Behavioral Neuroscience Vision

Front 1

How do sensory receptors differ from neurotransmitter receptors.

Back 1

sensory receptors are specialized neurons whereas, neurotransmitters bind to specialized proteins.

Front 2

the process by which sensory stimuli are transduced into slow, graded receptor potentials.

Back 2

sensory transduction

Front 3

Sensory tranduction cause changes in membrane potentials called

Back 3

Receptor potentials.

Front 4

More than 5 senses. Give examples of others.

Back 4

Vestibular
Somatosensation

Front 5

What are the wavelengths of light visible to humans? colors?

Back 5

380 to 760 (violet to red)

Front 6

The three dimensions of light that make a percieved color:

Back 6

1.) hue- the dominant wavelength.

2.) saturation- the relative purity of a color (mixed with other WL or not)

3.) brightness- the intensity of the light

Front 7

What is the relationship between frequuency of oscillations and wavelength.

Back 7

They are inversely proportional. As the frequency goes up wavelengths get shorter.

Front 8

For an individual to see an image it must...

Back 8

be focussed on the retina.

Front 9

The eyes are suspended in _____________, bony pockets in the skull. They are controlled by ______ (# of muscles) called _____________ muscles.

Back 9

Orbits
6
extraocular

Front 10

The eyes make three types of movement they are:

Back 10

1.) Vergence movement- cooperative movement of the eyes. ensures that the image falls at retina at same place

2.) Saccadic movement- rapid, jerky movements of the eyes used in scanning.

3.) Pursuit movement- the movement of the eyes to keep a moving object on the fovea.

Front 11

Changes in the thickness of the lens, accomplished by ciliary muscles to focus on distant or near objects.

Back 11

Accomidation

Front 12

Trace the anatomy of the eye as light enters.

Back 12

First it enters through the protective Conjuctiva. Then the cornea, iris, pupil lens, virious humor and retina.

C.C.I.P.L.V.R
"Call Cristy In Places Like Venice and Rome" (???)

Front 13

What are photoreceptors? how many of them? where are they found? What are the two kinds? what are they each used for?

Back 13

The body has 126 million photoreceptor. they are found in the retina. there are the rods (120 million) and the cones (6 million). Rods are used for black and white vision, while cones are used for colors.

Front 14

What is ironic about the ratio of rods:cones?

Back 14

Though there are more rods than cones, the cones provide far more visual information. Cones recall are necessary for daytime vision (color vision).

Front 15

Table 6.1

RODS VS CONES

1) Found where
2) sensative to
3) provide what kind of info
4) Acuity

Back 15

Central retina(in fovea) ; periphery (not in fovea)

moderate to high light; low light

Hue information; monochromatic info

Excellent acuity; poor acuity

Front 16

What anatomical structure is responsible for the blind spot?

Back 16

The optic disk

Front 17

What is umwelt?

Back 17

The idea of a perceptual world. Perception is arranged differently in differing species.

Front 18

Parts of the brain adapt to suit the sensations in the animal. what is the example given in class?

Back 18

Rats use olfacoty system reliably and therfore have larger olfactory bulbs in the brain than humans

Front 19

VERY IMPORTANT: What is something important to remember about sensory receptors?

Back 19

Most sensory receptors do not have axons. Their cell bodies synapse on dendrites or cell bodies of neurons

Front 20

Three overlying processes for vision to occur.

Back 20

Reception (stimulus to receptors)- absorption of physical energy (pressure on the skin will bend hair cells and raphe endings)

Transduction (receptor to neurons)- coversion of physical energy to electrochemical patterns. (generator potential, receptor potential)

Coding (neuron to brain)- one to one communication with physical system and nervous system

Front 21

Early work by Johannes Muller showed that

Back 21

when a neuron is excited the message it sends is always the same. "all sensory inputs result in action potentials"

Perception then, is based on which neurons are active not the degree of excitement of each. (?)

Front 22

there are several layers in the retina. what are they?

Back 22

Photoreceptor layer, bipolar cell layer and Ganglion cell layer

Front 23

About how many bipolar cells are there in the retina?

Back 23

1 million

Front 24

light entering the eye strikes which of the retinal sub layers first, second and last?

Back 24

Photoreception, bipolars and then ganglion cells.

Photoreceptors have synapse on bipolar cells, who have synapses on ganglion cells.

Front 25

We know light travels through photoreceptors, bipolar cells and ganglion cells. What anotomical structure makes up the optic nerve?

Back 25

The axons of ganglion cells.

Front 26

Inputs from all photoreceptors converge at the optic nerve at the same time. how is this possible?

Back 26

Outer or DISTAL receptors have higher conduction speeds than PROXIMAL receptors.

Front 27

Within the photoreceptors (rods and cones) we find the lamella whose function is...

Back 27

storage and release of photopigments.

Front 28

photopigments consist of two parts

Back 28

1. opsin (protein)
2. retinal (lipid)

Front 29

Rhodopsin is a photopigment. Different photopigments have a different retinal group or opsin group?

Back 29

Opsin

Front 30

How does rhodopsin fxn in vision.

Back 30

Incoming light breaks the bonds of rhodopsin and gives rod opsin and retinal. this breaking causes changes in membrane potentials and results in glutamate (excitatory neurotransmitter) release.

Front 31

How are membrane potentials in vision different than those involved in neurotransmittic release in the brain?

Back 31

In the dark cationic (NA and Ca) ion channels are open by cGMP and thus RESTING POTENTIAL IS LESS POLARIZED. thus, glutemate is constantly released in the dark.

In the light, rhodopsin is split and a cascade of reactions (enzyme phosphodiesterase) causes the destruction of cGMP, the closure of ion channels, and therefore, decrease in glutemate (excitatory) response.

Front 32

Low convergence in _____________ circuits. High convergence in ___________ circuits.

Back 32

Cone-fed; Rod-fed

Front 33

Rhodopsin is found in _________ while iodopsin is found in _______________.

Back 33

Rods only. Both rods and cones.

Front 34

How are photoreceptors and bipolar cells different than ganglion cells?

Back 34

They do not produce action potentials, while, ganglion cells do.

Front 35

Recall in the dark glutemate is released. What does glutemate do to bipolar cells?

Back 35

it can hyperpolarize or depolarize the membrane.

Since either effect can be seen when light strikes a hyperpolarizing or depolarizing input can be passed to ganglion cells.

Front 36

Light then has the opposite effect of ____________.

If a particular bipolar cell is hyperpolarized by glutemate (dark) then it will be depolarized when light shines.

Back 36

Glutemate.

Front 37

After the optic nerve where do such signals go?

Back 37

Optic nerve ----> dorsal lateral geniculate nucleus of the thalamus.

Front 38

The dorsal lateral geniculate nucleus (DLGN) has 6 layers of neurons. 2 large and 4 small. therefore they are called ___________, respectively.

Back 38

magnocellular layers; parvocellular layers.

Front 39

Message from the DLGN pass through a pathway known as _____________________.

Back 39

Optic radiations to the primary visual cortex (posterior occipital lobe) AKA STRIATE CORTEX.

Front 40

An X-shaped structure, where optic nerves join together...

Back 40

optic chiasm

Front 41

At the optic chiasm axons from the inner retina _____________________ while axons from the outer retina ___________________.

Back 41

cross through the chaism; stay on their side of the chiasm. Recall the lens inverts the image of the real world.

Front 42

the portion of a visual field where visual stimuli will cause alterations in the rate of neurons firing.

Back 42

Receptive fields.

Front 43

Why does our periperal vision have less acuity than our foveal vision?

Back 43

Receptor-to-axon relationship

Ganglion cells in the fovea are fed in by a smaller number of photoreceptors. At the periphery many photoreceptors will feed into the same ganglion cell.

Front 44

What are the three types of ganglion cells discovered? how is each activated or deactivated?

Back 44

On, Off, On/Off

On ganglion cells: excited by light falling in their central field and deactivated by light falling outside its central field.

Off- excited by light falling outside its central field, while deactivated by it falling inside its central field.

On/Off: briefly excited when lights are turned on or off. (reflex)

Front 45

What are some of the characteristics of the different types of ganglion cells (Mago and Parvocellular)

Back 45

Parvocellular
-smaller cell body
-smaller receptive fields
-mostly in the fovea
-highly sensitive to color
-high acuity
- synapse on parvocellular cells on the lateral geniculaate nucleus.

Magnocellular
-larger cell bodies
- larger receptive fields
- found in periphery
-lower acuity
- respond best to moving stimuli NOT color.
-important for brightness and depth preception

Front 46

Axons of cells from the _______________ and _________________ project to the temporal & parietal
cortices.

Back 46

Primary and secondary visual cortices.

Front 47

Other than the LGN there are other pathways of visual stimulation to the brain. Give both.

Back 47

RSCH- Retino-superchiasmatic-hypothalamic pathway- responsible for synchronizing diurnal activities.

RT pathway- Retino-tectal: responsible for muscle movements and control of the iris and pupil size.

Front 48

VERY IMPORTANT:

Back 48

Photoreceptors and bipolar cells do not produce action potentials. They produce
graded potentials.
Retinal ganglion cells produce action potentials.

Front 49

Very important:

Back 49

Glutamate hyperpolarizes some bipolar cells, and depolarizes other bipolar cells.
Bipolar cells also release glutamate, and glutamate always depolarizes retinal
ganglion cells.

Front 50

Very important

Back 50

Since bipolar cells can either increase or decrease their release of glutamate when
light is on, some bipolar cells provide hyperpolarizing input to ganglion cells, and
some bipolar cells provide depolarizing input.

Front 51

What is the role of horizontal cells?

Back 51

Horizontal cells also receive input from photoreceptors.
Horizontal cells perform an integrative function, providing
lateral inhibition of surrounding cells.

Front 52

What is the function of amacrine cells?

Back 52

Amacrine cells respond to alterations in the intensity of light - “on/off”.
The mechanism of action of horizontal and amacrine cells is not yet fully
understood.

Front 53

Amacrine and horizontal cells are part of the first ____________________.

Back 53

first level of processing in the visual system

Front 54

Bipolar cells have receptive fields from _____________. Ganglion cells have reveptive fields from ____________. Lateral geniculate cells have receptive fields from ____________.

Back 54

Photoreceptors; Bipolar cells; Ganglion cells.

Front 55

Topographic organization of the visual system

Back 55

See slides Chapter 6 53-56.

Front 56

Recall that Parvocellular ganglion cells are __________________ FED, whereas, Magnocellular ganglion cells are ___________________________.

Back 56

Cone-fed; Rod-fed.

Front 57

Horizontal cells allow us to _______________________. While, Amacrine cells allow us to ____________________.

Back 57

See the borders of things. Percieve changes in lighting.

Front 58

overlapping receptive fields create more...

Back 58

Contrast.

Front 59

humans and old world monkeys both have ______ forms of cones.

Back 59

3

Front 60

What is the trichromatic theory of color vision?

Back 60

The idea that all colors are made of three principal colors.

Front 61

what are the shortcommings of the trichromatic theory?

Back 61

It does not explain why YELLOW is a primary color. Nor does it explain why some colors are easily miscible and others are not (opposites).

Front 62

how does modern research show that the trichromatic theory is right?

Back 62

There are in fact three types of cones (RED, Green and blue cones) which absorb different amounts of light at different wavelengths.

Front 63

How many of each cones are there?

Back 63

Equal number of red (46%) and green (46%) cones and far less blue (8%).

Front 64

What are the genetic disorders of color vision? Where do these anomalies lie? What changes do they cause? What is believed to be the cause?

Back 64

Protanopia, deuteranopia and tritanopia.

X chromosome (much more common in males)

In pROtanopia, individuals confuse red and green as their red cones are filled with green opsin.
"ROjo esta ROTO"

In DEuteranopia- these individuals also confuse red and green but its because green cones are filled with red opsin.
"verDE esta roto"

Tritanopia- rare, non X Chromosome disorder where the individual cannot see short wavelengths (blues). Something wrong with blue cones.

Front 65

Where does the opponent process coding come in to play? What does it mean for color sensative retina cells?

Back 65

At the retinal ganglion level, the three color (trichromatic code) gets translated into an opponent-color system.

Thus, the retina contains TWO kinds of color sensative cells: red-green and yellow-blue.

Front 66

CONFUSING. There are _______ kinds of sensitivities in ganglion cells. There are ______ # of receptive fields.

Back 66

2 (red opposes green and blue opposes yellow)

3 (Blue on/yellow off) (Red on/ green off) (green on/red off)

Front 67

How is it we see RED?

Back 67

Light penetrates the eyes, photoreceptors and bipolar cellls causing differences in membrane potential.

In the ganglion cells "red cone" best absorbs red light and excites "red on/green off" ganglion cells while inhibiting "Green on/red off" cells.

Front 68

How do we see blue?

Back 68

Excitation of blue on yellow off. with minor inhibition of the other two ganglion receptive fields which cancel eachother out.

Front 69

How do we see yellow?

Back 69

Inhibition of Blue on yellow off ganglion receptive fields. ALSO, since yellow light is best absorbed by red and green cones, they are excited in equal amounts and cancel their input... leaving Yellow.

Front 70

According to opponent process, we cannot see what 2 combinations of color.

Back 70

Bluish-yellow and reddish-green.

Front 71

What is the cause of negative afterimages?

Back 71

Afterimages are a result of fatiguing cells (after staring at red, red cones are fatigued) when you now stare at a blank page "rebound effects" occur and the neurons that were initially inhibited fire faster and those that were excited are more inhibited giving the appearance of the opposite color.

Front 72

As previously mentioned info passes through photoreceptors, bipolar cells, ganglion cells, DLGN and finally the striate cortex . Where in the striate cortex do these info enter? What percentage of the striate is devoted to just the fovea.

Back 72

In primates at least, info enters the striate complex in a region labelled 4c. 25% of the striate is dedicated to the fovea, though it makes up a small portion of the visual field. That is why images at the fovea are seen with the most acuity.

Front 73

Recall that the vision also interprets positions by _______________________ ganglion cells.

Back 73

Magnocellular

Front 74

How is the position determined by neurons?

Back 74

Certain neurons fire when the stimuli is horizontal, vertical or at some oblique angle. Information from these RATES of firing and their particular settings, can be translated to a position.

Front 75

An orientation-sensative neuron in the striate crotex whose receptive field is organized in OPPOSITE fashion.

Back 75

Simple Cell

Front 76

Still other cells responsible for orientation can also pick up on movements. These neurons still respond to a particular orientation regardless of backgrounds (especially when it moves perpendicular to its orientation).

Back 76

Complex cells

Front 77

A neuron in the visual cortex that responds to the presence of a line segment wth a particular orientation taht ends at a particular point within the cell's receptive field.

Back 77

hypercomplex cell

Front 78

Which of the last three would then be responsible for detecting the "ends of things."

Back 78

Hypercomplex cell

Front 79

Information that collects at the DLGN then splits and travels to different paths known as:

Back 79

The ventral stream and the dorsal stream.

Front 80

Where does the ventral stream end up? what information does it carry? is it the what or the where?

Back 80

inferior temporal cortex

it carries THE WHAT. it is responsible for recognition of objects and people. Simple recognition occurs in the posterior segments while complex recognition occurs in the anterior of the parietal lobe.

Front 81

Where does the dorsal stream end up? What message is it responsible for carrying? Does it carry the what or the where?

Back 81

The dorsal stream ends up in the posterior parietal lobe. It is responsible for the spatial location information. It is responsible for the where.

Front 82

Neurons that are highly responsive to movement are found where.

Back 82

Outside the strait cortex (extrastriate) in the V5 position more commonly known as MT (for medial temporal).

Front 83

what imputs does the MT recieve?

Back 83

inputs from
-striate cortex
-other extrastriate regions
-SUPPERIOR COLLICULUS.

Front 84

The neurons of the MT are responsible for figuring out an objects movements. What important difference do these neurons exhibit?

Back 84

They are thick and heavily myelinated to have fast action potentials.

Front 85

Further analysis of movement, beyond that of the MT is performed by the _______. What does it do?

Back 85

MST; analyzes complex movements and optical flow (movement differences when you move your head).

Front 86

Where in the brain does image stabilization take place?

Back 86

The MST again as in the last slide.

Front 87

How does one measure depth?

Back 87

By a combination of monocular cues and binocular cues.

Front 88

What are examples of the monocular cues as they pertain to depth perception.

Back 88

-perspective
-relative retinal size
-loss of detail in the distance
-relative movement of your head

Front 89

What are examples of the binocular cues as they pertain to depth perception.

Back 89

Most cells in primary visual cortex are binocular

each eye "sees" a
3-dimensional sense

mediated mainly by the magnocellular pathway