Ch 2

Question 1

research methods in cognitive neuroscience can be divided into 2 methods

Answer 1

a. Perturbational methods
b. Monitoring methods

Question 2

Perturbational methods

Answer 2

change the workings in the brain, then measures cognition = shows causal relationship

Question 3

monitoring methods

Answer 3

measures brain activity = showing correlational relationship between behaviour and brain activity

manipulates cognitive process, then measures the brain

Question 4

Perturbational methods

Answer 4

a. brain lesions
b. pharmacological perturbations
c. intracranial brain stimulation
d. extracranial brain stimulation

Question 5

PM: brain lesions

Answer 5

observing the effect of damage to the brain resulting from stroke, tumor, trauma

Can be natural or directed (in animals)

Major limitation for natural
- not under control
- lesion isn’t focal
- no 2 patients are the same, therefore can’t generalise
solution is to group patients together and look at the overlap

Disadvantages for directed
- ethical issues
- diaschisis

Question 6

Natural brain lesions: advantages/ disadvantages

Answer 6

Advantages: naturally occurring,

Disadvantages:
- no control
- no temporal resolution
- damage is not focal (it impacts many areas of the brain)
- complex effects of recovery
- difficult to generalise as no 2 patients are the same
solution: use fMRI to look at the overlap of multiple patients with similar lesions

Question 7

Directed brain lesions in animals

Answer 7

Advantages:
- control
- temporal resolution

Disadvantages
- difficulty in training animals to perform a particular task
- ethical reasons
- animals are different from humans
- Diaschisis: the brain is very interconnected, therefore damage to one area may affect another due to the lack of input for example

Question 8

Diaschisis

Answer 8

damage to one area may cause damage to another due the brain’s interconnectedness

= decrease activity in surviving neurons after damage to other neurons

Question 9

PM: pharmacological perturbations

Answer 9

involves interfering with neurotransmitters and their signalling

2 methods:
Method I: measuring the effects of chronic drug on cognition

Method II: controlled pharmacological experimentation

Disadvantages:
- very unspecific (drugs affect the whole brain)
solution: drugs can be injected directly to an area of an animal’s brain

Question 10

Agonist drugs

Answer 10

drugs that activate receptors, identical to neurotransmitters (such as nicotine for acéthylcoline)

Question 11

Antagonist drugs

Answer 11

drugs that bind and block receptors ex: antipsychotic drugs

Question 12

PM: Intracranial Brain Stimulation

Answer 12

electrical stimulation works to perturb the brain with chronically implanted electrodes

— > mostly done in animals but also in patients with severe Parkinson’s disease

Wilder Penfield mapped the somatosensory and motor cortex with this method

Advantages: we can map brain regions, it is very specific

Disadvantages: invasive method, limited to animals

recently developed technique: optogenetics

Question 13

Somatotropic organisation

Answer 13

adjacent body parts have adjacent cortical representations proportional to sensitivity of the body part

Question 14

Optogenetics

Answer 14

only in animals, a virus with genetic material to make light-gated ion channels is injected into a targeted brain area

light-gated ion channels: channels that open or close in response to light. when a laser is targeted at the ‘infected’ area, this causes an influx of ions, which can inhibit or excite neurons

advantages: very specific, high temporal resolution
disadvantage: expensive, can only be done with animals

Question 15

Extracranial brain stimulation

Answer 15

2 methods:
a. TMS: Transcranial Magnetic Stimulation
b. TES: Transcranial Electrical Stimulation or tDCS

Question 16

TMS

Answer 16

a strong magnetic field creates a changing electric field in the underlying brain areas, which can activate neurons

2 types:
a. single pulse TMS: pulse is delivered at each trial, when a stimulus is presented
b. repetitive TMS: series of pulses that change underlying brain areas for a longer period of time

Advantages: non-invade, high temporal resolution

Disadvantages: limited to outer cortex, non-specific areas of the brain are affect: LOW SPATIAL RESOLUTION, can cause seizures

Question 17

TES (or tDCS)

Answer 17

A constant but weak electrical current directly on the scalp to either increase or decrease excitability
used to treat depression

Anodal (positive) stimulation: increases excitability of the stimulated area

Cathodal stimulation: decreases excitability of the stimulated area

Advantages; higher temporal resolution

Disadvantages: low spatial resolution, can’t target deep areas, pulses cause unpleasant scalp and head muscle contractions, can cause seizures

Question 18

Monitoring methods

Answer 18

a. Direct electrophysiological recordings
b. EEG
c. MEG
d. PET
e. fMRI

Question 19

Direct Electrophysiological Recordings (Single Cell Recordings)

Answer 19

electrical recordings directly in the brain

a. intracellular: recordings in the cells, single neurons are penetrated with an electrode tip, provides insights on how neurons behave while the brain carries out a function

b. extracellular: monitoring electrical activity of neurons near the tip of the electrode, provides info on how groups of neurons behave

Peristimulus time histogram
Tuning curves

Advantages: HIGH TEMPORAL AND HIGH SPATIAL RESOLUTION, control, specific

Disadvantages: very invasive, cannot identify networks

Question 20

Peristimulus time histogram

Answer 20

compilation of spikes = when a neuron has an action potential from all trials when a stimulus is presented. This illustrates how responsive a neuron is to the stimulus

Question 21

Tuning curve

Answer 21

measuring the response time of a neuron when a stimulus is varied, for example orientation
If a neuron is tunes to a specific orientation, it will fire the most for that type of stimulus

Question 22

EEG

Answer 22

measures electrical recordings outside the skull

a cap with 28-128 electrodes is placed on a participant’s scalp and can measure changes in electrical potential

Advantages: temporal resolution, non-invasive, rapid

Disadvantages:
- inverse problem: patterns observed could have been cause by something else
- low spatial resolution
- not sensitive to deep brain structure or sulci

Question 23

How and what do we measure with EEG

Answer 23

HOW: LFP: local field potential is produced when many neurons at the same location have similar changes in potential

If LFP strong enough, EEG will pick it up

WHAT:
- summed dendritic field potentials
- extracellular return current
- electrical fields in gyri
= electrical potential at the level of electrodes, not the brain

IT DOES NOT MEASURE:
- individual action potentials
- intracellular current
- electrical fields in sulci (cause must be perpendicular to the electrodes
- activity in deep bain structures

Question 24

How is the information extracted with EEG

Answer 24

a. Oscilllations
h. ERPs : even related potentials: voltage differences that are triggered by something

—> epoch: EEG data is ‘cut’ in portions, then averaged so the most frequent signal of a certain time remains

• topographic maps show the spatial-temporal patterns of ERPs, we can observe how activity at the electrodes dynamically change over time and space

Question 25

MEG: magnetoencephalography

Answer 25

an electrical current produces a circular magnetic field
it detects ERFs : event-related magnetic-field responses over space and time

Advantages:
- no obstruction from skull, non-invasive, can reach deep brain structure, sensitive to sulci, HIGHER SPATIAL RESOLUTION than EEG

Disadvantages: more expensive than EEG, restricts movement, inverse problem

Question 26

PET: positron Emission Tomography

Answer 26

a tracer = radioactive substance, is injected into the blood
since active brain areas require more oxygen and therefore more blood = detection of active brain areas

related to metabolic activity: activity related to the supply of energy

Disadvantages:
- scary; very expensive, slow process: uptake in blood, transport to brain, time required to get a clear signal, blocked design only

Question 27

fMRI: functional magnetic Resonance Imaging

Answer 27

Oxyhemoglobin vs deoxyhemoglobine

active brain areas require more oxygen, resulting in a local increase of oxyhémoglobine
an fMRI scanner can detect active brain areas by picking up BOLD signals (Blood Oxygenation Level Dependant signals)

uses event-related design : switching between 2 conditions can be done without the need to wait 10 minutes as in PET

fmri adaptation: helps the understanding of brain areas by making use of repetitive suppression

advantages: HIGH SPATIAL RESOLUTION
- better temporal resolution than PET
- even-related design, non invasive

Disadvantages
- expensive

Question 28

MR scanner

Answer 28

used for DTI: diffusion tensor imaging -, which reveals white matter tracts of the brain (such as axons)

Question 29

Analysing activation patterns in a brain area in fMRI

Answer 29

most fMRI research is concerned with the activation of different bran areas in response to a manipulated variable

researchers use multivoxel pattern analysis for this: machine learning techniques are used to make sense of activation patterns in brain areas

or principal and independent component analysis: where data is being decomposed to find brain areas that behave similarity

• structural equation modelling: incorporates anatomical connections
• dynamic causal modelling: incorporates functional connections