1. WHAT STUDIES HAVE SHOWN AND EXPLAINED ABOUT HOW THE BRAIN DEVELOPS Human Brain Development Krunal Patel and John Kim

2. THE DIFFERENT STAGES OF PRENATAL BRAIN DEVELOPMENT Brain development during the foetal stage

3. First trimester Formation of neural plate Formation and closure of neural tube and brain fold Differentiation of brain Dispersal and connection of neuronal cells Limb movement

4. Second trimester Chest and diaphragm movements Schwann cell overlapping of nerve cells Reflex actions develop further Brain stem near full maturity Baby can detect loud noises/rapid movements Brainwave activity including sleep cycles and REM

5. Third trimester Rapid growth of brain  Develops more grooves and folds  Specifically the cerebellum and the cerebral cortex Nervous system expands further Brain near full maturity

6. STUDIES BY HUBEL AND WIESEL Animal Models for Brain Development

7. Hubel and Wiesel Visual deprivation Sutured one eye at birth Reopened eye after a period of time Eye had lost function and ability to perceive  Changes in visual cortex  Changes in neuron count Concept of important visual development early in life of animals

8. Hubel and Wiesel Black and white- Bars and dots Variety of shapes and intensities of black were projected onto a screen in front of a cat Cat’s visual cortex was observed relative to specific shapes Eventually a response was discovered (by an accident) Concept of a nearby cells reacting to specific stimuli

9. FOCUSING ON KEY PERIODS DURING THE DEVELOPMENT OF THE VISUAL CORTEX OF THE OCCIPITAL LOBES The ‘critical window’ of Brain Development

10. Growth of the brain Cell division occurs at the highest rate during the prenatal period – up to 250,000 neurones produced per minute. Many of the cells produced eventually undergo apoptosis (‘programmed cell death’) as part of the development of the tissue in the brain. At birth, the brain is 25% of its projected adult weight; reaching 80% after 2 years of age. In the post-natal period:  Neurones grow in size  Axons elongate  Synaptic connections form – with one neurone forming synapses with 1000s of other neurones.  Only a few additional neurones form during this period.

12. Critical periods of growth of the visual cortex The ‘critical periods of growth’ are also known as ‘windows of opportunity’ or ‘critical windows’. Evidence for critical periods of growth of the visual cortex includes the findings of the Hubel and Wiesel experiments, discussed earlier.

13. How does vision develop prior to birth?

14. Ocular dominance columns

15. The visual cortex in the critical period

16. Evidence for this critical period of visual cortex development The appearance of ocular dominance columns in the visual cortex of kittens was affected by monocular deprivation in the ‘6-13 weeks’ period after birth. C.J. Shatz (1978) Rats reared in visually complex environments develop greater numbers of visual cortex synapses than those in control groups reared in ‘standard’ animal cages. W.T. Greenough (1985)

17. STUDYING THE MORAL AND ETHICAL IMPLICATIONS OF USING ANIMALS TO ADVANCE MEDICAL RESEARCH Animal Use in Medical Research

18. For – we should use animals in research From one perspective, experimenting on animals could be viewed as acceptable if (and only if):  Suffering is minimised in all experiments.  Human benefits are gained which could not be obtained by using other methods. Utilitarianist approach It’s either us or the animals

19. For – we should use animals in research The Three Rs approach:  Reduction  Refinement  Replacement The three Rs are a set of principles that scientists are encouraged to follow in order to reduce the impact of research on animals.

20. Against– we shouldn’t use animals in research Experimenting on animals is always unacceptable because:  It causes suffering to animals, without their consent.  The benefits to human beings are not justifiable.  Any benefits to human beings that animal testing does provide could be provide in other ways. People who argue that animals rights are just as significant as human rights may claim that we should place the same ethical constraints on animal testing as we do on human trials.

21. Hubel and Wiesel Video https://www.youtube.com/watch?v=IOHayh06LJ4