During slow wave sleep, cortical neurons jump between an Up, depolarized membrane potential and a Down, hyperpolarized membrane potential
Figure 5. Intracellular recording from a cortical neuron in vivo during slow wave sleep and waking. Note the jumps in membrane potential of approximately 10-15 mV in amplitude, between the hyperpolarized Down state and the depolarized Up state. During waking, the distribution of membrane potential covers approximately 15 mV (lower right).