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Neurophysiology > EEG > Flashcards

EEG Flashcards

1
Q

What is EEG a measure of?

A

Electrical activity of the brain

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2
Q

Is EEG an indirect or direct measure of activity?

A

Direct

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3
Q

What is EEG used for in clinic?

A

Diagnosis tool for cerebral dysfunction such as epilepsy

Analysing sleep and distinguishing sleep stages

Legal determination of brain death

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4
Q

What exactly does EEG measure?

A

Sum of extracellular potentials from a group of neurons

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5
Q

Which cell type is largely recorded by EEG?

A

Cortical pyramidal cells

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6
Q

How are amplitude fluctuations measured on EEG?

A

uV (microvolts)

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7
Q

What are the advantages of EEG?

A

Good temporal resolution

Direct measure of brain activity

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8
Q

What are the disadvantages of EEG?

A

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

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9
Q

How has the placement of electrodes been standardized?

A

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

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10
Q

Where is the nasion?

A

Between the eyes

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11
Q

Where is the inion?

A

Base of the skull

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12
Q

What is a series of electrode placements referred to as?

A

Montage

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13
Q

What are field potentials on EEG?

A

Extracellular recordings of synchronised activity of a large number of cells

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14
Q

How do field potentials appear on EEG?

A

Single electrical spikes

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15
Q

What does a single electrical spike indicate on EEG?

A

Field potential

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16
Q

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

A

Negative deflection

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17
Q

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

A

Positive deflection

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18
Q

What can cause mixed orientation of dendrites?

A

Folding of cerebral cortex

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19
Q

What does synchrony of neuronal activity cause on EEG?

A

Large amplitude and low frequency waves

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20
Q

What frequency are beta waves?

A

13 - 30 Hz

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21
Q

When are beta waves the dominant wave pattern?

A

Awake and alert, focused on a task

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22
Q

What frequency are alpha waves?

A

8 - 13 Hz

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23
Q

When are alpha waves the dominant wave pattern?

A

Awake and relaxed

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24
Q

What frequency are theta waves?

A

4 - 7 Hz

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25
Q

When are theta waves the dominant wave pattern?

A

During memory encoding and recall

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26
Q

What frequency are delta waves?

A

Below 4 Hz

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27
Q

When are delta waves the dominant wave pattern?

A

During sleep, unconscious

28
Q

What is the dominant brain wave pattern in infants?

A

Delta waves

29
Q

What brain waves are observed in stage 1 NREM sleep?

A

Theta waves

30
Q

What brain waves are observed in stage 2 NREM sleep?

A

Spindles and K complexes

31
Q

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

A

Delta waves

32
Q

What are sensory evoked potentials?

A

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

33
Q

How are sensory evoked potentials extracted from EEG recordings?

A

Signal averaging of recordings over multiple trials

34
Q

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

A

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

35
Q

What are three examples of sensory evoked potentials?

A

Visual evoked

Auditory evoked

Somatosensory evoked

36
Q

How can sensory evoked potentials be used in clinic?

A

Assess neurological function

37
Q

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

A

Multiple sclerosis

38
Q

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

A

Delayed VEP

39
Q

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

A

Negative peak 70ms

Positive peak 100ms

Negative peak at 140ms

40
Q

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

A

5 to 60

41
Q

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

A

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

42
Q

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

A

Progressively slower VEPs

43
Q

What causes alterations in visual evoked potentials in multiple sclerosis?

A

Progressive demyelination

44
Q

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

A

Assess severity of hearing loss

Identify and diagnose hearing impairment in young children

Assess brainstem function

45
Q

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

A

Activity at a different part of the auditory processing pathway

46
Q

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

A

Action potential of vestibulocochlear nerve

47
Q

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

A

Cochlear nucleus and vestibulocochlear nerve

48
Q

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

A

Ipsilateral activation of the superior olivary nucleus

49
Q

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

A

Nucleus or axons of the lateral lemniscus

50
Q

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

A

Inferior colliculus

51
Q

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

A

Medial geniculate nucleus of the thalamus

52
Q

What nerve is stimulated to induce somatosensory evoked potentials?

A

Cutaneous nerve, usually in the wrist

53
Q

What are somatosensory evoked potentials used in clinic?

A

Diagnose/assess multiple sclerosis and other demyelinating diseases

Assess spinal function in spinal conditions or during surgery

54
Q

What is the definition of epilepsy?

A

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

55
Q

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

A

10%

56
Q

What percentage of the population experiences recurrent epileptic seizures?

A

0.5 to 1%

57
Q

What are potential causes of non-epileptic seizures?

A

Electrolyte imbalances

Hyper/hypoglycaemia

Drug/alcohol withdrawal

Acute brain injury

58
Q

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

A

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

59
Q

What is a generalised epileptic seizure?

A

Involves both hemispheres of the brain

60
Q

What is electrocorticography?

A

Electrophysiological measurement method that places electrodes directly on the brain

61
Q

What are the advantages of electrocorticography over EEG?

A

Improve spatial resolution and avoids filtering of signal through the skull

62
Q

What are the disadvantages of electrocorticography over EEG?

A

Invasive - requires craniotomy

63
Q

How are intracortical local field potentials recorded?

A

Electrodes are inserted directly into brain

64
Q

What is intractable epilepsy?

A

Drug resistant therapy

65
Q

How do implanted electrodes aid surgical treatment of intractable epilepsy?

A

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

Neurophysiology (5 decks)

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