Fig. 4.

Extracellular APs (spikes) along the apical trunk of an L5 pyramidal neuron. The spikes are shown in a plane through the apical trunk. The perisomatic AP initiation results in negative polarity spikes around the soma, with a peak absolute potential of around 1 mV. The fast capacitive phase increases with distance along the apical trunk until there are positive polarity spikes along the apical trunk around 200–300 μm from the soma. The maximum amplitude for the positive spikes, at points nearly touching the apical trunk, is around 150 μV. The model was tuned to reproduce negative spikes from a single unit recorded at multiple locations (see Fig. 5); the simulated electrode track matching recordings is shown in white.