We recognise that we have no awareness of our own state, emotions and motivations. Even as older children we can speak have very limited insight into our own actions. We who have raised a boy is familiar with the blank look on our teenager’s face when we ask him why he did something particularly rash. A shrug and “I dunno—it seemed like a good idea at the time” is the most we’ll hear.
Although a newborn lacks self-awareness, the baby processes complex visual stimuli and attends to sounds and sights in its world, preferentially looking at faces. The infant’s visual acuity permits it to see only blobs, but the basic cortical circuitry necessary to support simple visual and other conscious percepts is in place. And linguistic capacities in us are shaped by the environment we grow up in. Exposure to maternal speech sounds in the muffled confines of the womb enables the foetus to pick up statistical regularities so that the newborn can distinguish its mother’s voice and even her language from others. A more complex behaviour is imitation: if Dad sticks out his tongue and waggles it, the infant mimics his gesture by combining visual information with proprioceptive feedback from its own movements. It is therefore likely that the baby has some basic level of inflective, present-oriented consciousness.
The Road to our Awareness
But when does the magical journey of consciousness begin? Consciousness requires a sophisticated network of highly interconnected components, nerve cells. Its physical substrate, the cortical complex that provides consciousness with its highly elaborate content, begins to be in place between the 24th and 28th week of gestation. Roughly two months later synchrony of the electroencephalographic (EEG) rhythm across both cortical hemispheres signals the onset of global neuronal integration. Thus, many of the circuit elements necessary for consciousness are in place by the third trimester. By this time, pre-term infants can survive outside the womb under proper medical care. And as it is so much easier to observe and interact with a pre-term baby than with a foetus of the same gestational age in the womb, the foetus is often considered to be like a pre-term baby, like an unborn newborn. But this notion disregards the unique uterine environment: suspended in a warm and dark cave, connected to the placenta that pumps blood, nutrients and hormones into its growing body and brain, the foetus is asleep.
Invasive experiments in rat and lamb pups and observational studies using ultrasound and electrical recordings in humans show that the third-trimester foetus is almost always in one of two sleep states. Called active and quiet sleep, these states can be distinguished using electroencephalography. Their different EEG signatures go hand in hand with distinct behaviours: breathing, swallowing, licking, and moving the eyes but no large-scale body movements in active sleep; no breathing, no eye movements and tonic muscle activity in quiet sleep. These stages correspond to rapid-eye-movement (REM) and slow-wave sleep common to all mammals. In late gestation the foetus is in one of these two sleep states 95 percent of the time, separated by brief transitions.
What is fascinating is the discovery that the foetus is actively sedated by the low oxygen pressure (equivalent to that at the top of Mount Everest), the warm and cushioned uterine environment and a range of inhibitory and sleep-inducing substances produced by the placenta and the foetus itself: adenosine; two steroidal anaesthetics, allopregnanolone and pregnanolone; one potent hormone, prostaglandin D2; and others. The role of the placenta in maintaining sedation is revealed when the umbilical cord is closed off while keeping the foetus adequately supplied with oxygen. The lamb embryo now moves and breathes continuously. From all this evidence, neonatologists conclude that the foetus is asleep while its brain matures.
Dreamless Sleep?
One complication ensues. When people awaken during REM sleep, they often report vivid dreams with extensive narratives. Although consciousness during dreams is not the same as during wakefulness—most noticeably insight and self-reflection are absent—dreams are consciously experienced and felt. So does the foetus dream when in REM sleep? This is
not known. But what would it dream of?
After birth, dream content is informed by recent and more remote memories. Longitudinal studies of dreaming in children suggest that dreaming is a gradual cognitive development that is tightly linked to the capacity to imagine things visually and to visuospatial skills. Thus, preschoolers’ dreams are often static and plain, with no characters that move or act, hardly any feelings and no memories. What would dreaming be like for an organism that spends its time suspended in a sort of isolation tank, with no memories, and no way to imagine anything at all? I wager that the foetus experiences nothing in utero; that it feels the way we do when we are in a deep, dreamless sleep.
The dramatic events attending delivery by natural (vaginal) means cause the brain to abruptly wake up, however. The foetus is forced from its paradisal existence in the protected, aqueous and warm womb into a hostile, aerial and cold world that assaults its senses with utterly foreign sounds, smells and sights, a highly stressful event.
A massive surge of nor-epinephrine—more powerful than during any skydive or exposed climb the foetus may undertake in its adult life—as well as the release from anaesthesia and sedation that occurs when the foetus disconnects from the maternal placenta, arouses the baby so that it can deal with its new circumstances. It draws its first breath, wakes up and begins to experience life.
Our conscious mind — believe it or not — is not in charge of our day-to-day behaviour. That claim may seem counter intuitive and contrary to our experience, but it has been demonstrated in controlled experiments time and again. By the time our conscious mind is aware of any particular decision or action, it has already been made or enacted by some other part of our brain.
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