Modeling and analysis of extracellular field potentials in the brain
Year: 2010
Type: dissertation
Abstract: In order to model processes occuring in the brain it is necessary to have reliable measures of neural activity, with a clear intepretation rooted in the biophysics of the neural tissue. One of the most important probes of neural activity is the measurement of extracellular field potentials. The potential picked up by an electrode placed inside the brain is typically filtered in to two distinct frequency bands: the high-frequency part (>500 Hz) captures the spiking output of nearby cells (termed multi-unit activity or MUA), while the low-frequency part (<200-500 Hz) called local field potential (LFP) is thought to mainly reflect synaptic input of the cells in a local volume surrounding the electrode. The ability of the LFP to sample activity in whole populations of neurons makes it an important tool for understand neural network dynamics. Despite its wide use, there is however only limited knowledge about the relation between the measured LFP signal and the underlying neural activity.\nThis thesis addresses different aspects of the relation beween activity at the single-cell or population level and the measured extracellular potential. First, we characterize the salient features of extracellular potentials generated by a single synaptic input. We use a forward-modeling approach where we simulate the LFP generated by neurons with realistic morphologies. We describe how dendrites, due to passive cable properties, filter the signal between input current and measured potential, and propose simplified models of LFP generation.\nSecond, we show how distributions of synapses on to single cells give power-law scaling in power spectra of soma currents, soma potentials and current dipole moments.\nThird, we investigate the size of the cortical region that contributes to LFP recordings. By a combination of a simplified model and numerical simulations of populations of neurons, we identify the main factors determining the size of this region. Specifically, we highlight the role of correlations in the underlying synaptic activity.\nFinally, we analyze data from monkey motor cortex and relate oscillations in the LFP to temporally precise synchronized spiking activity. In summary, the findings presented in this thesis provide building blocks for further modeling and interpretation of the LFP, as well as other extracellular potential measures such as the electroencephalogram (EEG).
Source: BIBSYS Brage (BIBSYS (Norway))
Author: Henrik Lindén
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2588698978