Attenuation of backpropagating action potentials in three types of dentate granule cells

Backpropagating action potentials (bpAPs) are retrograde electrical signals crucial for modulating synaptic plasticity. They play a pivotal role in regulating neuronal computation and memory formation. In dentate gyrus granule cells, which are key neuronal populations responsible for pattern separation and memory storage, bpAPs-mediated signaling is particularly important for integrating synaptic inputs and fine-tuning network activity. However, this neuronal population has marked structural and functional heterogeneity, including regular granule cells (GCs), semilunar granule cells (SGCs), and hilar ectopic granule cells (HEGCs). The influence of the distinct biophysical properties of these GC subtypes on backpropagation dynamics such as attenuation amplitude, velocity, and spatial spread remains unclear. Here, we utilized multi-compartment models of three types of GCs to systematically investigate the backpropagation efficiency across three metrics: attenuation amplitude, attenuation rate, and propagation distance. We found that higher dendritic K ${}^{+}$ channel density drove strong attenuation of bpAPs in SGCs (highest rate, shortest propagation), whereas higher dendritic Na ${}^{+}$ channel density in HEGCs minimized attenuation. Dendritic branching patterns modulated attenuation amplitude secondarily, while passive axial resistance had negligible effects. These findings establish dendritic active properties rather than morphology as the dominant regulator of attenuation intensity and reveal how activity regulation in these neuronal subtypes contributes to pattern separation and memory storage.