Figure 9.
Findings generalize to both more complex and simplified populations. The PSD modulation, defined as the LFP-PSD from a population with an Ih-like conductance, normalized by the LFP-PSD from the same population with the Ih-like conductance removed. A, B, The synaptic input is distributed at the distal apical dendrite (A), or uniformly on the entire cell (B), and is either uncorrelated (c = 0) or fully correlated (c = 1). Results from four different population types are shown in different colors: (1) black, The quasi-active model used in Figures 4 (column 1), 6, and 7, with 1000 cells; (2) cyan, a population of 1000 cells with a similar quasi-active conductance, but composed of 67 distinct cell morphologies; (3) pink, a population of 1000 reconstructed cortical layer 5 pyramidal cells from the Blue Brain Project (Markram et al., 2015), receiving conductance-based synaptic input with a realistic time course (synaptic time constant, 2 ms; the PSD modulation is calculated from the LFP-PSD of a population with a single Ih conductance, normalized by the LFP-PSD from a passive population; however, using the fully active cell models with all 11 active conductances gave similar results); and (4) orange, a simplified population of 1000 cylindrical cell models (1000 μm long, 2 μm thick) receiving current-based, white-noise synaptic input (i.e., very short synaptic time constant), in this case distributed either to the top half (A) or uniformly along the entire cell (B). The PSD modulation was calculated by the LFP-PSD from a population with a single quasi-active restorative conductance that was fivefold stronger in the top half of the cells, normalized by the LFP-PSD from a population with a uniform passive conductance. For all cases, the LFP-PSD is calculated at a single position in the lower region of the population (corresponding to the somatic region for the pyramidal cells).