Sleep/wake changes in perturbational complexity in rats and mice.

The level of consciousness can be assessed in humans by measuring the spatiotemporal complexity of cortical responses, quantified by the Perturbational Complexity Index (PCI) and its variant PCIst (state transitions). This study validates PCIst in freely moving rats and mice, showing it is lower during NREM sleep and slow wave anesthesia compared to wakefulness or REM sleep, mirroring human findings. Low PCIst is associated with an OFF period of neuronal silence. Stimulation of deep, but not superficial, cortical layers reliably changes PCIst across sleep/wake and anesthesia. These results support the hypothesis that PCIst is low when an OFF period disrupts causal interactions in cortical networks.

Study at a glance

Abstract

In humans, the level of consciousness is assessed by quantifying the spatiotemporal complexity of cortical responses using Perturbational Complexity Index (PCI) and related PCIst (st, state transitions). Here we validate PCIst in freely moving rats and mice by showing that it is lower in NREM sleep and slow wave anesthesia than in wake or REM sleep, as in humans. We then show that (1) low PCIst is associated with the occurrence of an OFF period of neuronal silence; (2) stimulation of deep, but not superficial, cortical layers leads to reliable PCIst changes across sleep/wake and anesthesia; (3) consistent PCIst changes are independent of which single area is being stimulated or recorded, except for recordings in mouse prefrontal cortex. These experiments show that PCIst can reliably measure vigilance states in unresponsive animals and support the hypothesis that it is low when an OFF period disrupts causal interactions in cortical networks.