EDKP 261: Motor Development - FINAL EXAM

What is motor development?

process through which we pass during the course of our life
- changes that occur in ability to move

Characteristics of motor development

- changes in movement behaviour
- sequential, age-related, continuous
- depends on underlying process

Motor learning

relatively permanent gains in motor skills capability associated with practice or experience

Motor control

the neural, physical, and behavioural aspects of movement

Constraints

- limit or discourage certain movements
- permit or encourage other movements
- "shape" movement
- individual, environmental, task

Individual constraints

- inside the body (internal)
- structural: related to body structure (height, muscle mass, etc.)
- functional: related to behavioural/cognitive function (attention, motivation)

Environmental constraints

- outside the body (property of world around us)
- global, not task specific
- gravity, surfaces, sociocultural (gender/cultural norms)

Task constraints

- external to body
- related to specific task or skill
- goal of task, rules guiding task performance, equipment

Research study designs

- sequential or mixed longitudinal
- longitudinal
- cross-sectional

Sequential or mixed longitudinal studies

- Follows cohorts over time
- changes can be observed
- mixed longitudinal = mini-longitudinal studies with overlapping ages

Longitudinal studies

- an individual or group is observed over time
- study can require lengthy observation

Cross-sectional studies

- individuals or groups of different ages are observed
- change is inferred, not observed
- advantage: fast to collect data
- disadvantage: artefact due to exposition to technical advances

Theories of motor development

- maturational perspective
- information processing perspective
- ecological perspective

Maturational perspective

- motor dev set in psychology field
- behaviourism = dominant theory with emphasis on distinguished environmental role
- motor dev driven by maturation of systems (CNS especially)
- minimal environmental influence
- qualitative, discontinuous
- suggested invariable, genetically determined

Maturational perspective - problems

- basic motor skills emerge automatically
- no need for special training
- mild deprivation does not arrest development
- CNS most important

Information processing theory

- perceptual cognitive processes (brain = computer)
- basic tenet: brain like a complex computer
- response links, feedback, knowledge of results
- focus on product of motor dev rather than underlying processes
- study at one period of time rather than across time
- perceptual motor dev = sub field within this theory, tried to link learning disabilities to delayed perceptual motor dev

Ecological perspective

- perception-action approach: body scaling and affordance
- dynamic system approach: rate limiter and controller, influenced by Bernstein N.
- development driven by interrelationship of individual, environment, and task (multiple systems!)
- neural system one of many responsible for action
- reject CNS as executive controller of nearly limitless opportunities for movement
- control distributed throughout body

Ecological perspective - problems

difficult to explain:
- toddler learning to walk
- child learning to ride a bike
- teens having difficulty swimming

Perception Action Approach (body scaling and affordance)

- based on work of JJ Gibson
- affordable is function an environmental object provides to an individual
- visual motion perception helps to predict movement
- body scaling example: facing stairs
--> infant: what are these
--> toddler: one step
--> adult: alternate step
--> arthritic elder: one step at a time

Growth and aging - patterns

- universality: patterns that hold for all humans
- specificity: individual variation

Prenatal development

- controlled by genes
- embryo or fetus sensitive to extrinsic factors

Embryonic development

- conception to 8 wks
- differentiation of cells to form specific tissues and organs
- limbs formed at 4 wks
- human form noticeable at 8 wks

Fetal development

- 8 wks to birth
- continued growth in cell # (hyperplasia) and size (hypertrophy)
- development from head to toe (cephalocaudal), aka: upper body develops first then lower
- plasticity: capability of taking on new function

Fetal nourishment structure

- the placenta: an interface between mother and fetus
- multiple villi: increase surface of exchange of oxygen/nutrients as well as toxic/teratogenic substances

Abnormal prenatal development

- congenital defects (present at birth) can be genetic or extrinsic
-

Genetic causes of congenital defects

- dominant disorders (defective gene from one parent) or recessive disorders (defective gene from each parent)
- variable effects on growth and maturation

Extrinsic causes of congenital defects

- affect fetus through nourishment or physical environment
- teratogens act as malformation-producing agents
- teratogenic effects result from too much or too little of a substance
- placenta screens some but not all harmful substances
- viruses during pregnancy: cytomegalovirus (inflammation of retina, jaundice, large spleen and liver, low birth weight, mineral deposits in brain, rash at birth, seizures, small head), congenital rubella, chicken pox
- harmful environmental factors: pressure, temperature, X and gamma rays, oxygen-deficient atmosphere, pollutants
- age: down syndrome more common with older mothers (>40)
- exercise: moderate related to increased birth weight, vigorous predicts lower bw
- stress: in humans, extreme maternal stress related to lower birth weight and children with emotional problems

Teratogens

- agents from environment which can harm developing fetus
- only cause damage if exposure occurs during sensitive period of prenatal development
- critical factors = amount and length of exposure, individual diffs in susceptibility
- alcohol, cigs, weed, coffee, raw fish
- malnutrition (folic acid important!)

Postnatal development

- growth follows sigmoid pattern
- timing of spurts and steady periods variable
- timing differs bw sexes

Height

- sigmoid pattern
- longer growth period of males = taller
- girls start 2 yrs before growth spurt
- girls: peak height velocity 11.5-12 yrs, growth tapers off ~14, ends ~16
- boys: peak heigh velocity 13.5-14 yrs, tapers ~17, ends ~18
- individual variation

Body type

- somatotype: persons body build
- endomorph: soft and round
- mesomorph: muscular and balanced
- ectomorph: lean
- somatotype affected by growth, age, diet, stress, PA (can change, not just genetic)

Relative growth

- body proportions change from head-heavy, short-legged at birth to adult proportions
- in adolescence, boys increase shoulder breadth

Body proportion changes in postnatal development

- head circumference, shoulder, hips, trunk, limbs
- growth is relative to head size
- at birth, head ~ 1/4 total body length

Weight

- follows sigmoid pattern
- susceptible to extrinsic factors, esp diet and exercise
- individuals can grow up then fill out (peak weight velocity follows height velocity by 2.2-5 months in boys, 3.5-10.5 mo in girls)

Physiological maturation

- children vary in maturation rate
- early maturation will stop growth
- difficult to infer maturity from just age and size

Secondary sex characteristics = indicator of maturation

- maturational changes in women: breasts, pubic hair, menses, decrease in growth velocity
- men: not as easy to identify... growth of testes and scrotum, pubic hair, no clear landmark (sperm production is gradual and constant through life, quality may decline)

Extrinsic influences on postnatal growth

- individuals sensitive during periods of rapid growth
- nutrition, socioeconomic status, well-being, disease prevention...

Adulthood and aging

- height is stable in adulthood but may decease in older adulthood (compression of cartilage, osteoporosis)
- avg adults start gaining weight in 20s (diet/exercise, loss of muscle mass, aging of body systems, production of hormone changes)

Growth and physiological function

- muscular strength, cardiorespiratory efficiency, processing speed
--> peak 25-30 yo
--> females: 22-25
--> males: 28-30
- bones continue to grow
--> long bones till age 25
--> max strength late 20s

Aging

- diminished capacity to regulate in eternal environment, reduced survival probability
- study of aging = gerontology
- advanced aging causes bone loss, muscle loss, fat increase
- problems with advanced aging due to inactivity and other poor health habits

Theories of advanced aging

- genetic theory (cellular clock)
- wear and tear
- cellular garbage/mutation (free radicals and cross linking)
- immune system theories
- hormonal theories

Sigmoid pattern

whole body growth follows sigmoid pattern with timing differences between the sexes and individuals

Variability in advanced aging

determined by extrinsic factors

Assessment of prenatal growth

- invasive: amniocentesis, chorionic villus sampling
- noninvasive: ultrasound, 3D imaging
- distance curves show extent of growth
- velocity curves show rate of growth
- peaks on velocity curves show ages with faster growth rates

Body systems as rate-limiters

- a system that lags in development can be a developmental rate limiter
- development lag occurs in patients with muscular dystrophies caused by genetic mutations, affects muscle strength

Skeletal system development

- embryo has cartilage model of skeleton
- ossification begins at primary centres in mid-portions of long bones: primary and secondary ossification centres

Postnatal growth in skeletal system

- growth in bone length occurs at secondary centres at the end of bones
- centres called epiphyseal plates, growth plates, or pressure epiphyses
- increase in bone girth = appositional growth
- traction epiphyses are where muscle tendons attach to ones, traction shapes bones

Cessation of bone growth

- growth at epiphyseal plates stops at diff times for diff bones
- typically close by age 18/19
- closure occurs at younger age in girls (links skeletal growth to maturation)

Adult skeletal system

- bones remodel throughout life span
- constant need of calcium and vit d
- old bone absorbed, new bone formed
- through adulthood: bone growth slows, fails to keep pace with reabsorption
- bones become more brittle, high mineral content and less organic (cells)
- effects of exercise on bone density

Adult skeletal structure

- structure changes very little unless one has osteoporosis
- osteoporosis leads to rib cage collapse, stooped posture, reduced height (detected by bone density)
- extent of bone loss influenced by hormones, diet, exercise

Bone loss = aging

- bone loss in women begins slowly during third decade and increases shortly before or after menopause
- total bone loss for women by age 70 is ~25-30%
- bone less estimates for men at age 70 = ~half of wha women experience (12-15%)

Factors inducing osteoporosis

- hormone levels: menopause and male menopause (andropause) - due to drop in estrogen and testosterone
- bed confinement/medical conditions
- medication
- alcohol and smoke

Skeletal system as a limiter

- patellofemoral syndrome = irritation of patella on femoral epiphysis
- osgood-schlatter disease = traction on epiphysis
- genu valgus/varus

Development of muscular system

- prenatal growth involves hyperplasia (increased cell #) and hypertrophy (increased cell size)
- postnatal growth = mainly hypertrophy
- growth and repair by recruitment of satellite cells

Muscle development

- muscle growth follows sigmoid pattern
- at birth 25% of bw
- muscles increase in diameter and length by addition of sarcomeres

Muscle fibre type

- after 16th wk of fetal dev, first muscle fibres identified
- fibre type at birth:
--> type I 50%
--> type II 25 %
--> transitional fibres 25%
- by age 1, fibre type distribution similar to adult
- exact proportions vary bw individuals

Adult muscular system

- natural loss of muscle mass minimal until age 50
- by 80, ~30% muscle mass lost
- loss occurs in # and size of muscle fibres (size usually after age 70)

Effect of sex hormones

- diference bw sexes becomes marked in adolescence (esp in upper body musculature)
- testosterone affects muscle growth (binding to receptors resulting in protein synthesis)
- constant production in order to maintain muscle mass

Cardiovascular development

- prenatally, heart grows by hyperplasia and hypertrophy
- postnatally, heart follows sigmoid pattern
- at birth, right ventricle slightly bigger
- heart and blood vessel size appropriate for body size (childhood/adolescence)
- old age, heart can lose elasticity and valves become more fibrotic (lifestyle dependent)

Adipose system

- fat needed for energy storage, insulation, protection
- brown fat: bw the shoulder blades, nape of sternum
- white fat: storage
- fat increases rapidly until 6 mo, gradually until 8 yrs
- two hyperplasia periods: first 6 mo and puberty
- adolescence: girls increase fat more than boys
- growth through hyperplasia and hypertrophy (hypertrophy more dramatic in adolescence and adulthood)
- great individual variability

Fat distribution

- changes with growth
- children have more internal than subcutaneous
- subcutaneous fat increase from 6/7 yr till 12/13 yr in boys and girls but continues beyond for girls

Adipose tissue in older adults

- both men and women gain fat during adulthood, not inevitable
- increases in trunk fat are notable but subcutaneous fat on limbs decrease
- implications: excess fat is rate-limiting

Endocrine system

- role in growth and maturation through hormones
- major growth hormones: pituitary growth hormone, thyroid hormones, two gonadal hormones
--> stimulate protein anabolism (tissue building)
- endocrine - neurological feedback loops regulate hormone levels
- each hormone may have critical developmental role at diff phases
- insulin = indirect role, vital for CHO metabolism

Growth hormone

- secreted by anterior pituitary gland under control of somatotropic hormones
- necessary for normal growth
- action:
--> direct: binds to its receptor on target cells
--> role in anabolism: stimulation of fat, protein, CHO metabolism
--> indirect: action on liver, induces release of insulin like growth factor 1
- GH deficiency can result in gigantism
- modulation of GH release by exercise, sleep, stress, nutrition
- secreted under control of hypothalamic hormones, stomach hormones

Thyroid hormones

- secreted by thyroid gland
- triiodothyronine (T3) and thyroxine (T4)
- synthesis stimulated by TSH produced by axis pituitary gland and hypothalamus
- influence whole body growth
- need T3 for brain structure development (from mother during prenatal dev at 20 wks)
- effect serotonin and acetylcholine
- hashimotos thyroiditis (hypothyroidism): fine motor movement problems, tremors, depression

Gonadal hormones

- influence on growth, sexual hormones (sex organs, secondary sex characteristics)
- androgens: secreted by testes (boys) and adrenal glands (girls), hasten epiphyseal growth plate closure, promote growth of muscle mass

Insulin

- indirect role on growth by regulating glycaemia
- insulin secretion similar in adult and young

Endocrine system in older adults

- imbalances may develop bw nervous, endocrine, and immune systems
- thyroid disorders more prevalent
- decreasing gonadal hormone levels associated with loss of bone and muscle tissue

Factors influencing nervous system development

- genes direct its development (84% of all genes expressed somewhere in brain)
- extrinsic factors influence formation of synaptic connections, variability

Prenatal neural development

- process includes neuron formation and differentiation
- important cell types: atrocities, oligodendrocytes, microglia, Schwann cells
- neurons develop axon to carry signals to glands, organs, muscles
- teratogens might disturb normal migration and branching, eg: fetal alcohol syndrome effects migration of purkinje cells in cerebellum

Early neural development

- late in prenatal period, neurons start to fire electrical impulses (random first then form circuits)
- experience impacts synaptic proliferation
- neural network more efficient with experience
--> stimulating babies in belly

Postnatal neurological growth

- brain growth increases rapidly after birth
- growth involves these factors: increase neuron size, prolific branching to form synapses, increase in glial cells for support and nourishment of neurons
- stimulation of learning increase # of synaptic connections
- majority of brain synapses or connections form by age 3, 85% of a childs brain dev completed by age 5

Motor control and the brain - cerebral cortex

- frontal lobe: long postnatal development linked to evolutionary advanced functions (decision making)
- parietal lobe: sensory info for spatial sense and navigation
- temporal lobe: memory
- occipital lobe: visual processing
- cerebral cortex uses 20% of glucose

Brain structures involved in motor control

- motor cortex
- sensory cortex

Homonculus

Representation of a human by area of the brain devoted to body parts
- sensory homonculi: topographic representation of body parts along post-central gyrus of parietal lobe
- motor homunculi: topographic representation of body parts along pre-central gyrus of frontal lobe

Cortico-spinal tracks for motor control

direct between motor area in brain and spinal cord

Extrapyramidal tracks for motor control

goes through 'filters'

Cerebellum

- lies outside of cerebral cortex
- connected to brainstem
- processing centre for: coordination, balance, equilibrium, posture

Basal ganglia

- deep in cerebrum
- mediation bw brain structures
- function with dopamine
- processing centre for: speed of movement, hyperkinesis

Brainstem

autonomic function

Gait

- ataxic gait: presence of abnormal, uncoordinated, staggering gait
- neuropathic gait: foot drop in gait due to attempt to lift foot high enough to step so foot is not dragging on floor

Spinal cord

- descending fibres (motor) and ascending fibres (sensory)
- at level of spinal cord reflex loop: basic unit controlling motor movement, reflexes
- dorsal (sensory) and ventral (motor) roots
- transport of fibres
- reflexes: simple monosynaptic, complex (knee jerk), babinskis reflex

Central pattern generators

- neural network produces rhythmic patterned outputs without sensory feedback
- true for autonomic system
- CPG studied from patients with spinal cord injury

Myelination

- myelination of axons allows faster conduction of neural impulses
- direction of myelination tends to follow direction of conduction
- postnatal process finishing in second decade

The GABA switch

- postnatal brain development requires balance bw excitation and inhibition
- impairments of balance may cause disorders like ASD
- glutamate: excitatory
- y-aminobutyric acid (GABA): inhibitory

Brain development

- 4 yrs old: motor cortex, language
- 6 yrs old: somatosensory cortex, visual cortex
- 9 yrs old: reasoning
- 10+ yrs old: fine motor skills

Neurodevelopment through movement

- pons: 1-5 mo
- midbrain: 4-13 mo
- cortex: 8-96 mo
- prefrontal cortex: until 25 yrs

Brain development and neural plasticity

- immature brain, myelination after birth: consequence = variability
- embryo = overproduction of cells
- experience dependent process

Brain structure

- cerebral cortex gradually more functional after birth
- development of brain cortex: pattern of human evolutionary expansion is similar to pattern of human postnatal expansion

Nervous system in older adults

- aging = loss of neurons, dendrites, synapses, neurotransmitters, and myelin
- one theory: breaks in neural network links cause detours and therefore slowing
- exercise promotes cognitive function

Neuronal theories

- reductionists: approach to understanding complex things by reducing them to interactions of their parts or fundamentals
- selectionists: evolution or genetic variation occurs as a result of natural selection
- constructionists: brain development is growth rather than selection

Brain development pathologies

- autism: little genetic basis (difficulty with motor skills)
- down syndrome: strong genetic basis (late to reach early motor milestones like grasping, sitting, walking..)

Motor dev through life

- skillfulness: 11 yo
- context-specific motor skills: 7-11 yo
- fundamental motor patterns: 1-7 yo
- pre-adapted period: 2 wk-1yo
- reflexive period: birth - 2 wk

Early motor behaviour

- reflexive: stereotypical responses elicited by specific external stimuli
- spontaneous: movements not caused by known external stimuli

Spontaneous behaviours or motor stereotypes

- patterned and periodic movement
- disappears after 24 mo
- different from tic: consistent and fixed, not linked to stimulation
- theory: building blocks similar to voluntary movements
--> ex: spontaneous arm movement resembles reaching, spontaneous kicking resembles walking

Stereotypes

- seen in autism
- exacerbated by stress/excitation
- similar stereotypic movement can occur in typically developing children and those with developmental disorders
- examples: alternating leg movement, head banging, finger flexion, hand flapping/waving

Reflexes

- occur quickly after onset of stimuli
- involve single muscle or specific muscle group (not whole body)
- cannot be extinguished at any one time
- persistance indicates neurological problems

Purpose of reflexes

- facilitate survival
- allow interaction with environment
- adaptations
- building blocks for future movement

Postural reactions

- begin ~4 mo
- maintain posture in changing environment
- initially similar to reflexes, incorporated into general repertoire
- gravity reflexes: 2mo-18 mo (overrides by voluntary movements by 18mo), come back when individuals thrown off balance

Locomotor reflexes

resemble voluntary movements that do not appear until months after the reflexes have disappeared