Researchers have established that when people are mentally,bio-chemical changes occur in the brain
请问这个句子中brain后的that属于句子的那个成分,还有其后的指代词it 指代的是什么,这个句子该怎么分析成分,谢谢!
Researchers have established that when people are mentally engaged，bio-chemical changes occur in the brain that allow it to act more effeetively in cognitive（认知的）areas such as attention and memory. 不好意思刚才句子不完整，请大家帮我分析一下，谢谢！