Methods and the Brain

Question 1

Dependent variable

Answer 1

The variable that is measured in the experiment

Question 2

Independent variable

Answer 2

The variable that is manipulated in the experiment

Question 3

Confounding Factors

Answer 3

Uncontrolled variables that could also influence the

dependent variable. Should be kept constant across manipulations

Question 4

Statistical significance

Answer 4

If it is sufficiently unlikely that a result occurred by chance (< 5%), the IV is said to have a “statistically significant” effect on the DB; describes how reliable an effect is, not how large it is

Question 5

Statistical test to determine if something is statistically significant

Answer 5

Mean/variance

Question 6

Factorial design

Answer 6

An efficient way to combine variables — you perform all

combinations of manipulations; possible results are main effect and interaction

Question 7

Main effect

Answer 7

The effect of one IV on the DV, ignoring all other IVs

Question 8

Interaction

Answer 8

When the effect of one IV on the DV depends on the level of the other IV

Question 9

Marr’s 3 levels of analysis

Answer 9

1. Computational (broadest)
2. Algorithmic (intermediate)
3. Implementation (specific)

Question 10

Computational

Answer 10

What is the purpose?

Question 11

Algorithmic

Answer 11

How does it work?

Question 12

Implementation

Answer 12

Physical processes behind it

Question 13

How does understanding how the brain supports cognition at an implementation level give insights into how cognition works at computational and algorithmic levels?

Answer 13

1. If two cognitive abilities are neurally independent, we can assume that they are cognitively independent
2. Long-standing cognitive debates often can’t be resolved with behaviour alone — sometime neural findings show that both theories are right, just
   implemented in different parts of the brain!
3. Discoveries in the brain can give us new clues about how cognition works

Question 14

Materalist/physicalist philosophy

Answer 14

Argues that “the mind is what the brain 
does” - mental states can be generated in so 
many ways. We can only understand how 
human mental states work by knowing 
how they are generated by the brain

Question 15

Dualist philosophy

Answer 15

Mind and the brain are two separate entities and biology can’t explain how the mind works

Question 16

What do some materialists argue that opposes the view that we need to fully understand the brain to understand the mind?

Answer 16

That the mind is best explained at computational

and algorithmic levels; the implementation level is too reductionist

Question 17

Arguments against reductionism

Answer 17

Higher levels of analysis may emerge but not be fully explained by lower levels - we might not be able to build up from those very basic concepts and they might not even be relevant to the problems we want to solve

Question 18

Santiago Cajal

Answer 18

Discovered neurons

Question 19

Neural Doctrine

Answer 19

• Neurons are the basic units (cells) of the brain
• Neurons contain cell bodies, dendrites and
  axons
• Neurons communicate via synapses, not
  physical connections
• Neurons are connected in circuits, not
  randomly

Question 20

Resting potential

Answer 20

Difference in the electrical charge between the inside and outside of an axon: -70mV

Question 21

Action potential

Answer 21

• APs travelling along an axon maintain the same
  amplitude; you can’t have a big or small AP
• APs trigger the release of neurotransmitters
  from the axon terminals -> can excite dendrites
  of other neurons

Question 22

What triggers an action potential?

Answer 22

When neuron is excited, the membrane
potential increases; if it reaches -55mV an
Action Potential (AP) is triggered

Question 23

Strength of a sensation

Answer 23

Proportional to the rate of neural firing

Question 24

Qualities of an experience or thought are related to _____

Answer 24

which neurons fire

Question 25

Feature Detectors

Answer 25

Neurons identified in primary visual cortex (V1) that respond to specific visual features, such as orientation, size, or the more complex features that make up environmental stimuli.

Question 26

Blakesmore and Cooper’s experiment on how experience shapes perception and the brain

Answer 26

Kittens raised in vertical striped environments only
perceive vertical lines + only have feature detectors for
vertical lines

Question 27

Hierarchical processing

Answer 27

Progression from feature detectors in lower brain regions to more complex preferences in higher
regions (visual cortex which senses simple stimuli -> temporal lobe which senses more complex stimuli; neurons that respond to simple stimuli -> neurons that respond to complex geometrical shapes -> neurons that respond to faces)

Question 28

Neurons in the temporal lobe of monkeys

Answer 28

Have preferred stimuli — they prefer specific 
complex objects (e.g. hands or faces)

Question 29

Sensory coding

Answer 29

How neurons represent various characteristics of our environment - includes specificity, population and sparse coding

Question 30

Specificity coding

Answer 30

Individual neurons represent (only fire in response to) individual stimuli/concepts — “grandmother cells”

Question 31

Population coding

Answer 31

Stimuli/concepts are represented in the pattern of firing across a large number of neurons

Question 32

Sparse coding

Answer 32

Like population coding but the pattern is coded within a small proportion of neurons — most neurons are relatively silent

Question 33

What does the specificity of cognitive impairments suggest?

Answer 33

That functions are localized in different areas of the brain

Question 34

Occipital lobe damage

Answer 34

Damage to soldiers’ brains demonstrated that this

lobe is necessary for vision

Question 35

Prosopagnosia

Answer 35

Damage to a region of the temporal lobe selectively impairs face perception

Question 36

Double dissociation

Answer 36

• Lesioning one brain area impairs cognition A but
  not B; lesioning a different area impairs B but not A.
• Required to demonstrate independence of cognitive functions

Question 37

fMRI

Answer 37

A brain imaging technique that measures how blood flow changes in response to cognitive activity.

Question 38

How fMRI is used in perception experiments

Answer 38

In perception experiments, participants look at different types of pictures while undergoing fMRI; many regions have preferred stimulus types

Question 39

Fusiform face area (FFA)

Answer 39

An area in the temporal lobe that contains many neurons that respond selectively to faces.

Question 40

Parahippocampal place area (PPA)

Answer 40

An area in the temporal lobe that contains neurons that are selectively activated by pictures of indoor and outdoor scenes.

Question 41

Lateral occipital complex

Answer 41

Responds most strongly to pictures of objects

Question 42

Extrastriate body area

Answer 42

An area in the temporal cortex that is activated by pictures of bodies and parts of bodies, but not by faces or other objects.

Question 43

Distributed representations

Answer 43

Even if some functions are localized, the
representation of an experience is distributed
across areas of the brain

Question 44

Brain networks

Answer 44

How areas of the brain are connected to each other - some areas are connected more strongly than others and these strongly connected regions communicate with each other to support cognitions (e.g. regions of frontal and parietal lobe –> attention)

Question 45

How can we study brain networks?

Answer 45

Through neuroimaging tools that measure physical connections (DTI) and functional connections (functional connectivity)

Question 46

Converging methods

Answer 46

Researchers use multiple techniques with complementary strengths to answer the same question

Question 47

Lesion techniques

Answer 47

Assess cognitive impairments which occur following damage to a brain region (can be used to infer causality)

Question 48

Lesion mapping

Answer 48

Determining the probable source of the cognitive deficit by identifying a set of patients who all have the
same cognitive deficits and identify where
the damage overlaps

Question 49

Transcranial magnetic stimulation

Answer 49

• Can be used to temporarily inhibit a brain region (type of lesioning)
• More precise localization but can only be performed
  on certain brain regions & only reduces function

Question 50

EEG

Answer 50

Electrodes placed on the scalp measure coordinated neuronal responses over large areas of the brain

Question 51

Event Related Potentials

Answer 51

The measured brain response that is the direct result of a specific sensory, cognitive, or motor event, the result of many thousands of neurons near the electrode that fire together.

Question 52

Strengths/weaknesses of EEG

Answer 52

Has a high temporal resolution (milliseconds) but poor spatial resolution — you learn more about when neural processes occur but little about where they occur

Question 53

MEG

Answer 53

Provides similar temporal information as EEG but has a higher spatial resolution

Question 54

How can you enhance spatial resolution in EEG?

Answer 54

EEG can also be recorded with implanted intra-cranial electrodes to further increase spatial resolution

Question 55

How does MRI work?

Answer 55

Allows us to take pictures of the brain by producing very strong magnetic fields, and radio waves disrupt the alignment between atoms and the magnetic field. Different tissue (fat, water) re-align at different rates and MRI machines measure the time taken for this to happen.

Question 56

Strengths of MRI

Answer 56

Provides high spatial resolution (~.3mm) images of

brain anatomy

Question 57

How does fMRI work?

Answer 57

Works like anatomical MRI, but:

• Takes a picture of the whole brain every ~2 seconds
• Targets the concentration of oxygen in the blood
• Blood oxygen increases when neurons in a brain region are active

Question 58

Strengths/weaknesses of fMRI

Answer 58

• Provides high spatial resolution (~2.5mm) images of brain function
• Temporal resolution is relatively low (1-2 seconds) and the measurement is indirect

Question 59

Diffusion tensor imaging (DTI)

Answer 59

• Conducted using MRI scanner
• Measures the strength of anatomical connections
  (structural connectivity) between brain regions by
  detecting the movement of water molecules
• Water tends to move along the main axis of axons

Question 60

What does DTI allow?

Answer 60

Allows researchers construct the brain’s “connectome” - a wiring diagram of brain networks

Question 61

How is functional connectivity measured?

Answer 61

Measured using fMRI (sometimes MEG)

Question 62

How is functional connectivity determined?

Answer 62

• Involves analyzing fMRI data in a different way — asking whether regions activate and deactivate
  together, called a correlation
• Often measured when people are told to “rest” to identify resting state networks
• Regions within resting state networks tend to have
  strong anatomical connections, co-activate during
  tasks, and be reliable across people

Question 63

Principle of neural representation

Answer 63

Everything a person experiences is based on representations in the person’s nervous system.

Question 64

Broca’s aphasia

Answer 64

A condition associated with damage to Broca’s area, in the frontal lobe, characterized by labored ungrammatical speech and difficulty in understanding some types of sentences.

Question 65

Wernicke’s aphasia

Answer 65

A condition, caused by damage to Wernicke’s area (in the temporal lobe), that is characterized by difficulty in understanding language, and fluent, grammatically correct, but incoherent speech.