How can I run sleep and anesthesia studies with intracranial EEG?

The similarity of sleep and general anesthesia has fascinated scientists for a longtime. At first glance, both states are characterized by similar behavioralcorrelates, namely decreased responsiveness, arousal and movement. Previously,non-invasive scalp electroencephalographic (EEG) recordings demonstratedhighly comparable spectral signatures of both states, such as the ubiquitouspresence of slow waves or delta oscillations. More recently, intracranialrecordings in humans provided a more fine-grained perspective and revealedthat sleep and anesthesia reflect highly distinct entities.Here, we outline how intracranial sleep and anesthesia recordings can beembedded into the clinical routine. We discuss caveats and shortcomings thatneed to be considered, especially in the context of epilepsy as the underlyingneurological disorder. Subsequently, we provide a practical road map to obtainstate-specific neural recordings and discuss technical prerequisites as well asimportant analytical considerations. Finally, we summarize how intracranialrecordings extend our understanding about the mechanism-of-action ofanesthetic drugs at the network level and to which extent these signaturesoverlap with physiologic sleep networks. Collectively, here we review howintracranial recordings in humans can be leveraged to gain important insightsinto sleep physiology and the neural correlates of (un-) consciousness.