Bistability breaks-off deterministic responses to intracortical stimulation during non-REM sleep
Pigorini Andrea, Sarasso Simone, Proserpio Paola, Szymansky Caroline, Arnulfo Gabriele, Casarotto Silvia, Fecchio Matteo, Rosanova Mario, Mariotti Maurizio, Lollino Giorgio, Palva Matias, Nobili Lino, Massimini Marcello
Neuroimage May 15, 2015 DOI: 10.1016/j.neuroimage.2015.02.056 (opens in new tab) via Semantic Scholar
Summary
AI-generated from the abstractDuring 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.
Study at a glance
| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 8 |
| Population | Epileptic patients undergoing intra-cerebral stimulations/recordings for clinical evaluation |
| Keywords | Psychology Medicine Computer science |
| Key finding | The intrinsic bistability of cortical neurons during NREM sleep prevents the emergence of stable causal interactions among cortical areas. |
Abstract
During non-rapid eye movement (NREM) sleep (stage N3), when consciousness fades, cortico-cortical interactions are impaired while neurons are still active and reactive. Why is this? We compared cortico-cortical evoked-potentials recorded during wakefulness and NREM by means of time-frequency analysis and phase-locking measures in 8 epileptic patients undergoing intra-cerebral stimulations/recordings for clinical evaluation. We observed that, while during wakefulness electrical stimulation triggers a chain of deterministic phase-locked activations in its cortical targets, during NREM the same input induces a slow wave associated with an OFF-period (suppression of power>20Hz), possibly reflecting a neuronal down-state. Crucially, after the OFF-period, cortical activity resumes to wakefulness-like levels, but the deterministic effects of the initial input are lost, as indicated by a sharp drop of phase-locked activity. These findings suggest that the intrinsic tendency of cortical neurons to fall into a down-state after a transient activation (i.e. bistability) prevents the emergence of stable patterns of causal interactions among cortical areas during NREM. Besides sleep, the same basic neurophysiological dynamics may play a role in pathological conditions in which thalamo-cortical information integration and consciousness are impaired in spite of preserved neuronal activity.