Structural plasticity of dendritic spines: A computational study

Recent evidence indicates that the morphology and density of dendritic spines are regulated during synaptic plasticity. High-frequency stimuli that induce long-term potentiation (LTP) have been associated with increases in the number and size of spines. In contrast, low-frequency stimuli that induce long-term depression (LTD) are associated with decreases in the number and size of spines. Decreases in spine density also occur due to excitotoxicity associated with very high levels of activity such as during seizures.;On the computational side, two new algorithms based on the Chebyshev spectral collocation methods were introduced and the results were compared with the finite difference scheme. It was found that these algorithms were about fifteen times more efficient than the finite difference approach in spite of the fact that spectral collocation requires more steps and more function evaluations.;In this work, continuum models were used to investigate the calcium dependent morphology and density of dendritic spines. The models were based on the standard dimensionless cable equation for the changes in membrane potential in a passive dendrite. Additional equations characterized the change in potential in the spine head, calcium dynamics in the spine head and calcium-dependent changes in spine structure and density along the dendrite. When the level of calcium in the spine head is in the medium range, elongation of existing spine and formation of new spines occurs, while very low or very high calcium concentrations lead to spine shrinkage and pruning. In contrast, a prolonged low-frequency stimulation paradigm that would typically induce LTD results in a decrease in stem resistance (correlated with spine shortening) and an eventual decrease in spine density.