The Role of Animal Models in Research (Edexcel A (SNAB) A Level Biology)

• The human brain is very difficult to study
  • The brain is complex and its tissues are delicate meaning that it is easy to cause damage during a surgical examination
  • Different regions work together to bring about brain function so often cannot be studied in isolation
• For this reason, animal models have historically been used in brain research
  • Some animals have similar brain structure to humans, so the findings from such models can reasonably be applied to the human brain
  • Many consider experimenting on animals for medical reasons to be more ethically acceptable than experimenting on humans
• Note that a model in science is something that provides a representation of real events e.g.
  • Computer modelling can be used to predict the future of global warming
  • Balls can be used to represent the molecules of a solid, liquid, or gas
  • Scaled down models of vehicles can be used in design and safety testing

The work of Hubel and Wiesel

• Hubel and Wiesel carried out research into the brain's visual systems during the 1960s and 1970s
• They studied the long-term impact of depriving various animal models of vision in one eye, and in doing so learned about the development of the brain's visual cortex
  • The visual cortex is the region of the cerebral cortex in which visual information is processed
• Hubel and Wiesel began their research using kittens as animal models
  • They stitched one of a subject's eyes closed soon after birth, meaning that as the kitten grew it could only see out of one eye
  • After 3 months they found that the kittens were blind in the eye that had been stitched shut
  • When they studied the activity of the neurones in the kittens' visual cortexes using electrodes, they found that the ocular dominance columns corresponding to the stitched shut eye were smaller than in normal kittens while the columns corresponding to the open eye were larger than normal
    • Ocular dominance columns are groups of neurones in the visual cortex that respond only to input from one eye or the other
      • Right ocular dominance columns receive information from the right eye while left columns receive information from the left eye
  • They concluded that the ocular dominance columns for the blinded eye were able to redistribute in order to correspond to the normal eye; they had switched dominance
• The research was then repeated using adult cat models
  • They found that no blindness resulted from the 3-month loss of vision, and no changes took place to the distribution of the ocular dominance columns
• They were able to replicate these results in young and adult monkeys, demonstrating the essential nature of light stimulation to the visual cortex during the early months of development
  • Without early stimulation to both eyes the ocular dominance columns in the visual cortex are unable to develop normally

Ocular dominance columns are stripes of neurones in the visual cortex that receive information from either the left or right eye

• The use of animals in medical research is common as it allows for the testing of new medications and research into anatomy and physiology without endangering the lives of humans
• Despite this, the use of animals in scientific research is highly controversial

Animal Research Ethical Arguments Table