Electroencephalography; EEG

Question 1

Electroencephalography; EEG

Answer 1

Electrical recordings outside of the skull. Cap with electrodes is placed on the skull and registers change of action potentials

Question 2

Local Field Potentials (LFPs)

Answer 2

Due to EPSPs and IPSPs the membrane pot. changes. If many in same location change it creates LFPs. If these are strong enough they can be measured at the skull. So EEG measures combined input to the dendrites

Question 3

Current that it measures

Answer 3

The extracellular return current is measured. Electrical fields are only seen in neurons that are perpendicular, so the gyri

Question 4

Oscillations

Answer 4

Power of different frequency bands. Data can be decomposed in sum of weighted sine waves

Question 5

Event related potentials (ERPs)

Answer 5

Voltage difference in EEG due to sensory/cognitive events. Like when stimulus is presented it changes the waves. Data is cut into epochs and aligned to the onset of presentation

Question 6

Epochs

Answer 6

portions of EEG data seen as wave. All epochs are averaged and the signal that is most common in all remains.

Question 7

Disadvantages

Answer 7

Tells you about electrical potential at the level of electrodes, not at brain level

Can’t measure deep tissue

Inverse problem; can be caused by infinite number of activations

Low spatial resolution. Skull blurs signal