Anesthesiology
February 7, 2012
Robert D. Sanders, Giulio Tononi, Steven Laureys et al.
478 citations
Consciousness—subjective experience—persists during sleep and anesthesia, as evidenced by dreaming. A defining feature of dreaming is disconnection from the environment. Anesthesia aims to prevent the experience of surgery (connected consciousness) by inducing either unconsciousness or disconnection. The isolated forearm technique reveals that consciousness, connectedness, and responsiveness can uncouple during anesthesia; under clinical conditions, a median 37% of patients demonstrate connected consciousness. Potential neurobiological constructs explain this: during light anesthesia, subcortical mechanisms for spontaneous behavioral responsiveness are disabled, but information integration within the corticothalamic network continues producing consciousness, while unperturbed norepinephrinergic signaling maintains connectedness. These concepts emphasize the need for anesthetic regimens and depth-of-anesthesia monitors targeting mechanisms of consciousness, connectedness, and responsiveness.
Scientific Reports
November 5, 2018
Matthieu Darracq, Chadd M. Funk, Daniel Polyakov et al.
49 citations
Sleep and anesthesia alter conscious experience, which can be absent (unconsciousness) or take the form of dreaming where sensory stimuli are not incorporated (disconnected consciousness). Using transcranial magnetic stimulation-electroencephalography over parietal regions, evoked alpha power (8-12 Hz) decreased during disconnected consciousness in rapid eye movement sleep and ketamine anesthesia compared to wakefulness. In unconscious states of propofol anesthesia and non-rapid eye movement sleep, evoked low-gamma power (30-40 Hz) decreased compared to wakefulness or disconnected consciousness. These findings, confirmed with dream reports from serial awakenings, suggest suppression of evoked alpha activity may mark sensory disconnection.
Frontiers in Neuroscience
February 13, 2024
Benedetta Cecconi, Javier Montupil, Sepehr Mortaheb et al.
6 citations
Disconnected consciousness, where subjective experience persists but is cut off from the external world, often occurs during sleep or sedation but is difficult to study because unresponsive people may still be conscious and amnesia can erase memories of events. This research uses a serial awakening paradigm during mild propofol sedation: participants hear sounds and are interviewed while still sedated to determine whether they are connected or disconnected from the environment, bypassing the need for behavioral responses and amnesia. Functional MRI data reveal neural activity patterns during these states, testing whether sensory disconnection arises at the thalamus or from disrupted information flow to higher brain regions. Slow-wave activity's role is also explored via high-frequency BOLD oscillations. Findings could improve anesthesia monitoring and assessment of patients with reduced consciousness.