Week 6

Question 1

Levels of investigation

Answer 1

Molecules -> synapses -> neurons -> networks -> maps -> systems -> CNS

Question 2

Two viewpoints on the brain

Answer 2

• Specialized processing
• Coordinated interactions

Question 3

Structural connectivity

Answer 3

Physical connections

Question 4

Functional Connectivity

Answer 4

Connections inferred between regions based on similar changes over time

Question 5

Effective connectivity

Answer 5

Connections inferred between regions based on similar changes over time, that vary in directionality

Question 6

Magnetic Resonance Imaging (MRI)

Answer 6

• discovered in 1946: Nobel Prize Medicine
• applied to medicine in 70s, first clinical scan 80s
• magnet strengths measured in Teslas: 1.5, 3.0, 4.0, 7.0 (3T = 3 Teslas)
• 1 Tesla ~ 20,000 times earth magnetic field
• Structural MRI: anatomical images of the brain

Question 7

Functional MRI (fMRI)

Answer 7

• different magnetic susceptibility properties of oxygenated and deoxygenated hemoglobin
• neurons fire, requiring additional oxygen -> changing the balance and producing : blood oxygen level dependent (BOLD) signal
• measures a hemodynamic (blood) response related to the neural response

Question 8

United of MRI and fMRI

Answer 8

Voxel: volume element (3D)

Question 9

Functional Connectivity measured with fMRI

Answer 9

Correlations of BOLD activity between brain regions over time
- regions that are functionally related have highly correlated activity even at rest
- regions not functionally related do not have highly correlated activity

Question 10

Resting State Functional Connectivity

Answer 10

Brain regions correlate

Question 11

Functional networks

Answer 11

• visual
• auditory
• somatomotor (face)
• somatomotor (body)
• default-mode
• fronto-parietal task control
• cingulo-opercular task control
• dorsal attention
• ventral attention
• salience

Question 12

Advantages: Functional connectivity with fMRI

Answer 12

• Non-invasive
• can be quick
• can measure many areas at once
• related to anatomical and task evoked networks
• reproducible between and within individuals

Question 13

Disadvantages: Functional Connectivity with fMRI

Answer 13

• extremely susceptible to motion confounds
• indirect measure of neuronal [functional/structural] connectivity
• limited temporal resolution
• correlation, not causation

Question 14

Functional connectivity is related to anatomical and task-evoked measurements

Answer 14

• spontaneous correlation pattern
• evoked response pattern
• anatomical connectivity pattern

Question 15

Functional Networks are reproducible across individuals

Answer 15

Main cohort
Replication cohort
Single subject

Question 16

By looking at “Network” connectivity in the brain

Answer 16

Study systems that support cognitive, sensory, motor, and social functions

Question 17

The three axioms of cognitive science

Answer 17

1) The mind is what the brain does
2) What the brain does, i.e., thinking
3) The brain does probabilistic computation

Question 18

1) The mind is what the brain does

Answer 18

There is no “spooky stuff”

Question 19

What the brain does, i.e., thinking, is a kind of computation

Answer 19

Love at first sight is a computation

Question 20

The brain does probabilistic computation

Answer 20

Probability is the “language of thought”; in order to deal with the uncertain nature of the world

Question 21

Neural Nets

Answer 21

Brain-like computational models; can train neural nets to do what we want even with many layers of processing just like our brains

Question 22

Humans are fast at combining information to:

Answer 22

• understand sentences
• disambiguate words
• read ambiguous letters
• recognize faces

Question 23

A real Neuron

Answer 23

• axon (output)
• cell body (soma)
• dendrites (input)

Question 24

A model “Neuron”

Answer 24

• inputs (from another unit or the outside world)
• connection strengths (or weights)
• Internal “potential”
• output, representing firing frequency

Question 25

Neural nets (PDP nets, connectionist networks)

Answer 25

- Networks of simple units - Connected by weighted links - Compute by spreading activation and inhibition

Question 26

The Interactive Activation Model

Answer 26

- word level - letter level - feature level

Question 27

Feature level

Answer 27

- bar detectors: the first stop in the visual part of brain - enough to represent every letter - copied to make bar detectors for each letter in a word

Question 28

Letter level including feature level

Answer 28

- the features excite compatible letters and inhibit incompatible ones - negative and positive links - the letter fight it out through inhibitory links because only one can be in each position (Winner Take All)

Question 29

Word level including letter and feature level

Answer 29

- the word level units are activated by compatible letters - word units feed back on the letter units, making them more active than they would be otherwise - “word superiority effect”, better at seeing letters when they are part of a word than when they are in a non word letter string

Question 30

How does the brain make the mind?

Answer 30

Through concerted actions of billions of nerve cells that work together to interpret the world. When they activate, compete, and then settle into a stable coalition, that’s what we perceive

Question 31

Spacial reference frames

Answer 31

Perspective “Where am I?”

Question 32

Imagination

Answer 32

Hippocampus Post- posterior parietal cortex

Question 33

Episodic memory

Answer 33

Hippocampus, an event in order with context

Question 34

Posterior parietal cortex neurons map progress through a route

Answer 34

By exhibiting spatial firing patterns and making correlations