HOCK - Chapter 1 More experience = bigger brain

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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)

10. HOCK - Chapter 1More experience = bigger brain • Discussion and Criticisms • Stress • Impoverished rats had stressful life • Completed another experiment to show stress differences

11. 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 isin humans

12. 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

13. 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?