HOCK - Chapter 1 More experience = bigger brain

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HOCK - Chapter 1More experience bigger brain

• History of Brain Studies
• Studies were shown as early as 1785
• Malacarne used pairs of dogs and birds
• From each pair one was trained extensively while
  the other was not
• Trained subjects showed more folds and fissures
  in Autopsied brains, believed to be more complex
  for this reason
• Research stopped for an unknown reason

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HOCK - Chapter 1More experience bigger brain

• New Technology (1960)
• Experiments at University of California
• Measure brain activity with great magnification,
  noting brain enzymes and neurotransmitters
• Mark Rosenzweig, Edward Bennett, and Marian
  Diamond used these techniques in 16 experiments
  over 10 years
• Used rats in the experiments

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HOCK - Chapter 1More experience bigger brain

• Why Rats?
• Convenient
• Cerebral cortex is smooth,
• - easy to measure
• Small and inexpensive
• Large litters
• Inbred rats allow researchers to include genetics
  in experiments if desired

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HOCK - Chapter 1More experience bigger brain

• Experiment
  
• Believed rats raised in a highly enriched
  environment will demonstrate differences in brain
  growth and chemistry vs non stimulated
• 3 rats chosen from each litter
• Randomly chosen for one of 3 environments
• 12 rats in each condition for 16 experiments

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HOCK - Chapter 1More experience bigger brain

• The Three Environments
• Standard colony cage
  
• Several rats with adequate space and plenty of
  food/water
• Impoverished environment
• Slightly smaller cage in an isolated room with
  adequate food and water
• Enriched environment
• 6-8 rats lived in large cage with many different
  objects to play with, a new set everyday

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HOCK - Chapter 1More experience bigger brain

• Results
  
• The cerebral cortex was significantly heavier and
  thicker in the enriched rats
• The cerebral cortex deals w/ experience,
  movement, memory, learning and all sensory input
• Greater chemical activity of acetylcholinesterase

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HOCK - Chapter 1More experience bigger brain

• Results

• Same number of neurons but neurons were larger
• Ratio of RNA to DNA (important for cell growth)
  was larger in enriched rats
• Synapses of enriched rats brains were 50
• larger than the impoverished rats

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HOCK - Chapter 1More experience bigger brain

• Results
• Although differences were not large they were
  consistent and repeatable
• There can now be no doubt that many aspects of
  brain anatomy and brain chemistry are changed by
  experience.
• - M. R. Rosenzweig

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HOCK - Chapter 1More experience bigger brain

• Discussion and Criticisms
  
• Handling
• Enriched rats handled more
• Solved this problem by handling impoverished rats
  in different experiment (no brain growth simply
  from handling)
• Then ran enrichment experiment again handling
  rats equally this time (same results as before)

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HOCK - Chapter 1More experience bigger brain

• Discussion and Criticisms
• Stress
• Impoverished rats had stressful life
• Completed another experiment to show stress
  differences

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HOCK - Chapter 1More experience bigger brain

• More Criticisms
• - Tame lab mice used
• To solve Wild deer mice used in enrichment
  experiment showed similar gains as lab mice
• Deer mice had larger cerebral cortex initially,
  coming from a natural setting
• Greater brain mass
• - Relevance to humans
• Hard to compare even rats to rats let alone show
  how it is in humans

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HOCK - Chapter 1More experience bigger brain

• Recent Applications
• Human autopsies
• Blind people less developed cortex in
• corresponding area
• Baby study
• Early stress in life and mental illness
• Early intervention

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Discussion Questions

• Why were rats used?
• How were the three environments different in this
  experiment?
• How were the enriched rats brains different from
  the impoverish rats brains?
• Why were deer mice used?
• Why is this relevant to human brains?