cognition and brain > Vision > Flashcards

Vision Flashcards

(46 cards)

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1
Q

Describe the structure of neurons

A

Much longer than cells and are thin.

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2
Q

Describe the structure of axons

A

Can be several metres long
Brain axons are few mils long

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3
Q

What do axons transmit

A

Bursts of axons potentials down to the terminal buttons .

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4
Q

What are the frequency of axons potentials

A

500hz

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5
Q

What wraps around the axon

A

Fatty cells ( mkein sheath ) produced from gilal cells which increase velocity to about 100 metres per second

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6
Q

What is the gap between the mylein sheath

A

Nodes or ranvier -conductions jump

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7
Q

Neurons are polarised but can be depolarised, how does this happen

A

Ion channels in the dendrites open, positive ions flow in and cell depolarised.

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8
Q

What do neurons maintain

A

A resting membrane potential 70 millivolts , meaning positively charged particulars will flood if can

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9
Q

What happens if depolarisation crosses a certain threshold

A

At the trigger zone in the axon hillock a burst of action potentials fires down the axon

The axon hillock is a specialised region of a neuron where the cell body (soma) transitions into the axon.

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10
Q

What do excitatory and inhibitory neurotransmitters do

A

E- bins to receptors on dendrites causes sodium ions to open and depolarised e.g glutamate
I-chloride ions flow in and cell becomes less likely to depolarised e.g gaba

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11
Q

What is glutamate

A

Amino acid . Receptors evolved from single celled organisms as food detectors in bacteria

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12
Q

Describe synapse and neurotransmitters

A

Action potentials -neurotransmitters are released into synaptic cleft-neurotransmitters will excit or be inhibited - more /less likely to depolarised

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13
Q

What are the two visual receptor cells

A

Cones and rods

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14
Q

What are cones

A

Detect colour and detail perception ( sharpness)
Located in fovea (centre field of vision)

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15
Q

What are rods

A

Responsible for vision in dim light and luminance and are located in the periphery

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16
Q

What are retinal ganglion cells

A

Recieve input from few cones or hundreds of rods

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17
Q

Describe features of the eye

A

Back to front
Blind spot - gap in retina were wires leave the eye and go to the brain
The retina contains photo sensitive cells
2d ray light receptors

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18
Q

From eye to correct there are stages what are they

A

Reception
Transduction
Coding

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19
Q

What is reception

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A

The absorption of physical energy

20
Q

What is transduction

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A

Physical energy is converted into neurochemical Patterns in the neurons

21
Q

What is coding

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A

one-to-one correspondence between certain aspects of the physical stimulus and patterns of activity in the nervous system.

22
Q

How do we process information in the brain from what we see

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A

We process in opposite cerebral hemispheres .
Left retina -right side of world - lGN-primary visual cortext

23
Q

What is the parvocellur paathway- retina-geniculate-striate system

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A

It is sensitive to colour and fine detail. Most input is from cones object recognition

24
Q

What is the magnocellular pathway-retina-geniculate-striate system

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A

Most sensitive to motion . Most input from rods

25
Brain projections -ehat is latency
How long does it take for a neuron to fire from cells in response to the stimulus when it has been presented
26
How does information reach the V1 ( primary visual cortext )
Light reception (converts to neural signals )- retinal processing( preprocessed signals ) -optic nerve( transmits and sorts by VF) -optic chiasm -lateral geniculate nucelus( process information from retina (thalamus) by organising and regulating signals -v1 via projections where it is processed
27
Who purposes functional specialisation theory and what is it
Zeki 1993,2016 where different corticol areas are specialised for different visual functions
28
What is the V1 and V2 V3 and v3a v4 V5 responsible for- zecki
1) basic visual processing 2) form perception 3) shape and colour perception 4) motion perceptions (MT)
29
What is Loc ofa and FFA for
Lateral occipital cortext - object perception Occipital face area- face perception Fusiform face area - face perception
30
Describe examples of the selectivity of cells in the visual cotext
Cells in each area respond selectively to stimulus features e.g MT didn't respond much to colour but a higher percentage was shown for mt to respond and code direction of motion
31
Evaluate zekli functional specialist theory
Influential and ambitious approach Visual brain areas are shown to be less specialised than previously assumed Binding problem isn't solved Visual brain more complex than assumed(e.g., V1 is connected to at least 50 other brain areas)
32
What is the binding problem aka the binding by synchrony hypothesis
states that neurons code different dimensions start to osillate in synchrony providing a constant object not separate attributes
33
Give an example of the binding problems
Some cells code colour and some code shape but will still form one complete image
34
Who purposes the perception- action model and what does it compose of
Milner and goodale 1977 Composes if the ventral and dorsal stream
35
What is the ventral, stream Key questions : What does it do How does it code What is the input What system does it use What can happen if damaged
Vision for perception : conscious object coding Allocentric coding : object centred recognises object from any angle Sustained detailed representation Input mainly from fovea Uses pavo system Damage : can't name or recognise objects
36
Dorsal pathway (where ) key features
Vision for action : guides movement and spatial location Egocentric coding : body centred , based on observers position Short lived transient representation Unconscious processing
37
What are the effects of brain damage on the perception action model
Visual form agnosia - ventral optic ataxia-dorsal | optic -problems making visually guided movements decpit intactperception ## Footnote visual form agnosia- issues with shape perception but can make reasonably accurate visually guided actions
38
Describe the Muller lyer illusion
Mainly in the ventral stream - does the illusion affect how we see or act
39
Explore Bruno et als findings for the Muller layer illusion
Pointing (dorsal) : asked to point to where lines end . Effect of illusion was smaller meaning was less fooled . Illusion size :5.5% Verbalising: verbally judge which line was longer . Effect much larger . Illusion size :22.4% . Conscious perception is more suseotible to illusion
40
What is the ebbinghaus illusion
Both centre circles are same size but one looks larger than other . Illusions greater with vision perception system than vision for action system . Only perceptual judgements influenced by distance between centre and contextual circles - knol etal
41
when does grasping objects use the ventral and dorsal stream
Infi from memory is required to control grasping movement and when conceptual knowledge is needed to make the most appropriate grasping movement
42
Evaluate the perception action model
Influential Two systems less independent and more interactive than assumed Variable findings Those with visual agnosia and optic ataxia have issues with perception and action meaning no clear double association ( no neat seperaton)
43
Evaluate the 2 dorsal systems
Dorso- dorsal= grasp objects rapid Ventro-dorsal= memorised object knowledge to use objects appropriately
44
what is the main pathway from the eye and the cortex
geniculate- straite pathway which transmits information from the retina to V 1 AND V2 via the lateral geniculate nucleus
45
where does the optic nerve connect to
the optic chaism- and optic radiation - LGN- primary visual cotext in occipital lobe
46
what is a receptive field
the region of the retina where light influences the activity of a neuron
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