Title: Psychology / Biopsychology / 09_Neuroimaging
Tags: Biopsychology::09_Neuroimaging Biopsychology::Semester_2

Q: What two dimensions can neuroimaging methods be categorized into?
A: non-invasive - invasive methods
central measures - peripheral measures
(central: directly measure neuronal activity or modulate it
peripheral: indirectly measure neurons, e.g. oxygen levels of areas)

Q: What are spatial and temporal resolution of neuroimaging methods?
A: Temporal: how precise can the timing of neuronal activity be measured?
Spatial: how precise can the location of neuronal activity be measured?

Q: What is the basic idea behind EEG?
A: Elektroencephalography
Electrodes are placed at the scalp surface and measure tiny changes of electrical potential in dendrites.

Q: What are the drawbacks of EEG?
A: Very susceptible to noise and artifacts
No action potential can be measured, only summation of EPSP and IPSP
Poor spatial resolution (10cm)

Q: How does EEG perform in spatial and temporal resolution?
A: Poor spatial resolution (10cm)
Great temporal resolution (ms)

Q: How can the spatial accuracy of EEG be improved?
A: 3D EEG source analysis
distributing multiple electrode sides across the brain can be used to more accurately determine where a signal comes from

Q: What is "Event Related Potential" and how does it related to EEG analysis??
A: A common analysis method for EEG data:
The stimulus is shown multiple times -> all EEG responses are averaged -> the noise should vanish in the result
The resulting signal should be the original brain response, the ERP (it consists of components that are associated with particular cognitive functions)

Q: What is the basic idea behind MEG?
A: Magnetencephalography
The postsynaptic potentials generate tiny magnetic fields -> sensors of the MEG measure those

Q: What are the advantages and disadvantages of using MEG over EEG?
A: + Much better spatial resolution while retaining temporal resolution
- Much more expensive and susceptible to outside influences

Q: What is the idea behind PET?
A: Positron Emission Tomography
1. Radioactive tracers are injected into the bloodstream
2. Those bind glucose
3. Under the influence of gamma rays, this glucose emits positrons when used
4. The location of these emitted positrons is measured

Q: What do PET actually measure?
A: Metabolism in the brain (use of glucose)

Q: How are spatial and temporal resolution for PET?
A: Spatial in the range of cm
Temporal in the range of minutes (baaaaad)

Q: What is the idea behind MRI?
A: Magnet Resonance Imaging
A strong magnetic field aligns the molecules in the tissue (50/50 in direction)
But! some molecules remain in a labile state and can be flipped by short pulses that are perpendicular to the magnetic field.
When they then flip back, tiny bits of energy are released, which is measured by sesors.
-> Different kinds of tissue will emit different levels of energy, so brain tissue can be imaged
! This approach is limited to structure, it does not measure functionality. !

Q: What is the idea behind fMRI?
A: functional MRI
The oxygenation of blood influences the magnetic properties (time delay before molecules flip back and send out energy)
-> This information can give insight into how oxygenated blood is  (BOLD)
-> active brain regions are oversupplied with oxygen (this allows us to link MRI responses to activity)

Q: What is a BOLD signal?
A: Blood Oxygen Level Dependant Signal
-> used to infer functional information in the fMRI

Q: How does fMRI hold up in spatial and temporal resolution?
A: Spatial: few mm
Temporal: several seconds :(

Q: What is the idea behind fNIRS?
A: functional Near-Infrared Specroscopy
similarily to fMRI, it measures oxygen in the brain.
However, it achieves this by emitting IR light into the brain and using the fact that oxygenated blood reflects more IR-light -> stronger signal in oxygenated regions

Q: Advantages and disadvantages of using fNIRS over fMRI?
A: + it is cheaper and more convenient (no loud noise, portable)
- the spatial resolution is worse and subcortical information cannot be extracted

Q: What is Faraday's law (layman explanation)?
A: When there is electrical current on a wire, a perpendicular electrical field is generated that also induces electricity on other wires in the field.

Q: What is the basic idea of TMS?
A: Transcranial Magnetic Stimulation
Faraday's law is utilized: a rapid change in of current in a coil near the brain creates a magnetic field that induces current in tissue

Q: What are 3 uses of TMS?
A: 1) Action potential can be elicited
2) Virtual lesions (simulated patients with very short-term disabilities in brain areas)
3) Exitability can be modulated

Q: What are the spatial and temporal resolutions of TMS?
A: spatial: mm to cm
temporal: ms

Q: What is the idea behind tDCS?
A: Transcranial direct current stimulation
A weak current is constantly applied to the brain for several minutes
-> cathodal stimulation leads to decreased cortical activity
-> anodal stimulation leads to increased cortical activity

Q: Compared to tDCS, what does tACS do differently?
A: The current that is applied is not constant but rather alternating

Q: From all neuroimaging methods discussed in the lecture, which can get information from subcortical regions?
A: PET and fMRI

Q: What is the idea behind optical imaging?
A: Injection of a dye that changes based on neuronal activity or chemical conditions → a window is put into the head of an animal to observe these changes

Q: What is the idea behind optogenetics?
A: "Viruses" are inserted that change ion channels so that they respond to light. Glass fibres are then inserted into the animals brain to accurately control these ion channels. (very precise)

Q: Why is it futile to stimulate the amygdala with TMS?
A: The amygdala is subcortical, TMS can only stimulate cortical areas.

Q: When using EEG to measure brain activity in response to a stimulus, how often should the stimulus be presented?
A: Very often (100s of times), so that the unsystematic noise of the signal gets cancelled out.