EEG

Question 1

What is EEG a measure of?

Answer 1

Electrical activity of the brain

Question 2

Is EEG an indirect or direct measure of activity?

Answer 2

Direct

Question 3

What is EEG used for in clinic?

Answer 3

Diagnosis tool for cerebral dysfunction such as epilepsy

Analysing sleep and distinguishing sleep stages

Legal determination of brain death

Question 4

What exactly does EEG measure?

Answer 4

Sum of extracellular potentials from a group of neurons

Question 5

Which cell type is largely recorded by EEG?

Answer 5

Cortical pyramidal cells

Question 6

How are amplitude fluctuations measured on EEG?

Answer 6

uV (microvolts)

Question 7

What are the advantages of EEG?

Answer 7

Good temporal resolution

Direct measure of brain activity

Question 8

What are the disadvantages of EEG?

Answer 8

Poor spatial resolution due to filtered signal through blood, tissues, and skull

Measures only a small fraction of total brain activity due to variability in conductivity, mixed orientation of dendrites, and lack of synchronous activity

Question 9

How has the placement of electrodes been standardized?

Answer 9

International 10-20 system based on scalp measurements, relative to nasion and inion

Question 10

Where is the nasion?

Answer 10

Between the eyes

Question 11

Where is the inion?

Answer 11

Base of the skull

Question 12

What is a series of electrode placements referred to as?

Answer 12

Montage

Question 13

What are field potentials on EEG?

Answer 13

Extracellular recordings of synchronised activity of a large number of cells

Question 14

How do field potentials appear on EEG?

Answer 14

Single electrical spikes

Question 15

What does a single electrical spike indicate on EEG?

Answer 15

Field potential

Question 16

What type of deflection occurs on EEG following an excitatory post-synaptic potential?

Answer 16

Negative deflection

Question 17

What type of deflection occurs on EEG following an inhibitory post-synaptic potential?

Answer 17

Positive deflection

Question 18

What can cause mixed orientation of dendrites?

Answer 18

Folding of cerebral cortex

Question 19

What does synchrony of neuronal activity cause on EEG?

Answer 19

Large amplitude and low frequency waves

Question 20

What frequency are beta waves?

Answer 20

13 - 30 Hz

Question 21

When are beta waves the dominant wave pattern?

Answer 21

Awake and alert, focused on a task

Question 22

What frequency are alpha waves?

Answer 22

8 - 13 Hz

Question 23

When are alpha waves the dominant wave pattern?

Answer 23

Awake and relaxed

Question 24

What frequency are theta waves?

Answer 24

4 - 7 Hz

Question 25

When are theta waves the dominant wave pattern?

Answer 25

During memory encoding and recall

Question 26

What frequency are delta waves?

Answer 26

Below 4 Hz

Question 27

When are delta waves the dominant wave pattern?

Answer 27

During sleep, unconscious

Question 28

What is the dominant brain wave pattern in infants?

Answer 28

Delta waves

Question 29

What brain waves are observed in stage 1 NREM sleep?

Answer 29

Theta waves

Question 30

What brain waves are observed in stage 2 NREM sleep?

Answer 30

Spindles and K complexes

Question 31

What brain waves are observed in stage 3 and 4 NREM sleep?

Answer 31

Delta waves

Question 32

What are sensory evoked potentials?

Answer 32

Potentials observed in EEG that are reliably reproduced at specific times in response to particular sensory stimuli

Question 33

How are sensory evoked potentials extracted from EEG recordings?

Answer 33

Signal averaging of recordings over multiple trials

Question 34

What does signal averaging do to EEG, when searching for sensory evoked potentials?

Answer 34

Removes/minimises random variations to leave only the stimulus-evoked potential

Question 35

What are three examples of sensory evoked potentials?

Answer 35

Visual evoked Auditory evoked Somatosensory evoked

Question 36

How can sensory evoked potentials be used in clinic?

Answer 36

Assess neurological function

Question 37

What condition can be detected in its early stage via abnormal visual evoked potential recordings?

Answer 37

Multiple sclerosis

Question 38

What change to visual evoked potentials is associated with early stage multiple sclerosis

Answer 38

Delayed VEP

Question 39

What are the reliably reproducible components of a visual evoked potential?

Answer 39

Negative peak 70ms Positive peak 100ms Negative peak at 140ms

Question 40

For which age range is the visual evoked potential timings reliable?

Answer 40

5 to 60

Question 41

What change is associated with visual evoked potentials in individuals over the age of 60?

Answer 41

P100 slows with ageing at a rate of approx 1ms per decade

Question 42

What changes in visual evoked potentials are associated with later stages of multiple sclerosis?

Answer 42

Progressively slower VEPs

Question 43

What causes alterations in visual evoked potentials in multiple sclerosis?

Answer 43

Progressive demyelination

Question 44

What are brainstem auditory evoked potentials used to assess for in clinic?

Answer 44

Assess severity of hearing loss Identify and diagnose hearing impairment in young children Assess brainstem function

Question 45

What does each peak of the auditory evoked potential correlate to?

Answer 45

Activity at a different part of the auditory processing pathway

Question 46

What does wave I of the auditory evoked potential correlate to?

Answer 46

Action potential of vestibulocochlear nerve

Question 47

What does wave II of the auditory evoked potential correlate to?

Answer 47

Cochlear nucleus and vestibulocochlear nerve

Question 48

What does wave III of the auditory evoked potential correlate to?

Answer 48

Ipsilateral activation of the superior olivary nucleus

Question 49

What does wave IV of the auditory evoked potential correlate to?

Answer 49

Nucleus or axons of the lateral lemniscus

Question 50

What does wave V of the auditory evoked potential correlate to?

Answer 50

Inferior colliculus

Question 51

What does wave VI of the auditory evoked potential correlate to?

Answer 51

Medial geniculate nucleus of the thalamus

Question 52

What nerve is stimulated to induce somatosensory evoked potentials?

Answer 52

Cutaneous nerve, usually in the wrist

Question 53

What are somatosensory evoked potentials used in clinic?

Answer 53

Diagnose/assess multiple sclerosis and other demyelinating diseases Assess spinal function in spinal conditions or during surgery

Question 54

What is the definition of epilepsy?

Answer 54

Sudden change in behaviour that is caused by electrical hypersynchronisation of cortical neuronal networks

Question 55

What percentage of the population will experience a single, isolated seizure?

Answer 55

10%

Question 56

What percentage of the population experiences recurrent epileptic seizures?

Answer 56

0.5 to 1%

Question 57

What are potential causes of non-epileptic seizures?

Answer 57

Electrolyte imbalances Hyper/hypoglycaemia Drug/alcohol withdrawal Acute brain injury

Question 58

What is a 'partial' epileptic seizure called and where do they originate?

Answer 58

Focal epilepsy Originate in a region of abnormal brain tissue that becomes a focal point for the seizure. Some areas of the brain will have normal wave patterns

Question 59

What is a generalised epileptic seizure?

Answer 59

Involves both hemispheres of the brain

Question 60

What is electrocorticography?

Answer 60

Electrophysiological measurement method that places electrodes directly on the brain

Question 61

What are the advantages of electrocorticography over EEG?

Answer 61

Improve spatial resolution and avoids filtering of signal through the skull

Question 62

What are the disadvantages of electrocorticography over EEG?

Answer 62

Invasive - requires craniotomy

Question 63

How are intracortical local field potentials recorded?

Answer 63

Electrodes are inserted directly into brain

Question 64

What is intractable epilepsy?

Answer 64

Drug resistant therapy

Question 65

How do implanted electrodes aid surgical treatment of intractable epilepsy?

Answer 65

Electrodes are inserted into the brain for presurgical evaluation to determine the location of the seizure origin accurately