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Visual Science > Lecture 5: Striate Cortex > Flashcards

Lecture 5: Striate Cortex Flashcards

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1
Q
  1. Visual Field: 1-9 is your visual field range.
    a. Left Eye sees what?
    b. Right eye?
A
  1. a. 1-8

b. 2-9

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2
Q
  1. Midget cells to what of LGN
  2. Parasol?
  3. Bistratified?
A
  1. Parvo: Layers 3-6
  2. Magno: Layers 1-2
  3. K3-K4
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3
Q
  1. First stage of Cortical Processing occurs within what Cortex?
  2. Cortical Tissue consists of what?
  3. Human cortex weighs how much?
A
  1. Striate Cortex (primary target for projections from the LGN). (Fundamental aspects of visual analysis occur w/in this structure)
  2. Superficial Gray Matter (Cell bodies), and White matter (Myelinated Axons)
  3. 3 lbs. Has about 10^10 cells, 10^15 synapses, and 2000 miles of axonal connections.
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4
Q

Cortex

  1. What are the 4 lobes?
A
  1. Frontal, Parietal, Temporal, and Occipital
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5
Q
  1. In which hemisphere of the brain are there visual cortexes?
  2. Left Hemisphere gets signals from what part of VF?
  3. Right Hemisphere?
A
  1. In each hemisphere
  2. from Right VF
  3. From Left VF
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6
Q
  1. Number of Cortical Layers in the Striate cortex?
A
  1. 6 Cortical Layers, then below that is WHITE MATTER
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7
Q
  1. What is the Striate Cortex referred to? (3)
  2. What is the Striate Cortex?
  3. It’s comprised of how many layers?
A
  1. Primary Visual Cortex, Visual Area 1 (V1) and Brodmann Area 17
  2. A Plexus of GENICULATE AXONS that forms a DISTINCTIVE STRIA in Layer 4B: Referred to as the LINE of GENNARI (and everything else in 1.)
  3. 6 layers. Layer 1 is most superficial.
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8
Q
  1. What does the Striate Cortex Project to?
A
  1. to Extrastriate Cortex (region of Visual cortex NOT distinguished by the Line of Gennari)
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9
Q

Name the Extrastriate Areas. (4)

A
  1. Visual Area 2 (V2, or Brodmann Area 18)
  2. Visual Area 4 (V4)
  3. Inferotemporal Cortex (IT)
  4. Visual Area MT/V5 (Middle Temporal Cortex (MT) or Visual Area 5 (V5)
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10
Q
  1. Ventral processing stream is what system?

a. What do we think it receives input from?

A
  1. Temporal System or the “what” system
    a. Predominantly from The PARVO Retinogeniculate Pathway.

Also receives from the Dorsal Processing Stream (also PARIETAL Pathway, or “where” system)

*Significant communication occurs b/w the 2 processing streams

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11
Q
  1. So striate cortex projects to the extrastriate cortex, but where does it also send info to?
  2. How does info flow from Extrastriate Cortex?
A
  1. Sends a reciprocal Projection to the LGN, to the Pulvinar (this is a thalamic nucleus we think is associated with Visual Attention, Motion processing, and visually guided movement)
  2. Info flows back toward the Striate Cortex from Extrastriate Cortex via RECIPROCAL PATHWAYS (basically, feedback loops)
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12
Q

Cortical Magnification of Foveal Vision

  1. Fovea is what % of the retina area?
    a. What % of Striate Cortex is used?

b. Why is this?

A
  1. 0.01%
    a. 8%
    b. Because of the LARGE AREA of CORTEX devoted to the FOVEA. More for this reason than for the high density of ganglion cells found in the fovea.
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13
Q

Simple and Complex Cells

  1. What was seen in Cat and monkey cortexes?
  2. Simple cells are most sensitive to what?
    a. What must the stimulus be?
A
  1. neurons were SENSITIVE to ELONGATED STIMULI, like BARS and EDGES
  2. to an Edge or Bar of a specific Orientation
    a. If it’s a BAR, then it has to be a SPECIFIC WIDTH
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14
Q
  1. Receptive Fields are divided into what 2 regions?
  2. What cells are MAXIMALLY SENSITIVE to DARK or LIGHT BARS?
  3. Others Respond Best to what?
A
  1. Antagonistic Excitatory and Inhibitory Regions
  2. (B and D)
  3. to Edges (A and C)
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15
Q
  1. Where do receptive Fields of SIMPLE CELLS come from?

2. Hierarchical Processing: What is it?

A
  1. From Input of LGN neurons whose Receptive Fields lie along a STRAIGHT LINE
  2. Formation of Increasingly complicated Receptive Field Arrangements (ie, simple cells) from Less Complicated Arrangements (ie, Concentraic LGN Cells)
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16
Q
  1. What do COMPLEX CELLS respond best to?
  2. Stimulus Position w/in a receptive field of a simple cell is CRITICAL, but where can the stimulus be positioned for a COMPLEX Cell?.
    a. What are many complex cels characterized by?
A
  1. Elongated Stimulus of a SPECIFIC ORIENTATION
  2. Stimulus can be positioned ANYWHERE w/in a COMPLEX Cell’s Receptive Field.
    a. By DIRECTION SELECTIVITY: For cell to be stimulated, the stimulus MUST MOVE IN A SPECIFIC DIRECTION!
17
Q
  1. Unlike Simple Cells, Receptive Fields of Complex CELLS CANNOT Be what?
A
  1. Can’t be divided into SEPARATE Excitatory and inhibitory regions.
18
Q
  1. Complex cells (unlike simple) do not manifest what?

2. Nonlinear LGN Cells (Magno Cells) may play a larger role in the formation of what?

A
  1. Don’t manifest Separate Excitatory and Inhibitory Areas as would be Expected if there was linear addition of simple cell input.
  2. In formation of the REceptive Fields of Complex Cells than they do for Simple Cells
19
Q
  1. Certain Cortical Neurons are Sensitive to what?

2. What are these neurons called?

A
  1. to the LENGTH of the STIMULUS
  2. End-Stopped Neurons originally classified as hypercomplex cells. But, we have come to see that sensitivity to stimulus length is a feature common to many cortical cells!
20
Q
  1. End-Stopped Cortical Neurons show what?

a. A stimulus LONGER than this optimal length will do what?

A
  1. A MAXIMUM Response to a Bar of Light of a Specific Length.
  2. Will ELICIT LESS of a RESPONSE.
21
Q
  1. What does a cone respond to?
  2. A Ganglion Cell?
  3. A Simple Cell?
  4. A Complex Cell?
  5. So the Higher up in the Visual System, what happens?
A
  1. Diffuse Light
  2. Spot of Light of a Specific Diameter
  3. Bar of Light of a specific orientation
  4. to the same bar of light but MOVING in the PROPER DIRECTION
  5. The more stringent are the Requirements to Drive a Visual Neuron
22
Q
  1. Hierarchical Processing Occurs along what?
  2. First elements in the Parvo pathway are what?
    a. Follow by what?
  3. Cortical Neurons respond well to what?
    a. They are also selective for what?
A
  1. Along each of the parallel pathways
  2. are Cones
    a. Spatially summing horizontal cells, then spatially and chromatically antagonistic bipolar cells, and so on.
  3. to Sine Wave Gratings
    a. for a Particular Spatial Frequency
23
Q
  1. Info from the 2 eyes is first combined in what?
    a. Most cortical neurons here are what?
  2. What do Binocular Cortical Cells mediate?
A
  1. in V1
    a. are Binocular
  2. Mediate Steropsis
24
Q
  1. Stimulation of a neuron thru the “Dominant” eye will cause what?
  2. Ocular dominance is laid out in what way?
    * RANDOT
A
  1. Will cause a STRONGER response than stimulation thru the other eye.
  2. in a less regular pattern of alternating Right and Left ocular dominance bands, sometimes called Ocular Dominance Slabs or Columns.
25
Q
  1. A Cell in Group 1 is influenced only by what?
  2. A cell in Group 7 is influenced only by what?
  3. Cells in group 4 are driven by what?
  4. Simple cells tend to belong to what groups?
  5. Complex cells are spread how?
A
  1. Only by Contralateral Eye
  2. Only by the Ipsilateral Eye
  3. Are driven EQUALLY by Both Eyes
  4. to Groups 1 or 7.
  5. are Spread more evenly Across Ocular Dominance Groups
26
Q
  1. Striate Cortex is organized according to what 2 things?
  2. A Complete set of Ocular Dominance Columns (both eyes) and Orientation Columns (All orientations) forms what?
  3. Each of these: dimensions?
A
  1. Orientation and Ocular Dominance
  2. Forms a HYPERCOLUMN
  3. Each Hypercolumn has dimensions of about 1x1 mm (range is higher in the periphery)
27
Q
  1. Cells in LAYER 4 tend to have what organization?
    a. Similar to what 2 things?
  2. Cells lying along a line drawn vertically thru the Cortex have SIMILAR what?
A
  1. Concentric Organization (like a beach ball shape)
    a. similar to those in the Retina and LGN
  2. Have similar Ocular Dominance and Orientation Preferences.
28
Q
  1. What percent of STRIATE CELLS have Chromatically Opponent REsponse?
  2. The cell has a spatially opponent receptive field that contains what?
    a. But spectrally opponent responses can be found where?
A
  1. 41%
  2. That contains Excitatory and Inhibitory Zones
    a. In Both Zones
29
Q
  1. Cylindrical pillars are how far apart?
    a. how are they arranged?
    b. How are they centered?
A
  1. About 0.5 mm apart
    a. In Parallel rows.
    b. Centered on Ocular dominance Columns
30
Q
  1. What are Striate Blobs?

2. These cells are optimally responsive to stimuli that manifest what?

A
  1. Rich w/concentrically organized, double color-opponent neurons that result from PARVO input.
  2. that manifest color contrast.
31
Q
  1. What is the superficial region of the striate cortex?

a. It also appears to receive what?

A
  1. b/w Blobs (the interblob region)

a. Substantial Parvo Input

32
Q

The Magno pathway apparently bypasses what 2 things?

A

Bypasses BLOBS and the INTERBLOB Regions

33
Q

Parvo and Magno pathways provide input to what 2 streams?

A
  1. to ventral and dorsal processing streams respectively
34
Q

Outputs of the Striate Cortex

  1. Layers 2,3, and 4B
  2. Layer 5
  3. Layer 6
A
  1. Projects to other cortical Areas
  2. Projects to Superior Colliculus and Pons
  3. Projects back to the LGN

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