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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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The effect of changing synaptic gains on the LFP power spectra.(A) LFP power spectra were obtained using LCM with different combinations of excitatory () and inhibitory () synaptic gains. Black lines show the power spectra of spontaneous LFPs and red lines correspond to the activated LFPs. A more detailed synaptic gain dependent frequency map is provided in Figure S1. (B) The time serials of LFPs obtained in one run with two synaptic gain combinations (i)  V/spike, and (ii)  V/spike, as corresponding to sub-figures (i) and (ii) in (A).
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pcbi-1002733-g003: The effect of changing synaptic gains on the LFP power spectra.(A) LFP power spectra were obtained using LCM with different combinations of excitatory () and inhibitory () synaptic gains. Black lines show the power spectra of spontaneous LFPs and red lines correspond to the activated LFPs. A more detailed synaptic gain dependent frequency map is provided in Figure S1. (B) The time serials of LFPs obtained in one run with two synaptic gain combinations (i) V/spike, and (ii) V/spike, as corresponding to sub-figures (i) and (ii) in (A).

Mentions: Figure 3 shows the power spectra of the LFPs obtained with different synaptic gains. The LCM was able to generate LFPs with different types and envelopes of oscillation, depending on the combination of excitatory and inhibitory synaptic gains used in the simulation. For example, when either excitatory or inhibitory synaptic gain was small, the frequency spectrum of background activity had an inverse-frequency shape. Stimulation resulted in an increase in gamma frequency. In contrast, when the excitatory and inhibitory synaptic gains were both large, particular frequency peaks dominated the LFP power spectra. Thus, variations of synaptic gains had a strong impact on LFP frequencies.


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 synaptic gains on the LFP power spectra.(A) LFP power spectra were obtained using LCM with different combinations of excitatory () and inhibitory () synaptic gains. Black lines show the power spectra of spontaneous LFPs and red lines correspond to the activated LFPs. A more detailed synaptic gain dependent frequency map is provided in Figure S1. (B) The time serials of LFPs obtained in one run with two synaptic gain combinations (i)  V/spike, and (ii)  V/spike, as corresponding to sub-figures (i) and (ii) in (A).
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1002733-g003: The effect of changing synaptic gains on the LFP power spectra.(A) LFP power spectra were obtained using LCM with different combinations of excitatory () and inhibitory () synaptic gains. Black lines show the power spectra of spontaneous LFPs and red lines correspond to the activated LFPs. A more detailed synaptic gain dependent frequency map is provided in Figure S1. (B) The time serials of LFPs obtained in one run with two synaptic gain combinations (i) V/spike, and (ii) V/spike, as corresponding to sub-figures (i) and (ii) in (A).
Mentions: Figure 3 shows the power spectra of the LFPs obtained with different synaptic gains. The LCM was able to generate LFPs with different types and envelopes of oscillation, depending on the combination of excitatory and inhibitory synaptic gains used in the simulation. For example, when either excitatory or inhibitory synaptic gain was small, the frequency spectrum of background activity had an inverse-frequency shape. Stimulation resulted in an increase in gamma frequency. In contrast, when the excitatory and inhibitory synaptic gains were both large, particular frequency peaks dominated the LFP power spectra. Thus, variations of synaptic gains had a strong impact on LFP frequencies.

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