Defintion Oscillation
Oscillation refers to the repetitive variation or fluctuation of a system or quantity around a central value or between two or more states, typically in a regular time interval.
What do you know about Hans Berger
German psychiatrist best known for inventing electroencephalography (EEG) and discovering human brain waves
Which event led Hans Berger to his study and what did he believed
He fall from the horse and his sister had a wirde feeling and insisted father too look after him.
He believed that electromagnetic forces generated by the human brain could be the carrier waves of telpathy
How ist the alpha rhythm also called and why is it called alpha
alpha -> first detected rhythm
also called Berger wave
What is an EEG?
What is an EEG signale?
An EEG (electroencephalogram) is a valuable tool in neurology used to assess and diagnose a variety of conditions by measuring brain activity through electrodes placed on the scalp.
a summed potential difference of post synaptic potentials from 10^7-10^10 cortical neurons
Activity from about 6cm2 cortical area per electrode
mostly from synchronized cortical activity
List the spatial and time level architecture from the nervous system and their oscillation
Microscopic scale -> 1 msec -> spikes
Mesoscopic scale -> 10 msec -> high frequency oscillation
Macroscopic scale -> 100 msec -> slow oscillation
action potential
Brief electrical impulse in a neuron caused by rapid ion exchange across the membrane, allowing the nerve to transmit signals
Resting Potential (–70 mV) – Inside of the neuron is negatively charged. – Maintained by the sodium-potassium pump and leaky K⁺ channels.
Depolarization (–55 mV to +30 mV) – A stimulus reaches threshold (≈ –55 mV). – Voltage-gated Na⁺ channels open, Na⁺ rushes in, making the inside more positive. – Membrane potential rapidly rises to around +30 mV.
Repolarization (+30 mV to –70 mV) – Na⁺ channels close, K⁺ channels open. – K⁺ rushes out, restoring the negative charge inside.
Hyperpolarization (below –70 mV) – K⁺ channels stay open slightly too long. – Membrane becomes more negative than resting potential.
Return to Resting State (–70 mV) – K⁺ channels close. – Na⁺/K⁺ pump restores ion balance (3 Na⁺ out, 2 K⁺ in).
What is EPSP and what happens here?
excitatory synapse
positiv energy from out to inside
extracellular energy sinks on the synapse and rise in intracellular recordings
extracellular recordings at soma rises
What is IPSP and what happens here?
Inhibitory Synapse
negative energy from inside to outside
extracellular energy rises on the synapse and sinks in intracellular recordings
extracellular recordings at soma sinks
Why can synchronized neural activity be detected in EEG, but unsynchronized activity often cannot?
Because in unsynchronized activity, the electrical fields of individual neurons have different timings and directions, causing their voltages to cancel each other out. Only large-scale, synchronized postsynaptic potentials generate a summated field strong enough to be detected by EEG.
What is the purpose of the conductive gel in EEG recordings?
The gel reduces the electrical resistance between the scalp and electrodes, improves signal quality by enhancing conductivity, and minimizes noise, enabling accurate detection of the brain’s weak electrical signals.
Q: What does amplitude represent in a brain wave?
A: Amplitude is the height of the wave and reflects the strength or intensity of the signal; higher amplitude means stronger or more synchronized neural activity.
Q: What is the phase of a neural oscillation?
A: Phase describes the position within a wave cycle (e.g., rising, peak, falling) and determines how oscillations align in time across brain regions.
Q: What does frequency indicate in brain activity?
A: Frequency is the number of wave cycles per second (measured in Hertz) and shows how fast neural oscillations occur; different frequency bands are linked to different cognitive states.
What to do if you have no basline and too many drops in a raw microelectrode signal?
Filter with less heart frequency
How do changes in brain size and neural pathways with aging affect EEG signals?
Aging causes brain shrinkage and loss of white matter pathways, leading to fewer active neurons and slower signal transmission; this results in lower EEG amplitude, slower frequencies, and reduced synchrony of brain waves
How do EEG patterns differ between sleep and wakefulness?
During wakefulness, EEG shows alpha (8–12 Hz) waves when relaxed and beta (13–30 Hz) waves when alert; during sleep, slow delta (0.5–4 Hz) and theta (4–8 Hz) waves dominate, especially in deep (NREM) sleep, along with sleep spindles and K-complexes in lighter stages.
Q: What is the gray matter in the brain composed of and what is its main function?
A: Gray matter consists of neuron cell bodies, dendrites, and synapses; it processes and integrates information.
Q: What is the white matter in the brain composed of and what is its main function?
A: White matter is made of myelinated axons; it transmits electrical signals between different brain regions.
What are ripples?
high frequency oscillation around 100-150 Hz
(during NREM sleep)
hippocampus
What are sleep spindles, and when do they occur?
Sleep spindles by 11-16 Hz
short bursts of rhythmic brain activity
originate from thalamocortical circuits and are involved in memory consolidation and sleep stability
Name two Synchronous Rhythm Generator
Pacemaker leads
Arise trough collective behavior
Why are dlophins capable of unihemisperic sleep and what is it and why do they do that
Only one side of the brain can sleep
The two thalsmus in the brain of a dolphin are independent (control signal/information that goes in)
lack automatic breating
Name all 5 oscillation categories that can be measured in the human brain
gamma
beta
alpha
theta
delta
gamma oscillations
32-100 Hz
learning, problem solving
betha oscillations
13 - 32 Hz
excitement
motor function
also detected by Berger
alpha oscillations
8-13 Hz
physically and mentally relaxed
cognitive and memory process
eyes closed
sleep (spindles)
Theta oscillations
4-8 Hz
creativity
Jung und Kornmüller
sleepiness and light sleep
delta oscillations
0.5-4 Hz
deep sleep
detected ny w. grey walter
typical sleep wave
anasthesia wave
What is forces synchronization
It is when an external signal compels neurons or brain regions to align their oscillation phases and frequencies, overriding their natural rhythms.
e.g: sleep, anasthesia, epilectic seizure
What is glutamate
important neurotransmitter
leads to depolarisation/activation
create EPSPs
excitation
What is GABA
Sinks activity
creates IPSPs
What is Joseph Fourier known of?
Decomposition of the EEG into sine and cosine waves in the frequency domain
What EEG changes are seen with propofol administration?
Propofol causes increased frontal alpha and delta waves, progressing to burst suppression at high doses, reflecting deep unconsciousness and reduced brain connectivity.
Propofol, a commonly used intravenous anesthetic
GABAergic Inhibition
What EEG patterns are seen with sevoflurane anesthesia?
Sevoflurane causes frontal alpha and slow-delta activity, progressing to dominant slow waves and possible burst suppression at deep levels, similar to but slower-acting than propofol.
commonly used general anesthetic — especially in children and during inhaled anesthesia
GABAergic inhibition + others
What EEG changes occur with ketamine anesthesia?
Ketamine increases gamma and theta activity, suppresses alpha waves, and produces a desynchronized EEG — reflecting a dissociated but active brain state, unlike the slow waves or burst suppression seen with other anesthetics.
NMDA inhibition
What EEG patterns are seen with dexmedetomidine?
Dexmedetomidine produces strong slow-delta waves and spindle-like activity, mimicking natural non-REM sleep, without burst suppression even at high doses.
a2 Adrenergic-mediated Inhibition
Name a three different wavelets?
db Wavelets
Morlet W
Biorthogonal W
Spline W
Mexican Hat
Haat
Gaussian
Coiflect
What does synchrony mean in EEG, and how does frontal group coherogram reflect changes from wakefulness to sedation and anesthesia?
Synchrony means different brain regions show coordinated, simultaneous activity (similar EEG waveforms at the same time).
A frontal group coherogram measures this synchrony (coherence) between frontal EEG signals across frequencies.
From wake to sedation to anesthesia, synchrony (coherence) increases, especially in slow frequencies (delta, theta, alpha).
Wakefulness shows low/moderate coherence (asynchronous activity), sedation increases alpha/theta coherence, and anesthesia shows very high delta/alpha coherence indicating strong synchronization.
What is the role of the Hilbert transform in analyzing EEG synchrony?
converts a real EEG signal into a complex form, allowing extraction of instantaneous amplitude and phase.
The phase information is crucial for measuring phase synchrony (coherence) between brain regions by examining how stable the phase difference is over time.
What is the key role of information theory in neuroscience? And who invented it?
Information theory quantifies how neurons encode, transmit, and process information by measuring uncertainty (entropy), the shared information between stimuli and responses (mutual information), and the efficiency of neural communication—helping to understand neural coding, decoding, and brain function.
Claude E Shannon
What is Power Spectral Density (PSD) in signal analysis?
PSD shows how the power (energy) of a signal is distributed across different frequencies, helping identify dominant frequency components like brain waves in EEG signals.
How can you describe the relationship between two channels and which ciriteria you need to use it?
coherence
coupling of two power spectra
normalized cross power spectrum
criteria:
Linearity
stationarity
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