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L2 Neural Circuits > Neural Circuits of Object Recognition > Flashcards

Neural Circuits of Object Recognition Flashcards

1
Q

How do bats recognise water? (4)

A
  • Echolocation
  • Bats make a sound stimuli which reflects off the surface below
  • If the surface is smooth, the sound is reflected directly back
  • Bat recognises the smooth surface as water and tries to drink it
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2
Q

How do electric fish recognise objects? (3)

A
  • Electroreception
  • Electric fish creates an electric field around itself
  • If the electric field is disrupted it tells the fish that something is nearby
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3
Q

What is orientation invariance?

A

Ability to recognise an object independent of the orientation

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4
Q

What is scale invariance?

A

Ability to recognise an object independent of the scale

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5
Q

What is the hierarchical model of object recognition? (6)

A
  • Detection of edges
  • Detection of combination of edges and contours
  • Detection of object parts (e.g. face)
  • Detection of objects from one POV
  • View-invariant object detection (recognise despite variations)
  • Categorisation
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6
Q

How is object recognition studied? (2)

A
  • Lesions in the inferior temporal cortex decrease the ability to recognise objects
  • Electrophysiology and mathematical modelling
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7
Q

What does the hierarchical model of object recognition demonstrate? (2)

A
  • The responses of the neurons increase in complexity along the ventral stream
  • The receptive field size of neurons increases along the ventral stream
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8
Q

What are the 2 types of ganglion cells?

A
  • Parvocellular
  • Magnocellular
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9
Q

Which ganglion cells are responsible for detection of motion?

A

Magnocellular

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10
Q

Which ganglion cells are responsible for object recognition?

A

Parvocellular

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11
Q

Where do the ganglion cells send their projections to?

A

Lateral geniculate nucleus

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12
Q

How many layers does the lateral geniculate nucleus have?

A

6

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13
Q

Which layers of the lateral geniculate nucleus do the parvocellular cells send their input to?

A

First 4 layers

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14
Q

Which layers of the lateral geniculate nucleus do the magnocellular cells send their input to?

A

Last 2 layers

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15
Q

How many eyes does each layer of the lateral geniculate nucleus receive input from? (2)

A
  • Each layer receives input from one eye
  • First layer receives from the contralateral eye, next layer from the ipsilateral eye and so on
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16
Q

What does the lateral geniculate nucleus (LGN) do? (5)

A
  • Sends information to the primary visual cortex
  • Ganglion cell axons make 1:1 connections with LGN projection neurons
  • Receptive fields of of LGN neurons are similar to those of retinal ganglion cells so not much processing happening
  • 60% of synaptic input to the LGN is from the cortex but mechanism unknown
  • Local interneurons in LGN so some kind of modification happening
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17
Q

What are the 2 visual pathways in the cortex?

A
  • Ventral ‘what’ stream
  • Dorsal ‘where’ stream
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18
Q

What is the ventral stream? (2)

A
  • ‘What’ pathway for object recognition
  • Inferior temporal
19
Q

What is the dorsal stream? (2)

A
  • ‘Where’ pathway for object localisation/speed/movement etc.
  • Posterior parietal
20
Q

What is the ventral stream pathway for object recognition? (6)

A
  • Parvocellular ganglion cells
  • LGN
  • V1 cortex
  • V2 cortex
  • V4 cortex
  • Inferior temporal cortex
21
Q

What are the 2 key features of the cortical structure?

A
  • Layering
  • Columns contain neurons of similar properties
22
Q

How many layers are in the cortex?

A

6

23
Q

What are the 3 main columns in the cortical structure?

A
  • Ocular dominance (receives information from one eye)
  • Orientation (direction)
  • Blobs (colour)
24
Q

How could you observe the ocular dominance columns in the cortex? (2)

A
  • Inject radioactive proline into one eye and look at which columns are radioactive
  • Inject radioactive glucose into the cortex and stimulate one eye with light
25
Q

How could you observe the blob (colour) columns in the cortex?

A

Stain for cytochrome oxidase

26
Q

What do the blobs do in the cortex? (3)

A
  • Columns process information about colour
  • Receive input from parvocellular cells from the LGN
  • Not orientation selective
27
Q

What does the orientation column do in the cortex?

A

Neurons are separated into columns depending on which orientation of stimulus they respond to

28
Q

What does the ocular dominance column do in the cortex?

A

Neurons are separated into columns depending on which eye they receive input from (contralateral/ipsilateral)

29
Q

What is a hypercolumn?

A

A section of the cortex containing all 3 columns which can process information about the entire stimulus

30
Q

What is a simple cell?

A

A cell in the primary visual (V1) cortex which responds to bars of particular orientations

31
Q

Who discovered simple cells?

A

Wiesel and Hubel

32
Q

Where are simple cells located? (2)

A
  • In layers 4 and 6 of the V1 cortex
  • In the orientation columns depending on which orientation they respond to
33
Q

Where is the lateral geniculate nucleus?

A

Thalamus

34
Q

What are the receptive fields of the simple cells like? (3)

A
  • Elongated oval shaped
  • Larger than the receptive fields of the ganglion cells and LGN neurons
  • Respond to a bar in a certain orientation in the centre of the receptive field
35
Q

Why is the receptive field of the simple cell elongated? (2)

A
  • Record from the simple cell and its presynaptic inputs
  • The receptive fields of the presynaptic input neurons are all located on one line which causes the receptive field of the simple cell to be elongated
36
Q

What is a complex cell?

A

Responds to bars of a particular orientation presented anywhere in the receptive field

37
Q

What is the difference between simple and complex cells? (2)

A
  • Simple cells respond to bars of a certain orientation but only when they are presented in the centre of its receptive field (centre-surround organisation, outside of the centre is inhibitory)
  • Complex cells respond to bars of a certain orientation when they are presented anywhere in the receptive field
38
Q

Where are complex cells located?

A

In layers 2, 3 and 5 of the V1 cortex

39
Q

Why does the mechanism of complex cells differ from simple cells?

A

The idea is that complex cells receive inputs from many simple cells which respond to similar orientations but sample from different areas of the visual space

40
Q

What is a hypercomplex/end-stopped complex cell? (2)

A
  • Similar to complex cell but when the line extends beyond the receptive field the cell is inhibited
  • However if the section of the line that extends beyond is at an angle the firing resumes
41
Q

What does the hierarchical model say happens downstream of V1? (2)

A
  • Increase in complexity of responses
  • Increase in receptive field size
42
Q

Where are face-sensitive neurons located?

A

Inferior temporal lobe

43
Q

What is a ‘Jenifer Aniston’ neuron? (2)

A
  • Neuron that specifically responds to images of Jenifer Aniston
  • Demonstrates that 1 or few neurons recognise specific objects
44
Q

What are the problems with the ‘Jenifer Aniston’ neuron evidence for the hierarchical model? (3)

A
  • Doesn’t explain scale/orientation invariance
  • Doesn’t take into account feedbacks from higher cortical areas
  • Hard to replicate the experiment

L2 Neural Circuits (13 decks)

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