Ever Wanted to Know Why Some Things Happen After Sex?

Understanding how sex affects your brain can improve your roll in the hay, and it may also shed light on other parts of your health, says Barry R. Komisaruk, PhD, distinguished professor of psychology at Rutgers University in Newark, New Jersey. It's not the easiest subject to study— -- test subjects might have to masturbate in an MRI machine— -- so research is still developing. But scientists are starting to unravel the mystery. Here's what we know so far about your brain on sex.

SEX CAN WIPE YOUR MEMORY CLEAN

Each year, fewer than 7 people per 100,000 experience "global transient amnesia," a sudden but temporary loss of memory that can't be attributed to any other neurological condition. The condition can be brought on by vigorous sex, as well as emotional stress, pain, minor head injuries, medical procedures, and jumping into hot or cold water. The forgetfulness can last a few minutes or a few hours. During an episode, a person cannot form new memories or remember very recent events. Fortunately, there seem to be no lasting effects.

SEX CAN (SOMETIMES) BE A DOWNER

Those feel-good chemicals may be going full blast during the act, but after? According to researchers, there is such a thing as post-sex blues(technical term: postcoital dysphoria). About one-third of the women participating in one study reported having experienced sadness after sex at some point in time. While it's possible that regret or feeling coerced might be the reason why, researchers can't explain the connection at this point for sure.

SEX MAY BOOST YOUR MEMORY

Or at least it might if you're a rodent. A 2010 study found that, compared with rats who were allowed only one one-night stand, rodents who engaged in "chronic" sex (once a day for 14 consecutive days) grew more neurons in the hippocampus, a region of the brain associated with memory. The findings were backed up by a second study, also in mice. It remains to be seen if regular sex also has this effect in humans (but you can always tell yourself it does).

SEX MAKES YOU SLEEPY

Sex is more likely to make men sleepy than women, and scientists think they know why: The part of the brain known as the prefrontal cortex winds down after ejaculation. This, along with the release of oxytocin and serotonin, may account for the "rolling over and falling asleep" syndrome. Now women should forgive their men for dozing off immediately after the doings. It's nature.