Infancy: Physical & Brain Development

• Infancy is the period from birth to 18-24 months after, requiring extreme dependence on adults.
• At birth, infants possess a few physical skills.
• Development may vary depending on gestational age at birth.
• Newborns are defined as being in the first 3 months of life or the 4th trimester.

Physical Changes

• Highest degree of physical change occurs in the first 2 years after prenatal development.
• During infancy, babies grow 25-30 cm and triple their body weight in the first year.
• At the toddler stage, girls are about 2x their height at birth and boys are about 2.5x
• 2-year-olds have proportionately larger heads than adults.
• The cephalocaudal growth pattern describes growth from head to tail.
• The proximodistal pattern describes growth starting at the center of the body and moving outward.

Brain Development

• The brain and nervous system develop rapidly during the first two years.
• The midbrain and medulla, which regulate vital functions, are most developed at birth.
• The least developed part of the brain at birth is the cortex.
• The cortex is involved in perception, body movement, thinking, and language.

Cerebral Cortex Lobes

• Frontal lobe is at the front of the head, responsible for cognitive functions, speech and language, motor control, memory and learning, and personality and emotion regulation
• Parietal lobe - located at the top back of the brain, behind the frontal lobe and is responsible for sens processing, mathematical and logical thinking, navigation, attention and perception, and language comprehension
• Occipital lobe - located at the back of the head and plays an important role in interpreting visual information
• Temporal lobe - located on the sides of the brain crucial for processing hear memory, language, and emotions.
• Lateralization is the specialization of function in one hemisphere or the other, starting before birth and can be observed in newborns when listening to speech.
• Synaptogenesis, the creation of synapses, is followed by synaptic pruning to make the brain more efficient.
• A one-year-old’s brain has denser dendrites and synapses than an adult’s, enabling neuroplasticity and reorganization in response to experience.
• However, the one year old's neural network operates far less efficiently compared to that of an adult
• Synaptic pruning refers to the brain's removal of weaker or unnecessary synapses.
• Axons and dendrites are two types of fibres extending from the neuron’s cell body.
• Neurotransmitters are chemicals released from terminal buttons at the end of axons allowing information to pass through gaps between neurons.
• Individual differences in neurotransmitters are associated with behavioural differences, such as shyness and aggression.
• Dendrites receive information from other neurons, muscles, or glands through the axon.
• Axons transmit information away from the cell body.
• A myelin sheath covers most axons and speeds information transmission.
• As the axon ends, it branches out into terminal buttons.

Myelinization

• Myelin (fat cells) gradually covers individual axons, electrically insulating them and improving nerve conductivity.
• Myelinization is most rapid during the first two years after birth but continues throughout childhood and adolescence.
• The reticular formation, which regulates attention, is not fully myelinized until the mid-20s.

Brain Activity

• Scientists have discovered exciting links between brain and behaviour
• Electroencephalogram (EEG) is a measure of the brain's electrical activity.
• Functional near infrared spectroscopy (fNIRS) uses very low levels of near infrared light to monitor changes in blood oxygen.
  • Increasingly being used to asses infants' brain activity as they move about their environment
• MRIs for early Autism diagnosis