Cortical and thalamic components of augmenting responses: A modeling study

Abstract

Augmenting responses in neocortical pyramidal cells can be elicited by cortical or thalamic repetitive stimulation around 10 Hz. A realistic model of a cortical pyramidal (PY) cell and an interneuron (IN) was developed to explore possible intracortical mechanisms. The interaction between strong feedforward hyperpolarizing inhibition, deinactivation of a low-threshold Ca 2+ current and depression of fast inhibitory currents in the PY cell resulted in only weakly augmented responses. The incremental nature and frequency dependence of intracortical augmenting responses was reproduced in the model pair of cortical cells that included short-term plasticity of inhibitory, lateral and thalamocortical synapses. Hyperpolarization-activated currents were not needed in the model to obtain these effects. Thalamic stimulation in a simplified thalamocortical model with short-term plasticity of cortical connections resulted in a small additional cortical augmentation of the already augmented thalamocortical inputs.