What can the developing brain do?
The BRAIN magazine

During childhood and into early adulthood, the brain undergoes more changes than any other body part. These changes happen in stages, each profoundly affecting our abilities and behaviour. Most of these developments happen in the first five years of life.
In the womb
The brain starts to develop within four weeks of conception. In the first two trimesters of pregnancy, development is about producing neurons, establishing brain architecture and wiring up the circuitry. Toward the end of gestation, the foetus can hear sounds and feel sensations, which begin to shape the brain.
Birth to age 6
Although all five senses begin to function before birth, the somatosensory cortex, which controls voluntary movements, reasoning and perception, becomes active between two and three months after birth.
Between six months and one year, activity in the frontal lobes triggers the development of emotions, attachments, planning, working memory and attention.
A sense of self develops as the frontal lobe circuits become more integrated at around 18 months. At around age 3-4, important psychological concepts begin to emerge such as the ‘theory of mind’, in which a child begins to understand that other people have their own minds. At this stage, the brain is about 80% of its adult size.
By age five, the brain is 90% of its adult weight. At this age, children start to apply logic to their thought processes.
A child undergoes more than a decade of rapid growth and development, in which every experience contributes to the person they will become.
Teenage years
By the teenage years, the brain is full size but continues to mature its circuitry into early adulthood. Connections continue to be made, pruned, and remade throughout life.
When is a brain conscious?
Before we get to the question of when consciousness may begin, first, we must consider what consciousness is.
"Consciousness appears to develop in sync with rapid eye movement (REM) sleep, during which we have our most vivid dreams"
He says, "this suggests REM sleep is not just about dreaming but is part of becoming conscious: where we consolidate and curate the predictive models we build of the world, like expecting pain from touching a hot stove. These predictive models help us understand how we interact and fit with the world – they are part of the conscious mind."

A coloured Positron Emission Tomography (PET) scan of the human brain during REM sleep. Colour coding depicts active cerebral brain areas (red) through to inactive areas (blue). During the REM sleep phase, the brain is active and dreaming, showing similar activity when awake. In the non-REM phase of sleep, the brain is in a deeper, less active sleep. Image: Hank Morgan/Science Photo Library
A coloured Positron Emission Tomography (PET) scan of the human brain during REM sleep. Colour coding depicts active cerebral brain areas (red) through to inactive areas (blue). During the REM sleep phase, the brain is active and dreaming, showing similar activity when awake. In the non-REM phase of sleep, the brain is in a deeper, less active sleep. Image: Hank Morgan/Science Photo Library
Having discovered that fruit flies might experience something similar to REM sleep, the van Swinderen lab is using this genetic model to better understand the evolution of consciousness in animals with simple brains.
“We know that during development in the womb, babies experience REM sleep,” says Professor van Swinderen. “This may be the origins of the consciousness we experience later in life. Understanding the complex way consciousness evolves may also help us better understand cognitive disorders.”
Sleep through a lifetime
As we age, we sleep less. But that is not all; we also change how we sleep. The largest decrease in sleep duration is due to a reduction of the portion of REM (rapid eye movement) sleep.
In new borns, REM sleep accounts for up to 50% of all sleep. In adults, this drops to only about 10%. The reason for this lies in the function REM sleep serves our brains. During REM sleep, brain activity increases to allow the processing of new information and the reinforcement of memories and learning.
The brains of new borns and young children are exposed to relatively more new information through never-before-seen or experienced things and events, and their brains require more time to process all this.
REM sleep is also when most of our dreaming occurs - considered a manifestation of our subconscious processing lived experiences and events - which explains why babies and children dream more than adults do.

Image: Kelly Sikkema/Unsplash
Photo by Kelly Sikkema on Unsplash

The hours of sleep our brains need changes as we age. Image: Queensland Brain Institute
The hours of sleep our brains need changes as we age. Image: The Queensland Brain Institute