Methods of looking at the brain

Question 1

What method type is EEG/ ERP and is it invasive and what brain property is used?

Answer 1

It is a recording technique that is non-invasive. Is uses electrical brain properties

Question 2

What method type is single cell and multi unit recording and is it invasive and what brain property is used?

Answer 2

It is a recording technique that is invasive and uses electrical brain properties

Question 3

What method type is TMS and is it invasive and what brain property is used?

Answer 3

It is a stimulation technique that is non-invasive and uses electromagnetic brain properties

Question 4

What method type is MEG and is it invasive and what brain property is used?

Answer 4

It is a recording technique that is non-invasive and uses electromagnetic brain properties

Question 5

What method type is PET and is it invasive and what brain property is used?

Answer 5

It is a recording technique that is invasive and uses haemodynamic brain properties

Question 6

What method type is fMRI and is it invasive and what brain property is used?

Answer 6

It is a recording technique that is non-invasive and uses haemodynamic brain properties

Question 7

Is it possible to record from single neurons in the brain?

Answer 7

No, only in giant squid axons

Question 8

How does single cell recording work?

Answer 8

A very small electrode is implanted into the axon (intracellular) or outside the axon membrane (extracellular) and records neural activity from population of neurons.

Question 9

What is an Electroencephalography?

Answer 9

The measurement of the electrical activity of the brain by recording from electrodes placed on the scalp. The resulting traces are known as an eletrocephalogram and represent an electrical signal from a large number of neurons. EEG signals represent the change in the potential difference between two electrodes placed on the scalp in time. The EEG obtained on several trials can be averaged together, time locked to the stimulus to form an event related potential (ERP)

Question 10

What are ERPs?

Answer 10

voltage fluctuations that are associated in time with a particular event (visual, auditory, olfactory stimuli)

Question 11

How can ERPs be extracted from the ongoing EEG?

Answer 11

By filtering and signal averaging

Question 12

How are electrodes labelled

Answer 12

p stands for parietal ect.

• even numbers on the right
• odd numbers on the left

Question 13

How can we use an ERP to see how our brain responds to a particular stimulus?

Answer 13

Look at the EEG trave for the next 5 seconds after the stimulus is presented

Question 14

What are ERPs useful for medically?

Answer 14

• Seeing if someone has Alzheimer’s disease (their P300 will be much lower)
• picking up mental health issues

Question 15

What is magnetocephalography?

Answer 15

An imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices known as SQUIDS. They have excellent temporal and spatial resolution but are very expensive.

Question 16

What is magnetic resonance imaging and when do we use it?

Answer 16

Uses different magnetic properties of types of tissue and of blood to produce images of the brain. We use it when we are interested in where things are happening in the brain.

Question 17

What is the difference between structural and functional?

Answer 17

Structural: different types of tissue (skull, grey matter, white matter, CSF fluid) have different physical properties - used to create STATIC maps (CT and structural MRI)
- Functional: temporary changes in brain physiology associated with cognitive processing (PET and fMRI - often used in cognitive neuroscience)

Question 18

What does PET do and how does it work?

Answer 18

• measure local blood flow (rCBF)
• radioactive tracer is injected into the blood stream
• the tracer takes up to 30 seconds to peak
• when the material undergoes radioactive decay a positron is emitted, which can be picked up by the detector
• areas of high radioactivity are associated with brain activity, based on blood volume
• the more red the image the more blood flow was there
• measures blood volume directly

Question 19

What does fMRI do and how does it work?

Answer 19

• It directly measures the concentration of deoxyhaemoglobin in the blood (the BOLD response - blood oxygen level dependent contrast response)
• it measures deoxygenated blood after there has been a large amount of brain activity and oxygenated blood is used
• this change in BOLD response over time is called the haemodynamic response function
• oxygenated and deoxygenated blood have different magnetic properties which is why we can measure deoxygenated blood
• this haemodynamic response function peaks in 6-8 seconds which limits the temporal resolution of fMRI
• it measures activity in voxels (or volume pixels) which are the smallest distinguishable box shaped part in the 3D image

Question 20

What are fMRIs used to study?

Answer 20

The correlation between brain activity and stimulus timing. They can produce activation maps showing which parts of the brainn are involved in a particular mental process

Question 21

What does it mean to say a brain region is active?

Answer 21

It is active if it shows a greater response in one condition relative to another

Question 22

What is cognitive subtraction and what is the problem with it?

Answer 22

Activity in a control task is subtracted from the activity in an experimental task
- problem: difficulty of the baseline control task

Question 23

Can there ever be disagreement between imaging and lesion studies?

Answer 23

Yes

Question 24

What is diffusion tensor imaging (DTI)?

Answer 24

An imaging method that uses a modified MRI scanner to reveal bundles of axons in the living brain. Measures white matter organisation based on limited diffusion of water molecules into axons. Used to visualise connections within the brain

Question 25

What does functional near infrared spectroscopy (fNRIS) do? What are it’s advantages and disadvantages?

Answer 25

• measures the same BOLD response as fMRI but in a completely different way. ‘Light’ in infrared range passes through the skull and scalp but is scattered differently by oxy versus deoxyhaemoglobin. It is portable and more tolerant of head movement but can’t image deep structures

Question 26

What is intracranial electro cephalography and why is it useful?

Answer 26

We record directly from the inside of the human brain when people are undergoing neurosurgery. It is the only method that gives us the high resolution in both place and time. It records straight from the cortical surface approximately from tens of thousands of neurons