Limits...
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.

Show MeSH

Related in: MedlinePlus

Current source densities (CSD) generated by the LCM.Shown are (A) CSDs for the central elements of each cortical layer, and (B) temporal profile for current source density of the central line of layer IV (see Figure 6). The CSD plots show the difference between CSD at each time point and the mean value in the entire epoch. Time values are in milliseconds after the onset of transient LGN input. A positive CSD value indicates a current source. Results are calculated from the same dataset as Figure 6.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3475685&req=5

pcbi-1002733-g007: Current source densities (CSD) generated by the LCM.Shown are (A) CSDs for the central elements of each cortical layer, and (B) temporal profile for current source density of the central line of layer IV (see Figure 6). The CSD plots show the difference between CSD at each time point and the mean value in the entire epoch. Time values are in milliseconds after the onset of transient LGN input. A positive CSD value indicates a current source. Results are calculated from the same dataset as Figure 6.

Mentions: The laminar distribution of the LFP power spectrum amplitude was examined. Figure 5C shows the laminar distribution of the average of the LFP power distribution in the gamma frequency (30–100 Hz) and sub-gamma frequency (5–20 Hz) ranges for spontaneous activity and general stimulation. Higher frequency powers were observed in layers IV and VI. This is in agreement with experimentally measured laminar LFP amplitude profiles in the primary visual cortex [38]. Since layers IV and VI are the main layers of the visual cortex receiving and sending projections to the LGN, the observed variation in LFP power spectra amplitudes between layers most likely results from these projections. We simulated the propagation of one spike source in the cortex using LCM. In Figure 6 we provide the result when a spike source is placed in the four central elements of layer IV for 20 milliseconds after 60 seconds of spontaneous activity. Following spike onset, a strong potential is observed in the center of all cortical layers except layer I. The potential is decreased in elements surrounding the source, simulating surround inhibition. We display the temporal profiles of current source density along a transverse line through the central point in layer IV and for the central elements of each cortical area in Figure 7.


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

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

Current source densities (CSD) generated by the LCM.Shown are (A) CSDs for the central elements of each cortical layer, and (B) temporal profile for current source density of the central line of layer IV (see Figure 6). The CSD plots show the difference between CSD at each time point and the mean value in the entire epoch. Time values are in milliseconds after the onset of transient LGN input. A positive CSD value indicates a current source. Results are calculated from the same dataset as Figure 6.
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1002733-g007: Current source densities (CSD) generated by the LCM.Shown are (A) CSDs for the central elements of each cortical layer, and (B) temporal profile for current source density of the central line of layer IV (see Figure 6). The CSD plots show the difference between CSD at each time point and the mean value in the entire epoch. Time values are in milliseconds after the onset of transient LGN input. A positive CSD value indicates a current source. Results are calculated from the same dataset as Figure 6.
Mentions: The laminar distribution of the LFP power spectrum amplitude was examined. Figure 5C shows the laminar distribution of the average of the LFP power distribution in the gamma frequency (30–100 Hz) and sub-gamma frequency (5–20 Hz) ranges for spontaneous activity and general stimulation. Higher frequency powers were observed in layers IV and VI. This is in agreement with experimentally measured laminar LFP amplitude profiles in the primary visual cortex [38]. Since layers IV and VI are the main layers of the visual cortex receiving and sending projections to the LGN, the observed variation in LFP power spectra amplitudes between layers most likely results from these projections. We simulated the propagation of one spike source in the cortex using LCM. In Figure 6 we provide the result when a spike source is placed in the four central elements of layer IV for 20 milliseconds after 60 seconds of spontaneous activity. Following spike onset, a strong potential is observed in the center of all cortical layers except layer I. The potential is decreased in elements surrounding the source, simulating surround inhibition. We display the temporal profiles of current source density along a transverse line through the central point in layer IV and for the central elements of each cortical area in Figure 7.

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