Fig. 2: Cortical bistability and its network effects during physiological sleep.
From: Sleep-like cortical dynamics during wakefulness and their network effects following brain injury
The presence of bistability during NREM sleep impacts the ability of cortical circuits to engage in stable, reciprocal interactions and explains the breakdown of effective connectivity and network complexity. A During wakefulness, direct cortical stimulations with TMS trigger a chain of recurrent waves of activity and long-range interactions, resulting in widespread EEG spatiotemporal dynamics (left column). This is quantified by a broadband increase in power at the stimulated site, a long-lasting phase locking, and high values of PCI (right column). B During NREM sleep (and general anesthesia with various anesthetics), such distributed, rich spatiotemporal dynamics is lost (left column), and cortical activations are characterized by a local, slow response associated with a significant suppression of high-frequency power >20 Hz (matching the EEG criteria for a full-blown OFF-period), a short-lived phase locking, and low values of PCI (right column). For both panels, EEG activity is presented from six representative electrodes (yellow disks) uniformly distributed along the antero-posterior axis of the two hemispheres. For both panels, the red trace highlights the EEG recorded from the channel closest to the TMS coil.
