Brain & Perceptual Motor Development

Myelinization

General Processes in Brain DevelopmentVarious complex cellular changes occur in the transformation of the neural plate and groove of the embryonic ectoderm to the final form of the brain:localized proliferation in different regionsmigration of cellsaggregation of cellsdifferentiation of immature neuronsformation of connections between neuronsselective death of some cellselimination of some initial connections

Fully developed brain: 100 billion neurons Multiplication ceases before birthTherefore, average rate of over 25,000 per minute, with most occurring in the first three months.Mitosis occurs in cells prior to migration except in cerebellar cortexFollowing migration dendrites and a single axon are generatedas neurons mature the number of dendrites and axon connections is reduced.

Brain Growth SpurtMidpregnancy to 4 yearsMidpregnancy to 18 months glial cells18 months to 4 years myelinization

Cerebellum Growth Spurt(starts later, finishes earlier)Development & maintenance of neuromuscular co-ordination, balance, muscle toneSpurt 1 month before term to 18 monthscell contents at adult levels whereas forebrain and brainstem only at 60% of adult levels.

Neurological AgeSpecific patterns of motor, reflex and bioelectrical activity characterize specific gestational ages, and do not correlate well to the weight of the infant.Other indicators of maturity such as bone age are more closely correlated with growth of somatic variables such as weight or length.

Maturity GradientsGradients in brain development are present in the two years after birthMost advanced part of the cortex is the primary motor area (precentral gyrus)Next the primary sensory area (postcentral gyrus)Then primary visual area in occipital robe

Maturity GradientsLagging behind are the association areas comparison and integration of impulsesWithin the Motor AreaCells controlling arm & trunk develop ahead of leg Same in Sensory area By 3 months all primary areas are relatively mature

Brain Growth & DevelopmentGrowth of Skull reflects the growth of the brainPeak head breadth velocity13 weeksPeak head circumference15-17 weeksVelocity high until 32-34 weeksGrowth of the vault of the skull depends on and is controlled by the growth of the brain

Brain Growth & Development6 month after birthHead circ. velocity is 15% of 34 week value1 year after birth Head circ. velocity is 7% of 34 week valueAt birth brain weighs 25% of adult valueAt 6 months weighs 50% of adult value

Fetal Stimulation

Hookers findings on ages (weeks) at which specialized movements appear in the fetusupper trunk8.5head and neck8.5shoulder and arms9.5 - 11lower trunk9.5 - 11eye muscles11.5 - 12.5lips, jaw and tongue11 - 12.5ankles and toes12 - 14.5wrists and fingers12 - 14.5

Responses in the NewbornHead and arm responses. Closes hand in response to tactual stimulation of fingers and palm. Arm flexion can be elicited with pricking the hand or a tap on the hand. The startle response is evident-throws arm outward if startled.

Responses in the Newborn

Startle responsethis response consists of throwing the arms out, spreading the fingers, extending the legs and throwing the head back. It sometimes occurs with no apparent stimulation but is usually a response to stimuli which could frighten it such as noise, falling or other sudden occurrences.

Responses in the NewbornSpringing positionthis occurs when the infant is held upright and inclined forward. The arms extend forward and the legs brought up. Fencing positionthis occurs when the baby's head is rotated to one side, the arm toward which the head is rotated will extend and the opposite arm will flex.

REFLEXIVE MOVEMENTSAfter the first weeks after birth a few reflex patterns exist that resemble later voluntary movementsWALKING REFLEXby 2 wk 58% of infants have itNo arm componenthappens upside down

REFLEXIVE MOVEMENTSTHE CRAWLING REFLEXpressure alternately applied to soles of feet7th month gestation to 3rd or 4th month after birthdistinct delay before voluntary creeping at 7th to 9th month

REFLEXIVE MOVEMENTSSwimming movements2nd week to 5th month

REFLEXIVE MOVEMENTSCLIMBING MOVEMENTSan upward arm movement and the palmar-grasp reflex in one palm. Some experimenters have noted that reciprocal movements of the legs occur under these circumstances.toward end of first year and into 2nd year

Baby Reflexes VideoBaby Swimming Video

INTERACTION OF REFLEXESAND THE PHASING IN OF VOLUNTARY MOVEMENTS

Can a prolonging of a reflex inhibit the introduction of a voluntary movement?e.g. for a child to assume an upright stance and begin to walk it is necessary that the "grasping" (or prehensile) reflex in the feet be terminated

VOLUNTARY INDEPENDENT LOCOMOTIONCREEPING - occurs after prolonged front-lying. Usually elicited in response to a reach for an objectCRAWLING develops from creepingone limb moved at a timeprogresses to smooth contralateral motionSLIDING - bypassed by mostslide forward in seated position

VOLUNTARY INDEPENDENT LOCOMOTIONSTANDING UP creep then crawl from front-lying positionusually assume an upright position from the back lying positionvia seated positionUPRIGHT GAIT10 TO 15th monthwide stance, feet turned outwards, knees slightly flexed

VOLUNTARY INDEPENDENT LOCOMOTIONIndividual variabilitySome phases sometimes missed out

Perceptual-Motor Development

PERCEPTUAL-MOTOR DEVELOPMENTrelates to changes or improvements in the childs afferent or sensori-perceptual abilitieswith age there is an increase in capacity to perceive increasingly more complex kinds and quantities of sensory information

INFORMATION PROCESSINGAdult highly efficient only relevant cues processed rapid, accurate responseChildren slower, and frequently pick-up irrelevant cuesChildren can pick up as much information from their sensorsShort Term MemoryChildren lose information more rapidlyAttention, no planful scanning of informationadults actually take in less informationrehearsal, encoding strategies

SHIFT IN DOMINANCE IN SENSORY SYSTEMSMove from a reliance on tactile-kinesthetic information to primary reliance on the visual systemrope jumping4 yrs child can not co-ordinate with rope7 yrs can

IMPROVED INTERSENSORY COMMUNICATION

More skilled at using multiple sensory inputsclose eyes while rope jumping

IMPROVED INTRASENSORY DISCRIMINATION

Greater ability of each of the senses to discriminate stimuliGreater ability to discriminate speed, direction, pattern of movement

Perceptual-motor Development depends upon the development of the perceptual processes and the motor functions.

SENSORY DOMINANCEhandedness, footedness, eyednessBy 4.yrs handedness may be established period of ambivalence 5-9 yrs In footedness, no period of ambivalence In eyedness, not so much dominance

Developmental SequencesOrderly predictable sequence of motor controlCephalocaudalGradual progression of increased control over the musculature, moving from head to the feetProximodistal Gradual progression of increased control over the musculature, from centre of the body to its most distant partsLarge to small muscle sequenceDominance of large muscle in movement replaced by smaller muscle control in refined movement

Developmental VariabilityThere are age variations in the rate of movement skill acquisitionHeredity and environmental circumstances ensure varying rates of developmentReadinessConditions within both the individual and the environment that make a particular task appropriate for the child to masterSensitive PeriodsTime periods where skills can be more easily acquired

Differentiation & IntegrationDifferentiationGradual progression from the gross globular (overall) movement patterns of infants to the more refined and functional movements of children as they matureIntegrationCoordinated interaction of the opposing muscle and sensory systemsGraspingChanges from ill-defined corralling movements to more mature and visually guided reaching and grasping behaviour

Early RunningLarge muscle movementHurried walk (maintains contact) 18 months

RunningMore advanced arm and leg movements

GROSS VISUAL-MOTOR SKILLS

Throwing, catching, kicking, striking and ball bouncingEyes are required for tracking

Stages of Development of Catching a Ball1) Whole body2) Arms3) Hands

Ball BouncingShould one handed or two handed be taught first?

Kicking

Throwing

Throwing

SEX DIFFERENCESParents often treat boys and girls differently from birthOne yr old boys spend more time in gross motor activity while girls spend more in fine motor activityBoys are more vigorous in their play and are more exploratory than girls

SEX DIFFERENCESfrom 2 to 5 yrs girls excel in tasks requiring jumping, hopping, rhythmic locomotion and balanceboys generally better in tasks requiring strength and speedfrom 5 to 6 yrs on, boys generally perform better in running, jumping, and throwing activities girls excel in hoppingbalancing shows no clear pattern

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