How can we study function in the brain? Flashcards Preview

Structure and Function in the Brain > How can we study function in the brain? > Flashcards

Flashcards in How can we study function in the brain? Deck (41)
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1
Q

What are the methods for measuring electrical activity?

A
  1. Extracellular recording (1928)
  2. Intracellular voltage recoding with glass micro- electrodes (1949)
  3. Voltage clamp recording of currents (1952)
  4. Patch clamp (1976)
2
Q

What are the different ways we can apply a tracer in electrophysiology?

A
  • Pressure injection (tracer expelled by pressure from pipette)
  • Iontophoresis (electrically charged tracers expelled from pipette)
  • Insertion of dye crystals down concentration gradient
3
Q

How are tracers distributed?

A
  • Active transport in vesicles
  • lateral diffusion within the cellular membrane
  • viral transporters
4
Q

What are the different directions of tracer movement?

A

Anterograde (cell body to axon terminal)

Retrograde (axon terminal to cell body)

5
Q

How can we establish anatomical reorganizations of neuronal networks?

A

By combining both anterograde and retrograde movement.

6
Q

How are viral tracers different to non viral tracers?

A
  • Viral tracer signals are amplified rather than diluted.
7
Q

Give an example of viruses binding to receptors on neurons

A

Rabies virus binds to cellular receptors via its external glycoprotein.

8
Q

How does viral tracing work?

A
  1. Insert TVA and RVG (rabies virus glycoprotein) genes
  2. Apply pseudotypes virus containing EGFP and not RVG (enveleoped in EnvA protein)
  3. Only TVA’s containing RVG will be infected, allowing these cells to spread to pre-synaptic neurones.
9
Q

What is TVA and what is it for?

A

It is the gene for receptors, so the virus can enter

10
Q

What is RV-G and what is it for?

A

It is the gene for rabies virus glycoprotein, so the virus can spread to synaptically coupled cells

11
Q

Listen to recording for slide 7

A

listen to recording for slide 7

12
Q

What are the functions of the amygdala?

A

hormonalsecretion,

emotional responses, control of autonomic functions.

13
Q

What are the functions of the hypothalamus?

A
  • homeostasis

- hunger and thirst - regulation, heart rate (through regulation of the pituitary gland)

14
Q

How can we demonstrate different types of cells respond different types of food even in the same brain region

A
  1. Single neurones stimulated in different brain areas in moving hungry rats
  2. During hunger/satiety, different pathways are activated to regulate homeostasis and weight
  3. These results show diff types of cells in the same region respond differently to food.
15
Q

How can we study brain rhythms and the sleep cycle?

A

Using EEG

16
Q

Give examples of functional imaging

A

PET (position emission tomography)

fMRI (Functional magnetic resonance imaging)

17
Q

What is functional imaging

A

Techniques to measure changes in metabolism, blood flow, chemical composition and absorption during brain activity.

18
Q

What is part of our brain’s rhythmic environment?

A

Temperature, day and night

19
Q

What makes up our brain rhythms

A
  • Sleep and waking
  • Breathing cycles
  • Walking
  • Stages of night sleep.
20
Q

What do EEG’s (Electroencephalography) measure?

A

Voltage changes in the cortex. Displays the difference in electrical potentials between two different sites on the head.

21
Q

What are EEG’s used for?

A
  • Diagnosis of disease such as epilepsy
  • Diagnosis of conditions such as: Coma, encephalopathy, brain death
  • Studies of sleep
22
Q

What are the basic requirements for signal detection for EEG?

A
  • A whole population of neurons must be active in synchrony to generate a large enough electrical field at the level of the scalp.
  • This population of neurons must be aligned in a parallel orientation so that they summate rather than cancel out.
23
Q

What is EPP?

A

A current that flows from extracellular to intracellular

24
Q

What is IPP?

A

A current that flows from intracellular to extracellular

25
Q

What is synaptic potential?

A
  • The sum of action potentials

- Most important source of extracellular current flow (measured by the EEG)

26
Q

What do the amplitude of EEG signals depend on?

A
  • how synchronous the activity of the underlying neurones is
  • number of active cells
  • total amount of excitation
  • timing of activity.
27
Q

What would the EEG of a person with acute depressive periods show?

A
  • Normal background activity

- One single brief, generalised asymmetrical discharge with atypical spikes.

28
Q

What are the advantages of EEGs?

A
  • Non-invasive
  • Not sensitive to movement
  • No radiation or radio-isotopes required
  • Very high time resolution (msec)
29
Q

What are the disadvantages of EEGs?

A
  • Very low spatial resolution
  • Only activity close to the surface can be detected
  • Only activity of large cell populations can be measured
  • High signal to noise ratio
30
Q

Facts about PET

A
  • Measures change of blood flow to a region

- Measures gamma rays.

31
Q

What does the fMRI pick up?

A

It is sensitive to the concentration of oxygen in the blood. (either de-oxy-haemoglobin or oxyhaem)

32
Q

Describe the relationship between the brain and oxygen

A

It consumes 20% of the body’s oxygen but it can’t store any (it just stores a little bit of glucose)

33
Q

How is a PET scan carried out?

A
  1. Patient is given safe dose of FDG (radioactive compound)
  2. FDG enters the bloodstream and travels to the brain
  3. FDG emits positrons, which collide with electrons
  4. Two photons are produced 180 degrees to eachother
  5. Detectors detect the photons in pairs
  6. Computer makes an image of all the photons detected by the scanner.
  7. Areas of the brain that have the most photons will produce more intense PET signals
34
Q

What do the colour on a PET scan indicates?

A

The intensity of activity.

Red = highest brain activity
Green = medium activity
Black = No activity
35
Q

How can we diagnose a disease earlier and more accurately?

A
  • By combining PET and CT scan into a single imaging device

- Disease can be both identified and localised and you can recognise anatomy and function.

36
Q

Why are fMRI’s better than PET scans?

A
  • Less invasive
  • Cheaper
  • Less dangerous
  • Higher resolution.
37
Q

Advantage of PET scan over fMRI?

A

Can be used to visualise NT receptor pools and can be used to investigate pharmacokinetics of new drugs.

38
Q

Facts about MRI

A
  • Views anatomical structure.
  • Studies water molecules’ hydrogen nuclei
  • Higher resolution imaging of difference between tissue types
  • High spatial res
  • Detect radiowaves
39
Q

Facts about fMRI

A
  • Views metabolic functions.
  • Calculates the level of oxygen.
  • Imaging shows the tissue in real time
  • Long-distance temporal resolution.
  • No radioactivity
40
Q

What is the temporal and effective spatial resolution in a PET scan?

A

temp: 30”
Spatial: 10mm

41
Q

What is the temporal and effective spatial resolution in a fMRI scan?

A

temp: 1-4”
Spatial: 1mm