The following text is a paragraph from a student essay to answer the question "Discuss ethical considerations in animal research used to study the brain and behavior." Add the next paragraph, making reference to three different ethical considerations.

One study that had a major impact on education was the study by Rosenzweig, Bennet, and Diamond (1972). In this study, they wanted to see if stimulation in a rat's environment would lead to changes in the structure of the brain - or neuroplasticity. Rats were randomly allocated to one of three conditions. In the control condition, there were three rats in a cage. In the impoverished condition, the researchers placed each rat in an individual cage. The individual cages lacked the toys that were in the enriched environment. For the enriched condition, the researchers placed 10 - 12 rats in a cage containing different stimulus objects to explore and play with. All groups had free and adequate access to food and water. After 30 days, the rats were killed and their brains were examined. The rats in the enriched environment had a thicker cerebral cortex than those in the impoverished condition. The rats in the control condition also had more development than in the impoverished condition. This indicates that social interaction as well as playing with the objects had an effect on brain development. Although this early study was important in our understanding of how the environment can affect the brain, the study's ethical practice needs to be discussed..