Brain & Perceptual Motor Development

Myelinization

General Processes in Brain Development Various 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 regions –migration of cells –aggregation of cells –differentiation of immature neurons –formation of connections between neurons –selective death of some cells –elimination of some initial connections

–Fully developed brain: 100 billion neurons –Multiplication ceases before birth –Therefore, 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 cortex –Following migration dendrites and a single axon are generated –as neurons mature the number of dendrites and axon connections is reduced.

Brain Growth Spurt Midpregnancy to 4 years Midpregnancy to 18 months – glial cells 18 months to 4 years – myelinization

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

Neurological Age Specific 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 Gradients Gradients in brain development are present in the two years after birth Most 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 Gradients Lagging behind are the association areas –comparison and integration of impulses Within the Motor Area –Cells controlling arm & trunk develop ahead of leg –Same in Sensory area By 3 months all primary areas are relatively mature

Brain Growth & Development Growth of Skull reflects the growth of the brain –Peak head breadth velocity13 weeks –Peak head circumference15-17 weeks –Velocity high until weeks Growth of the vault of the skull depends on and is controlled by the growth of the brain

Brain Growth & Developmen t 6 month after birth –Head circ. velocity is 15% of 34 week value 1 year after birth –Head circ. velocity is 7% of 34 week value At birth –brain weighs 25% of adult value At 6 months weighs –50% of adult value

Fetal Stimulation

Hooker’s findings on ages (weeks) at which specialized movements appear in the fetus upper trunk8.5 head and neck8.5 shoulder and arms lower trunk eye muscles lips, jaw and tongue ankles and toes wrists and fingers

Responses in the Newborn Head 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 response –this 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 Newborn Springing position –this occurs when the infant is held upright and inclined forward. The arms extend forward and the legs brought up. Fencing position –this 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 MOVEMENTS After the first weeks after birth a few reflex patterns exist that resemble later voluntary movements WALKING REFLEX –by 2 wk 58% of infants have it –No arm component –happens upside down

REFLEXIVE MOVEMENTS THE CRAWLING REFLEX –pressure alternately applied to soles of feet –7th month gestation to 3rd or 4th month after birth –distinct delay before voluntary creeping at 7th to 9th month

REFLEXIVE MOVEMENTS Swimming movements 2nd week to 5th month

REFLEXIVE MOVEMENTS CLIMBING MOVEMENTS an 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 Video Baby Swimming Video

INTERACTION OF REFLEXES AND 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 LOCOMOTION CREEPING - occurs after prolonged front-lying. –Usually elicited in response to a reach for an object CRAWLING develops from creeping –one limb moved at a time –progresses to smooth contralateral motion SLIDING - bypassed by most –slide forward in seated position

VOLUNTARY INDEPENDENT LOCOMOTION STANDING UP –creep then crawl from front-lying position –usually assume an upright position from the back lying position –via seated position UPRIGHT GAIT –10 TO 15th month –wide stance, feet turned outwards, knees slightly flexed

VOLUNTARY INDEPENDENT LOCOMOTION Individual variability Some phases sometimes missed out

Perceptual-Motor Development

PERCEPTUAL-MOTOR DEVELOPMENT relates to changes or improvements in the child’s afferent or sensori-perceptual abilities with age there is an increase in capacity to perceive increasingly more complex kinds and quantities of sensory information

INFORMATION PROCESSING Adult highly efficient – only relevant cues processed – rapid, accurate response Children slower, and frequently pick-up irrelevant cues Children can pick up as much information from their sensors Short Term Memory –Children lose information more rapidly –Attention, no planful scanning of information –adults actually take in less information –rehearsal, encoding strategies

SHIFT IN DOMINANCE IN SENSORY SYSTEMS Move from a reliance on tactile-kinesthetic information to primary reliance on the visual system rope jumping 4 yrs child can not co-ordinate with rope 7 yrs can

IMPROVED INTERSENSORY COMMUNICATION More skilled at using multiple sensory inputs close eyes while rope jumping

IMPROVED INTRASENSORY DISCRIMINATION Greater ability of each of the senses to discriminate stimuli Greater ability to discriminate speed, direction, pattern of movement

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

SENSORY DOMINANCE handedness, footedness, eyedness By 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 Sequences Orderly predictable sequence of motor control Cephalocaudal –Gradual progression of increased control over the musculature, moving from head to the feet Proximodistal –Gradual progression of increased control over the musculature, from centre of the body to its most distant parts Large to small muscle sequence –Dominance of large muscle in movement replaced by smaller muscle control in refined movement

Developmental Variability There are age variations in the rate of movement skill acquisition Heredity and environmental circumstances ensure varying rates of development Readiness –Conditions within both the individual and the environment that make a particular task appropriate for the child to master Sensitive Periods –Time periods where skills can be more easily acquired

Differentiation & Integration Differentiation –Gradual progression from the gross globular (overall) movement patterns of infants to the more refined and functional movements of children as they mature Integration –Coordinated interaction of the opposing muscle and sensory systems Grasping –Changes from ill-defined corralling movements to more mature and visually guided reaching and grasping behaviour

Early Running Large muscle movement Hurried walk (maintains contact) 18 months

Running More advanced arm and leg movements Hurried walk (maintains contact) First true run (nonsupport phase) Efficient and refined run Speed of run increases, mature run* 18 months 2-3 years 4-5 years 5 years

GROSS VISUAL-MOTOR SKILLS Throwing, catching, kicking, striking and ball bouncing Eyes are required for tracking

Stages of Development of Catching a Ball 1) Whole body 2) Arms 3) Hands Chases ball; does not respond to aerial ball Responds to aerial ball with delayed arm movements Needs to be told how to position arms Fear reaction (turns head away) Basket catch using the body Catches using the hands only with a small ball Mature catching pattern* 2 years 2-3 years 3-4 years 3 years 5 years 6 years

Ball Bouncing Should one handed or two handed be taught first?

Kicking Pushes against ball; does not actually kick it Kicks with leg straight and little body movement (kicks at the ball) Flexes lower leg on backward lift Greater backward and forward swing with definite arm opposition Mature pattern (kicks through the ball)* 18 mos. 2-3 years 3-4 years 4-5 years 5-6 years

Throwing Body faces target, feet remain stationary, ball is thrown with forearm extension only Same as above but with body rotation added Steps forward with leg on same side as the throwing arm. Boys exhibit more mature pattern than girls Mature throwing pattern* 2-3 years years 4-5 years 5 years and over 6 years

Throwing

SEX DIFFERENCES Parents often treat boys and girls differently from birth One yr old boys spend more time in gross motor activity while girls spend more in fine motor activity Boys are more vigorous in their play and are more exploratory than girls

SEX DIFFERENCES from 2 to 5 yrs girls excel in tasks requiring jumping, hopping, rhythmic locomotion and balance boys generally better in tasks requiring strength and speed from 5 to 6 yrs on, –boys generally perform better in running, jumping, and throwing activities –girls excel in hopping –balancing shows no clear pattern