Physical Growth Neurological, Physiological, and Motor Development
A. Neurological development: Neural tube: Prosencephalon (forebrain) Mesocephalon (midbrain) Rhombencephalon (hindbrain)
Neural tube continues developing: • At the end of the bumpy neural tube—telecephalon followed by the diencephalon. • Both make up the forebrain.
Prenatal Neuronal Development: • Neurons & glial cells proliferate rapidly in prenatal development. • Fetus has majority of neurons it will have in life by third trimester (7-8 month). • Neuronal migration—cells migrate to different CNS locations.
Prenatal synaptic development • Synapses (synaptogenesis) are formed at a rapid rate. • There are trillions of synapses present at birth. This drops dramatically by adulthood.
Why do we lose cells? • 1. Programmed cell death- as new synapses are formed, surrounding neurons die to provide space for the new connections. • 2. Synaptic pruning- inactive neurons-- removed to free up room for active neurons.
Brain Development: Infancy Brain Growth: • myelination: Areas associated with motor & mental functions. • cortical & subcortical connections • lobe activity • neural plasticity: capacity of brain to change in response to experience & chemicals.
Brain development: Toddlerhood • Rapid development 2nd & 3rd yr • Cerebral cortex: Auditory & Visual cortex Movement & coordination Language Frontal cortex
Brain Development: Childhood • By 6 yrs old brain is 90% of adult weight Increased connections between all brain regions • Communication abilities • Memory • Motor control • Cognitive abilities
Brain Development: Adulthood • Aging Brain • weight after 30 How? -loss of white matter or loss of gray matter Prefrontal cortex • connections
Hemispheric Specialization: • Right H.Left H. • Left side of body right side of body • Music/melodies language/speech • Visual-spatial abilities logic, analytic
Infants show hemispheric specialization early. • The majority of newborns process speech sounds by the left hemisphereas measured by scalp potentials.
Neural Plasticity: Rosenzweig study • Rats from same litter put into 1 of 2 environments: enriched (E) or impoverished (I) for 3 months. • “E” environment- large, well-lit, communal cages- with toys (wheels, ladders, platforms) changed daily. Rats also explored a maze once a day. • “I” environment- each rat was placed in a small, isolated, dimly lit cage .
Rosenzweig (1996): Findings • 1. “E” rat brains weighed 4% more than “I” rat brains. • 2. Occipital region of “E” rat brains showed greatest gain (6%). • Neurotransmitter enzyme levels were greater in the “E” rats. • Dendritic connections were grater in “E” rat brains.
B. Motor Development: • Infants--born with little motor development. • Within a year, most infants crawl & walk.
Factors Influencing motor development • 1. Maturation. • 2. Enriched environment–interesting & novel stimuli promotes cortical development. • 3. Caregivers—encouragement works.
1. Grasping: • Infants vary -grip on an object based on its size, shape, texture, & their hand size. • For small objects, infants use thumb & index finger. They use all fingers of 1 hand or both hands for larger objects. • Older infants (8 mos.) use visual cues to guide their grasping, younger infants rely on touch.
2. Locomotion: • 1.First transition -infants show stepping reflex –ends at 3-4 mos. • 2. Second transition- in 2nd half of year, stepping movements occur again. • 3. Third transition – Infants walk unsupported (12 mos.+)
Theories as to how we learn to walk? • 1. Motor cortex develops– frontal lobe takes 1 year to mature for us to walk. • 2. Motor programs– we develop motor programs in spinal cord that guide walking. • 3. Cognitive plans—infants have mental representations for walking. • 4. Dynamic Systems view—interaction of multiple factors (perceptual, neurological, emotional, etc.)
Factors that promote early walking: • 1. Physically handling infants • 2. Giving infants practice in motor tasks • Zelazo & coworkers (1972) --mothers of newborns had infants practice stepping reflex a few min. a day. • These babies walked--earlier than a control group given no practice.
C. Physical Growth: • Why do we grow slowly? • We need exposure to social environmental stimulation to develop the frontal lobes.
Growth patterns in development: • 1. Cephalocaudal (from head downward). 2.Proximal-distal (from center outward). Internal organs develop earlier than the arms and hands.
Factors that influence height & weight: • 1. Genetic factors – accounts for most of the variance. • 2. Gender- • Girls-taller than boys from 2-9 yrs. • Girls have growth spurt from 10-14 yrs. • Boys show growth spurt from 10+ Weight pattern is similar.
3. Hormonal influences-Growth Hormone (GH) • GH, produced by the pituitary gland (brain), induces growth in the body. • GH stimulates the liver & skeleton to release somatomedin, which promotes cell duplication in the bones. • This promotes growth beyond (4 feet).
Environmental factors (growth): • 1. Nutrition – When healthy food is rationed, growth rates decline. • E.g., During WWII growth rates declined. In prosperous times, when food is easy to come by growth rates increase.
2. Does food supplementation improve growth rates? • Yes!! • Super et al., (1990) showed that giving food supplements to families for 3-4 yrs, prevented growth retardation compared with controls. • Also works with vitamin supplements.
3. Can children with retarded growth catch up to their peers? • Yes. It depends on severity, duration, & timing of deprivation (nutrition) & therapy. • Catch-up growth due to severe malnutrition may be limited to certain aspects of growth. • Children starved early (prenatal+) will show only modest gains if that.
Are we growing heavier? • Yes. Obesity rates are rapidly rising. • Appears to have risen in children dramatically within the last decade. • Why? • Sedentary lifestyle • High-fat food
Why do kids gain too much? • 1. Genetics- • Adoption studies show biological children of “heavy” parents reared apart—are more likely to be heavy themselves (Stunkard et al., 1986). • 2. Modeling (what & how do parents eat) • 3. SES
Critical periods for obesity: • 1. Infancy- • 2. Child is 4 yrs-old