LGN To Cortex

Question 1

What does LGN stand for

Answer 1

Lateral Geniculate Nucleus

Question 2

Where is the LGN located

Answer 2

In the thalamus

Question 3

Are LGN cells monocular or binocular

Answer 3

Monocular

Question 4

Retinotopy

Answer 4

Spatial map where neighbouring retinal points project to neighbouring neuron’s in cortex/LGN

Question 5

Layers 1 and 2

Answer 5

Magnocellular, large cell bodies, high contrast, receive input from M ganglion cells, process coarse features and motion

Question 6

How many layers does LGN have

Answer 6

7

Question 7

Layers 2-6

Answer 7

Parvocellular, small cell body, receive input from P panglion cells, low contrast, process fine features and colour

Question 8

What is the magnocellular pathway process

Answer 8

Motion, coarse features, high contrast, low spatial detail

Question 9

Parvocellular pathway process

Answer 9

Colour, fine detail, high spatial resolution

Question 10

Function of LGN

Answer 10

Magno and Parvocellular layers repsond in similar way as thier input ganglion cells
Centre surround receptive fields
LGN - richly connected to other parts of the brain, locus at retinal information, relay station

Question 11

Why is LGN not just a relay station

Answer 11

It modulates feedback from cortex and other brain areas

Question 12

LGN projection

Answer 12

Primary Visual Cortex V1

Question 13

V1 neurons

Answer 13

Most neurons are binocular, they receive input from both eyes

Question 14

Organisation v1

Answer 14

Retinotopic map, map is distorted by cortical magnification

Question 15

Cortical magnification

Answer 15

Disproportionately large cortical area devoted to the fovea

Question 16

Cortical magnification pt2

Answer 16

The cortex magnifies your visual field, more neurons are needed for centre field, than peripheral

Question 17

LGN receptive fields

Answer 17

Centre-surround

Question 18

V1 cells receptive fields

Answer 18

Elongated, orientation-selective
Respond best to light, lines, bars and edges
Retinal ganglion cells/LGN neuron’s are centre-surround

Hubel and Wiesel Nobel prize 1981

Question 19

V1 stimulus neurons responses best to

Answer 19

Lines, bars, edges

Question 20

Orientation selectivity

Answer 20

Selectivity in the V1, discovered by hubel and Wiesel

Question 21

Anstis 1974

Answer 21

Cortical magnification consequences

Discrimination becomes more difficult as more neurons are needed when all letters/symbols are the same size, when the peripheral letters/symbols are bigger and centre smaller it is a lot easier as cortical magnification can be used

Question 22

Simple cell

Answer 22

Orientation selective with separate ON and OFF regions

Question 23

Complex cell

Answer 23

Orientation selective but less position-specific and often motion sensitive

Question 24

Why do we need do we need differentent amonts of neurons for the visual fields

Answer 24

Brain patches together snapshots of final resolved with eye movements

Question 25

Monocular

Answer 25

Just one eye, not both

Question 26

Optic chiasm

Answer 26

Part where both side axons cross over

Question 27

Receptive fields V1

Answer 27

V1 simple cell — array of ganglion cells/LGN cells —- array of receptors Stimulus needs to be appropriate triggered onto the retina simple for a response to occur but in the centre cell and not surrounding When surrounding cells also have light shined on it can cause decrease in hibtion When just the centre is hit, the stimulus is triggered

Question 28

Orientation tuning

Answer 28

Neurons respond best to one orientation and less to others

Question 29

What is hyper complex cells sensitive to

Answer 29

Line length and endings (endings stopping)

Question 30

Single neuron ambiguous

Answer 30

Same firing rate can reflect different combinations of intensity and orientation

Question 31

What is a population code

Answer 31

Information represented by the pattern of activity across many neurons

Question 32

What features are encoded by population coding

Answer 32

Orientation, intensity, size and other visual properties

Question 33

Eye movements importance

Answer 33

Place important information onto the high-acuity fovea