B&C Info

• Blakemore and Cooper aimed to study the effects of restricted early visual experience on development of cells in the visual cortex
• Hirsch and Spinelli raised cats so that one eye was only exposed to horizontal stripes and the other eye only to vertical stripes. They found that all the cells in the visual cortex only responded to one eye, showing that the visual cortex is "plastic"
• Sample of B+C: 2 newborn kittens, 5 months old during behavioural tests and 7.5 months old during neurological tests
• A special cylinder was constructed for B+C, which had no corners or edges. The surface was covered with black and white stripes that were either vertical or horizontal
• B+C was a lab experiment
• B+C Used an independent measures design
• The IV of B+C was whether kittens' early experience was of a totally horizontal or totally vertical environment
• The DVs of B+C were

  1. Behavioural differences between the vertically and horizontally raised kittens
  2. Neurophysiological differences e.g how cells in the visual cortex responded to lines of different orientations
• B+C also aimed to test whether brain plasticity occurred due to experience (nurture) or nature
• Early experience of kittens in B+C: For the first 2 weeks of the procedure, newborn kittens were placed in a completely dark room
• After 2 weeks, they were placed into the special cylinder for an average of 5 hours a day, and then put back into the dark room
• After 5 months, the visual deprivation was stopped, and the kittens who were now cats were taken into a small room which had lighting. They were given artificial lenses to ensure visual difficulties were not due to astigmatism
• The period of time they waited was 5 months as this is how long it takes for cats to have a fully developed visual system
• After these 5 months, a behavioural assessment was conducted where cats' raised in a vertical environment could detect horizontal items and vice versa, as well as their initial response to the real world
• At 7.5 months, Neurophysiological tests were carried out. The cats were paralysed and had an electrode inserted into cells in the visual cortex, in order to measure their activity
• At 7.5 months, the cats were also shown lines at all angles to test their neurophysical responses
• B&C found that the Cats' early experiences led to permanent visual deficits, for example the cats often reached out to touch objects that were far away
• B&C also found that cats' visual cortex naturally adjusted to the visual changes, while visual reflexes were not shown immediately, within 10 hours they were normal
• If the horizontal cat was shown a vertical rod, it would initially not be able to identify it as being there
• Results from Neurophysiological assessment:

  Most cells in the visual cortex responded in the way that any normal animal would

  In the horizontal cat, cells in the visual cortex did not respond to lines within 20 degrees of the vertical orientation and 12 out of 52 responded within 45 degrees of the vertical orientation, meaning vertical lines were not seen
• B&C Conclusion: The brain is modified by experience, so that the biological system fits the needs of the environment. This supports the idea that the brain is "plastic"