Chapter 7 Synchronized Oscillations in Thalamic Networks : Insights from Modeling Studies

The early work of Morison and Bassett 1945 strongly suggested that the thalamus generates coherent r h ythmicity in the spindle frequency range 7-14 Hz. Since then the cellular correlates of this rhythmicity h a ve been investigated in detail by in vivo and in vitro techniques reviewed in Steriade et al., 1993a, and Steriade et al. in this volume. The interaction between thalamocortical TC and thalamic reticular RE cells is involved in the genesis of this rhythmic activity, but the exact mechanisms are still uncertain and contrasting data remain to be resolved. Andersen and Rutjord 1964 proposed a model of thalamic rhythmicity o ver thirty y ears ago that depended on rebound bursts in thalamic neurons following inhibition. Although the anatomical details of their model need to be revised, and much more in now known about the intrinsic currents of thalamic neurons as well as their synaptic receptors, the primary mechanism for thala-mic rhythmicity in their model is now believed to be substantially correct, based on a wide range of experimental and theoretical studies. Computational models have been used to study the dynam-ical behavior of single thalamic cells, which are suuciently complex that the consequences of their intrinsic ionic mechanisms are often diicult to predict. Based on precise voltage-clamp data for these ionic currents, well-deened computational models have been used to explore the spatial and temporal organization of coherent r h ythmicity in networks of neurons in thalamic nuclei. In this chapter, we review recent computational models for thalamic oscillations that were developed independently by several investigators. These thalamic models are more mature than those developed for other parts the mammalian central nervous system, and are as mature as the best models of invertebrate central pattern generators Selverston, 1985. These advances should lead