Stimulus evoked propagating neuronal activity in silico and in vitro

Previous in vitro studies of propagating neuronal activity have found a layer-specific response to electric field stimulation. In particular layer 5 has been found to be required for activity to spread in partially disinhibited slices. We have investigated the layer-specific response to the stimulation of layer 4 in slices of rat somatosensory cortex made hyper excitable by perfusion with convulsant 4-amino-pyridine. A larger and more prolonged response was found in the deeper layers, in particular in the multi-unit activity. As more detailed anatomic maps of the cortical microcircuit are becoming available, it is possible to investigate the implications that they have on the activity in particular circumstances. Using a detailed map of cell type-specific synaptic connectivity of the rat somatosensory cortex we have generated a three dimensional multi-layered network representative of an in vitro brain slice preparation. Using VERTEX (the Virtual Electrode Recording Tool for EXtracellular potentials) it has been possible to simulate the neuronal dynamics and the resulting local field potential generated by this network after transient stimulation of layer 4 pyramidal cells. This has shown a greater response in the deeper layers as a result of the increased number of connections from layer 4 to layer 5, matching with the experimental results.