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. >. 20. Hz), 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.
|Titolo:||Bistability breaks-off deterministic responses to intracortical stimulation during non-REM sleep|
|Parole Chiave:||Causality; Consciousness; Down-state; Intracranial; Phase-locking|
|Settore Scientifico Disciplinare:||Settore BIO/09 - Fisiologia|
|Progetto:||Computations and Organization of Retes Through the Interaction of\nComputational, Optical and Neurophysiological Investigations of the Cerebral cortex|
|Data di pubblicazione:||15-mag-2015|
|Digital Object Identifier (DOI):||10.1016/j.neuroimage.2015.02.056|
|Appare nelle tipologie:||01 - Articolo su periodico|