Week 3, Perfect Paragraph

During the methods part of Rosenzweig's research, several experimental factors had to be considered. In order to avoid bias, the examiners were not told which rat’s brain belonged to which of the three environments. After the treatment period, the brains were measured, weighed and analyzed to determine cell growth and levels of neurotransmitter activity. A neurotransmitter called acetylcholinesterase was the focus of the chemical examination. This neurotransmitter is responsible for faster and more efficient transmission of neural impulses. The cerebral cortex of the brain is responsible for experiences, movement, learning and sensory input. It was found to be heavier and thicker in rats raised in the enriched environment compared to the rats raised in the impoverished environment. The rats that inhabited the enriched environment also had increased acetylcholinesterase activity, had larger neurons and a higher RNA to DNA ratio. No differences were found between the number of neurons. Rosenzweig assumed that these differences implied higher levels of chemical activity had taken place. These results were seen again when they performed the same experiment several more times. The cortex increased in weight in response to the type of experience in each environment type, but the sub-cortex (the rest of the brain) changed very little. This measurement of the cortex to the sub-cortex was the most accurate measurement because overall brain weight varies with the overall weight of each animal (there is no correlation). They also found that enriched synapses were much larger in the rats that came from the enriched environment. These experimental results all supported the hypothesis which stated that animals raised in highly stimulating environments would demonstrate differences in brain growth and chemistry when compared to animals reared in plain/dull circumstances.