Chapter 3: The Visual Brain

Question 1

Functional Specialization

Answer 1

specialization of different neural pathways and different areas of brain for representing different kinds of information

Question 2

Retinotopic Mapping

Answer 2

signals from RGC with receptive fields are next to each other on retina travel to neurons that are next to each other in visual area of brain

Question 3

Optic Chiasm

Answer 3

location where optic nerve from two eyes split half and half axons from each eye crosses over to other hemisphere

Question 4

Optic Tract

Answer 4

continuation of optic nerve past optic chiasm

Question 5

Contralateral Organization

Answer 5

opposite- side organization

Right hemisphere- looks at left visual field
Left hemisphere- looks at right visual field

Question 6

Primary pathways from RGC to area V1

Answer 6

Geniculostriate pathway:

• looks at detail and color
• 80-90% of all visual info goes through this pathway

Tectopulvinar pathway:

• bypasses LGN
• info about motion
• optic tectum in midbrain to pulvinar nucleus in thalamus

Suprachiasmatic Nucleus (SCN):
- structure in hypothalamus that deals with circadian rhythm

Question 7

Lateral Geniculate Nucleus

Answer 7

part of thalamus
- receives visual signals via axons of RGCs

Magnocellular cells: layer 1 and 2
Parvocellular cells: layers 3-6
Kiniocellular layers: thin layers in between all the other layers

Ipsilateral: layers 2, 3, 5
Contralateral: layers 1, 4, 6

Question 8

Magnocellular Layer

Answer 8

responds best to info about motion from parasol RGC
large cells bodies
responds to rods and cones

Question 9

Parvocellular Layers

Answer 9

responds best to static properties (color, texture, form, and depth) information from midget cells
small cell bodies
high acuity and cones

Question 10

Koniocellular Layers

Answer 10

respond best to color information from bistratified cells
very very small
in response to size of perceptive field

Question 11

Superior Colliculus (SC)

Answer 11

one each SC in each hemisphere of the brain
form tectum (roof) of midbrain together with inferior colliculi

• helps control eye movement
• can respond to any visual stimulus
• also receives signals from auditory and somatosensory systems
  site of multisensory integration
• sends signals to areas beyond V1 without going through V1, creating blind spot

Question 12

Multisensory Integration

Answer 12

function of brain areas in which signals from different sensory systems are combined

Question 13

Primary Visual Cortex (Area V1)

Answer 13

part of occipital lobe where signals flows from LGN

• highly organized, with columns for ocular dominance and orientation
• organized retinotopically and shows cortical magnification

Cells in V1: simple , complex, and end-stopped cells

Question 14

Cortical Magnification

Answer 14

nonuniform representation of visual space in cortex

more cortical space dedicated to certain place

amount or cortical territory devoted to the central part of the visual field is much greater than the amount devoted to the periphery

many more V1 neurons have receptive fields in the fovea than in areas in the periphery of the retina (reason why acuity is power in periphery)

Question 15

End-Stopped Cells

Answer 15

response increases as length of edge increases (up to point) and then weakens

Question 16

Simple Cells

Answer 16

responds best to stimulus with particular orientation in location of receptive fields

• looks at light on dark background

Question 17

Preferred Orientation

Answer 17

stimulus orientation that produces strongest response

Question 18

Orientation Timing Curve

Answer 18

curve on graph that shows average response of orientation-tuned neuron

Question 19

Population Code

Answer 19

consistent difference in patterning of relative responses of population of differently tuned neurons

Question 20

Complex Cells

Answer 20

include neurons in area V1 that respond best to a stimulus with a particular orientation

• differ from simple cells in the variety and location of stimuli that generate a response
• responds to dark on light and light on dark

Question 21

Organization of V1

Answer 21

Cortical Columns- small volume of neural tissue running through layers if cortex perpendicular to its surface

      - consists of neurons that respond to similar types of stimuli type that have highly overlapping receptive fields
      - gives spatial info

Ocular Dominance Columns- cortical columns consisting of neurons that receive signals mainly from left eye or mainly from right eye

Orientation Columns- cortical columns consisting of neurons with same (or similar ) orientation tuning

Question 22

Hypercolumns

Answer 22

organizes info like orientation and dominance

Question 23

Functional Specialization

Answer 23

functional specialization is starts with the neurons that transduce light into neural signals, the rods and cones –>
specialization continues in the different functions of midget, parasol, and bistratified RGCs, which send signals to neurons in the parvocellular, magnocellular, and koniocellular layers if the LGN –> signals from the layers of the LGN then travel to separate layers of area V1, where populations of neurons encode edge orientation and other visual features

Question 24

Functional Areas and Pathways

Answer 24

• areas differ according to the types and distributions of neurons within them
• areas differ according to the other areas in the brain from which they receive signals or ton which they send signals
• areas differ according to the properties to which their constituent neurons are tuned
• each visual area contains a retinotopic map of the visual field

*when two brain areas are connected, the connection is always reciprocal

Question 25

Dorsal Pathway

Answer 25

V1 and V2 –> MT –> parietal cortex

• is responsible for representing properties related to object’s motion or location; info also used to guide action
• the “where” pathway and/or the “how” pathway

Question 26

Ventral Pathway

Answer 26

V1 and V2 –> V4 –> inferotemporal cortex

• is responsible for representing properties related to object’s identity, such as its color and shape
• the “what” pathway

Question 27

Optic Ataxia

Answer 27

deficit in ability to guide movements visually

Question 28

Area V4

Answer 28

color and curvature

• ventral pathway
• can look at orientations and fine tunes there
• area in occipital lobe consisting of neurons that respond selectively to color of stimuli and to curvature of edges
• includes lateral occipital cortex and inferotemporal cortex (specialized for responding to complex shapes)
  Damage to V4 and other attached areas is called achromatopsia

Question 29

Achromatopsia

Answer 29

cortical color blindness

- inability to perceive colors despite having normal array of cones in retina

Question 30

Lateral Occipital Cortex

Answer 30

• ventral pathway
• object-selective region
• responds strongly when person views pictures of faces, animals, buildings, tools, appliances, or other objects but don’t respond well to random texture viewing

Fusiform face area (FFA)
Parahippocampal place area

Question 31

Fusiform face area (FFA)

Answer 31

faces

fusiform gyrus of IT cortex

Question 32

Parahippocampal place area

Answer 32

large-scaled spatial layouts

parahippocampal gyrus of IT cortex

Question 33

Inferotemporal Cortex (IT)

Answer 33

cortex in bottom part of temporal lobe

- object- selective regions of visual system

Question 34

Area MT (V5) neurons

Answer 34

• dorsal pathway
• medial temporal area
• respond selectivity to direction and speed of motion of stimuli

Question 35

Visual Neuroprosthetic Devices

Answer 35

designed to help the blind see

• use neural stimulators implanted in area V1 to activate the visual system on the bases of signals received from and external camera
• relay signals from camera/ photocells to implanted stimulators that activate visual systems

Question 36

Prosopragnosia

Answer 36

damage to FFA leading to impairment of ability to recognize faces