The ability to dream may be genetic

Two genes associated with dreaming have been discovered in mice, according to a study published this week in Cell Reports.  

Researchers found that when they removed these genes (known as Chrm1 and Chrm3), the mice were incapable of experiencing REM sleep.

When researchers deleted one of the genes, the mice had less REM sleep. When they removed both, the mice had no REM sleep. This result suggests the genes work together to determine how much REM sleep we get.  

Since REM sleep, or rapid eye movement sleep, is the stage of sleep people most often dream in, the assumption is that if the mice don't have REM sleep, they can't dream either.

The importance of REM

A person normally cycles through about five rounds of REM sleep during the night.

One study deprived rats of REM sleep and found they only lived for five weeks as a result. The study couldn't tell if the rats were dreaming or not, but it did illustrate the importance of REM to our overall brain health.

We also know from past observational studies that REM sleep can be affected by depression and alcohol consumption.

Sleep studies of people who suffer from depression show they also dream less as a result of lower REM sleep times, which may compound the mental illness.

Alcohol also disrupts the REM sleep patterns making it more difficult to dream. That could be a part of the reason why people who suffer from alcoholism may also suffer from depression.

Genes for dreaming

Chrm1 and Chrm3 are part of a pathway in the brain that uses a chemical called acetylcholine, which is involved in a wide array of brain processes—including REM sleep.

But these genes don't seem to disrupt all sleep because the mice survived when they were deleted—unlike in the rat study where the rats only survived five weeks without REM.

The researchers aren't sure how the mice can sleep with little or no REM, but it suggests that Chrm1 and Chrm3 may have a more subtle function. They assume that it's merely limiting the mice's ability to dream.

While there is no way of assessing whether the mice are dreaming, it can be said that they are in REM sleep that is characteristic of dreaming.

Looking ahead

Researchers plan to continue this study with mice to see what effects the lack of these genes have on mouse cognitive capacity and memory and look at other ways to assess the different theories of dreaming.

Humans have the same genes that very likely function in the same way. Future research could look for subtle sequence differences in the human genome to see if there is an association between how much dreaming people report and how much variation there may be in the Chrm1 and Chrm3 genes.

While there is no suggestion that these are the only dream genes in the human or mouse genome, the finding is significant to begin to address why we dream at all and how it is controlled.