Most hours of the day, my mind is going a mile a minute from one topic to the next-- who is waiting on a response from me at work? This morning's meeting didn't go so well. Did I send a birthday card to Grandma? And so on.
I've noticed that, if one of these many topics I think about makes me feel bad or causes me stress (an unfinished project, the memory of an altercation with an especially nasty bus driver, and so on), I still feel kind of icky long after I've filed that thought away and moved on to the next.
A new study out of the University of Iowa offers one explanation of why this might be. Researchers studied patients with damage to their hippocampus (part of the brain that affects short-term memory), which can be caused by Alzheimer's, epilepsy, or stroke. Patients watched either very sad or very uplifting short clips from classic movies. About 30 minutes later, patients couldn't remember anything about the movies they'd watched, but they were feeling the emotions they drew from the experience. They were still happy or sad, depending on which set of clips they watched, but couldn't remember why.
Justin Feinstein, one researcher involved in the study, suspects that emotions are captured by a different part of the brain than the memories to which they correspond. One very positive aspect of this, which Feinstein suggests, is that even if a friend or family member with Alzheimer's (or another condition that affects their memory) doesn't remember a visit from a loved one, the good feelings that come from that visit might linger. Check out NPR's podcast on the study for more information.