Critical Periods of Human Development

1. Critical Periods of Human Development Raising Capable Children Symposium on Early Childhood Development Gilgit May 22-24, 2006 Camer Vellani AKU Human Development Programme

2. Introduction • “Education is a great equaliser ifall children have an equal opportunity to take advantage of it” -- Ramphela Ramphele, Managing Director, World Bank • “As economic historians have pointed out, improved health, competence, and coping skills were a significant factor in the economic growth of Western countries after the industrial revolution” -- Fraser Mustard “From Early child Development ot Human Development” Editor: Mary Young; World Bank, 2000

3. Adaptive property of the brain Functions required for long term survival Ability to learn Responsible social behaviour Maintenance of health

4. Functions of the brain influencing the ability to learn • Memory • Sensory perception – all modalities – stimulated by curiosity, motivation, interest • Association • Thought and conceptformation • Revision of concept • Emotion

5. Concept A concept is an abstract idea that is synthesised from several elements of knowledge The synthesis has broader meaning and application than its elements considered separately

6. Functions of the brain influencing behaviour • Memory of experience • Concepts • Self esteem • Emotion • Sex • Application of thought • Impulse

7. Functions of the brain influencing health • Psychological determinants of behaviour • Competence of the immune system • Central control of voluntary and involuntary activities of all organ systems

8. Burden of mental and behavioural disorders • Present at any one point in time in about 10% of the adult population • Around 20% of all patients seen by primary health care professionals have one or more mental disorders • One in four families is likely to have at least one member with a behavioural or mental disorder The World Health Report 2001

9. Unique property of the human brain Man’s ability to process, apply, innovate and express abstract thought distinguishes him from other primates and all other animals Abstract thought is a complex versatile function of the cerebral cortex

10. Language Words (symbols) and gestures are used to express thought The sound and use of words is memorised accurately The meanings of words and gestures are learnt by correspondence with action, through processing of complex sensory perception

11. Spectrum of human development

12. D. OPTIC SULCUS C. NEURAL GROOVE OTIC PLACODE YOLK SAC SOMITE 1 AMINON (CUT EDGE) B. SOMITE 7 A. NEURAL GROOVE The dorsal aspect of a reconstruction of a 7-somite human embryo of about the 22nd day. The early optic sulcus is seen in the prosenephalic region. A — partially segmented paraxial mesoderm; B — roof of neural tube; C — pericardial area; D — branchial arch region. X c.47. Modified from Payne (1925).

13. ROOF OF IVTH VENTRICLE MIDDLE VENOUS PLEXUS POSTERIOR VENOUS PLEXUS MIDBRAIN CERVICAL FLEXURE ANTERIOR VENOUS PLEXUS OTIC VESICLE OPTIC CUP EXTERNAL AUDITORY MEATUS FOREBRAIN VESICLE HAND A photograph of the left side of a 13.4 mm. C.R. length human embroyo (estimated age, 40 days). The supra-umbilical swelling of the ventral body wall is produced by the liver and the pericardium. The heart can be seen within the latter. X c. 6.5. UMBILICAL CORD

15. Schemes to show successive stages in the differentiation of the cerebellar cortex. The superficial cortex and its derivatives are shown in red. The arrows in B indicate the probable migration of the cells. [Note synapses in the Dentate Nucleus in C]

16. Development of the cerebral cortex • Begins when the embryo is 15 mm long • The germinal matrix lining the cortical lumen releases 100 K neurones per day from weeks 8-24 then at a slower rate to a total of 100 billion at birth • Neurones migrate under the influence of regional genetic control to their locations in the mantle of grey matter beneath the surface and aggregates deep within the substance of the cerebrum (parietal first)

17. Development of the cerebral cortex • Neuronal migration results in layers of cells which connect later with the axons of cells located elsewhere but targeting cells in the cortex • Differential cell death begins around 24 weeks with the reduction of cell release from the germinal matrix

18. Development of the cerebral cortex • Once located each neurone synapses with 100 neurones • Synapses progress rapidly until the age of 5 years, then more slowly to 18 years and continue through life

19. Development of the cerebral cortex With increase in the size and weight of the brain at the end of the second trimester behaviour becomes complex Sucking on hands and fingers, grasping, extending, flexing, rotating, sleeping and waking periodically and reacting to sound

20. Superimposed photographs of foetuses between the 3rd and 5th months of pregnancy. (Original)

21. Structural modulation of the cerebral cortex • Utilisation of neural pathways modifies neuronal structures and connections over long distances • Changes in activity of distant yet synaptically related structures alter inputs to the cortex and result in new physical and chemical relations between cells

22. Factors affecting growth and development in utero Foetal nutrition and immunity which are dependent on maternal stores and nutrition, some requirements are small • Folic acid, iron, vitamin A • Insufficiency results in failure of closure of the neural tube, anaemia and delayed development particularly of the brain

23. Factors affecting growth and development in utero • Infections especially viral during organ formation e.g. Rubella • results in faulty development of the inner ear, eye, brain and heart • Environmental toxins absorbed by the mother e.g. lead, mercury, industrial waste and products of combustion • Drugs and alcohol • Radiation

24. A measure of the rate of growth of the brain after birth is the rate of the growth of the head relative to the length of the body

25. Conditions Influencing Human Development

26. Conditions Influencing Human Development

27. ‘Plasticity’ and critical periods of development • Human development is shaped by interaction between biology and experience • Structural platforms develop early through sensory perception that support learning, health and behaviour - the period for vision is critical • Distinction between normal variations, maturational delays, transient disorders and persistent impairments is difficult • Therefore, strive for conditions that support development for all and, for the disabled, conditions that support functional capability

29. Social environment in rural and urban Sindh (2002) • Cross-sectional study of the growth and development of 1247 children aged less than 3 years and their social environment, funded by AKU at AKU • Children with stunting (low height for age – indicator of chronic malnutrition) 39% Bilal Iqbal, CHS: AKU National Health Sciences Research Symposium Sept 2003

30. Psychomotor Development Study of the social environment of children under 3 years in urban and rural Sindh2002 by Bilal Iqbal (AKU-CHS)

31. Potential studies • Effectiveness and limitations of formal education in relation to children’s learning ability • Early nutritional determinants of proneness to chronic disease (diabetes, coronary disease, hypertension) • Factors affecting • mental health and immune competence • resilience and gene expression for child development and its sequelae • violence and tolerance of individuals and communities • economic growth, allocation of resources, and well-being of individuals, families and communities