FOUNDATIONS: METHODS AND IMAGING

Question 1

What is an MEG?

Answer 1

MEG measures the magnetic field generated by neurons and is better than EEG for looking at neural activity in brain and measures activity much faster than MRI.

Question 2

What do researchers study on the mesoscale?

Answer 2

researchers see how smaller regions of the brain communicate along single axons at micrometre or submicrometre resolution. It is like adding in the lanes of highways and local streets.

Question 3

What does mesoscale mean?

Answer 3

Complex cellular networks in brain regions

Question 4

What do researhers study in the macroscale?

Answer 4

Detecting how bundles of axon fibres connect large regions together (brain regions and areas)

Question 5

What do researchers study in the microscale?

Answer 5

Cells in complex cellular networks. Microscale images reveal individual neurons and synapses at resolutions of a few nanometres — akin to a map that shows even footpaths and stepping stones.

Question 6

What is the nanoscale?

Answer 6

Receptor mosaics within a cell membrane.

Question 7

What quantity of neurons does the mesoscale look at?

Answer 7

1000-1M neurons

Question 8

What quantity of neurons does the microscale look at?

Answer 8

1-100s of neurons

Question 9

What is studied in the microseconds?

Answer 9

Channel openings

Question 10

What is studied in the milliseconds?

Answer 10

Action potentials

Question 11

What is studied in the tens of milliseconds?

Answer 11

Perception, motor control, reaction times

Question 12

What is studied in seconds and above?

Answer 12

Learning

Question 13

What is studied in years?

Answer 13

Neurodevelopment; diseases such as alzheimers, MS, parkinsons

Question 14

What is the difference between MRI and fMRI?

Answer 14

MRI is the energy emitted from the ‘spin’ of H atoms in a strong magnetic field.

• fMRI is when localised changes in brain activity are associated with changes in blood oxygenation. fMRI can detect magnetisation changes b/w oxygenated and deoxygenated haemoglobin.

Question 15

In FMRI what does BOLD stand for?

Answer 15

Blood Oxygen Level Dependent

Question 16

What is functional connectivity?

Answer 16

Correlation between spatially distinct brain

regions

Question 17

What applications can we use functional connectivity in?

Answer 17

Looking at how people with schizophrenia are functionally different from siblings

Question 18

What is an EEG?

Answer 18

Measures potential difference across the head (b/w pairs of electrodes)

• has much better temporal resolution than fMRI
• is done when someone is performing tasks
• inexpensive
• poor spacial resolution

Question 19

What is temporal resolution?

Answer 19

The amount of time it takes to acquire multiple images one after another in imaging.
e.g. If the TR is 10ms and there are 5 views per segment, the temporal resolution would be 50ms.

Question 20

What is spacial resolution?

Answer 20

The size of the voxels which is determined by the matrix size, field of view (FOV) and the slice thickness

Question 21

What is the approximate resting membrane potential?

Answer 21

Approx -65mV

Question 22

What are the electrodes made from in INTRAcellular recordings?

Answer 22

Saline filled micro pipettes (KCl, NaCl)

Question 23

What are the electrodes made from in EXTRAcellular recordings ?

Answer 23

Insulated metal

Question 24

What is Transcranial Magnetic Stimulation?

Answer 24

Induces a change in current flow in localised sections of the brain

Question 25

What is intracellular microstimulation?

Answer 25

When current is injected into a single cell that changes the membrane potential (similar to a neurotransmitter being released)

Question 26

What is CT?

Answer 26

Computerised tomography

• X RAY source rotated around the head in plane of ideal cross section
• computer uses relative radiopacity to make an algorithm

Question 27

What did CT scans reveal?

Answer 27

Gross organisation of gray and white matter AND position of ventricles

Question 28

What is DTI?

Answer 28

Diffusion Tensor Imaging

• Large visualisation of axons in the brain (connecting of different regions)
• The position of H atoms in H2O can be measure d in brain

Question 29

What is the name for the imaging method that measures the diffusion of water in the brain over time?

Answer 29

DTI (Diffusion Tensor Imaging)

Question 30

What can an MRI reveal and what type of signal does it involve?

Answer 30

Involves radio signals and can reveal lesions in brain (tumors and inflammation increase extracellular water)

Question 31

What is a PET scan?

Answer 31

Positron Emission Tomography

• Looks at blood flow in the brain and metabolism ( like fMRI)
• Radioactive solution containing atoms that emit positrons (e+) is injected in bloodstream
• 19F9 is radio isotop used

Question 32

In PET scans, how is the positron emission (flourine) used to detect tumors?

Answer 32

• It is attached to 2-deoxyglucose (2-DG- analogue of glucose) in bloodstream
• Migrates to brain
• Metabolically active neurons that use glucose normally take up 2-DG and phosphorylate it so it can’t get out of cell
• Amount of radioactive 2-DG and number of beta+ emissions accumulated in neuron indicate the level of metabolic activity hence tumor growth (high metabolic activity)

Question 33

What is common (in a general sense) between PET and fMRI scans?

Answer 33

They BOTH look at blood flow in the brain and metabolic activity

Question 34

What does intracellular recording involve?

Answer 34

Impaling the neuron or axon with microelectrode
- It measures the potential difference between the tip of the INTRACELLULAR ELECTRODE (filled with concentrated KCl solution) and another electrode connected to ground

Question 35

What do extracellular electrodes contain and what is the purpose of them?

Answer 35

• Electrodes (fine glass capillary with salt solution or metal)are placed NEAR the membrane