Lecture 5 Cortex and Beyond

Question 1

TRUE or FALSE: the dorsal stream shows function for only location

Answer 1

FALSE: both location and action

Question 2

Describe the behaviour of patient D.F. that demonstrates a double dissociation of the what and how streams for information.

Answer 2

• patient damage ventral pathway
• was NOT able to match orientation of sample card (held by experimenter) while holding it in their hand (‘passive’ condition)
• was ABLE to match orientation if physically placing card in a slot (‘action’ condition)

Question 3

Describe the Ganel experiment. What was it used to demonstrate? What kind of subjects were used? What were the 2 conditions?

Answer 3

• demonstrate a separation of perception and action in ‘healthy’ subjects
• passive length estimation vs grasping length estimation
• line 2 looks longer than line 1, but is actually shorter
• different conditions seemed to recruit different streams (what vs how)

Question 4

The organization of V1 represents a(n) ___________ map of the retina which is _____________.

Answer 4

electronic; retinotopic

Question 5

Describe the retinotopic map of V1.

Answer 5

two points that are close togehter on an object (retinal image) are also represented in parts of the cortex that are closer together

Question 6

what is cortical magnification?

Answer 6

a small area of the fovea is represented by a large area on the visual cortex

Question 7

What is one mechanism that conrtibute to high-acuity vision at the level of the cortex?

Answer 7

cortical magnification

Question 8

neurons in the _____________________ respond to more complex stimuli than neurons in V1

Answer 8

inferotemporal (IT) cortex

Question 9

Gross et al. realized that some IT neurons were tuned to respond to _______________ stimuli.

Answer 9

hand-like

Question 10

What are modules? Provide an example

Answer 10

dedicated neural mechanisms that are specialized for processing particular kinds of stimuli (e.g. the FFA to process faces)

Question 11

Give two pieces of evidence for modularity.

Answer 11

• we experience difficulty in detecting abnormalities in upside down faces
• temporal lobe damage in humans can result in prosopagnosia

Question 12

What is prosopagnosia? Which part of the brain is damaged?

Answer 12

• temporal lobe damage
• inability to perceive faces

Question 13

Inversion effects are particularly strong for what kind of visual stimuli?

Answer 13

faces

Question 14

Give an example of experience-dependent plasticity.

Answer 14

fMRI experiments show that training results in areas of the FFA responding more to Greeble stimuli after training

Question 14

What is the expertise hypothesis?

Answer 14

developing expertise in something can lead to recruitment of the FFA for associated stimuli

Question 15

Which lobe and which structures are extremely important for memory?

Answer 15

• medial temporal lobe (MLT)
• parahippocampal cortex, entorhinal cortex, hippocampus

Question 16

Signals coming from __________ cortex project to medial temporal lobe.

Answer 16

inferotemporal (IT)

Question 17

What did Quiroga et al. attribute perception in their study to?

Answer 17

memory

Question 18

What is sensory coding?

Answer 18

refers to the way perceived objects are represented through neural firing

Question 19

What are 3 theories that explain how sensory coding of more complex objects be accomplished?

Answer 19

1. specificity coding
2. population coding
3. sparse coding

Question 20

What is specificity coding?

Answer 20

specific (individual) neurons respond to specific stimuli

Question 21

What is the grandmother cell hypothesis? what kind of coding does it refer to?

Answer 21

• specificity coding
• there are specific neurons that respond to presentation of specific faces (e.g. one’s grandma)

Question 22

What are the problems with specificity coding?

Answer 22

• too many different stimuli to assign specific neurons
• most neurons respond to a number of different stimuli…how do you know if other neurons are also firing?

Question 23

What is population coding?

Answer 23

PATTERN of firing across MANY neurons codes specific objects

Question 24

TRUE or FALSE: In population coding, a large number of stimuli can be coded by a few neurons.

Answer 24

TRUE

Question 25

What is sparse coding?

Answer 25

relatively small number of neurons are necessary to code for each concept/identify, etc.