The Laminar Cortex Model: A New Continuum Cortex Model Incorporating Laminar Architecture

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.

MRI signal phase oscillates with neuronal activity in cerebral cortex: Implications for neuronal current imaging

“…We used the LCM (Du et al, 2012) to simulate neuronal activity of a grid of cortical columns. For a detailed description of the LCM the reader is referred to our previous work (Du et al, 2012), however we provide a general outline of the method here.…”

“…For a detailed description of the LCM the reader is referred to our previous work (Du et al, 2012), however we provide a general outline of the method here. The LCM treats the same type of neurons within a column as a group, which acts as a single entity in a network of neurons.…”

“…The LCM treats the same type of neurons within a column as a group, which acts as a single entity in a network of neurons. The neuron groups have similar features to single neurons, but their dynamics and connections are averaged using the mean-field approximation (see Du et al, 2012;Wright, 2009). A synaptic connection map is used to control neuron group connections (Binzegger et al, 2004).…”

“…where ( ) q Q x is the spike generation function (see Du et al, 2012 for details), q V is the neuron membrane potential of the group of neurons, and t D is the time step, which was set to one millisecond. Each neuron was able to receive synaptic input from multiple presynaptic neuron groups.…”

“…In the present work, we predicted the nc-MRI signal using the laminar cortex model (Du et al, 2012), a three-dimensional cortical network model incorporating realistic cortical architecture. We also simulated temporal variations in neuronal activity associated with realistic cortical architecture and neuronal morphology.…”