Eye movements in sleeping mice are aligned with the direction of gaze in their dreams

When sleeping, mice have rapid eye movements that match their dreaming perception

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Introduction

In the past, researchers have had trouble determining whether rapid eye movement reveals anything about perception during dreams. Researchers tried to determine this by measuring eye movement during sleep and then waking a person to ask them what they were dreaming about. The problem with this is that people are not good at remembering or describing their dreams.

To get around this obstacle, researchers looked for a more objective measurement that they could use, and they found the solution in mice. Here's a quick summary of their work and findings.

The researchers

The authors of A cognitive process occurring during sleep is revealed by rapid eye movements describe their August 25 publication, here. Yuta Senzai is a postdoctoral scholar in the lab of Massimo Scanziani at the University of California, San Francisco.

In addition to performing and publishing their research, the pair also wrote a summary, Rapid eye movements in sleeping mice match where they are looking in their dreams, new research finds.

Background

Rapid Eye Movement (REM) has been recognized since the 1950s. This is the time during sleep when your eyes move around beneath your eyelids. This is also the time of sleep when people experience vivid dreaming.

In the past, scientists have attempted to get an understanding of whether or not that eye movement matches our dream perception by monitoring the eye movement and interrupting sleep to ask the research subjects about their dreams. However, the results have been contradictory.

Two challenges were that eye movements are difficult to measure when our eyes are closed, and people may not be great at describing our dreams in the detail that would be needed. So Senzai and Scanziani set about finding a more objective way to answer the question.

Mice turned out to be suitable objects of study for two reasons. First, they don't close their eyes completely when sleeping, which means that their eye movements can be measured with precision. Second, they - like humans - have a sort of internal compass that keeps track of the direction that the animal is gazing or moving.

What the researchers did

It was already known that mice experience REM sleep and that they had their internal compasses, so Senzai and Scanziani built from there in two steps.

First, when the mouse was awake, they measured its eye movements and mapped them to the firing of the neurons that were linked to the internal compass. Second they compared their observation with a similar comparison when the mouse was sleeping. They describe their finding like this:

Strikingly, we discovered that eye movement direction in sleeping mice precisely matched changes in heading direction, very much like gaze shifts in mice that are awake. This meant that eye movements during REM sleep may disclose gaze shifts in the virtual world of dreams, providing a window into the cognitive processes occurring in the dreaming brain

What comes next?

One question arising out of this work is to ask whether the other brain functions experience similar coordination during dreams, this could include neurons responsible for sensory perception, location awareness, or emotions. When awake, the internal compass gets its information about direction from the senses for sight and balance, so a second question is how the internal compass is changed without movement or changes in direction of gaze.

The authors conclude with this description of their future work:

Our next steps are to figure out what moves the brain’s internal compass during REM sleep, how it moves with the eyes and how different senses work together to generate the realistic experience of dreams.

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Thank you for your time and attention.

As a general rule, I up-vote comments that demonstrate "proof of reading".

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Steve Palmer is an IT professional with three decades of professional experience in data communications and information systems. He holds a bachelor's degree in mathematics, a master's degree in computer science, and a master's degree in information systems and technology management. He has been awarded 3 US patents.

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^{Pixabay license, source}

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