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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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Power spectra of membrane potentials for SSVEPs generated with the LCM.The figure shows (A) the power spectra of membrane potential in layers I, II/III, IV, V, VI and (B) power spectra of the LFP produced by the LCM under intermittent light stimulation. The black lines show power spectra of spontaneous LFPs, and red lines illustrate stimulated LFP power spectra. In (C) an example of LFPs before and after intermittent light stimulation in a single run is also shown. The following parameters were used: ,  for spontaneous activity.
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pcbi-1002733-g008: Power spectra of membrane potentials for SSVEPs generated with the LCM.The figure shows (A) the power spectra of membrane potential in layers I, II/III, IV, V, VI and (B) power spectra of the LFP produced by the LCM under intermittent light stimulation. The black lines show power spectra of spontaneous LFPs, and red lines illustrate stimulated LFP power spectra. In (C) an example of LFPs before and after intermittent light stimulation in a single run is also shown. The following parameters were used: , for spontaneous activity.

Mentions: The LCM was used to simulate LFPs with 10 Hz intermittent light stimulation represented by a Gaussian distribution of spike rates for neurons projecting from the LGN to the visual cortex. The peak and standard deviation of the Gaussian shape was 30 spikes/second and 6.25 milliseconds, respectively (see Figure 2). Figure 8 shows the variation of LFPs with time and the associated power spectra. Simulations using the LCM reproduced the power spectra reported in experimental data [39]. The LFP power spectrum had peaks at frequencies that were multiples of the stimulus frequency (i.e. capturing multiple harmonics). Notably, the amplitude of fundamental harmonic (i.e. frequency peak at 10 Hz) was smaller in layer II/III than other layers. This is probably because there are fewer projections from LGN to layer II/III than other layers. Experimentally observed sub-harmonics were not obvious in simulations using the LCM [39].


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

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

Power spectra of membrane potentials for SSVEPs generated with the LCM.The figure shows (A) the power spectra of membrane potential in layers I, II/III, IV, V, VI and (B) power spectra of the LFP produced by the LCM under intermittent light stimulation. The black lines show power spectra of spontaneous LFPs, and red lines illustrate stimulated LFP power spectra. In (C) an example of LFPs before and after intermittent light stimulation in a single run is also shown. The following parameters were used: ,  for spontaneous activity.
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1002733-g008: Power spectra of membrane potentials for SSVEPs generated with the LCM.The figure shows (A) the power spectra of membrane potential in layers I, II/III, IV, V, VI and (B) power spectra of the LFP produced by the LCM under intermittent light stimulation. The black lines show power spectra of spontaneous LFPs, and red lines illustrate stimulated LFP power spectra. In (C) an example of LFPs before and after intermittent light stimulation in a single run is also shown. The following parameters were used: , for spontaneous activity.
Mentions: The LCM was used to simulate LFPs with 10 Hz intermittent light stimulation represented by a Gaussian distribution of spike rates for neurons projecting from the LGN to the visual cortex. The peak and standard deviation of the Gaussian shape was 30 spikes/second and 6.25 milliseconds, respectively (see Figure 2). Figure 8 shows the variation of LFPs with time and the associated power spectra. Simulations using the LCM reproduced the power spectra reported in experimental data [39]. The LFP power spectrum had peaks at frequencies that were multiples of the stimulus frequency (i.e. capturing multiple harmonics). Notably, the amplitude of fundamental harmonic (i.e. frequency peak at 10 Hz) was smaller in layer II/III than other layers. This is probably because there are fewer projections from LGN to layer II/III than other layers. Experimentally observed sub-harmonics were not obvious in simulations using the LCM [39].

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