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Neuroscientists Measure the Activity of Individual Neurons During REM Sleep for the First Time

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Posted August 12, 2015

An international team of scientists had recently discovered that the rapid twitching of the eyes seen in people undergoing shallow (REM) sleep are associated with moving on to the next dream “episode”, rather than with visually surveying the so-called dreamscape.

Observing the activity of individual neurons during REM sleep for the first time, a group of neuroscientists from around the world had found that the infamous “rapid eye movements” do not correspond to the surveying of a particular dream’s visual landscape, but rather anticipate the next “dream frame”. Image credit: alexramos via pixabay.com, CC0 Public Domain.

Observing the activity of individual neurons during REM sleep for the first time, a group of neuroscientists from around the world had found that the infamous “rapid eye movements” do not correspond to the surveying of a particular dream’s visual landscape, but rather anticipate the next “dream frame”. Image credit: alexramos via pixabay.com, CC0 Public Domain.

The discovery was made by recording the neural activity of 19 patients with electrodes implanted in their brains to monitor seizures over the course of four years.

“It’s a unique opportunity to look at what’s happening inside the human brain,” said study co-author Dr. Yuval Nir from the Tel Aviv University in Israel. “We’re very thankful to the epilepsy patients who volunteered to take part.”

Recording mostly from electrodes placed in the medial temporal lobe – an area of the brain involved in memory processing, but not vision – the researchers found that neural activity in this region coincided with the rapid eye movements characteristic of REM sleep.

These neurons are “tasked” with relaying a certain concept to the brain and fire regardless of whether there’s an actual picture in front of us, or whether we’re simply imagining something with our eyes closed. This “concept” relates to the memories and emotional content associated with the physical or mental image in question.

For a long time, researchers have assumed – without much in the way of actual evidence – that the rapid eye movements observed during REM sleep correspond to the visual portion of dreams, but now it seems much more likely that they indicate a certain reset, i.e., the beginning of a new chapter in a given dream or a new dream altogether.

This might also explain why unborn babies and people with congenial blindness also move their eyes in a rapid manner during the REM phase – those with no vision certainly aren’t surveying any visual landscape.

The study has received near-universal acclaim, with many sleep researchers commending it as an important contribution to our current – and ever-growing – body of knowledge on the subject.

For instance, Professor Jim Horne of the Sleep Research Centre at Loughborough University, who did not participate in the research, noted how it ties in with other findings, indicating that REM sleep has many similarities to wakefulness.

“I see REM sleep as rather like the screensaver on your computer; all you need is the touch of a button and your computer leaps to life. It’s very close to wakefulness. Non-REM sleep is more like when you switch your computer off, and waking up requires a process of rebooting.”

Another commenter, William Wisden, a neuroscientists at the Imperial College in London, said that while he was just as convinced of the kinship between brain activity during REM sleep and wakefulness as his colleagues, he wants to see some more scientific grappling with an even more important question – why do our brains have the circuitry for REM sleep in the first place?

“This paper doesn’t answer that, but it does emphasise how similar being awake and in REM sleep are, for certain aspects of the cortex.”

The study was published on August 11th in the science journal Nature Communications.

Sources: study, bbc.com.

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