Neuroscience Techniques

Question 1

What does MRI stand for

Answer 1

Magnetic resonance imaging

Question 2

What does MRI measure? And how?

Answer 2

It measures the presence of water in the brain. It detects the protons making up the hydrogen atom in the water molecule. This is achieved by combining a strong magnetic field and radio pulses which has the effect of the protons emitting radio signals. These signals are then picked up by the MRI. It shows the different levels of water in different shades of gray

Question 3

How much water is there in the brain tissue?

Answer 3

73%

Question 4

What happens to the protons?

Answer 4

Normally they are randomly spinning around. Exposure to the magnetic field aligns their orientation. When the radio frequency pulse is applied, the axes of the protons are shifted in a predictable manner and when the pulse is turned off the protons release their energy as they spin back to the orientation of the magnetic field.

Question 5

what is the difference between white and grey matter?

Answer 5

grey matter is cell bodies and dendrites; white matter is axons (cabling)

Question 6

Does MRI have high spatial or temporal resolution?

Answer 6

It has a spatial resolution of 1 mm

Question 7

What does DTI stand for?

Answer 7

Diffusion Tensor Imaging

Question 8

What does DTI measure? What can it help understand?

Answer 8

It is a kind of MRI that measures how the water in the brain moves, and not just its presence. As water doesn’t just run freely, but rather MOSTLY along the axons > DTI can help giving high-resolution structural images of long-range axons running in white matter. It can measure white-matter connectivity

Question 9

What’s the movement of water?

Answer 9

anisotropic > restricted by the various cell membranes. It diffuses best between the sheath and the axon.

Question 10

what is in vitro measurement

Answer 10

making observation from outside of a living organism.

Question 11

what is in vivo and what does it measure?

Answer 11

In vivo measures action potentials inside the living brain > this requires opening up the skull and putting electores directly onto the skull.

Question 12

what do direct measures do?

Answer 12

They measure either the primary or volume currents in the brain

Question 13

what to indirect measures do?

Answer 13

They measure blood flow in the brain

Question 14

What are pyramidal cells?

Answer 14

They make up around 80% of neurons in the brain. They have two types of dendrites: APICAL DENDRITES > long that stretch towards the surface of the cortex and BASAL DENDRITES > horizontal direction and cover less distance.

Question 15

How are pyramidal cells organised?

Answer 15

They are organised into cortical columns which are interconnected, so they seldom get activated alone. So a signal from outside the column, activates the whole column and the ones near.

Question 16

What is a large number of pyramidal cells called

Answer 16

A neural mass.

Question 17

What does EEG measure?

Answer 17

It measures the voltage between two locations on the scalp. (It two brain regions have a different electric potential, meaning that one has more positive ions than the other, electric current would flow between them till they become equal). The electric potential is measured in Volts and that’s what we measure.

When ions are being packed into the area underneath one electode and pulled away from another, this creates voltage difference which is measured.

So: it measures electric potential fluctuations caused by the volume currents due to neurons becoming active

Question 18

what does neuronal activity change? And how can this be measured?

Answer 18

It changes electric potential and can be measured through EEG

Question 19

Main difference between EEG and MEG

Answer 19

EEG measures the volume current, which MEG measures the primary current.

Question 20

What does MEG measure?

Answer 20

It measures the magnetic field of the primary currents. It needs to be measured in a magnetically shielded chamber

Question 21

What is better in MEG than EEG

Answer 21

It has a higher spatial resolution

Question 22

What is MEG blind to?

Answer 22

Activity in the gyri because they reverse down, away from the measuring field.

Question 23

What are the types of brain oscillations? And how is freuquency and amplitude

Answer 23

Gamma (high-frequency and low amplitude), Beta, alpha, theta, delta (low-frequency, high amplitude). They all refer to different brain activity.

Question 24

What are the advantages of EEG and MEG

Answer 24

They are direct measures, are non-invasiveand have a high temporal-resolution. EEG is also relatively cheap

Question 25

What are disadvantages of EEG and MEG

Answer 25

They have a low spatial resolution and can't solve the inverse problem.

Question 26

What is the change in bloodflow in the brain called?

Answer 26

Haemodynamics

Question 27

What does the fMRI measure

Answer 27

It measures the level of oxygen in the blood: Active neurons take oxygen from the blood (so blood is deoxygenated) and this can tell you which neurons were active at the time.

Question 28

what is a voxel?

Answer 28

A 1mm cube of neurons

Question 29

What is the signal measured by the fMRI called?

Answer 29

BOLD signal

Question 30

What are advantages of fMRI?

Answer 30

It is non-invasive and has a good spatial resolution as it allows to study any area of the brain. It has no inverse problem

Question 31

What are disatvantages of fMRI

Answer 31

It has low temporal resolution as oxydation of blood takes around 2 seconds and rises to a peak at around 4-6 seconds. Also because of the nature of comparison it is difficult to see what activation is due to the stimulus and what is because of nothing. Complex Statistical analysis and complexity of equipment. Replication crisis.

Question 32

What are PET and NIRS

Answer 32

PET is semi-invasive and older; NIRS measures oxygenation in blood through infrared light and is mainly used in infant studies. The problem is it can't reach rubcortical regions of the brain.

Question 33

What do brain perturbations question?

Answer 33

What is the effect of a perturbation of brain activity on task performance and stimulus processing?

Question 34

What are optogenetics?

Answer 34

Genetically modified neuron so that the ion channels become sensitive to light and can be switched on and off at will.

Question 35

What and how does TMS measure?

Answer 35

It's a coil-shaped conductor that generates a magnetic field, placed next to the skull. This penetrates through the skin and generates a focal electric field in the brain, which depolarises neurons locally, changing their normal activity. This can induce plastic changes to the brain and can have long-lasting beneficial effects for clinical stuff.

Question 36

What and how does tDCS measure?

Answer 36

It has two electrodes at the sides of the skull, the anode and the cathode.

Question 37

What are advantages and disadvantages of TMS and tDCS?

Answer 37

They both have high spatial and temporal resolution. They are safe, portable and relatively cheap and can have major advantage. But the neurophysiological effects are not yet certain. And they don't reach deeper than the cortex.