title: An analysis of the transitions between down and up states of the cortical slow oscillation under urethane anaesthesia.
abstract: We study the dynamics of the transition between the low- and high-firing states of the cortical slow oscillation by using intracellular recordings of the membrane potential from cortical neurons of rats. We investigate the evidence for a bistability in assemblies of cortical neurons playing a major role in the maintenance of this oscillation. We show that the trajectory of a typical transition takes an approximately exponential form, equivalent to the response of a resistor-capacitor circuit to a step-change in input. The time constant for the transition is negatively correlated with the membrane potential of the low-firing state, and values are broadly equivalent to neural time constants measured elsewhere. Overall, the results do not strongly support the hypothesis of a bistability in cortical neurons; rather, they suggest the cortical manifestation of the oscillation is a result of a step-change in input to the cortical neurons. Since there is evidence from previous work that a phase transition exists, we speculate that the step-change may be a result of a bistability within other brain areas, such as the thalamus, or a bistability among only a small subset of cortical neurons, or as a result of more complicated brain dynamics.
authors: Marcus T
authors: MT
authors: Wilson
authors: Melissa
authors: M
authors: Barry
authors: John N J
authors: JN
authors: Reynolds
authors: William P
authors: WP
authors: Crump
authors: D Alistair
authors: DA
authors: Steyn-Ross
authors: Moira L
authors: ML
authors: Steyn-Ross
authors: James W
authors: JW
authors: Sleigh