Abstract
Current sinks and sources spatially separated between the apical and basal dendrites have been believed to be essential in generating local field potentials (LFPs). According to this theory, LFPs would not be large enough to be observed in the regions without laminar structures, such as striatum and thalamus. However, LFPs are experimentally recorded in these regions. We hypothesized that focal excitatory input induces a concentric current sink and source generating LFPs in these regions. In this study, we tested this hypothesis by the numerical simulations of multicompartment neuron models and the analysis of simplified models. Both confirmed that focal excitatory input can generate LFPs on the order of 0.1 mV in a region without laminar structures. The present results suggest that LFPs in subcortical nuclei indicate localized excitatory input.
Highlights
Local field potentials (LFPs) have been reported in the neocortex [1] and in the subcortical structures such as the striatum [2,3,4,5], thalamus [6,7,8,9], and other regions including the basal ganglia [10,11]
The present study examined the hypothesis that, in nuclei without laminar structures, focal excitatory input induces a concentric current sink and source that generate LFPs
Both the simulations with multicompartment models and the analysis of simplified models showed that focal excitatory input into non-laminar nuclei can induce a concentric sink–source structure, which generates LFPs with approximately one-fourth of the amplitude of LFPs observed in the laminar cortex
Summary
Local field potentials (LFPs) have been reported in the neocortex [1] and in the subcortical structures such as the striatum [2,3,4,5], thalamus [6,7,8,9], and other regions including the basal ganglia [10,11]. Stellate neurons in layer IV have been believed to contribute little to cortical LFPs because the sink and source would cancel out due to the randomly radiating dendritic arbors (Fig 1B) [1]. There might be a local imbalance between the sink and source, which could generate electric potentials [1], but it has not been examined whether LFPs generated in this manner are large enough to be observed or negligible. It remains poorly understood how LFPs are generated in these subcortical structures without layers [14,15]
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