In general, adding return currents (via the inclusion of passive morphologies) and, in a subsequent step, increasing membrane leakiness (via the inclusion of active membrane conductances) leads to attenuation of the LFP amplitude and spatiotemporal width. Given the linearity Metabolism inhibitor of the extracellular resistive
milieu (Anastassiou et al., 2011 and Logothetis et al., 2007 but also see Bédard et al., 2004), the LFP plotted in Figures 2E–2G is the sum of extracellular contributions from synapses and neurons distributed across two layers. In Figure 3, we segregate the LFP contribution of each neural type (top
to bottom: L4 pyramids, L5 pyramids, L4/5 basket cells) for the case shown in Figure 2G. We observe that the LFP contributors within both layers are currents associated with L4 and L5 pyramids. More specifically, in L4, L4 pyramids contribute 46% ± 18% of the LFP (L5 pyramids contribution: 45% ± 18%), whereas in L5, L5 pyramids contribute 52% ± 20% (L4 pyramids contribution: 39% ± 18%). These results support the view that, under the conditions studied here, the http://www.selleckchem.com/products/ldn193189.html LFP does not reflect only local population processing but also outer-layer activity (Figures 3A and 3B), especially in L4. The LFP in L5 is larger than in L4 due to the large size of L5 pyramidal neurons as well as PASK the powerful synaptic drive they receive along their basal (mainly) and apical dendrites (Figure 2G). This elicits membrane currents along the whole depth axis (Figure 3B) so that,
while perisomatic compartments still contribute mostly to the LFP, the apical dendrites of these neurons also contribute to the LFP in L4, especially during the transition from DOWN to UP, i.e., during the highly synchronous barrage of excitation impinging on L5 pyramidal neurons. Comparatively, L4/5 basket cells, making up only 13% of all cells with their temporally narrow EAPs (Figure 1, bottom) (Schomburg et al., 2012) and fairly symmetric and localized dendritic arbors, contribute very little to the LFP in either layers (basket cell contribution is 9% ± 2% in L4 and 9% ± 6% in L5; Figure 3C). The negligible contribution of L4/5 basket cells to the LFP is in stark contrast to their particularly high level of activity (their spiking rate reaches up to 75 Hz during UP, Figure 2D), compared to L4 and L5 pyramidal neurons in our simulations.