Convergence of cortical DSs produces thalamic hyperpolarization (that is, a DS) by removing depolarizing input from the cortex (that is, disfacilitation, open red arrows; see ). This thalamic hyperpolarization de-inactivates IT and activates Ih, evoking a thalamic spindle that is reinforced by rhythmic feedback inhibition from thalamic reticular neurons (see ). The thalamic spindle, in turn, is focally projected to the cortex (see ), arriving during the cortical down-to-upstate transition (see ). PY, pyramidal; RE, thalamic reticular; TC, thalamocortical.