A new study has investigated the link between pupil dilation/contraction and memory processing during sleep. The study titled, “Sleep microstructure organizes memory replay”, published in the journal Nature and conducted by scientists at Cornell University, Ithaca, claims that pupil size while sleeping could indicate the memories you are reliving in your dreams.

Using advanced eye-tracking technology combined with EEG (electroencephalogram), the researchers monitored the sleep patterns of mice to record their brain activity. Notably, the mice were fed new information such as navigating the maze during the day and allowed to sleep at night.

Upon analysing the data, it was found that two substages happened during the NREM (Non-Rapid Eye Movement) sleep. The pupils contracted in one phase, suggesting new memories were being replayed while pupils dilated when the mice were likely processing or reliving past experiences in their dreams. Both phases took place in quick succession.

“It’s like new learning, old knowledge, new learning, old knowledge, and that is fluctuating slowly throughout the sleep,” neuroscientist Azahara Oliva of the Department of Neurobiology and Behaviour told ScienceAlert.

Also Read | The Science Behind A Good Night’s Sleep: Sleep-Wake Cycles Explained

Creating new memories but not at the expense of other

The study helps find answers to why the creation of new memories does not erase the old ones; for example, learning to play an instrument without forgetting to ride a car.

“Our results suggest that the brain can multiplex distinct cognitive processes during sleep to facilitate continuous learning without interference,” the researchers wrote.

“We are proposing that the brain has this intermediate timescale that separates the new learning from the old knowledge.”

One of the key insights from this research is the brain’s ability to separate the two sleep substages which prevents a “catastrophic” forgetting of memories at the expense of previous memories.

“This finding provides a potential solution for the long-standing problem in both biological and artificial neural networks of preventing catastrophic interference while also enabling memory integration,” write the researchers.

The study results have encouraged the scientific community which hopes to see the results on humans that might lead to better memory enhancement techniques and also help train artificial intelligence.

Police in the United States have arrested a Cornell University students for allegedly making violent threats against his Jewish peers. The US Justice Department identified the students as 21-year-old Patrick Dai from Pittsford, New York. He is accused of posting threatening messages to the Cornell section of an online discussion website, including those calling for the deaths of Jewish people and a post that said “gonna shoot up 104 west”. The term 104 west refers to Cornell University dining hall that is located next to the Cornell Jewish Centre, the Justice Department further said.

Dai also allegedly threatened to “stab” and “slit the throat” of any Jewish males he sees on campus, to rape and throw off a cliff any Jewish females, and to behead any Jewish babies, according to Cornell University Police.

He was arrested after the investigators traced the deranged posts to Dai’s IP address at his off-campus apartment, NBC News reported citing federal complaint.

His family, however, believe their son is innocent.

“My son is in severe depression. He cannot control his emotion well due to the depression. No, I don’t think he committed the crime,” his father told New York Post in a text message, asking that his name not be used.

He also claimed that Dai sank into depression in 2021, one year after his engineering studies at the prestigious university.

At Cornell, Dai worked as an undergraduate consultant helping other engineering students with MATLAB, a computer programming language.

His parents said the man never had a history of violence.

“He was always very nice to society, well organised, helpful to my family and his classmates before 2021. He told us he lost his life goal and motivation. As parents, we tried to give him more love,” Dai’s father told the Post.

The US Justice Department website said the charge against Dai carries a maximum sentence of five years in prison and a fine of up to $250,000 (Rs 2.08 crore).

He will be presented before a federal court in Syracuse, New York, on Wednesday.

The investigation against him is being done by FBI’s Joint Terrorism Task Force (JTTF), which includes the New York State Police.