week 4 - feature detectors

Question 1

What are the 3 types of feature detectors?

Answer 1

• simple cortical cells
• complex cortical cells
• hyper complex (end-stopped) cortical cells

Question 2

simple cortical cells

Answer 2

• excitatory and inhibitory areas arranged by side
• responds best to bars of a particular orientation

Question 3

complex cortical neurons

Answer 3

• responds best to movement of correctly orientated bar across the receptive field
• many cells respond best to a particular direction of movement

Question 4

hyper complex (end-stopped) cortical cells

Answer 4

responds to corners, angles, or bars of a particular length moving in a particular direction

Question 5

Describe the movement of visual information from the visual field to the primary visual cortex.

Answer 5

Visual field → retina and LGN (center-surround receptive fields) → primary visual cortex: 1. Simple (angle/position) 2. Complex (direction of movement) 3. Hyper-complex (angles and length)

Question 6

selective adaptaion

Answer 6

neurons tuned to specific stimuli fatigue when exposure is long

Question 7

What does cell fatigue or adaptation to a stimulus cause?

Answer 7

1. neural firing rate to decrease
2. neuron to fire less when stimulus is immediately presented again

Question 8

What does selective in selective adaptation mean?

Answer 8

only those neurons that respond to the specific stimulus will adapt

Question 9

How does the vertical line circle relate to selective adaptation?

Answer 9

• Overstimulating the neuron with a specific, high contrast circle will tire out the neuron, causing the lower contrast circle to be perceived as a sold color
• Larger contrast is needed in order to fire neuron
• Changing the angle of the circle requires less firing because we are using other simple cortical neurons to read the orientation of lines

Question 10

What are the 3 types of sensory coding?

Answer 10

• specificity coding
• distributed coding
• sparse coding

Question 11

What is sensory code?

Answer 11

representation of perceived objects through neural firing

Question 12

specificity coding

Answer 12

• specific neurons respond to specific stimuli
• “grandmother” cell hypothesis

Question 13

What is the issue with specificity coding?

Answer 13

• we do not have enough neurons to account for every single stimuli we encounter
• most neurons respond to a number of different stimuli

Question 14

distributed coding

Answer 14

pattern of firing across many neurons codes specific objects

Question 15

What is the issue with distributed coding?

Answer 15

to have all neurons fire would be a waste of energy

Question 16

sparse coding

Answer 16

• only a relatively small number of neurons are necessary
• viewed as the midpoint between specificity and distributed coding

Question 17

What type of sensory coding do we predominately use?

Answer 17

sparse coding