Physical Development in Infancy Chapter 4 Physical Development in Infancy

The Newborn Baby What is the neonatal period? Newborn—neonate—about 20 inches long, 71/2 lbs. Are boys or girls bigger? Are first borns or later borns bigger? Some features: Large head (1/4 the body length) Receding chin—why? Head may be misshapen—why? Why do babies have “soft spots” on their heads? What are they called? Pinkish cast—thin skin covering capillaries where blood flows What is the fuzzy prenatal hair that newborns have on their bodies called? What is the oily protection that babies are covered with when they are born? What purpose does it serve?

Body Systems continued First few days secrete meconium—what is that? When bowels and bladder are full, sphincter muscles open automatically—no control yet Why do some babies have yellowish cast to skin 3-4 days after birth? If left untreated what can happen? Layers of fat that develop at end of fetal development help babies keep body temperature, as does increasing activity when air temp drops

Physical Growth ◦Directionality ◦Represent average outcomes General principles ◦Directionality ◦Cephalocaudal ◦Proximodistal Norms and Individual Differences ◦Represent average outcomes ◦Wide variation in individual differences occur within normal range ◦Growth affected by larger genetic and cultural factors Directionality--how body proportions change--cephalocaudal and proximodistal principles

Figure 4.2: Changes in Body Proportions from Prenatal Development Through Adulthood

Growth Chart

Figure 4.3: Differential Growth Rates in the Human Body

Development of the CNS Division of the nervous system that consists of brain and spinal cord Processes information and directs behavior Develops at many levels at the same time Reciprocal interplay between biology and context affects brain development Brain and nervous system develop rapidly during the first 2 years Reciprical interplay--Genetically predetermined developments of the brain give rise to new behaviors, and new behaviors lead to interactions with the environment that then foster brain development.

The Brain Brain development ◦Subcortical (below the cortex) structures—develop first—control states of arousal (asleep, awake, drowsy, etc.) ◦Limbic system—next, manages emotions ◦Cortex and association areas—last—involved with awareness, attention, memory, integration of information Subcortical structures that control state of arousal develop beginning during the prenatal period during brain development.

The Brain continued 2 halves—hemispheres, connected by corpus callosum—responsible for transferring information between hemispheres Visual cortex—regulates sight (occipital lobe) Auditory cortex—sound (temporal lobe) Sensorimotor cortex—processes touch Motor cortex—voluntary movement (rear portion of the frontal lobe) Frontal cortex—thinking, planning, initiative, impulse control, creativity In the left cortex—Wernicke’s area—language comprehension; Broca’s area—language production, speech Each hemisphere receives sensory information from the side of the body opposite to it and controls only that side—except the eyes. Visual information from both eyes is received by both hemispheres. The left hemisphere is largely responsible for verbal abilities like spoken and written language and positive emotion like joy. It is better at processing information in a sequential, analytic (piece-by-piece) way—a good approach for dealing with verbal and emotional language. The right hemisphere handles specific spatial abilities like judging distances, reading maps, recognizing geometric shapes and negative emotions such as distress. It is better at processing information in a holistic, integrative way, good for making sense of spatial information and regulating negative emotion. At birth, hemispheres have already begun to specialize. However, research on brain damaged children show that among children who sustained brain injuries in the first year of life deficits were milder than those observed in brain injured adults. Other structures in the brain compensated for the damaged areas. This speaks to the plasticity of the brain.

Figure 4.4—Areas of the Brain Frontal lobes--deals with higher level cognitive functions like reasoning and judgment. Sometimes called executive function, it is associated with the pre-frontal cortex. Most importantly the frontal lobe contains several cortical areas involved in the control of voluntary muscle movement, including those necessary for the production of speech and swallowing. The parietal lobe is associated with sensation, including the sense of touch, kinesthesia, perception of warmth and cold, and of vibration. It is also involved in writing and in some aspects of reading. The temporal lobe is associated with auditory processing and olfaction. It is also involved in semantics, or word meaning. Wernicke's area is located there on the first temporal gyrus. Occipital lobe--involved in vision. Wernicke’s Area--This area plays a critical role in the ability to understand and produce meaningful speech. Broca’s Area--This area is involved in the coordination or programming of motor movements for the production of speech sounds. The limbic system is a complex set of structures that lies on both sides of the thalamus, just under the cerebrum.  It includes the hypothalamus, the hippocampus, the amygdala, and several other nearby areas.  It appears to be primarily responsible for our emotional life, and has a lot to do with the formation of memories.  In this drawing, you are looking at the brain cut in half, but with the brain stem intact.  The hypothalamus is responsible for regulating your hunger, thirst, response to pain, levels of pleasure, sexual satisfaction, anger and aggressive behavior, and more.  It also regulates the functioning of the autonomic nervous system (see below), which in turn means it regulates things like pulse, blood pressure, breathing, and arousal in response to emotional circumstances. Hippocampus—has to do with memory. Amygdala—has to do with emotions and aggression, fear responses, and emotional memories.

3-D Brain http://www.g2conline.org/2022

Brain Cells Neurons ◦Cell body ◦Dendrites ◦Axon http://www.youtube.com/watch?v=GIGqp6_PG6k Neurons--nerve cells that carry information across the body and brain and within the brain. 3 main parts--cell body, dendrites, and an axon. Cell body contains the nucleus and biochemical mechanisms to keep the cell alive and whether the cell will send out signals to other cells. The dendrites pick up signals from other neurons like antennae. A neuron can have many dendrites. Axons carry signals away from the cell body toward other neurons. At their tips axons divide into many axon terminals. Neurons and their connections are what we mean by gray matter.

Figure 4.5: The Neuron and Synapse Synapse--the connection between one neuron’s axon and another’s dendrite. Referred to as the synaptic gap.

Synaptic Development Synaptogenesis Pruning ◦The creation of synapses—connections between neurons ◦ Occurs rapidly during first years after birth ◦ Happens in spurts ◦ Brain weight quadruples by age 4 Pruning ◦ Eliminating unused neural pathways and connections Prenatal brain development - YouTube

Synaptic Development Plasticity ◦ The brain’s ability to change in response to experience Use it or Lose it ◦ Intellectually challenging environment creates a more complex network of synapses. ◦ So stimulate your baby!!! Researchers Still Learning from Romania's Orphans : NPR Plasticity--the capacity of the brain to be modified by experience. Some connections are made, kept, some are pruned. Experience plays a large role in what is kept and what is pruned.

Brain Plasticity Experience-expectant processes ◦Prewired processes in the brain Experience-dependent processes ◦Involve the active formation of new synaptic connections in response to experience Types of plasticity ◦Modifiability: Development that asserts that, although cells are predestined for specific functions, their function can be changed Compensation: Cells substitute for others, permitting recovery of function after loss or damage

The Autonomic Nervous System Regulates many body activities without voluntary control ◦Many systems cycle in identifiable and predictable rhythms. ◦States of arousal ◦Regulation of sleep-wake cycle ANS regulates breathing, blood flow, digestion.

Reflexes and Development Reflexes are simple, involuntary responses to certain stimuli ◦Approach reflexes ◦Avoidance reflexes ◦Other reflexes Most develop before birth and are normally present for four to eight months after birth At birth much of an infant’s movement is reflexive. As the baby grows more behavior comes under the control of the baby. Many reflexes are designed to aid survival. Approach reflexes--concerned with intake, esp. breathing and rooting, sucking and swallowing. Avoidance reflexes--concerned with avoidance--coughing, sneezing, and blinking. Other reflexes--had more significance earlier in human history--e.g, Palmer grasp and Moro reflex. Most reflexes develop before birth and then disappear sometime before the 8th month of life. It is a sign that brain development is progressing normally. Doctors will test for these reflexes during infant physical examinations.

Reflexes and Behavioral States Adaptive reflexes Help survival ◦ Sucking ◦ Withdrawal from pain ◦ Opening and closing of pupil Weak or absent reflexes warn of possible neuronal development problems http://www.youtube.com/watch?v=a4qCKU45ucY&feature=related Babinski--Stroke down the little-toe side of baby’s foot with your finger. Instead of curling or flexing his little toes downward, he will lift them up in extension and splay them out.

Reflexes and Behavioral States Primitive Reflexes Controlled by less sophisticated parts of the brain—examples: ◦ Moro (or ―startle) Reflex, Babinski, Plantar, etc. http://www.youtube.com/watch?v=7oD6set72lo These primitive reflexes should disappear by eight months http://www.youtube.com/watch?feature=endscreen&v=ofGsMzdnXFY&NR=1 Persistence (just as in absence) may indicate neurological problems Babinski--Stroke down the little-toe side of baby’s foot with your finger. Instead of curling or flexing his little toes downward, he will lift them up in extension and splay them out.

Reflexes and Behavioral States States of Consciousness Patterns of sleep and wakefulness stabilize with age Neonates sleep 80% of the time By 8 weeks, babies begin to sleep through the night By 6 months, babies average 14 hours sleep per day Clear nighttime patterns and daytime naps are established

Reflexes and Behavioral States Cries ◦ Basic cry signals hunger – rhythmic pattern click ◦ Anger cry – louder and more intense ◦ Pain cry – very abrupt onset Cross-cultural studies suggest crying increases until 6 weeks then tapers off Can you spoil a baby?

Sensing and Perceiving Five senses ◦Seeing Pattern, shape, and form Depth Movement Color ◦Hearing ◦Touching ◦Tasting ◦Smelling

Vision Rapid development of visual acuity—adult-like by about 6 months (20-20) Color Vision Red, green and blue present by 1 month Infant’s ability to sense color almost identical to an adult’s by 4 months Tracking The process of following a moving object Initially inefficient but improves rapidly

What Babies Look At Babies initially scan for light/dark contrast. At 2 months, babies scan entire objects and scan for patterns Caron and Caron (1981) suggest that by 3 – 4 months babies can find and pay attention to patterns

What Babies Look At—Faces Prefer mother’s face from the earliest hours of life Focus on internal features of the face at about age 2-3 months

Depth Perception Visual Cliff – Gibson and Walk (1960)-- ◦ Initially showed that 6 - month old babies would not cross the visual cliff ◦ Recent Research Babies use kinetic information as early as 3 months Binocular cues are used at 4 months Linear perspective cues are used last, at 5 – 7 months ◦ 3 month olds have some depth perception http://www.youtube.com/watch?v=4OelrPzpQ6Q

Infant Perception of Motion and Object Continuity Infant’s perception of movement is quite good. In this experiment infants a shown an image in which a single rod appears to be moving left and right behind a box. Then they are shown an image of 2 separate short rods with no box in front. They are surprised by this—how do we know? They look longer at it than the original stimulus which suggests that they mentally connected the rod. These studies are called habituation studies. Habituation studies—babies are exposed to a stimulus and then presented with a surprising event and how long the baby looks at it is measured. In this particular study

Hearing, Smelling and Tasting, Touch and Motion Fetuses respond to sounds beginning at 3 months of gestation By 4 months will reach in the direction of sound Infants prefer infant-directed speech (motherese) Smelling and Tasting Newborns react differently to each basic taste as early as birth Prefer some tastes to others—sweet, sour, bitter substances produce facial expressions Touch and Motion Best developed of all senses Babies use touch to explore the world—central to Piaget’s theory about the sensorimotor stage Harlow demonstrated the importance of touch to development http://www.youtube.com/watch?v=KlfOecrr6kI

Multimodal and Cross-Modal Perception Our senses interact with another and fuse perceptions into wholes. Information obtain by sight, sound, and touch are coordinated very early in life. Self-knowledge might be based on the coordination of information.

Sudden Infant Death Syndrome—SIDS Leading cause of death in U.S. infants 1- 12 months More common in babies with apnea (brief cessations in breathing) More frequent in babies who sleep on their stomachs Higher risk if mother smokes during pregnancy or smoking in the home after birth