Having nightmares is an experience that almost every human being can relate to — as evidenced in our storytelling, from ancient Egyptian texts to Hamlet’s soliloquies to the wisecracking of Freddy Krueger. During spooky season, many of us thrill at experiencing the same fear and anxiety a nightmare can summon in the safety of a movie theater. But what’s the science behind bad dreams?

To learn more, we reached out to Shantée Ayala Rosario, a doctoral candidate in UCLA’s interdepartmental molecular, cellular and integrative physiology program. Her interest in the field was sparked when she participated in the UCLA Brain Research Institute’s summer undergraduate research experience pathway program and worked in the lab of her future mentor, Gina Poe, the Eleanor Leslie Professor of Innovative Brain Research.

In this special October installment of the UCLA College video series, “Silly Questions, Smart Bruins,” Ayala Rosario explains what our brains are doing while we sleep, how we can deal with nightmares and whether or not external entities really can sneak into our dreams on a Halloween night.

(Watch the previous installments of “Silly Questions, Smart Bruins.”)