ch 4 -- infancy & toddlerhood physical development

what are the three divisions of the brain?

1) forebrain (this is the part that contains the cortex and four sections we normally think of as controlling sensory info) 2) midbrain 3) hindbrain

pattern of motor development and age ranges

1) grasps cube -- 4 months 2) sits alone -- 7 months 3) crawls -- 7 months 4) pulls to stand -- 8 months 5) plays pat-a-cake -- 10 months 6) walks alone -- 1 yr 7) scribbles vigorously -- 1 yr, 2 months 8) jumps in place -- 2 yrs

after birth brain development

1) programmed cell death 2) synaptogenesis 3) myelination 4) synaptic pruning

brain development

a child undergoes massive brain development by the time of birth. after birth, still continuing development especially through infancy and toddlerhood, but even through to one's 20s. there is a high degree of folds and wrinkles even in the newborn brain, which allow people to fit more brain tissue in a small amount of space. throughout pregnancy, as more and more neurons are added, those wrinkles and folds are added with them -- until their brains look like adult brains, just physically smaller. nearer to adult size than any other physical structure, and it continues to develop heavily throughout infancy and toddlerhood.

depth perception

ability to judge the distance of objects from one another and ourselves. important for understanding the layout of the environment and for guiding motor activity. in visual cliff experiment, crawling babies readily crossed shallow side, but most avoided deep side by time they can crawl.

motor skills vid example 3

active play combines with problem solving, social skills, and emotional regulation. also muscle skills. as kids explore their environment and get better at grasping and manipulating, they also develop communication skills through interaction with parents and other caregivers. they build a sense of cooperation as they help more and collaborate in play, using their thinking skills. growing physical skills lead to more self-care skills and self-esteem and emotional development. caregiver interaction is extremely important in this process.

body growth

babies triple their birthweight by the time they are 1 yr old. their increase in height is not quite as steep -- around 50% of length more -- and not proportional to the weight growth rate as well. however, after 1st yr, both rates get steadily less steep and eventually meet. the biggest degree of change is in this first year of life. growth happens not only in physical maturity but also motor development.

relationship between lateralization and plasticity

brain has high capacity for learning, and if part is damaged, other parts can take over tasks that part would have handled. but once hemispheres lateralize, damage to specific region means the abilities it controls cannot be recovered to the same extent or as easily as earlier. research on children and adults who survive brain injuries offer evidence for plasticity in young brain. with injuries sustained in 1st yr of life, deficits in language and spatial abilities are milder than in adults, and other cortical structures compensated for damaged areas. however, when damage occurs to certain regions, like the PFC, recovery is limited because abilities are difficult to transfer to other areas.

speech perception

brain imaging evidence reveals that in young infants, discrimination of speech sounds activates both auditory and motor areas in the cerebral cortex. while perceiving those sounds, babies seem to generate internal motor plans that prepare them for producing these sounds. they learn to focus on meaningful sound variations as people talk. around 5 months, become sensitive to overall syllable stress rhythm of own language. between 6-8 months, start to screen out sounds not used in that tongue. bilingual children also do this, but more rapidly and effectively than monolingual agemates. increased responsiveness to native language sounds is part of a general tuning process in the second half of the first year, a possible sensitive period in which infants acquire a range of perceptual skills for picking up socially important info. soon, infants focus on larger speech units that are critical to figuring out meaning. they recognize familiar words and listen longer to speech with clear clause and phrase boundaries. around 7-9 months, infants extend this sensitivity to speech structure to individual words.

pincer grasp

by end of 1st yr, babies use thumb and index finger opposably in well-coordinated grasp. after this, ability to manipulate objects greatly expands. between 8-11 months, reaching and grasping are well-practiced, so attention is released from the motor skill to events that occur before and after attaining the object -- such as anticipating next action. the capacity to reach for and manipulate an object increases infants' attention to the way an adult reaches for and plays with that same object. as they watch, they broaden the range of actions that can be performed on various objects.

changes in body size and muscle-fat makeup

by the end of the first year, a typical infant's height is around 32 inches, more than 50% greater than at birth. by 2 years, it is 75% greater, and the weight has quadrupled to 30 lbs. early rise in baby fat peaks at about 9 months, and helps the small infant maintain a constant body temperature. in the 2nd year, most toddlers slim down, a trend that continues into middle childhood. in contrast, muscle tissue increases very slowly during infancy and will not reach a peak until adolescence.

kwashiorkor

caused by unbalanced diet very low in protein. strikes after weaning, from 1-3 yrs of age. body breaks down own protein reserves, resulting in swelling of abdomen and limbs, hair loss, skin rash, and irritable and listless behavior.

cultural variations in motor development

cultural values and infant rearing customs affect motor development. to ensure safety and ease toileting when parents work in the field, mothers in rural NE China place infants on backs in bags of sand; compared with diapered infants in same region, these babies become delayed in sitting and walking. among Kipsigis of Kenya and West Indians of Jamaica, babies hold heads up, sit alone, and walk earlier than North American infants. as parents in these cultures support babies in upright postures and rarely put them down on floor, their infants usually skip crawling. also, the Western practice of having babies sleep on backs to avoid SIDS delays gross motor milestones of rolling, sitting, and crawling. regularly exposing infants to the tummy lying position during waking hours prevents these delays.

what according to the dynamic systems theory do motor skills depend on for development?

demonstration of motor skills depends on multiple factors that all work together: 1) CNS development (ex. lack of crawling after 1 yr might indicate something is wrong here) 2) the body's movement capacities 3) the child's goals, including within a particular setting 4) environmental support for a particular skill; this affects what a child can learn and, in turn, what they are going to do change in any element makes the system less stable, so the child starts to explore and select new, more effective motor patterns.

regions of the cerebral cortex

divided into 4 different lobes (again, in the outermost part): 1) temporal lobe 2) occipital lobe 3) parietal lobe 4) frontal lobe the order in which these regions develop corresponds to the order in which various capacities emerge in the infant and growing child. for ex, burst of activity in auditory and visual cortexes and movement areas over 1st years; this corresponds with period of dramatic gains in these areas at this time. language skills esp. active from late infancy through preschool yrs, when language development flourishes

sensitive periods in brain development

early and extreme sensory deprivation results in permanent brain damage and loss of its functions, verifying the existence of sensitive periods.

pattern perception

even newborns prefer to look at patterned rather than plain stimuli. very young infants cannot resolve features in complex patterns bc of poor vision. around 2 weeks, when detection of fine-grained detail improves, spend more time looking at patterns like complex rather than simple checkerboards. in early weeks, infants respond to separate parts of pattern. at 2-3 months as vision improves, explore a pattern's features, pausing to look at each part. once they can take in all aspects of pattern, integrate parts into unified whole. around 4 months, so good at detecting pattern organization that they start to perceive subjective patterns that are not really there. older infants apply this to complex and moving stimuli. at 12 months, infants detect familiar objects represented by incomplete drawings even when as much as 2/3 of drawing is missing.

what are examples of things that might modify the brain in an experience dependent way?

examples of things that might modify the brain in an experience-dependent way include sports, learning an instrument, religion, multiple languages, rural vs urban home environments, and traveling.

which actions in the general pattern of motor development are fine motor skills?

grasping a cube, playing pat-a-cake, scribbling vigorously.

what is the difference between gray matter and white matter?

gray matter is made up primarily of dendrites and cell bodies, and makes up the cerebral cortex. white matter is white due to the amount of myelin across its axons, and it lies underneath the cortex.

proximodistal trend of growth

growth that moves from the center outward; head and trunk grow before arms and legs. during infancy and childhood, arms and legs continue to grow somewhat ahead of hands and feet.

left hemisphere

hemisphere largely responsible for verbal abilities and positive emotion. better at processing info in sequential, analytical way, a good approach for dealing with communicative information.

right hemisphere

hemisphere that handles spatial abilities and negative emotions. better for processing info in a holistic, integrative manner, ideal for making sense of spatial info and regulating negative emotion.

motor skills vid example 2

here, the kid is walking better as well as grasping and throwing. as kids learn to walk they fall often; over time, they get better at avoiding falling.

neurons

human brains have 85 billion neurons, and there are around 1 trillion connections between them. neurons receive info at dendrites, and a signal is sent down the axon and out the terminals. neurotransmitters are released from the terminal into the synapse, then detected by the dendrites of the next neuron. myelin is a fatty substance that covers an axon. an increase in myelination is a huge part of early brain development. myelin is made of glial cells and helps to speed up the impulse/make it more efficient as it travels. when full term babies are born, they have almost all the neurons they will need as adults. so it is not that the actual neurons are growing after birth in infancy and toddlerhood; it is the connections between the cells, the synapses, that are growing in synaptogenesis.

heredity and early physical growth

identical twins are more alike in body size than fraternal twins. when diet and health are adequate, height and rate of physical growth are largely influenced by heredity. even if malnourished slightly, generally catch up in growth. also affects body weight; weights of adopted children correlate more strongly with biological parents than adoptive parents.

individual and group differences in body growth

in infancy, girls are slightly shorter and lighter than boys with a higher fat to muscle; these differences persist throughout early and middle childhood and are greatly magnified at adolescence. ethnic differences are clear as well in differing growth norms/averages across different cultures -- Asian children are below US norms, and African American are above White children. children of the same age also may differ in physical growth. can use measure of skeletal age (bone development) to tell these differences.

where are neurons produced prenatally?

in the prenatal period, neurons are produced in the embryo's primitive neural tube. from there, they migrate to form the major parts of the brain. once in place, they differentiate, establishing unique functions by extending fibers to form synaptic connections with other cells.

gross motor development

includes crawling, standing, walking, and other similar activities. refers to control over actions that help infants get around in the environment.

fine motor development

includes reaching, grasping, and other activities. usually fine motor skills involve use of hands, but this might depend on the particular environment. has to do with smaller actions.

prefrontal cortex

lies in front areas of cortex controlling body movement, and is responsible for complex thought, in particular consciousness and various executive processes, including inhibition of impulses, integration of info and memory, reasoning, planning, and problem solving strategies. from age 2 months on, it functions more effectively, but it undergoes especially rapid myelination and formation and synapse pruning during preschool and school yrs, followed by an acceleration in adolescence

malnutrition and early physical growth

malnutrition contributes to 1/3 worldwide infant and early childhood deaths, and is also responsible for growth stunting. certain conditions exist, like Marasmus and Kwashiorkor. children who survive extreme malnutrition often suffer lasting damage to brain, heart, liver, pancreas, and other organs. tend to gain excessive weight, due to metabolism chances and loss of correct hunger signals. permanently reduces brain weight and laters productions of its NTs. poor fine motor coordination, difficulty paying attention, conduct problems, low intelligence scores, more intense stress response.

prenatal brain development

mostly involves increasing neurogenesis. some neurogenesis takes place later, including in adulthood, but it is very limited. neurons in general are not replaced after they are made, except sometimes in the olfactory system.

dynamic systems theory

motor skills build upon previous skills (ex., crawling, stepping, and standing unite into walking). mastery of motor skills involves acquiring increasingly complex systems of action; when motor skills work as a system, separate abilities blend together, each cooperating with others to produce more effective ways of exploring the world. the broader physical environment is also very influential. also, when a skill is first acquired, infants must refine it. as movements are repeated over and over, they promote new synaptic connections in the brain that govern motor patterns.

gross and fine motor skills

motor, social, cognitive, and language skills develop together and support one another in their development. as a kid develops more motor skills, it allows them to explore and learn more about their environment, which in turn increases their skills further. the rate of motor progress varies widely across children; there is a huge age range of acquisition.

myelination after birth

myelination of axons occurs in childhood and even in adolescence. glial cells are responsible for this process and make up about 1/2 of the brain's volume. glial cells multiple rapidly from the end of pregnancy through the second year of life. this then continues at a slower pace through middle childhood, and accelerates again in adolescence. gains in neural fibers and myelination account for the overall increase in the size of the brain during the first two years to 70% adult size. growth esp. dramatic in the first year.

what is the rate at which newborns form synapses?

newborns form synapses in their brains at the rate of 1 million new connections per second. during first two years, neural gibers and synapses increase at this astounding pace.

face perception

newborns prefer to look at photos and simplified drawings of faces with features arranged naturally rather than unnaturally. also track facelike pattern moving across visual field further than they track other stimuli. some researchers these behaviors reflect build in capacity to orient toward own species. others say newborns prefer any stimulus in which most salient elements are arranged horizontally in upper part of pattern, or that they are exposed to faces more than other stimuli. quickly learn to prefer caregivers' faces to others. around 2 months, prefer complex drawing of faces to complex other stimuli. around 3 months, make fine distinctions b/w facial features. at 5 months, infants perceive emotional expressions as meaningful wholes. experience influences face processing. for instance, sometimes show racial or gender preferences based on what they see most of when very young. development of areas specialized for face processing in right cerebral hemisphere plus extensive face to face interaction with caregivers contribute to refinement of facial perception. not until 10-11 are children as adept at this as adults.

nutrition and early physical growth

nutrition is especially crucial for development in the first two years due to rapid growth. infant's energy needs are 2x those of an adult. early on, breastfeeding ideally suited to infant's needs, hopefully for 2 yrs with solid foods added at 6 months. offers protection against respiratory and intestinal infections. popular in industrialized nations, but many stop by 6 months. many women in non-industrialized nations do not know about these benefits; many are not exclusively breastfed, and may suffer from contaminations in substitutes. most chubby babies with nutritious diets thin out during toddlerhood and early childhood as weight gain slows and they become more active. however, there is also a strengthening link between rapid weight gain in infancy and later obesity, which is made more preventable by breastfeeding.

reaching

of all motor skills, reaching may play greatest role in infant cognitive development. helps infants learn about sights, sounds, and feel of objects. promote manual coordination. start out as gross, diffuse activity and move toward mastery of fine movements.

ulnar grasp

once infants can reach, they modify their grasp by utilizing a clumsy motion in which the fingers close against the palm. still, even 4-5 month olds modify their grasp to suit an object's size, shape, and texture, which improves over second half of yr. when infants sit up, both hands become coordinated in exploring objects. will scan held object with fingertips, an transfer objects from hand to hand.

brain plasticity

our brains respond to our environments, including by changing structure. however, the responses depend on which experiences. these changes include more myelination in regions with increased activity, and the least active synapses being pruned (so that more active synapses are strengthened). it is an overabundance of synapses that promote brain plasticity. experience greatly influences the rate and success of its advancing organization.

perceptual development

perception is more active than sensation; when we perceive, we organize and interpret what we sense. for instance, babies start to organize sounds into complex patterns.

perceptual narrowing effect

perceptual sensitivity that becomes increasingly attuned with age to info most often encountered. babies must become skilled at making perceptual discriminations that are meaningful in their culture. happens around 6 months in hearing. similarly, 6 month olds are good at distinguishing between different monkey faces and human faces, but only retain the ability to do so with human faces by 9 months. also appears in musical rhythm perception. 6 month olds can detect common rhythmic changes that disrupt rhythmic forms in Western and non Western musical styles, but are no longer attenuated to these patterns enough to recognize deviations in style that is foreign to their environment at 12 months. heavy presentation of these culturally different styles can help babies retain the ability to distinguish, but not with adults. this tells use learning between 6-12 months is esp. rapid across several domains and is easily modified by experience.

cephalocaudal trend of growth

rapid growth that starts from the head down. at birth, the head takes up 1/4 body length. by age 2, the head accounts for only 1/5 and the legs for nearly 1/2 body length.

depth cues

research is currently looking at babies' ability to detect specific depth cues. includes: 1) motion -- blink eyes defensively when object comes to face like it will hit at 3-4 weeks 2) binocular depth cues -- arise bc our eyes have slightly different views of visual field; sensitivity emerges b/w 2-3 months and increases through first year 3) pictorial depth cues --sensitivity starts 3-4 months and increases 5-7 months; the cues artists use to make a painting look 3D -- receding lines, changes in texture (nearby textures more detailed), overlapping objects (if object is hidden by something else, it is further away) motor development may be involved in the order of these. control of head may help with motion and binocular cues, and ability to poke and feel objects may promote perception of pictorial cues. independent movement also has big role in refinement of depth perception.

which actions in the general pattern of motor development are gross motor skills?

sitting alone, crawling, pulling to a stand, walking alone, jumping in place.

general patterns of motor development

sitting comes before crawling, then standing, then walking and jumping. takes first steps somewhere around 1 year old. some kids just skip crawling. a kid can grasp a cube early, but more complex hand motions like pat-a-cake and scribbling take longer. scribbling happens a little after walking.

synaptic pruning after birth

synaptic pruning involves taking away synapses not being used that much. this is a consequence of normal use of our brains, even in adulthood. the process makes our existing connections more efficient by reducing the noise of under-utilized neurons. stimulation is vital to the survival of neurons and their connections; if they are continually stimulated by the environment, synapses will continue to be established. if they are not, they will return to uncommitted state to support future development. 40% synapses are pruned during childhood and adolescence.

synaptogenesis after birth

synaptogenesis (creation of synapses between neurons) is the major source of brain growth after birth, esp. in infancy and toddlerhood.

time course for synaptogenesis

the auditory and visual cortexes develop synapses heavily before birth and in the first few months, then the synaptic growth rate declines. language also develops in the first few months. higher cognitive functions (associated with PFC) develop a heavy synaptic growth rate at the end of the 1st year and over the first several years. learning and experiencing one's environment is a big job for newborns, so higher level thinking comes later along with those experiences. we get all the synapses we need in the prefrontal cortex by some point in adolescence -- meaning it is relatively mature -- but development continues through myelination and synaptic pruning (as well as in some other regions). in other words, synaptogenesis is a big part of brain development -- but that development does not STOP with synaptogenesis.

occipital lobe

the back-most part of the cortex. contains the visual centers of the brain.

temporal lobe

the bottommost edge of the cortex. contains the auditory centers of the brain.

experience expectant brain growth

the brain will develop normally if the child is exposed to some typical environmental experiences -- social interaction, exposure to language, physical exploration of environment w/ all of their different senses. our brains have evolved to expect these things. occurs early and naturally; resulting growth provides foundation for later development.

brain lateralization

the cerebral cortex has two hemispheres, each of which receives sensory info from the side of the body opposite to it and controls only that side (except the eyes). this may have evolved because it enabled humans to better cope with changing environmental demands.

prereaching

the first form of reaching, which newborns make. newborns will make poorly coordinated swipes toward an object in front of them, but they rarely contact the object. like newborn reflexes, prereaching drops out around 7 weeks of age, these early behaviors suggest that babies are biologically prepared to coordinate hand with eye in the act of exploring. around 3-4 months, reaching reappears as purposeful, forward arm movements in presence of nearby toy and gradually improves in accuracy. by 5-6 months, infants reach for object in room that has been darkened during the reach by switching off the lights. during next few months, infants become better at reaching with one arm and reaching for moving objects.

frontal lobe

the front-most part of the cortex. concerned with motor coordination, body movement, and higher level thinking. contains the prefrontal cortex, which is related to executive functioning -- selecting and successfully monitoring behaviors behaviors that facilitate the attainment of chosen goals (working memory, inhibiting impulses, etc). this is the region with the most extended period of development.

cerebral cortex

the outermost shell of the forebrain, made up entirely of gray matter. this means it primarily has dendrites and cell bodies. the cortex does not have many myelinated axons in it. this accounts for 85% of the brain's weight and is the last part of the brain to stop growing. sensitive to environmental influences for much longer period than any other part of the brain.

what is the pattern of toddler motor development like across cultures?

the pattern of toddler motor development is quite similar across cultures. does not vary from one cultural group to another significantly, but there are some variations based on environmental influences. for instance, can be affected by what is culturally valued or the routines in a particular culture and what motor skills they tend to emphasize. overall, similar order and similar age ranges.

parietal lobe

the upper middle part of the cortex. contains the touch centers of the brain.

changes in body proportions

there are two different directional trends in body growth: 1) cephalocaudal 2) proximodistal

toddler progress reports

these reports require significant time and effort for teachers. they serve as a general way to track whether and where children are on normal developmental paths. they contain detailed specificity rather than broad statements, allowing teachers and parents to identify developmental concerns. test development areas like large and small motor skills, practical life, social/emotional skills, cognitive skills, and language.

experience dependent brain growth

this relates to how differences in brain development will occur due to differences in environmental experiences. occurs throughout our lives; consists of additional growth and refinement of established brain structures as result of specific learning experiences that vary widely across people and cultures.

marasmus

wasted condition of body caused by diet low in essential nutrients. usually appears in first yr of life when mother is too malnourished to produce enough breast milk and bottle feeding is also inadequate.

programmed cell death after birth

we end up with far more neurons than ever needed, so after birth some start to die off. this happens based on them not being utilized and/or not forming connections with other neurons. around 40-60% neurons die depending on brain region.

intermodal perception

we make sense of running streams of light, sound, tactile, odor, and taste information -- simultaneous input from more than one modality/sense -- perceiving them as integrated wholes (ex, object's shape remains the same whether we touch it or taste it). based on ability to detect amodal sensory properties, info that overlaps two or more sensory systems, such as when visual and auditory info occur simultaneously and with same rate, rhythm, duration, and intensity. within first half yr, infants master huge range of intermodal relationships -- match faces with voices based on lip-voice synchrony, emotional expression, etc. young infants seem primed to focus on amodal info. intermodal sensitivity is important for perceptual development. enables babies to notice meaningful correlations between sensory inputs and rapidly make sense of surroundings. also facilitates social and language processing. when caregivers provide many concurrent sights, sounds, and touches, babies process more info and learn faster.

what most distinguishes brain development in toddlerhood?

what most distinguishes brain development during toddlerhood is a steep increase in synaptic connections.

motor skills vid example 1

what motivates the stumbling-walking here is catching up to the caregiver, an environmental circumstance that encourages motor development utilizing the caregiver-child relationship and social support. walking serves a functional purpose, and the kid's happy expression reflects happiness at his own skill.

victims of deprived early environments

when babies born with cataracts, show rapid improvement in vision with corrective surgery within 4-6 months, but the longer the surgery waits, the worse recovery is. infants placed in orphanages who were later exposed to ordinary family rearing show necessity of stimulating environment for psychological development; intellectual deficits, serious mental health problems, generalized decrease in size and activity of cerebral cortex esp. PFC, less left hemisphere activation. chronic stress can disrupt brain's ability to handle stress; extreme stress reactivity, high concentrations of cortisol linked to later learning, emotional, and behavior problems.