15. A century ago,Freud formulated his revolutionary theory that dreams were the disguised shadows of our unconscious desires and fear by the late 1970s,neurologists had switched to thinking of them as just "mental noise" - the random byproducts of the neural-repair work that goes on during sleep.

【分析】并列复合句。分号连接两个并列的分句。前一个分句的主干为Freud formulated his revolutionary theory,其中that引同位语从句补充说明theory。后一个分句的主干为 neurologists had switched thinking of them as just "mental noise",其中前句提到的dreams,破折号后内容是对mental noise的解释，其中包含that引导的定语从句修饰work。
【译文】一个世纪前，弗洛伊德阐述了他革命性的理论，即梦是我们无意识的欲望和恐惧经伪装后的虚幻事物；到了 20世纪70年代末期，神经专家们转而认为梦是“精神噪音”，即在睡眠中进行神经修复活动的一种随机的副产品。
【点拨】l）formulate意为“构想，制定”或“阐述”，本句中的意思是“阐述”。2）switch to“转换到......”

16. Now researchers suspect that dreams are part of the mind’s emotional thermostat, regulating moods while, the brain is "off-line".

【分析】多重复合句。句子主干为researchers suspect that..., that引导宾语从句,其中 regulating...现在分词短语作状语，其中又嵌套while引导的时间状语从句。