Lecture 2: EEG

Question 1

The cortex

Answer 1

• Major part of the brain
• Convolutions are the gyri and separations are the sulci.
• involved in higher brain functioning.
• divided into two hemispheres

Question 2

4 different lobes

Answer 2

1. occipital - involved in visual processing
2. temporal - involved in higher meanings
3. parietal - involved in spatial information processing
4. frontal lobe - involved in conscious thoughts and decisions

Question 3

cerebellum

Answer 3

• involved in the maintenance of balance and posture, coordination of voluntary movements, motor learning.

Question 4

brain stem

Answer 4

involved in the automatic body processes

Question 5

limbic system

Answer 5

involved in emotion, flight-or-fight

Question 6

Action potentials

Answer 6

• Message sparks with electrical signal, this moves down the neuron – called the action potential.
• When it reaches the end of the neuron, in order to reach the other neuron, this action potential is then transformed into a chemical signal called a neurotransmitter.
• The neurotransmitter is transferred from one neuron to the next through the synapse.
• When it reaches the next neuron, a new electrical signal called the post-synaptic potential is created.
• These signals could be excitatory or inhibitory.

Question 7

Pyramidal neurons

Answer 7

• triangular shape
• found in all the lobes
• EEG records these as they have constant shape and are perpendicular to the cortex.

Question 8

EEG

Answer 8

Records electrical activity from pyramidal neurons on the surface.

Question 9

Amplifier

Answer 9

Amplifier needed as signal is very weak.

Question 10

Richard Caton - 1875

Answer 10

First recording of electrical activity in animals
- found electrical activity varies with different mental states

Question 11

Adolf Beck - 1890

Answer 11

• found electrical activity varies with external stimuli

Question 12

Hans Berger - 1924

Answer 12

First human EEG recording
- electrical activity varies according to functional status of brain

Question 13

1936

Answer 13

First EEG laboratory opened

Question 14

EEG pros

Answer 14

• Relatively cheap, compared to fMRI for example – thousands not millions.
• Portable; consists of amplifier and electrodes.
• Excellent time resolution can record every millisecond as it happens.

Question 15

EEG cons

Answer 15

• Poor spatial resolution - Use EEG to find out when something happens in the brain, not where.

Question 16

MEG pros

Answer 16

• Records the magnetic fields generated by neural activity
• Excellent time resolution
• Captures deeper neural activity

Question 17

MEG cons

Answer 17

• Large, stationary, expensive
• Requires heavy maintenance, training etc.

Question 18

PET pros

Answer 18

• Monitors metabolic activity of neurons during cognitive tasks.
• Robust towards motion artefacts.

Question 19

PET cons

Answer 19

• Invasive – inject drug into participants.
• Poor time resolution – don’t use it to know when something happens, use it more to discover where something happens in the brain.
• Large, stationary, expensive

Question 20

fMRI pros

Answer 20

• Measures changes in blood flow associated with changes in neural activity.
• Excellent spatial resolution.
• Not invasive – don’t have to inject anything.
• This is the best research method to find out where something happens.

Question 21

fMRI cons

Answer 21

• Poor time resolution
• Large, stationary, expensive

Question 22

oscillations

Answer 22

repetitive patterns of neural activity. We see these when the neurons are in synchrony.

Question 23

Delta

Answer 23

• (1-4 Hz)
• Slow and of high amplitude.
• Known as Slow Wave Sleep (SWS): generated during meditation and deep sleep.
• Memory consolidation, healing, and regeneration are stimulated during Delta rhythm.

Question 24

Theta

Answer 24

• (4-8 Hz)
• Generated during meditation and light sleep
• Dreaming state, beyond normal conscious awareness

Question 25

Alpha

Answer 25

* (8-12 Hz) * Resting state – relaxed or when we close our eyes. * Helps mental coordination, calmness, alertness, mind/body integration, and learning * Appears when eyes close

Question 26

Beta

Answer 26

* (12-25 Hz) * Normal waking state, awake and engaging in activity. * Appears when we are alert, attentive, engaged in problem solving and decision making, focused

Question 27

Gamma

Answer 27

* ( > 25 Hz) * Role currently unknown * Hypotheses: - Expended consciousness and spiritual emergence - Integration of various sensory impressions of an object to form a coherent form. - By-product of other neural processes (eye-movements, micro-saccades).

Question 28

What is EEG used for?

Answer 28

- Healthcare - Behavioural research - Other applications

Question 29

wet electrodes

Answer 29

metal disks or pellets that connect with the skin via conductive gel, paste or cream, typically based on saline.

Question 30

dry electrodes

Answer 30

easier to use, put the cap on the head, but it is much less accurate, used less in research.

Question 31

number of electrodes

Answer 31

The choice of the number of electrodes usually depends on the purpose of the recording and, in research, on existing results and findings. * Usually use between 32 and 128. Any more is time consuming as you have to apply the gel to each electrode individually.

Question 32

Letters of electrodes

Answer 32

* Fp = Frontopolar region * F = Frontal lobe * P = Parietal lobe * O = Occipital lobe * T = Temporal lobe * C = Central region * A1 and A2 = reference electrodes

Question 33

Number of electrode

Answer 33

* Odd number = left hemisphere * Even number = right hemisphere. * Z = midline region, so no number.

Question 34

Why are eye electrodes needed?

Answer 34

To remove activity of the eyes during cleaning of the data

Question 35

reference electrodes

Answer 35

we record the brain activity that is not associated with brain functioning, need some neutral activity.

Question 36

Differential amplifier

Answer 36

activity from the brain Input 2: neutral activity (from reference electrodes) we subtract this activity and we get the output.

Question 37

average of mastoids or earlobes - re-referencing

Answer 37

Take references of both mastoids or earlobes and average this. If we take activity from one side of the brain, this might affect the results – as it relates to one side of the brains activity. So, we take two references and take the average.

Question 38

common average reference

Answer 38

don’t bother with reference electrodes, instead take all the averages of the brain and use that as the reference electrode.

Question 39

electrode placement

Answer 39

- measure naison and inion distance, place 10+20% increments - measure pre-auricular points, place 10+20% increments - measure circumference, place 10% - Join these dots and divide into 25%

Question 40

Cz

Answer 40

- Different size of caps - Cz is most important - Take measure of naison and inion, and pre-auricular points - Once found Cz, place rest of cap on