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Every night, without protest or panic, we cease to exist as subjects of experience. One moment, we\u2019re here, sensing, and responding. The next, we\u2019re gone. This phenomenon is so familiar that few of us stop to question it, but if you want to understand consciousness, there\u2019s no better place to look than sleep and dreaming.\u00a0<\/p>\n
In 1974, philosopher Thomas Nagel asked, \u201cWhat is it like to be a bat?<\/a>\u201d That question became a landmark in the philosophy of mind, precisely because it defined consciousness by its most essential property: What it is like to be. If experience is present, so is consciousness.<\/p>\n The problem is that this formulation is tough to fathom and even harder to operationalize. It\u2019s one thing to say experience lies at the heart of consciousness, but it\u2019s quite another to actually study it. Bats, after all, aren\u2019t answering questionnaires.\u00a0<\/p>\n Consciousness resists external analysis because its nature is interior. We may not know what it\u2019s like to be a bat, but each night, we brush up against the more basic question: What is it like to be anything at all?<\/p>\n While we\u2019re awake, conscious experience is shaped by sensation and action. Streams of sensory input flow in, motor output flows out, and this ongoing exchange with the environment anchors our subjective experience. But when we fall asleep, that architecture dissolves and rearranges itself.\u00a0<\/p>\n The stages of sleep are divided into two broad arenas: non-REM and REM. Neuroscientists can track these states and their distinct neural signatures using an electroencephalogram ( EEG), which records the collective electrical activity of cortical neurons. In deeper stages of non-REM sleep, these neurons fall into a slow, rhythmic oscillation of activity punctuated by stretches of silence. To be inside one of those slow waves, subjectively speaking, is to be nowhere at all. Studies using high-density EEG <\/a>have shown that when posterior cortical regions are dominated by slow-wave activity, conscious experience is typically absent.\u00a0<\/p>\n We fall into non-REM sleep knowing what it\u2019s like to be \u2014 and then, nothing. A total annihilation of is-ness. <\/p>\n Only in the dream-laden rhythms of REM sleep does consciousness reemerge, and we return with a sense of what it was like for it to vanish.<\/p>\n<\/blockquote>\n Outwardly, REM sleep looks like rest. The brainstem\u2019s motor command centers actively inhibit the muscles, rendering them temporarily paralyzed, and responsiveness to the external world falls away. But inside the brain, the lights blaze. Fast, desynchronized firing<\/a> remerges in the posterior cortex, with activity levels in sensory and emotional circuits that match \u2014 and in some regions exceed \u2014 those seen during the day. Our eyes are closed, and yet the visual cortex shows similar activation patterns as it does when processing a real scene.\u00a0<\/p>\n What emerges are dreams \u2014 internally generated episodes of consciousness, constructed in a perceptual vacuum. The other missing component is metacognition \u2014 the awareness of awareness \u2014 and a sense of agency. In REM, we are conscious without question. Fully immersed, yet without the capacity to watch ourselves from outside the moment. Most dreamers don\u2019t know they\u2019re dreaming; they simply exist within the experience. Dreaming is being without knowing that you are.<\/p>\n Lucid dreaming provides a counterexample. In rare cases, sleepers gain insight into the unreality of their dreams from within the dream itself. In sleep labs, researchers train dreamers to signal lucidity through deliberate eye movements, which can be time-stamped using electrooculography (EOG). Functional MRI and EEG data<\/a> show that the shift to lucidity coincides with a partial reactivation of the dorsolateral prefrontal cortex, anterior cingulate cortex, and the precuneus \u2014 regions that support metacognition that are typically offline during REM sleep. When a dream becomes lucid, it\u2019s not the experience that changes but the frame around it. The lights were on the whole time, and now, you know it.\u00a0<\/p>\n Ordinary dreams are, perhaps, the clearest articulation of what it is like to be. Rather than defining subjectivity from the outside, REM sleep allows us to map its loss and return from within<\/a>, revealing its structure through its disassembly. Dreaming becomes a lived rehearsal of Nagel\u2019s challenge: Consciousness is not something we perform nor a behavior we emit. It\u2019s a condition of self-sustaining internal activity, defined by the felt quality of experience.\u00a0<\/p>\n What remains when our conscious experience is stripped of memory, agency, and self-reflection? What\u2019s it like to be a creature without them? We may never know exactly, but we can step outside our dominant perspective to understand what it\u2019s like to be someone \u2014\u00a0 or something \u2014 in the most basic sense. In sleep, we are as close to Nagel\u2019s unreachable batness as we\u2019ll likely ever get.<\/p>\n\n