Which part of the brain grows rapidly between ages 3 and 6 and leads to the child having greater coordination between the left and the right hemispheres of the brain?

Brain development begins a few weeks after conception and skyrockets throughout pregnancy and your child's early life. Your baby's brain doubles in size during the first year, creating connections between neurons that control emotions, movements, communication, and more. While some of your child's brain development is controlled by genes, it's also greatly impacted by their environment – meaning you and other loved ones play a critical role.

Your baby's brain starts developing about two to three weeks after conception. By the time your little one is born, their brain has around 100 billion neurons, all they will ever need. And in the first few years of life, their brain creates more than 1 million connections (called synapses) between these neurons every second.

Neurons connect with each other to make up the brain's foundational architecture, upon which future neural connections are made. All of the outward milestones you watch for expectantly – your baby's first words, first steps, and more – reflect changes and development in their brain.

Because the process is ongoing, it's impossible to pinpoint exactly how much of your baby's brain is formed at certain ages. Brain development is a lifelong process!

However, we do know that the first several years of your child's life are a critical time for brain growth and learning. After this intensive period of brain development is over, it becomes more difficult to shape the brain in healthy ways.

Parts of your child's brain

The brain is made up of three main parts:

• The forebrain, which consists mostly of the cerebrum. This is the most highly developed part of the brain. It contains the lobes and controls functions like memory, planning, imagination, and thinking. It's the last part of the brain to develop.
• The midbrain includes the limbic system, thalamus, pituitary gland, amygdala, and other regions associated with voluntary movements, reflexes, and emotions. This is the part of the brain that's developing in your child's early years.
• The hindbrain, which includes the brain stem, upper section of the spinal cord, and the cerebellum. It controls involuntary vital functions like breathing and coordinates movements. This area of the brain is mostly developed at birth.

The brain is an ecosystem, with many parts working together to direct each and every one of your baby's movements, thoughts, and emotions.

Here's a primer on some of the main parts of your child's brain, and how they're developing in the first few months of life.

Cerebrum

The cerebrum is the part of the brain that's most responsible for higher functions, including memory and learning. Its wrinkly-looking outer surface, the cerebral cortex, is where complex activities like planning and decision-making occur. It's divided into two halves – the left and right hemispheres, which have different functions but communicate with each other. Each hemisphere has a set of four lobes:

Frontal lobe: The frontal lobe of the brain (located behind the forehead) handles all thought and voluntary behavior such as walking, speech, and problem solving, and some aspects of emotion. You'll know development in this area has really taken off as your baby becomes more mobile and verbal. But the frontal lobe is very underdeveloped in young children – which explains why toddlers are impulsive and preschoolers can't always control their behavior. Your child depends on you to help them develop skills like impulse control, delayed gratification, and emotional regulation.

Temporal lobe: The temporal lobe (aptly named because they're near the temples) controls hearing. Infants are born with a fully-developed sense of hearing. Within minutes of birth, babies startle and cry at loud noises and are able to recognize the voice of their parents.

The brain's temporal lobes are responsible for storing and retrieving memories as well as language comprehension. Babies begin to understand the meanings of words between the ages of 6 to 9 months, as they learn to interpret other people's goals and intentions. And babies form short-term memory – including the ability to recognize that an object is still there even when it's briefly out of sight – rapidly between 4 to 10 months of age.

Parietal lobe: The parietal lobe of the brain, located near the crown of the head, controls taste, touch, the ability to recognize objects, hand-eye coordination, and some visual recognition (the ability to understand what you're looking at).

Since this area of the brain controls body awareness and spatial orientation, it benefits greatly from environmental stimulation. As you give your baby new objects to play with and textures to touch and enjoy, you're stimulating development in the parietal lobe.

Occipital lobe: The occipital lobe (located near the back of the head) controls vision and visual recognition (the ability to understand what you're seeing).

Vision is one of the least developed senses at birth: Newborns can't see all colors and are only able to focus on objects 8 to 10 inches away. They can make out light, shapes, and movement, but everything else is still pretty fuzzy. Within the first three years of life, vision develops completely.

To fine-tune their eyes and this part of the brain, your baby needs to see a variety of objects. In the first year of life, your face (as you hold your baby in your arms) will do nicely: In fact, research shows babies prefer looking at human faces over all other objects.

Limbic system

The brain's emotional regulation center, featuring the amygdala, is located in the limbic system of the midbrain. This part of the brain handles your baby's feelings, especially anxiety or, on the flip side, calming down – and it develops slowly (hello toddler tantrums!).

Your patience, attention, and understanding are key to helping your baby develop a healthy way to handle emotions, now and far into the future. Holding and comforting your child when they cry, especially in the first year of life, goes a long way toward helping them develop the ability to calm themself later on.

Cerebellum

The cerebellum (located at the back of the head near the nape of the neck) is responsible for balance and muscle coordination, as well as fine motor movement. It's an area of the hindbrain involved in complex movements such as grasping objects, rolling over, crawling, and walking. It may also play a role in emotions, thought, and social behavior.

Brainstem

The brainstem is the bottom part of the hindbrain that connects the cerebrum with the spinal cord. It helps coordinate messages between the brain and body that regulate vital functions including breathing, blood pressure, heart rate, hearing, balance, consciousness, blood pressure, and sleep.

When is a child's brain fully developed?

The brain isn't fully developed until age 25, when the prefrontal cortex – a sophisticated part of the brain responsible for goal-oriented behavior – finishes forming. Even after that, the brain continues to be shaped and altered. Brain development is a dynamic and lifelong process.

Brain development stages

Beginning just two to three weeks after conception, the human brain begins developing, with the major groundwork for brain development occurring during pregnancy and in the first few years of life.

Kids' brains are so active that they use two to three times as much energy as an adult brain. Half of the calories consumed by the average 5-year-old are used by their brain, for example.

At birth, your baby's brain is approximately one-quarter the size of yours. It doubles in size during the first year and is 80 percent of its final adult size by age 3.

Baby and child brain development occurs in several stages:

Neurulation: Very early in pregnancy, the brain forms into a three-layered sphere known as the neural plate that folds over onto itself to produce the neural tube. After the neural tube closes (within the first six weeks of pregnancy) it begins to form the various structures in the forebrain, midbrain, hindbrain, and spinal cord.

Proliferation: After the neural tube is formed, neurons begin to replicate at rapid speed and migrate to the part of the brain that they're meant to serve. Neurons are the foundation of the nervous system, allowing the brain to send and receive signals throughout the body.

Differentiation: During this stage, some neurons develop into mature neurons with axons (the transmitter in the neuron) and dendrites (the receiving part of the neuron).

Synaptogenesis: This is the formation of synapses (connections between neurons), which is critical for brain function. These connections are what enable us to move, think, and communicate. The first synapses are formed in week 23 of pregnancy, with peak production occurring in the first year of life.

Synapse pruning: Over the first 2 to 3 years of life, many more synapses are formed that are eventually needed. After age 2, a lot of pruning happens. The brain is most "plastic" – able to be influenced – during this period, which is why early treatment for development delays is most effective.

Myelination: The axons of neurons are wrapped in fatty cells known as myelin to enable the neurons to transmit information much more quickly. As with the other stages of brain development, the timing of myelination depends on the region of the brain that's involved. The parts of the brain that control balance and coordination are myelinated during the preschool years, while those involved with higher processes like emotional regulation and decision-making don't complete myelination until a person is in their teens to 20s.

How to develop your baby's brain

The first three years of your baby's life are critical for their developing brain. To support your baby's brain development and raise a smart baby, aim to:

• Serve healthy, nutritious foods
• Follow your child's vaccination schedule
• Read to your baby
• Talk to your baby – a lot
• Listen to music together
• Cuddle
• Create routines throughout the day
• Use positive discipline to build emotional regulation
• Demonstrate your own healthy relationships to your child

Healthy brain development in babies and toddlers

Baby milestones are more than just exciting moments to capture and celebrate – they're also the outward signs that your little one's brain is developing healthily.

Here are some important milestones to watch for:

• social skills like smiling
• grabbing
• understanding words
• talking
• rolling over
• sitting
• crawling
• clapping
• walking

There are also a few warning signs of developmental delays to watch out for at various ages, such as:

• speech delay
• delayed rolling over, sitting, or walking
• difficulty with head and neck control
• muscle stiffness or floppiness

Keep in mind that every child develops at a different pace. Try not to compare your child's milestone progress with other kids you know (including your own!). However, you know your baby best. If you're concerned that your baby's development may be delayed, be sure to bring your concerns up with your child's doctor. Various physical, occupational, and speech/language therapies can help support your baby's development – and the earlier they're started, the better.

Which part of the brain grows most rapidly at ages 3 6?

What part of the brain grows most rapidly in early childhood?

What part of the brain develops at 3?

What important changes occur in the brain between 2 and 6 and again between 6 and 12 years of age?