Cortical and thalamic components of augmenting responses: A modeling study

Augmenting responses in neocortical pyramidal cells can be elicited by cortical or thalamic repetitive stimulation around 10Hz. 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 Ca2` 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 shortterm plasticity of inhibitory, lateral and thalamocortical synapses. Hyperpolarizationactivated currents were not needed in the model to obtain these e!ects. Thalamic stimulation in a simpli"ed thalamocortical model with short-term plasticity of cortical connections resulted in a small additional cortical augmentation of the already augmented thalamocortical inputs. ( 1999 Elsevier Science B.V. All rights reserved.