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】并列復合句。分號連接兩個并列的分句。前一個分句的主干為Freud formulated his revolutionary theory,其中that引同位語從句補充說明theory。后一個分句的主干為 neurologists had switched thinking of them as just "mental noise",其中前句提到的dreams,破折號后內容是對mental noise的解釋，其中包含that引導的定語從句修飾work。
【譯文】一個世紀前，弗洛伊德闡述了他革命性的理論，即夢是我們無意識的欲望和恐懼經偽裝后的虛幻事物；到了 20世紀70年代末期，神經專家們轉而認為夢是“精神噪音”，即在睡眠中進行神經修復活動的一種隨機的副產品。
【點撥】l）formulate意為“構想，制定”或“闡述”，本句中的意思是“闡述”。2）switch to“轉換到......”

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

【分析】多重復合句。句子主干為researchers suspect that..., that引導賓語從句,其中 regulating...現在分詞短語作狀語，其中又嵌套while引導的時間狀語從句。