L10 - Techniques #2

Question 1

Single-cell recordings

Answer 1

~ extracellular recordings
~ measures AP from one cell
~ occasionally sued in treating epilepsy

Question 2

What is used to measure single-cell recordings?

Answer 2

post-stimulus time histogram (PSTH)

measure average firing rates over time

Question 3

In a raster plot, what does each bar represent?

Answer 3

an action potential

Question 4

Single cell recording pros

Answer 4

best temporal and spatial resolution

Question 5

Single cell recording cons

Answer 5

very limited example of brain activity

invasive

Question 6

Positron Emmission Tomography (PET)

Answer 6

~ indirect as measures blood flow + oxygen use
~ radioactive isotope injected into blood
~ as isotope decays, releases gamma rays (photons) which are detected
~ positron + electron annihilation = photon
~ usually between controls and experimental condition
~ other isotopes can be used

Question 7

Functional Magnetic Resonance Imaging (fMRI)

Answer 7

~ indirect as measures block flow (same as MRI)
~ blood oxygenation level dependant (BOLD) signal
~ sluggish - response peaks several seconds after stimulus

Question 8

PET and fMRI pros

Answer 8

~ good spatial resolution

~ access to whole brain

Question 9

PET and fMRI cons

Answer 9

~ poor temporal resolution
~ indirect measurement
~ invasive (radioactive injection for PET)
~ expensive

Question 10

Electroencephalography (EEG)

Answer 10

~ wear a cap with lots of electrodes to measure neural activity directly
~ volume currents range the local balance of ions at each scalp location
~ measures potential different between two electrodes

Question 11

Magnetoencephalography (MEG)

Answer 11

~ big machine contains liquid H2 that measures neural activity directly
~ primary current causes magnetic field to be measurable outside the head
~ sensitive to primary current orientation
~ doesn’t compare magnetic fields, just measure directly

Question 12

EEG and MEG

Answer 12

~ synchronous activation of lots of aligned pyramidal neurons
~ they replete post synaptic currents in dendritic tree

Question 13

Synaptic current

Answer 13

+ve ions flowing INTO dendrite

Question 14

Primary current

Answer 14

current flowing along dendrite

Question 15

Secondary (volume) current

Answer 15

completes the circuit

Question 16

Which part of the primary current does MEG reflect?

Answer 16

tangential (head surface orientation)

Question 17

Which method is useful for auditory reasrch?

Answer 17

MEG because its near big sulci

Question 18

Electrocortogram (ECoG)

Answer 18

electric field potential measurements from the cortical surface

Question 19

Local field potential (LFP)

Answer 19

measured from inside cortex

Question 20

EEG and MEG Oscillations

Answer 20

both show oscillatory activity in different frequency bands
~ diff. cognitive states are associated with characteristic oscillations
e.g. fast, gamma waves = consciousness
slower, alpha waves = relaxing