EEG and EMG

Question 1

What does EEG record

Answer 1

Electrical activity in the outer regions of the brain, primarily cortex
Records mass acuity of 1000s-millions of neurones firing

Question 2

What is the mass discharge recorded by EEG

Question 3

EEG Used to examine

Answer 3

Coma, brain defects, brain death, epilepsy

Question 4

EEG Method

Answer 4

Electrodes placed at anatomically defined points
19 recordings, 1 reference

Question 5

What is each electrode connected to

Answer 5

Input amplifier (1000-100,000 times)

Question 6

What does EEG signal represent

Answer 6

Difference between voltages at 2 electrode sites

Question 7

Bipolar montage

Answer 7

Each channel represents difference between 2 adjacent electrodfe

Question 8

What is a montage

Answer 8

Can record eeg between different electrode combinations = montage

Question 9

What is used as a common reference

Answer 9

Average signal

Question 10

Normal activity is described in terms of:

Answer 10

Rhythmic activity and transients

Question 11

Rhythm is activity is divided into…

Answer 11

Frequency bands

Question 12

Describe delta waves

Answer 12

0-4Hz
Highest amplitude, slowest waves
Seen in slow wave sleep

Question 13

Describe theta waves

Answer 13

4-7Hz
Young children
Drowsiness and arousal in adults
Meditation

Question 14

Describe alpha waves

Answer 14

8-12Hz
Seen on closing eyes and relaxation
Disappears on opening eyes and mental maths

Question 15

Describe beta waves

Answer 15

12-30Hz
Disappear with motor movement

Question 16

Describe beta waves

Answer 16

12-30Hz
Disappear with motor movement
Associated with busy or anxious thinking

Question 17

Describe new-born waves

Answer 17

Mainly irregular theta and delta waves
Lacks rhythmic activity

Question 18

What is wakefulness characterised by

Answer 18

Alpha waves

Question 19

Drowsiness is characterised by:

Answer 19

Increased amplitude, slower alpha waves
Reduced HR and muscle artefact

Question 20

EEG and stage 1 sleep characterised by

Answer 20

Alpha waves suppressed, beta waves increase, some theta waves

Question 21

Stage 2 sleep:

Answer 21

Background beta and theta activity with some delta
Sleep spindles (sigma) 12-14Hz
Also K complexes - sharp wave followed by delta and spindle

Question 22

Stage 3 sleep:

Answer 22

Large amplitude delta waves <1Hz
Sleep spindles and K complexes remain

Question 23

Stage 4 sleep:

Answer 23

More prominent delta waves
Some K complexes

Question 24

Hyperventilation and EEG

Answer 24

Hypocapnia, decr BP, cerebral vasoconstriction
Increased theta waves

Question 25

Intermittent photic stimulation and EEG

Answer 25

Light lashes at 4-20Hz Cause visual evoked potentials Can be used to: identify sites of lesions and provoke epileptic activity

Question 26

Characteristic of epileptic EEG

Answer 26

Spike and wave activity Localised in focal Seen in every electrode in general focal can spread giving secondary generalised activity

Question 27

What does EMG record

Answer 27

Electrical activity from skeletal muscles

Question 28

What type of electrodes are used on EMG

Answer 28

Surface electrodes Intramuscular needle electrodes

Question 29

What is EMG used to distinguish

Answer 29

Neurogenic and myopathies causes of motor unit dysfunction

Question 30

What do nerve conduction studies involve

Answer 30

Stimulating nerve from 2 sides eg near elbow and at wrist

Question 31

EMG procedure

Answer 31

Fine needle inserted intramuscularly Potentials from fibres in vicinity of tip recorded Compound action potentials from fibres in the same motor unit recorded Upon insertion brief discharge normally subsides after a few sewconds

Question 32

EMG activity is examined for what

Answer 32

Activity at rest Number of motor units under voluntary control Duration and amplitude of AP in each motor unit

Question 33

What happens in weak voluntary contraction

Answer 33

Series of motor unit potentials recorded as different motor units are recruited

Question 34

What happens in maximal contraction

Answer 34

Potentials overlap, impossible to identify single potentials

Question 35

What is amplitude determined by

Answer 35

The number of fibres within the motor unit

Question 36

Characteristics of myopathic disease

Answer 36

Number of muscle fibres in each unit reduced as fibre atrophy and die