Cellular mechanisms of the slow (<1 Hz) oscillation in thalamocortical neurons in vitro

The slow (<1 Hz) rhythm is a defining feature of the electroencephalogram during sleep. Since cortical circuits can generate this rhythm in isolation, it is assumed that the accompanying slow oscillation in thalamocortical (TC) neurons is largely a passive reflection of neocortical activity. Here we show, however, that by activating the metabotropic glutamate receptor (mGluR), mGluR1a, cortical inputs can recruit intricate cellular mechanisms that enable the generation of an intrinsic slow oscillation in TC neurons in vitro with identical properties to those observed in vivo. These mechanisms rely on the window component of the T-type Ca2+ current and a Ca2+-activated, nonselective cation current. These results suggest an active role for the thalamus in shaping the slow (<1 Hz) sleep rhythm.