Bistability breaks-off deterministic responses to intracortical stimulation during non-REM sleep
Neuroimage May 15, 2015 Pigorini Andrea, Sarasso Simone, Proserpio Paola et al.
During deep NREM sleep (stage N3), when consciousness fades, cortical neurons remain active but their interactions are impaired. By recording cortico-cortical evoked potentials in 8 epileptic patients, the study found that during wakefulness, electrical stimulation triggers deterministic, phase-locked activations across cortical targets. In NREM, the same input induces a slow wave with an OFF-period (suppression of power above 20 Hz), reflecting a neuronal down-state. After the OFF-period, cortical activity resumes to wakefulness-like levels, but the deterministic effects of the initial input are lost, as shown by a sharp drop in phase-locked activity. This suggests that the bistability of cortical neurons—their tendency to fall into a down-state after activation—prevents stable causal interactions between cortical areas during NREM.