Summary Diagram of the Propagation of Spindle Waves
The activation of a single PGN neuron results in the inhibition of a number of thalamocortical cells. Some of these cells generate rebound bursts of action potentials and this activates more PGN neurons. Thus, even with the first loop of activity, the spindle wave propagates to additional cells. With each cycle of activity, the spindle wave propagates to more and more cells resulting in the generation of a propagating "wave" of activity through the geniculate slice. The generation of the refractory period for spindling results in a trailing edge of the "waning" of spindle waves. After 1 to 3 seconds the tissue becomes quiescent, waiting for the generation of another spindle wave.
see Kim, U., Bal, T., and McCormick, D.A. (1995) Spindle waves are propagating synchronized oscillations in the LGNd in vitro. Journal of Neurophysiology, 74, 1301-1323.