Corticothalamic feedback can induce hypersynchronous low-frequency rhythms in the physiologically intact thalamus.
Damien Debay, Alain Destexhe and Thierry Bal Neurocomputing 38: 529-538, 2001.

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Thalamic circuits are capable of generating oscillations of different frequency and level of synchrony. However, it is not known how these oscillation types are controlled in the intact brain. Here we consider the influence of corticothalamic feedback onto the thalamus by using thalamic slices and computational models. Models predicted that strong activation of corticothalamic feedback should transform the normal spindle oscillations (6-10 Hz) into hypersynchronous slow (2-4 Hz) oscillations. By implementing this feedback paradigm in ferret thalamic slices, we could observe this transformation. Thalamic reticular neurons show a dramatic increase of firing, but not interneurons, suggesting that this effect is mediated mostly through the reticular nucleus. We conclude that cortical inputs can induce slow hypersynchronous oscillations in the physiologically intact thalamus, which has clear implications for understanding the genesis of pathologies such as absence seizures, and more generally the downstream control of thalamic nuclei by the cerebral cortex.
See also the following related article:

Bal T, Debay D and Destexhe A. Cortical feedback controls the frequency and synchrony of oscillations in the visual thalamus. Journal of Neuroscience 20: 7478-7488, 2000.