Topic 8.11 Flashcards
System of electrode placement for eeg
10/20 % system
What is the nasion?
frontal suture
What is the inion?
occipital protuberance
What does an increased number of electrodes help with?
spatial resolution
4 types of montages EEG
- Sequential
- Referential
- Average reference montage
- Laplacian
alpha wave frequency and amplitude
- 8-13Hz
- 20-200 microV
Beta wave frequency and amplitude
- 14-30 Hz
- < 25 microV
Theta wave frequency
4-7 Hz
Delta wave frequency
0.5 - 4 Hz
Where can alpha waves be mostly found?
occipital lobe
Where can beta waves mostly be found?
temporal and frontal lobe
Gamma wave frequency
30-100 Hz
What are gamma waves for? (2)
- Intense mental activity
- Recollect something from short term memory
When can theta waves show up outside of sleep? (2)
- For children they are present even in awake state
- Disappointment and frustration in adults
When are delta waves present? (2)
- Normal deep sleep rhythm in adults
- Infancy
What is the signal in the EEG?
oscillations of extracellular (field) potentials : alternating EPSP and IPSP
What causes a positive EEG wave?
- Apical IPSP
- Perisomatic EPSP
Mechanism of synchronization of the waves?
thalamocortical synchronization
2 properties of thalamocortical neuron for oscillation?
- recurrent lateral inhibition
- post inhibitory rebound
What is an evoked potential?
Following presentation of a stimulus
What is ERP?
event related potentials : time locked to some “event” (can be different stimuli)
3 examples of evoked potentials
- Auditory evoked potential
- Visual EP
- Somatosensory EP
What is required to detect evoked potentials?
Averaging of multiple EEG
EEG following stimulus = ?
= evoked signal + random noise
Principle of MEG
Change in current flow generates a very low magnetic field, detected using SQUID
What is SQUID?
superconducting quantum interference device : a very sensitive magnetometer
Classification of epileptic seizures
Partial (focal) : simple / complex
Generalized : grand mal / petit mal
Other name for petit mal epilepsy
absence epilepsy
Example of partial simple epilepsy
Jacksonian march
Example of partial complex epilespsy
psychomotor epilepsy
What type of wave can we find in absence epilepsy?
spike and dome (involves thalamocortical activating system)
What entrains the circadian rythm?
light - dark cycle, suprachiasmatic nuclei
Waves in stage 1 and 2 sleep
theta waves
Characteristics of stage 2 sleep
- sleep spindles (higher frequency)
- K complexes
Stage 3 sleep waves
low amplitude delta waves
Stage 4 sleep waves
delta waves
3 characteristics of REM sleep
- EEG is desynchronized
- Muscle tone is lost, but presence of phasic contractions
- Autonomic changes
5 nuclei that are part of the arousal system
- TMN (tuberomammillary nucleus)
- LC (locus ceruleus)
- Raphé
- LDT : laterodorsal tegmental nuclei
- PPT : pedunculopontine tegmental nuclei
What activates LDT and PPT?
Ach
What activates TMN?
histamine
What activates raphé nuclei?
serotonin
What activates LC?
norepinephrine
Which nucleus inhibits the arousal system?
the VLPO (ventrolateral preoptic nucleus)
Which nt activate VLPO?
GABA / GAL (galanin)
Which neurons and molecules stabilize the arousal system?
Hypocretin neurons and orexin
What does orexin deficiency lead to?
Narcolepsy
What is cataplexia?
Sudden loss of muscle tone
