Synaptic excitability changes associated with dendritic atrophy in aged neocortical layer 3 pyramidal neurons: a modeling study

The impact of aging- and neurodegeneration-related atrophy of dendritic arborizations on the synaptic excitability was investigated on models of neocortical layer 3 pyramidal neurons with originally reconstructed and altered dendritic arborizations. The alterations included pruning of dendrites and reducing the dendritic spine density. To test the excitability, we investigated the organization (patterns) and frequency of the action potential firing evoked by tonic activation of excitatory synaptic conductivity homogeneously distributed over the dendritic arborizations. Our computational experiments demonstrated that synaptic excitability depended on the morphological alterations like earlier described intrinsic electrical excitability. Namely, with introducing dendritic atrophy the doublet bursting pattern generated in the intact case changed for continuous spiking with greater rate at greater atrophy, and these changes were also associated with increase in the whole cell input resistance.