Midterm 1 - Vision

Question 1

Lobes of the Brain

Answer 1

Question 2

3 Types of Neurons

Answer 2

Question 3

Entire Spectrum of Electromagnetic Radiation

Answer 3

Question 4

Visible Spectrum of Electromagnetic Radiation

Answer 4

Violet (400), Blue (450), Green (500), Yellow (550), Red (600)

Question 5

Human Eye Anatomy

(Picture)

Answer 5

Question 6

Fovea

Answer 6

• Retinal region of highest visual acuity.
• Color sensitive cones are the only type of photoreceptor in the fovea.
• There’s a round spot that the axons don’t go through so that there can be better signal transmission.

Question 7

Choiroid (Eye)

Answer 7

Back of retina.

Question 8

Optic Disk

Answer 8

• Exit point from the retina of fibers of ganglion cells that form the optic nerve.
• Produces a blind spot because no photoreceptors.

Question 9

Cones vs. Rods

Answer 9

Cones

• Fovea
• Moderate/High Levels of Light
• Color Vision (hue)
• Acuity

Rods

• Peripheral retina
• Low Levels of Light
• Monochromatic Information
• Poor Acuity
• Greater # of rods than cones in retina overall

Question 10

3 Varieties of Cones

Answer 10

1. Short - Blue
2. Medium - Green
3. Long - Red

There’s more than 3 colors so there must be an overlap between the different wavelengths. Colors are produced by a combination of different short, medium and long cones firing.

Question 11

Physical Structure of Human Retina

(Type and Order of Cells)

Answer 11

Back of retina –> photoreceptors (rods & cones) –> horizontal cells –> bipolar cells –> amarcrine cells –> ganglion cells

<————– LIGHT

Question 12

Flow of Information From Photoreceptors

Answer 12

1. Photoreceptor (Rod, Cone)
   * Horizontal Cells
2. Bipolar Cells
   * Amarcrine Cells
3. Ganglion Cells

–> Optic Nerve

Question 13

Horizontal Cells

Answer 13

Interconnects adjacent photoreceptors and outer processes of bipolar cells.

Question 14

Amacrine Cells

Answer 14

Interconnects adjacent ganglion cells and inner processes of bipolar cells.

Question 15

What Happens When Light Hits Photoreceptors?

Answer 15

1. Rhodopsin splits into opsin & retinal
2. Phosphodiesterase degrades cyclic AMP
3. Na+ channels close
4. Hyperpolarization of photoreceptor
5. Inhibition of release of glutamate onto bipolar cells
6. Bipolar cells depolarized
7. Bipolar cells release glutamate
8. If enough glutamate is released, the ganglion cell will fire

Question 16

Action Potentials: Photoreceptors, Bipolar & Ganglion Cells

Answer 16

Ganglion cells are the first cells to actually fire (i.e., have an action potential). Photoreceptors and bipolar cells merely have graded potentials.

Question 17

What Happens to Photoreceptors in the Dark?

AKA, “Dark Current”

Answer 17

Photoreceptors are depolarized (active) and release glutamate, causing a hyperpolarization of the bipolar cell.

Question 18

Vision Cranial Nerves

(4)

Answer 18

II. Optic (leaves eye)

III. Oculomotor (works iris, pupil)

IV. Trochlear (moves eyes up and down)

VI. Abducens (moves eyes side-to-side)

Question 19

Optic Pathway

Answer 19

Question 20

Visual of 12 Cranial Nerves

Answer 20

Question 21

Visual Pathway

Diagram 2

Answer 21

Question 22

Deficits to Visual Fields Caused by Cuts In Visual Pathways

Answer 22

Question 23

Where is the LGN & What Eye Does it Receive Information From?

Answer 23

The LGN is located in the thalamus of each side of the brain and each LGN receives information from 2 different eyes!

Question 24

Nasal Retinas

Answer 24

Cross

Question 25

Temporal Retinas

Answer 25

Stay on same side.

Question 26

6 Layers of the LGN

“See I? I see, I see”

Answer 26

Question 27

Parvocellular Layers of the LGN

Answer 27

• “Small”
• 3, 4, 5, 6
• Form, color, fine details
• 1 cone feeds into 1 ganglion cell
• Fovea over-represented

Question 28

Magnocellular Layers of the LGN

Answer 28

• “Big”
• 1, 2
• Many rods feeding into one ganglion cell
• Periphery
• Movement (larger visual field)

Question 29

Retinotopic Organization in the LGN

Answer 29

More axons come from the fovea than from the periphery - that is why there are more parvocellular layers (i.e., the fovea is over-represented in terms of space).

Question 30

Superior Colliculus

Answer 30

• Located in brainstem
• Allows for a “sampling of information”
• Visual information stops here before going to V1 from the LGN.
• Could be responsible for “blind sight” (a person can be blind due to an impairment in V1 and everything else can be intact - thus, they can move when a ball is thrown at their head).

Question 31

Dorsal & Ventral Streams

(Visual Representation)

Answer 31

Question 32

Dorsal Stream

Answer 32

• “WHERE”
• Goes up
• V1–>V2–>V5
• Movement
• Magnocellular

Question 33

Ventral Stream

Answer 33

• “WHAT”
• Goes down
• V1–>V2–>V3–>V4
• Parvocellular
• Sends information of high acuity to the temporal cortex

Question 34

3 Structures of Temporal Cortex Related to Vision

Answer 34

Receives information from the ventral stream and gets more refined as it moves along.

1. Inferior Temporal - facial recognition
2. Medial Temporal
3. Medial Superior Temporal

Question 35

Ice Cube Tray Model

(Class Drawing)

Answer 35

V1 (Striate Cortex)

Question 36

V1 Simple Cells

Answer 36

Make out 180 degrees of orientation (e.g., horizontal line)

Question 37

V2 Complex Cells

Answer 37

Orientation of a specific length

Question 38

Top-Down Processing

Answer 38

“I’ve seen this before…”

Explains how the brain flips a visual scene (goggles experiment).

Question 39

“Binding Problem”

Answer 39

Images in the brain are left-right reversed and top-bottom reversed. Somehow, it all straightens out and we don’t know how. Hence, the “binding problem.”

Question 40

How Much of the Brain is Used to See?

Answer 40

HALF!!!