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The laminar cortex model: a new continuum cortex model incorporating laminar architecture.

Du J, Vegh V, Reutens DC - PLoS Comput. Biol. (2012)

Bottom Line: The power spectra of LFPs were calculated and compared with existing empirical data.During simulated intermittent light stimulation, the LCM captured the fundamental as well as high order harmonics as previously reported.The power spectrum expected with a reduction in layer IV neurons, often observed with focal cortical dysplasias associated with epilepsy was also simulated.

View Article: PubMed Central - PubMed

Affiliation: The University of Queensland, Centre for Advanced Imaging, Brisbane, Queensland, Australia.

ABSTRACT
Local field potentials (LFPs) are widely used to study the function of local networks in the brain. They are also closely correlated with the blood-oxygen-level-dependent signal, the predominant contrast mechanism in functional magnetic resonance imaging. We developed a new laminar cortex model (LCM) to simulate the amplitude and frequency of LFPs. Our model combines the laminar architecture of the cerebral cortex and multiple continuum models to simulate the collective activity of cortical neurons. The five cortical layers (layer I, II/III, IV, V, and VI) are simulated as separate continuum models between which there are synaptic connections. The LCM was used to simulate the dynamics of the visual cortex under different conditions of visual stimulation. LFPs are reported for two kinds of visual stimulation: general visual stimulation and intermittent light stimulation. The power spectra of LFPs were calculated and compared with existing empirical data. The LCM was able to produce spontaneous LFPs exhibiting frequency-inverse (1/ƒ) power spectrum behaviour. Laminar profiles of current source density showed similarities to experimental data. General stimulation enhanced the oscillation of LFPs corresponding to gamma frequencies. During simulated intermittent light stimulation, the LCM captured the fundamental as well as high order harmonics as previously reported. The power spectrum expected with a reduction in layer IV neurons, often observed with focal cortical dysplasias associated with epilepsy was also simulated.

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Related in: MedlinePlus

The effect of changing cortical architecture on LFP power spectrum.This figure shows power spectra produced by LCM configured with different synaptic gains, and presynaptic neurons in layer IV decreased by 50%. The red lines and black lines illustrate the power spectra of activated and spontaneous LFPs.
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pcbi-1002733-g004: The effect of changing cortical architecture on LFP power spectrum.This figure shows power spectra produced by LCM configured with different synaptic gains, and presynaptic neurons in layer IV decreased by 50%. The red lines and black lines illustrate the power spectra of activated and spontaneous LFPs.

Mentions: Experimental models of neocortical epileptic foci suggest that reduced synaptic inhibition in layer IV plays an important role in epileptogenesis [34], [35]. Focal cortical dysplasias characterized by an absence or significant reduction in layer IV are also very frequently associated with epilepsy [36]. Figure 4 shows the LFP power spectrum shapes generated by the LCM when the numbers of synapses formed with presynaptic neurons in layer IV are decreased by 50%. Compared to Figure 3A, the power spectra show a small shift to small inhibitory gain. For example, for LFPs produced using excitatory and inhibitory synaptic gains of V/spike, the power spectrum changed from a frequency-inverse shape to one with spectral peaks as would be expected with seizures when presynaptic neurons of layer IV decrease by 50%. This suggests that, changes in neuron or synapse density may change the way LFPs oscillate dramatically. These alterations in dynamics may increase our understanding of how abnormalities in cortical architecture lead to seizures.


The laminar cortex model: a new continuum cortex model incorporating laminar architecture.

Du J, Vegh V, Reutens DC - PLoS Comput. Biol. (2012)

The effect of changing cortical architecture on LFP power spectrum.This figure shows power spectra produced by LCM configured with different synaptic gains, and presynaptic neurons in layer IV decreased by 50%. The red lines and black lines illustrate the power spectra of activated and spontaneous LFPs.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475685&req=5

pcbi-1002733-g004: The effect of changing cortical architecture on LFP power spectrum.This figure shows power spectra produced by LCM configured with different synaptic gains, and presynaptic neurons in layer IV decreased by 50%. The red lines and black lines illustrate the power spectra of activated and spontaneous LFPs.
Mentions: Experimental models of neocortical epileptic foci suggest that reduced synaptic inhibition in layer IV plays an important role in epileptogenesis [34], [35]. Focal cortical dysplasias characterized by an absence or significant reduction in layer IV are also very frequently associated with epilepsy [36]. Figure 4 shows the LFP power spectrum shapes generated by the LCM when the numbers of synapses formed with presynaptic neurons in layer IV are decreased by 50%. Compared to Figure 3A, the power spectra show a small shift to small inhibitory gain. For example, for LFPs produced using excitatory and inhibitory synaptic gains of V/spike, the power spectrum changed from a frequency-inverse shape to one with spectral peaks as would be expected with seizures when presynaptic neurons of layer IV decrease by 50%. This suggests that, changes in neuron or synapse density may change the way LFPs oscillate dramatically. These alterations in dynamics may increase our understanding of how abnormalities in cortical architecture lead to seizures.

Bottom Line: The power spectra of LFPs were calculated and compared with existing empirical data.During simulated intermittent light stimulation, the LCM captured the fundamental as well as high order harmonics as previously reported.The power spectrum expected with a reduction in layer IV neurons, often observed with focal cortical dysplasias associated with epilepsy was also simulated.

View Article: PubMed Central - PubMed

Affiliation: The University of Queensland, Centre for Advanced Imaging, Brisbane, Queensland, Australia.

ABSTRACT
Local field potentials (LFPs) are widely used to study the function of local networks in the brain. They are also closely correlated with the blood-oxygen-level-dependent signal, the predominant contrast mechanism in functional magnetic resonance imaging. We developed a new laminar cortex model (LCM) to simulate the amplitude and frequency of LFPs. Our model combines the laminar architecture of the cerebral cortex and multiple continuum models to simulate the collective activity of cortical neurons. The five cortical layers (layer I, II/III, IV, V, and VI) are simulated as separate continuum models between which there are synaptic connections. The LCM was used to simulate the dynamics of the visual cortex under different conditions of visual stimulation. LFPs are reported for two kinds of visual stimulation: general visual stimulation and intermittent light stimulation. The power spectra of LFPs were calculated and compared with existing empirical data. The LCM was able to produce spontaneous LFPs exhibiting frequency-inverse (1/ƒ) power spectrum behaviour. Laminar profiles of current source density showed similarities to experimental data. General stimulation enhanced the oscillation of LFPs corresponding to gamma frequencies. During simulated intermittent light stimulation, the LCM captured the fundamental as well as high order harmonics as previously reported. The power spectrum expected with a reduction in layer IV neurons, often observed with focal cortical dysplasias associated with epilepsy was also simulated.

Show MeSH
Related in: MedlinePlus