Brain DevelopmentBy Jay Patel

Development in the womb

• 3rd week – embryo formed 3 main parts of the brain• 4th week – brain begins functioning• 4th month onwards – brain making neural connections to all parts of

the body (synaptogenesis)• 8th month – foetus can recognise and remember its mother’s voice

Animal Models

• Similarities between animal and human brains• So same experimental results usually obtained• Using humans unethical so animal models used• E.g. Hubel and Wiesel’s experiment on development of ocular

dominance columns in kittens

Ocular Dominance Columns

• Visual cortex part of cerebral cortex at back of brain• Neurones in visual cortex receive and process visual information• Neurones grouped together in ocular dominance columns• Arranged in an alternating pattern

Hubel and Wiesel Experiment

• Stitched closed one eye from each kitten• When unstitched, kittens blind from previously stitched eye• Ocular dominance columns of stitched eyes decreased in size,

columns of unstitched eyes increased (switched dominance)• When repeated on adult cats, they recovered full normal vision and

ocular dominance columns unchanged• Same results found on young and adult monkeys• So both eyes need to be visually stimulated in early stages of life for

normal visual development

Critical Window

• Period of time in early stages of life when critical for humans to be exposed to visual stimuli for normal visual development• Hubel and Wiesel experiment – animal model applied to humans• Cataracts in humans – babies and adults

Animals in Medical Research

• Moral and ethical issuesAgainst ForPain/distress caused to animals Only done when necessary, scientists follow

strict rules (painkillers/anaesthetics used to minimise pain)

Alternatives to using animals in research (e.g. human cell cultures and computer models)

Cell cultures and computers not true representation of how cells may react when surrounded by other body tissues, only way to study behaviour

Animals different to humans, drugs tested on animals may have different effects on humans

Animals are similar to humans, animal research has led to many medical breakthroughs (e.g. antibiotics, insulin, organ transplants)

Animals have right to not be experimented on – animal right activists

Humans have greater right to life than animals because they have more complex brains