8- Bioelectrical signals from the central nervous system

Question 1

Cite the four main part of the brain.

Answer 1

1- Brain stem-medula oblongata and pons
2- Thalamus
3- Cerebellum
4-Cerebrum

Question 2

Describe the Brain stem-medula oblongata and pons

Answer 2

Connections from higher areas to the spinal cord and vice versa

Question 3

Describe the thalamus

Answer 3

Essential link and integration center in transfer of sensory information from periphery to cerebral hemispheres

Question 4

Describe the Cerebellum

Answer 4

Fine tuning of mvts, learning motor skils, balance and coordination, eye movements.

Question 5

Describe the Cerebrum

Answer 5

Cerebral cortex, 2-3mm thick

Question 6

Where are located motor areas ?

Answer 6

Parietal and frontal lobes

Question 7

where are located visual areas ?

Answer 7

Ocipital lobe

Question 8

where are located auditory areas ?

Answer 8

Temporal lobe

Question 9

Where are located sensory areas?

Answer 9

Central/parietal lobe

Question 10

When was discovered the EEG ?

Answer 10

In 1919 by Hans berger, published in 1929.

Question 11

What is the idea behing “relative placement” in EEG ?

Answer 11

The distribution of electrodes depends on the surface area of the skull. Electrodes are placed 10-20% steps (% of total longitudinal distance front to back) guided by anatomical landmark.

Question 12

Describe the electrodes used for EEG

Answer 12

Ag/AgCl (silver chloride) discs with long cables, 1 to 3mm of diameter, electrode-skin impedance <10K(omega)

Question 13

Describe the amplification sys used for EEG.

Answer 13

Amplification >10power6.
Signal amplitude resolution approx. 1µV, requires low input noise.
High input impedance
preamplification close to the electrode is preferable but expensive
Filtering to selectively record specific F ranges
Bandwidth ca. 1-100 Hz.

Question 14

What are the two technique for recording EEG ??

Answer 14

Unipolar recording or bipolar recording

Question 15

What is the principle of unipolar recording EEG ? then what is bipolar ?

Answer 15

Unipolar : One recording spot and a ground electrode. You take the opposite hear as reference.
Bipolar : Two contacts close to eachother and we record in between them. We sitll have a ground siting. You always record one electrode versus the other.

Question 16

What is the advantage of bipolar recording for ECG ? what are the cons ?

Answer 16

You really get the difference of potential in the small field.
Cons : the diff of potential at a short distance is smaller.

Question 17

Which caracteristics of the EEF signals can be defined ?

Answer 17

Waveforms

Frequency bands

Question 18

What depends on the spatial resolution of the recording ?

Answer 18

It depends on the electrode location.

Question 19

What can EEG signals (waves) can inform on ?

Answer 19

Different phase of wakefulness (relaxed, wakeful, sleepy, asleep, deep sleep or coma)

Question 20

What changes between different brain waves ?

Answer 20

Amplitude or frequency

Question 21

Can you define EEG along the development of the brain ?

Answer 21

It changes during childhood an generally slow down during adulhood.

Question 22

What are the most prominant EEG features that helps to detect anomalies ?

Answer 22

Excessive amplitude
Spikes
Waves

Question 23

What EEG features can define seizures in epilepsy ?

Answer 23

Waves and spikes

Question 24

What EEG features can define encephalitis ?

Answer 24

Slow waves and abnormal potentials

Question 25

What EEG features can define Tumours ?

Answer 25

Local EEG abnormalities

Question 26

What EEG features can define cerebrovascular disorder ?

Answer 26

Localisation , e.g in stroke.

Question 27

What EEG features can define Head trauma ?

Answer 27

Commotio cerebri Contusio cerebri : slow eeg, reduced intensity compressio cerebri

Question 28

What EEG features can define sleep medication overdose ?

Answer 28

Fast beta waves in early stage then slowing down

Question 29

What EEG features can define coma ?

Answer 29

suppresion -> flat line

Question 30

why is EEG relevant in epilepsy diagnosis ?

Answer 30

Seizure can differ in their location and can spread to different areas. it can therofore help to define the foci.

Question 31

What are the different determining sleep phase ?

Answer 31

Depth of sleep, REM phase Sequence of phases.

Question 32

What is the adtvantage of Brain computer interfaces ?

Answer 32

They extract control signals fron EEG in real time.

Question 33

What features define the different types of BCI ?

Answer 33

The feedback (continuous, discrete, abstract or realistic), the recording modality (eeg, ecog, intrakortical), the brain signal (oscillations, slow cortical potentials and cognitive EPS), the mental strategy (focus attention or motor strategy) and the mode of operation (synchroneous or not)

Question 34

What are evoked potentials ?

Answer 34

Stimulation of a sense causes arousal. They measure an associated electrical potential at the scalps. It tends to be low amplitude, it means it require averaging to resolve aginst backround noise of the brain).

Question 35

What is the general measurement setup for Evoked Potentials ?

Answer 35

Signal generator, measurement and signal processing.

Question 36

What are the diagnotic applications for evoked potentials ?

Answer 36

Visually evoked potentials (VEP) for disease of retina or of the optic nerve. Acoustically evoked potentials (brain deafness, check auditory pathways, tumour or head trauma) somatosensory evoked potentials (SEP) for numbness or decresed sensation in PNS dysfunction or spinal cord injury.

Question 37

How are EPs used in cognitive research ?

Answer 37

eg: presentation of unexpected words results in increased EP amplitude (information theory).