This work proposes a mathematical model for the thalamic gateway to the cortex. In this model, the ionic currents considered and the structural details are in accordance with the biomedical experimental data. To validate the model, three series of simulations were performed in different levels of complexity. First, some experiments show that the model captures the electrophysiological properties of a single thalamic cell, that is, the relay and burst modes of operation. Second, a complete neural network representing the thalamic gateway to the cortex is assembled and the influences of the cortical projections over the thalamus are analysed. Some interesting results about how the cortex opens and closes the thalamic gate, and the relation of this control policy with the phenomenon of attention, are shown. Finally, a third set of simulations establishes some mechanisms of interaction between neighboring thalamic regions, especially a form of somatosensory competition. The paper also hints at possible theoretical explanations for clinical facts like counterirritation, acupuncture analgesia and variations in the sensibility of somatosensory perception. The model seems to be an interesting and new way of understanding the thalamocortical interactions.