

47
Q

Hypercolumns

A

Complete set of orientation and ocular-dominance columns for a given retinal location. Like a ‘super-column’ that contains all the column types
A 1-millimeter block of striate c degrees, w/one sets of columns, each covering every possible orientation (0-180 degrees), with one set preferring input from the left eye and one set preferring input from the right eye.

48
Q

Spatial frequency

A

essentially, the amount of ‘stuff’ present per unit length • V1 cells are also tuned to spatial frequency
• Similar to orientation tuning

49
Q

Contrast sensitivity function

A

The psychophysical contrast threshold is a function of spatial frequency

50
Q

Ventral stream (the “What” pathway)

A

Processes shape/form

51
Q

Dorsal stream (the “Where” pathway)

A

Parietal lobe. Processes location, and HOW to interact with it based on location (used to plan action). • Location (e.g. left vs. right)

52
Q

Extrastriate cortex

A

V2, V3, V4, MT & IT

53
Q

V2

A

Illusory contours

54
Q

V3

A

Maybe combining info for 3D percepts

55
Q

V4

A

Color

56
Q

MT

A

Motion

57
Q

IT

A

Shapes, form, faces

psych 120B (4 decks)

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