Human Brain development

Brain development in the uterus (1) 3 parts of Brain formed by 3 rd week of conception Brain starts to function properly a week later Between the 4 th and 7 th months of gestation the brain is forming neutral connections to different parts of the body (synaptogenesis)

Brain development in the uterus (2) After month 8 brain grows quicker Hippocampus and prefrontal cortex formed- responsible for memory

Animal model use Lots of similarities between brain of humans and animals e.g. cats and monkeys Results on these animal brains usually reflect experiments performed on human brains However some see this as highly unethical

Visual cortex Part of cerebral cortex at back of the brain Neurones in the visual cortex process information from visions provided by the left and right eyes Neurones grouped together in ‘ocular dominance’ columns (either left of right column) Columns same size for both humans and animals with ‘normal’ vision

Hubel and Wiesel (1) Experiment preformed to find out about development of ocular dominance columns in visual cortex of kittens Each new born kitten used had 1 eye stitched closed in order they could only see out of 1 eye

Hubel and Wiesel (2) After a few months the closed eye was unstitched Scientists found that the kittens were blind in the stitched eye When experiment was performed on adult cats no blindness occurred as well as adult and young monkeys

Hubel and Wiesel (3) Experiment showed ocular dominance columns of stitched eyes has decreased in size However, columns in the unstitched eyes had increased in size This was so that the columns which were not stimulated by light were taken over

Critical window Experiment by Hubel and Wiesel provides evidence that it is critical for humans to be exposed to visual stimuli for visual cortex and ocular dominance to properly develop

Critical window (2) The cataract also provides sufficient evidence of a critical window This is when the lens becomes cloudy If it occurs in babies and not removed it can cause lack of development of the overall visual system However if it occurs within adults it is less of a problem as the vision is already developed Therefore clear vision returns after it has been removed

Moral reasons for animal testing (1) Only performed when absolutely necessary and is a highly regulated industry Animals have very similar anatomy to humans- has led to many breakthroughs Does not pose risk to human life as humans do not need to be tested

Moral reasons against animal testing Unnecessary animal deaths often occur in very high number Some feel animals have as right to life as humans Regulation does not always prevent abuse High pain and distress imposed on animal