The nervous system is characterized by multiple spatial and time scales. What are they?
spatial scales cover:
neurons
local networks of thousands of neurons
entire brain regions of millions of neurons
neuronal activites run at specific time scales:
spikes
local field potential
EEG recordings
Briefly sketch the action potential curve of a neuron
Resting Potential: (-70mV)
Deploarization: Stimulus -> Na+ channels open -> less negatively charged
Action Potential Peak: (+30mV)
Repolarization: Na+ channels close, K+ channels open -> K+ out -> negative charge in neuron
Sodium-Potassium Pump: restore ion distribution -> 3 Na+ out and 2 K+ in (using ATP)
Hyperpolarization: The K+ channels are slow to close -> excess outflow of K+ -> more negative than the resting potential
Return to Resting Potential: (-70mV)
difference EPSP and IPSP?
PSP —> Post-synaptic-Potential
EPSP = excitatory —> makes it easier for postsynaptic neuron to generate action potential (AP)
produces an extracellular negativity at apical dendrites
IPSP = inhibitory —> makes it harder to generate AP
produces extracellular positivity near the soma
can an EEG determine if activity is excititory or inhibitory?
no
How is synchronization and desonchronization of receiving EPSP, visible?
all have same firing rate (3Hz)
fired synchronously —> big waves, all EPSPs summed up to produce one EEG wave of 3 Hz
fired desynchronized —> lower amplitude and higher frequency (9 Hz)
What are the three important variables?
amplitude, phase, frequency
Which one is awake and which one asleep?
left: awake —> faster, less spikes
right: asleep
When do we get noise from the muscle and how to get rid of it?
the higher the frequency, the more noise
get rid of it with anaesthisia
Name the 5 different waves, their range of Hz, and list their associated situations.
Situations:
gamma —> problem-solving, learning, cognitive processing
beta —> busy/anxious thinking -> awake / open eyes (ketamine)
alpha —> relaxed —> eyes shut -> sleep spindles
theta —> light sleep -> memory consolidation in hippocampus
delta —> deep sleep -> anesthesia, coma, Alzheimer’s
when does the delta wave occur?
0.5 - 4 Hz
deep (dreamless) sleep —> typical sleep wave
loss of bodily awareness —> typical anesthesia wave, coma, Alzheimer’s
repair
Describe this dolpins’ three different wave situations:
(a) completely awake
(b) left brain awake, right brain sleep
(c) left brain sleep, right brain awake
When does the Theta wave occur?
4 - 8 Hz
Sleepiness and light sleep (EEG)
information integration (MEG)
memory consolidation in hypocampus (mouse runs and remembered where light was)
When does Alpha wave occur?
8 - 13 Hz
physically and mentally relaxed —> eyes closed
attention
visual awareness
sleep spindles —> most important
driven by Thalamus?
where are eyes closed and where open? in which wave state is this?
eyes closed - open - closed
alpha waves (8 - 13 Hz)
When do beta waves occur?
13 - 32 Hz
awake
busy or anxious thinking
motor function
occur with ketamine
What happens in these three states?
glutamate —> excitatory
GABA —> inhibitory
states:
less GABA —> forced synchronization -> epileptic seizure
more GABA, normal glutamate —> forced sleep
more GABA, normal/less glutamate —> anesthesia
Are glutamate and GABA excitatory or inhibitory transmitter?
glutamate = excitatory
GABA = inhibitory
What does LOC stand for?
Loss of consciousness
How to deconstruct EEG in sine / cosine waves?
Fourier-transformation
the slower the signal, the higher the amplitude
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