Brain & Perceptual Motor Development

1. Brain & Perceptual Motor Development

5. Myelinization

6. 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

7. 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.

8. Brain Growth Spurt • Midpregnancy to 4 years • Midpregnancy to 18 months • glial cells • 18 months to 4 years • myelinization

9. 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.

11. 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.

13. 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

14. 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

15. Brain Growth & Development • Growth of Skull reflects the growth of the brain • Peak head breadth velocity 13 weeks • Peak head circumference 15-17 weeks • Velocity high until 32-34 weeks • Growth of the vault of the skull depends on and is controlled by the growth of the brain

16. Brain Growth & Development • 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

17. Fetal Stimulation

18. Hooker’s findings on ages (weeks) at which specialized movements appear in the fetus • upper trunk 8.5 • head and neck 8.5 • shoulder and arms 9.5 - 11 • lower trunk 9.5 - 11 • eye muscles 11.5 - 12.5 • lips, jaw and tongue 11 - 12.5 • ankles and toes 12 - 14.5 • wrists and fingers 12 - 14.5

19. 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.

20. 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.

21. 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.

22. 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

23. 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

24. REFLEXIVE MOVEMENTS • Swimming movements • 2nd week to 5th month

25. 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

26. Baby Reflexes Video • Baby Swimming Video

27. 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

29. 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

30. 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

31. VOLUNTARY INDEPENDENT LOCOMOTION • Individual variability • Some phases sometimes missed out

32. Perceptual-Motor Development

33. 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

34. 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

35. 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

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

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

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

39. 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

41. 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

42. 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

43. 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

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

45. 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 Running • More advanced arm and leg movements

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

47. 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 2-3 years 3-4 years 3 years 5 years 6 years Stages of Development of Catching a Ball • 1) Whole body • 2) Arms • 3) Hands

48. Ball Bouncing • Should one handed or two handed be taught first?

49. 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 Kicking

50. 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 3.6-5 years 4-5 years 5 years and over 6 years Throwing