w2 neural time series analysis Flashcards
neural time series
recordings of ongoing brain activity
any data that we can represent over time: EEG, fMRI, a spike train (spike is 1, otherwise 0)
has sampling rate
in contrast to CT scan, structural MRI - they take a static image
neural time series: spatial and temporal resolution
amount of potassium and related voltage at rest
voltages of the resting potential
from action potentials to electrical fields in the brain
local field potential
if you measure the input like from the one neuron recording, but from multiple neurons
the way to measure the combined activity of hundreds of neural cells
electrical fields in the brain
all alligned in the same way, all active at the same time - field can be measured on the skull, because they are all just beneath the skull
collective activity of all the dipoles is building up into an electrical current that can activate the electrode
what’s the important information that one could extract from the EEG recordings?
dominant frequencies
particular oscillation, in this case around 11 Hz, is dominant in the signal
how to interpret Hz?
times per second
what does 11 Hz means with relation to seconds?
11 times per second
so every 1/11 = 0.09 second it happens
1 kHz in Hz and in seconds
1000 Hz
something happens 1000 times per second, so every 1/1000 = 0.001 second
benefits of EEG
drawbacks of EEG
EEG studies design for cognitive science
EEG measurement should be complemented with behavioral task (behavioral measurement) that will guide into the interpretation of the results
Examples of behavioral tasks: accuracy rate (how big is the percentage of correct responses), reaction times (the easier something is - the faster somebody can answer to that. We know this from the previous research. And this would help to interpret the EEG measurements).
what are the letters?
they are not the lobes, but the surface distribution
First letter: Anterior frontal, Frontal, Central, Central Parietal, Parietal, Occipital
Second character: z for zero, it’s in the middle, even for the right side, odd for the left side
what measures saccades?
EOGH – electrooculography horizontal
what measures blinks?
EOGV - electrooculography vertical
what does the reference electrode do?
our skin and our bones conduct electricity. We want to deduct this minimum conducted by the skin and by the bones from the brain activity measurements. Reference electrode could be anywhere, but most of the time on mastoids because those have both the skin and the bone. Some people do on the ear lobe, some - on the nose.
source separation
many overlapping sources of EEG signal - how to reconstruct the sources? - you create different conditions, and the only thing that is different - that thing is not the noise for sure
what are the solutions?
