Maps and Modules

Question 1

Maps are a ________ of neurons with similar ________ properties that is characterised by a gradual _________ of preferred stimulus values across the ________ sheet.

(aka: smooth, continuous representations)

Brain areas can have _______ maps encoding different _______ (eg: LGN)

Brain areas can encode ______ feature ______ in a single map (eg: V1)

Different maps serve different functions by _______ different types of _______.

Answer 1

clustering
functional
progression
cortical

multiple
features

multiple
representations

encoding
information

Question 2

Features are _____ and ______ constructs the brain is encoding eg: ________, ________, etc

(aka different types of information)

Answer 2

physical
cognitive

orientation
colour
edges

Question 3

A receptive field is a region of _____ that drives a ______ of a single neuron

Answer 3

area

response

Question 4

A module is a ______ of neurons with similar ______ properties that is characterised by discrete ______ with clear boundaries across which there is no _____ in preferred ________ values

(aka an area that encodes a similar thing)

Eg: ______ is a motion module. _____ is a module which encodes faces.

Answer 4

clustering
functional
regions
relation
stimulus

MT
FFA

Question 5

Name two examples of maps

Answer 5

visual cortex - retinotopic map

auditory cortex - tonographic map

Question 6

Why are maps important?

Answer 6

Minimal wiring constraint which saves resources

….maps enable shorter connections which conserves energy

Question 7

Name the first three stages of visual processing

Answer 7

1. retina - the visual world is first represented here.
2. lateral geniculate nucleus (LGN)
3. primary visual cortex

Question 8

The locations of things in space are represented in ________ on the retina. These locations ________ to locations on the LGN. However, the LGN is actually made up of 6 maps, not just 1.

Answer 8

reverse

correspond

Question 9

In vision, while the fovea has only ______ receptive fields, and direct connections with these neurons, the periphery has _____ circuitry. Hence, the periphery is full of receptive fields known as _______ ______ which has both _____ and ______ connections.

Answer 9

excitatory
convergent

centre surrounds

excitatory
inhibitory

Question 10

What is the consequence of centre surround?

Why is it important in vision?

Answer 10

• response changes as a function of light spot size and position
• the centre (fovea) is a “spot” detector
• It means we have getter vision during the day for finer acuity…important for things like reading.
• things are darker in the periphery eg: hermann grid illusion

Question 11

The LGN

Layers __, __ and __ receive information from the ipsilateral eye

Layers __, __ and __ receive information from the contralateral eye

Layers __ and __ are magnocellular layers and
layers __, __, __ and __ are parvocellular layers.

Answer 11

2, 3, 5

1, 4, 6

1, 2

3, 4, 5, 6

Question 12

Describe the two pathways involved in vision.
What retina inputs do they receive?
What layers do these inputs project to?
What are the pathways for?

Answer 12

Magnocellular pathway

• receives input from parasol cells in the retina
• layers 1 and 2 of LGN
• motion processing
• colour bind
• transient response
• where pathway

Parvocellular pathway

• receives input from midget cells in the retina
• layers 3-6 of LGN
• high spatial acuity - good for form, texture, colour, depth perception
• slow sustained attention
• what pathway

Question 13

The retinotopic organisation of vision is also preserved in the _____ ______. If the cortex is penetrated perpendicularly, the same ______ is found, but new _______ are tapped into. If you. Oblique penetrations will give you the same features but different ______.

We can study the representation in the cortex to see what areas the brain is giving particular ________ to.

Eg: fovea F–>1 is small on the retina, compared to 1–>2 BUT the cortex F–>1 is actually very large.

Answer 13

visual cortex
location
features - edges, motion, etc
locations
resources

Question 14

How does centre surround inform edge features?

Answer 14

Stack up centre surround receptive fields. In a simple V1 neuron this will be an edge detector.

Question 15

The “____” detectors of the LGN become “edge” detectors in V1.

V1 encodes multiple features. Each cube contains various ______ with different features. Studies have revealed a ______ structure in an effort to minimise _____ _______

Answer 15

dot

columns
pinwheel
wiring constraints