The term high-conductance state describes a particular state of neurons in specific states of the brain, such as for example during wakefulness, attentive states, or even during some anesthetized states. In individual neurons, the high-conductance state is formally defined by the fact that the total synaptic conductance received by the neuron is larger than its natural resting (or leak) conductance, so in a sense the neuron is "driven" by its inputs rather than being dominated by its intrinsic activity. High-conductance states have been well characterized experimentally, but they also have motivated numerous theoretical studies, in particular in relation to the considerable amount of "noise" present in such states. It is believed that this "synaptic noise" has determinant properties on neu