Lecture 3: Methods in cognitive neuroscience

Question 1

Key idea in cognitive psychology

Answer 1

we use mental representations that undergo internal transformations

Question 2

independent variable

Answer 2

the different conditions

Question 3

dependent variable

Answer 3

relevant measurement that is used

Question 4

The word superiority effect

Answer 4

shows that we do not need to identify all the letters of a word before we recognize the word.
we activate both the representation of the individual letters and the word in parallel

Question 5

The stroop test

Answer 5

the simultaneous activation of multiple representations is not always beneficial.

Question 6

Damaged brain is caused by? (5)

Answer 6

vasular disorders: disruptions in blood-flow
tumors
degenerative and infectious disorders (parkinson, alzheimers)
traumatic brain injury: damage to cell bodies, white matter, vascular systems.
epilepsy

Question 7

Main idea of studying the damaged brain?

Answer 7

brain injury disrupts/eliminates the processing ability of the affected brain structure

Question 8

Patient A: damage to the left inferior frontal cortex (Broca’s area)

Answer 8

can understand language but cannot produce fluent language (non-fluent aphasia)

understanding and production of language seem to be a separate processes and production is related to Broca’s area.

Single dissociation

Question 9

Single dissociation

Answer 9

when an impairment affects one cognitive function but leaves the other intact, indicating some level of functional independence

Question 10

Patient B: Damage to the left superior temporal gyrus (Wernicke’s area)

Answer 10

can produce fluent (but nonsensical) language but cannot understand language.

understanding and producing language are separate processes and take place in different brain areas.

double dissociation

Question 11

double dissociation

Answer 11

involves two different functions that are each impaired in one individual while remaining intact in another

Question 12

Diaschisis

Answer 12

a decline of cognitive function because of a brain leasion could also indicate that other brain areas dont receive input anymore and might not function properly anymore. Diaschisis is decreased activity in surviving neurons after damage to other neurons.

Question 13

Corpus callosotomy

Answer 13

split brain patient

Question 14

Methods to perturb neural function
1. pharmacological interventions

Answer 14

interfering with neurotransmitters changes signalling.
Agonists/antagonists
Disadvantage: very unspecific. administering a drug affects the whole brain.

Question 15

Agonists

Answer 15

Drugs that work like the real neurotransmitter
example: bromocriptine, a drug that binds to dopamine receptors and activates them as dopamine does.

Question 16

Antagonists

Answer 16

A drug that blocks neurotransmitters
example: haloperidol, binds to dopamine receptors and blocks them. prevents real dopamine to bind with receptors.

Question 17

Methods to perturb neural function
2. Genetic manipulations

Answer 17

used in animal research
knock-out animal: animal with specific genes manipulated vs. wild type: normal animal.

Question 18

Methods to perturb neural function
3. invasive stimulation methods

Answer 18

mostly animal research, but also in patients undergoing neurosurgery (epilepsy)
Deep brain stimulation: parkinsons disease.

Question 19

Methods to perturb neural function
3. invasive stimulation methods

Optogenetics

Answer 19

a biological technique that allows the control of neurons using light
light gated ion channels: channels that open or close in response to light.

Question 20

Methods to perturb neural function
4. non-invasive stimulation methods
Tanscranial magnetic stimulation (TMS)

Answer 20

Tanscranial magnetic stimulation (TMS): strong current is sent through coil and produces a strong magnetic field. this field induces a changing electrical field in the underlying brain area and causes neural activity (motor activity)

Single pulse TMS: during the experiment a TMS pulse is delivered on each trial (when a stimilus is presented)

Repetitive TMS: before the start of the experiment, a train of pulses is delivered that changes the underlying brain area for longer duration

Question 21

Effect of TMS

Answer 21

Effect of TMS depends on the strenght of the pulse. a strong pulse causes temporary lesions, weaker pulses can sometimes facilitate activation

Question 22

disadvantage of TMS

Answer 22

Spatial resolution is small: a pulse affects a relatively large brain area.
only target superficial brain regions, not possible to target structures deeper in the brain
a pulse contracts scalp and head muscles and could be annoying to the patient.
stimulation might trigger epileptic seizure.

Question 23

Methods to perturb neural function
4. non-invasive stimulation methods
Transcranial direct current stimulation (tDCS) & Transcranial alternating current stimulation (tACS)

Answer 23

in tDCS and tACS a small electical current is applied directly to the scalp. effects last for an extended period and is used in research and to treat clinical problems (depression)

could not be strong enough to have any effect on the brain at all

Question 24

Structural analysis of the brain:
Computerized Tomography CT or CAT scan

Answer 24

first method. based on Xray. currently only used in medical imaging

Question 25

Structural analysis of the brain: Magnetic Resonance imaging (MRI)

Answer 25

uses magnetic properties of atoms. most pervasive atom in the brain is hydrogen. structural image of the brain at high spatial resolution. image of the structural connectivity of the brain (diffusion tentsor imaging DTI) measuring the density and flow of water molecules in axons.

Question 26

Methods to measure neural activity: Single cell neurphysiology in animals

Answer 26

A visual stimulus is presented in the receptive field of the neuron that we are recording.

Question 27

Invasive neurophysiology in humans Electrocorticography (EGoG)

Answer 27

a grid of electrodes is placed directly on the cortex. neural activity often shows oscillatory activity: these oscillations can have different frequencies and amplitudes (power)

Question 28

Non-invasive electrical recordings Electroencephalography EEG

Answer 28

electrical recordings outside the skull cap with electrodes is placed on the subjects head. electrodes register changes in electrical potentials.

Question 29

Non-invasive electrical recordings Electroencephalography EEG oscillations

Answer 29

power of different frequency bands. EEG data can be decomposed in sum of weighted sine waves. example: during stage 1 of sleep, the power of the theta band is high (oscillations between 4 and 7 Hz). during slow-wave sleep (stage 3), the delta band (between 1 and 4 Hz) is very high

Question 30

Non-invasive electrical recordings Electroencephalography EEG Event related potentials (ERP)

Answer 30

small voltage differences in an ongoing EEG triggered by sensory and cognitive events

Question 31

Disadvantages of EEG

Answer 31

EEG tells you something about the electrical potential at the level of the electrodes but not about the electrical potentials at the brain level. inverse problem: the pattern observed at the sensors can be caused by an infinite number of different brain regions low spatial resolution: low conductance of CSF, meninges, skull and scalp blurs the electrical signal before it reaches the electrodes for similar reasons EEG cannot detect any activity from deep brain structures. electrical signal decayed before it reaches the electrodes.

Question 32

Non-invasive electrical recordings Magnetoencephalography (MEG)

Answer 32

an electrical current produces a magnetic field orthogonal to the electical field in contrast to EEG, MEG is sensitive to neurons that are parallel to the skull (Sulci neurons)

Question 33

MEG advantage over EEG

Answer 33

a magnetic field is not obstructed by the skull. more possible to obtain signals from deep brain structures better spatial resolution compared to EEG

Question 34

MEG disadvantage

Answer 34

much more expensive and patients are restricted.

Question 35

Hemodynamic response

Answer 35

when a brain area is active, the blood flow to that region, increases to supply that area with more energy (oxygen, glucose)

Question 36

Non-invasive electrical recordings Positron emission tomography (PET)

Answer 36

a radioactive substance (tracer) is injected into the bloodstream of subjects. The tracer becomes distributed in the brain an active brain area consumes more oxygen, so the tracer will be more present in active brain areas. because the tracer is radioactive, a series of events will cause it to emit radioactive beams that can be detected by specialized detectors.

Question 37

Disadvantage PET

Answer 37

scary to subjects: radioactivity & needles. Very expensive slow procress: uptake in blood, transport to brain

Question 38

Blocked design

Answer 38

many trials from one condition are presented in block brain activity in one block is compared to another block, with trials from another condition PET trace had to decay between blocks, this takes long

Question 39

Non-invasive electrical recordings Functional magnetic resonance imaging (fMRI)

Answer 39

blood with oxygen (oxyheamoglobin) has different magnetic properties than blood without oxygen (deoxyhaemoglobin) active brain areas use more oxygen. this results in a local increase in oxyheamoglobin. these small changes in the magnetic properties of the bloof (BOLD signals) are detected by the FMRI Scanner

Question 40

Event related designs

Answer 40

change conditions on a trial by trial level. this makes experimental designs possible. many more research questions can be investigated example: how does the previous trial affects the cognitive processing of the current trial

Question 41

Magnetic resonance spectroscopy

Answer 41

information about the chemical composition of tissue. example: measure the concentration of neurotransmittors in different brain areas.

Question 42

disadvantage FMRI

Answer 42

relatively low temporal resolution compaired to EEG brains of different participants need to be normalized to a common space (standardized template of the brain). analyses of this type of data requires a lot of preprocessingm meaning that the raw data you acuire from scanning a participants need to go through several steps before you can use them

Question 43

Connectivity maps

Answer 43

evidence for correlations between brain areas and cognitive functions. how the brain is connected feels like modern day phrenology brain regions do not work in isolation but as a complex interconnected network

Question 44

computational neuroscience

Answer 44

simulate cognitive processes in a computer model neural networks: makes predictions, what if we lesion a specific part of the model?

Question 45

converging methods convergence vs. complementary

Answer 45

integrating different methods use a method to generate hypotheses to test with different methods convergence: study a theoretical concept with different paradigms. a hypothesis is tested with different experimental designs that all give the same results, provides a very strong empirical evidence. complementarity: different methods provide different sorts of information. some have high temporal resolution some have high spatial resolution.