Some seizures have particular onset patterns in the EEG. For example, some seizures start with a EEG amplitude decrement and fast oscillations that slow into the dominant seizure rhythm. The ones we study here start slow with big, early discharges.
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There are a bunch of studies in brain slices (picture from Trevelyan et al. 2007) showing that some of these early discharges are inhibitory.pic.twitter.com/LH5iC4tMzN
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This has important implications for interpreting EEG for clinical purposes, as early discharges are often used to understand where the seizure is coming from. However inhibitory discharges are more of a response to a seizure elsewhere, rather than under the observed electrode.
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In this preprint, we used microeletrode array and ECoG recordings of human seizures to contextualize the clinically used LFP with action potential recordings. Can we see differences that would imply early inhibitory discharges?pic.twitter.com/70lwAPkozK
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First, early discharges are more broadly spatially distributed on ECoG, even more widespread than the later discharges that are associated with intense action potential firing, and phase-locked high frequency LFP that indicates seizing brain tissue.pic.twitter.com/EBYTLzHHxU
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Note the clear narrowband gamma peak in the above spectrogram, and the increased broadband high frequency LFP after about 40 seconds. The narrowband gamma doesn't distinguish seizing brain tissue, but the broadening of the spectrum in later discharges does.pic.twitter.com/WQ4VjEySdC
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We show this spectral broadening associated with seizing brain tissue can be clearly observed in the spectrum, or measured for each discharge in a seizure using information theoretic quantities.pic.twitter.com/EdPmeOmfmT
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Finally, back to that narrowband gamma, we show that action potentials measured on the microelectrode arrays differentially couple to narrowband gamma before and after the neuronal signature of recruitment into a seizure.pic.twitter.com/rgTOwKtloB
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These analyses were inspired by work from
@LMPrida's lab and further confirm that broadening of the high frequency LFP spectrum is associated with increased population neuronal firing under an electrode, even if that electrode may not be able to record action potentials.Prikaži ovu nit -
These results further emphasize the importance of examining the high frequency LFP spectrum to contextualize seizure recordings in epilepsy research and point to broadband high frequency LFP's utility for understanding seizure mechanisms in the clinical setting.
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