Methods of Cog Neuro

Question 1

What are lesion studies?

Answer 1

Lesion: abnormality or injury to any part of the brain

Neuropsychologists use labratory tasks to measure behaviour and limitations in patients with lesions

Reveal brain regions necessary for healthy cognition by studying limitations

Question 2

How does lesion network mapping work?

Answer 2

1. find different lesion locations linked to problems with a given behaviour in different people
2. look for a single network they are all part of
3. suggest disruption of network, not single region

Question 3

Lesion studies - advantages and limitations

Answer 3

Advantages:
- establish causal role for brain networks
- demonstrate a region is necessary for a particular function/not for another

Limitations:
- finding patients
- damage isn’t typically neatly limited to one region
- unknown whether the region or network is responsible (use lesion network mapping)

Question 4

What is transcranial brain stimulation?

Answer 4

TMS (transcranial magnetic stimulation) &
TES (transcranial electric stimulation)
- induces weak electric currents using rapidly changing magnetic field or direct electrical stimulation

Can activate or deactivate specific regions of cortex
- electromagnetic coil or electrodes ramp up or damp down neuron activity

Question 5

TMS & TES - advantages and limitations

Answer 5

Advantages:
- can activate or deactivate specific regions of cortex to create “temporary” lesions
- allow us to infer that a region is necessary for a function

Limitations:
- not great spatial resolution

Question 6

What is electroencephalography?

Answer 6

Electrodes on the scalp record the electrical activity of the brain
- brain waves reflect the electrical output of columns of cortical neurons

Tells you when activity occurs (good temporal resolution), but not where
- distant regions in synchrony = connectivity mechanism?

Question 7

What are event-related potentials?

Answer 7

ERPs
- averaged EEG signal following a stimulus or response
- compared between groups and conditions
- components are linked to specific cognitive processes

Question 8

What is magnetoencephalography?

Answer 8

MEG
- magnetic detectors surrounding head detect very small magnetic fluctuations in brain activity

• better than EEG for localizing signal source (not distorted by skull)

Question 9

What is electrocorticography?

Answer 9

ECoG
- a form of intracranial EEG that records activity from grids of electrodes
- typically on cortical surface, but can be deeper

• invasive; no control over electrode placement
• great temporal and spatial accuracy

Question 10

What is positron emission tomography?

Answer 10

PET
- radioactive tracers tag neurotransmitters

• expensive, slow, low spatial resolution
• can measure molecular processes

Question 11

What is magnetic resonance imaging?

Answer 11

Changes direction of magnetic field
- protons in nuclei of hydrogen atoms in water naturally resonate when direction is changed suddenly
- different tissues alter resonance (different relaxation rates of protons)

• very good spatial resolution anatomical or structural images (gray and white matter structure)

Question 13

What is functional magnetic resonance imaging?

Answer 13

Index of cognition in action - measures differences in activity between groups or experimental conditions
- doesn’t directly measure neuronal activity

Active parts of brain require more oxygen –> more oxygenated blood is delivered –> oxygen reacts to magnetic signal

Question 14

What is the BOLD response?

Answer 14

Blood Oxygen Level Dependent response
- changes in ration of oxygenated/deoxygenated blood are the DV in an fMRI study
- not a direct measure of neurons firing; statistics produce blobs

Question 15

fMRI -advantages and limitations

Answer 15

Advantages:
- good spatial precision
- non-invasive

Limitations:
- poor temporal precision
- indirect measure of brain activity
- correlational relationship between activation and cognition
- expensive