Figure 2. Biophysical LFP computation: features, examples, and interneuron activities. Ai, Schematic shows two raster plot examples for the given inhibitory cell population rasters. Aii, The resulting LFPs at the somatic layer, with positive and negative deflections is shown for the examples, labeled with dark- or light-colored squares. Parameter values are gsb = 1.5, gbs = 5.5 nS for positive and gsb = 0.5, gbs = 0.75 nS for negative deflections. Aiii, The color plot on the right shows the polarity at the somatic layer, SP, electrode 4. Dotted lines delineate four regions labeled as a, b, c, and d. Negative polarity: dark-colored squares, positive polarity: light-colored squares. Aiv, LFP output for all layers are shown for three examples where the polarity is negative, positive and negative at electrode 3 (left to right). Parameter values are (left to right): gsb = 0.5, gbs = 0.75; gsb = 1.5, gbs = 5.5; gsb = 5.75, gbs = 0.75 nS. Inset shows a blow up of LFP output at electrode 13 (SLM) to show positive deflections. Also shown is the intracellular somatic potential of the PYR cell. No basal excitation is present, csb = 0.21. Bi, Schematic includes one raster plot example. Bii, The resulting LFP output at SP has five peaks. A maximum of 29 peaks is possible (see text). Parameter values are gsb = 2, gbs = 0.75 nS. Biii, The color plot shows the number of peaks that appear in the 5-s LFP computation at SP, electrode 4. Dotted lines delineate the same regions as in A. Biv, An example of LFP output for all layers as well as the intracellular somatic output which also shows a loss of peaks. Parameter values are gsb = 2.25, gbs = 5.0 nS. No basal excitation is present, csb = 0.21. C, Interneuron activity for each interneuron population, normalized such that the number of spikes for a given pair of synaptic conductances is divided by the maximal number considering all pairs of synaptic conductances. Maximal number (5-s trace): 16 327 (BC/AACs), 6 808 (OLM cells), 4 589 (BiCs).