electroencephalography

Question 1

MEG

Answer 1

doesnt touch head

Question 2

EEG

Answer 2

on scalp

Question 3

ECoG

Answer 3

above/below dura mater

Question 4

MEA

Answer 4

pia mater
- To find the origin of epilepsy so the tissue can be removed
- Very invasive
- High spatial and temporal resolution (low noise)
* Unfiltered by skull and scalp
- Allow measurement of high gamma activity >70Hz

Question 5

SEEG

Answer 5

cortex
- Needles (about 10) into brain
- Less invasive than ECoG due to soft electrodes that push brain tissue to the side
- Can be used to do task to record high quality brain activity

Question 6

what does EEG measure and which technique measures something else

Answer 6

EEG does not measure action potentials only MEA does
- The rest measure local field potentials  accumulation of many individual action potentials
* IPSP
* EPSP

Question 7

fMRI

Answer 7

• fMRI measure changes in blood flow in brain areas due to neuro-activity (NVU - neurovascular coupling)

Question 8

frequency domains

Answer 8

• Spectral power decreases with increasing frequency
• 1Hz –> strong frontal activity (eye movement)
• 10Hz –> occipital alpha activity
• 60Hz –> power line noise (USA)

Question 9

EEG-rhythms

Answer 9

• Neuronal oscillations = rhythmic or repetitive neuronal activity
• Synchronization of larger cortical areas lead to oscillatory activity
• Examples:
• Alpha rhythm: occurs in absence of sensory stimuli
  o Occipital regions  8/13Hz
• Mu rhythm: suppressed during motor and imagination activity
  o Sensorimotor regions  8/13Hz
• Gamma rhythm: cognitive activity
  o Various regions  >60Hz
• Theta rhythm: hippocampal activity during memory formation
• These frequency bands are strongly person and author dependent

Question 10

EEG topography

Answer 10

• Bad spatial resolution
• Still helpful to find out spatial patterns

Question 11

event-related potentials

Answer 11

• An Event-Related Potential (ERP) is the brain’s electrical response shortly after an event
• Mostly measured by EEG and MEG
• Typically triggered by an external sensory stimulus
• Can be internal stimulus (e.g. associated with the execution of a motor, cognitive, or psychophysiological task)
• ERPs can provide information about brain function (clinical use)

Question 12

ERP complex

Answer 12

• ERPs are composed of several ERP components
• Parts of the waveform called positive (P) or negative (N) according to their polarity
  o Warning: Sometimes negative is upwards!!
• Followed by a number indicating
  o Component’s ordinal position in the waveform (e.g., P1, N1, P2, N2, P3)
  o Latency in milliseconds (e.g., N100, N170, P300)

Question 13

parameters ERP

Answer 13

• Important parameters of ERP components
• Peak amplitude in μV (often normalized to 200ms pre-stimulus interval)
• Peak latency in ms
• Mean amplitude of an ERP component (intervals more robust than peak)
• Electrode location (spatial focus)

Question 14

clinical use EEG

Answer 14

epilepsy diagnosis (spatial)
sleep disorders –> sleep staging
brain tumours
brain damage
stroke