Removing the uterus from a rat has a detrimental impact on its spatial and working memory, according to a new study from Arizona State University.
The study involved 60 female rats, divided into four groups: one group had their uteruses removed (hysterectomy), one had their ovaries removed (ovariectomy), one had both their uteruses and ovaries removed, and a control group underwent a small incision but had no organs removed.
The rats were then tested in a classic laboratory examination of working memory, which involved placing the animals in a water maze and allowing them to find standing platforms.
The rats were then tested on their ability to find those platforms again after they were removed and then returned to the maze.
The researchers found that the rats with hysterectomies performed extremely badly on the working memory tests and could not find the platforms again.
A large amount of previous research has indicated that female sex hormones such as oestrogen and progesterone affect brain function and have a role in the brain outside of reproductive purposes. Female sex hormones have been implicated in executive control, memory and neuroplasticity in the brain.
However this is the first study to imply that the uterus could play a profound role in cognitive processes.
Stephanie Koebele, lead author of the study, told BuzzFeed News that while researchers were initially surprised to see the results, the connection between the uterus and the brain appears to make sense.
"There are direct connections of the nervous system between the uterus and the brain — we already know the ovaries-brain connection is important for brain health, so it makes good sense that this uterus-brain connection exists too," she said.
The brain, ovaries and uterus are connected in female bodies in a link known as the hypothalamic-pituitary-gonadal axis, which regulates the reproductive cycle. Koebele said that disrupting this connection can have surprising outcomes such as impaired memory, even though medical texts overlook the non-pregnant uterus as a useless or dormant organ.
Koebele said the experiment emphasises the idea that scientists still have a great deal to learn and understand about how memories are formed. Her team is currently investigating exactly how the uterus is involved in memory formation.
Approximately 30,000 women in Australia undergo a hysterectomy procedure every year to alleviate the issues associated with medical conditions such as uterine fibroids, endometriosis, uterine prolapse and cancer.
Hysterectomies have been associated with cognitive issues such as early onset dementia, but the precise reason for this connection is still unknown.
Koebele believes that more time should be dedicated to researching these associations for the thousands of women who undergo the procedure, as it is critical to understand "how this very common gynaecological surgery could be impacting women's health, including cognition, across their lifespan".