Sleep Aid Increases Negative Memories
Had a bad day at the office? Saw a horrific traffic wreck on the way home? Had a nasty argument with your parents? If so, you might want to avoid taking any sleep aids tonight, unless you really want to remember the negative event.
Turns out the primary ingredient in Ambien, zolpidem, can help your brain turn short-term memories into long-term memories, but there’s a catch. Zolpidem’s memory-enhancing effect only works with memories which trigger negative emotions.
Memory, Zolpidem and Sleep Spindles
Research by University of California at Riverside psychologist Sara Mednick discovered the brain generates bursts of energy during stage 2 sleep. These rapid energy bursts, or sleep spindles, play a role in forming long-term memories, especially emotional memories.
Mednick and her team wanted to see what happened to memory formation when sleep spindle density increased or decreased. They used two sleep aids: zolpidem, which increases sleep spindle density, and sodium oxybate, which decreases density levels.
Participants in the study were given the medication, and asked to view a series of images designed to create a positive or negative response. Participants then went to sleep, and on awakening were asked to recall the images.
Members of the zolpidem group showed an increase in memory recollection, but only for negative images. Recall was strongest for images which produced the most emotional response, such as violent images. People were more likely to recall images of a vicious dog, for instance, than a crying baby.
Sodium oxybate, despite lowering sleep spindle density, seemed to have no effect on the ability to recall negative memories.
Memory, Medication, and Mental Disorders
Why should zolpidem enhance only negative memories? According to Mednick, the human brain seems to favor negative memory retention. Perhaps it’s a survival trait — back in caveman days it may have been pleasant to remember Oog’s smile, but much more important to remember Oog’s brute of a mate knocked your teeth out when you smiled back. The negative memory was — and still is in some cases — more likely to keep you alive.
Today, we’re less likely to encounter jealous cavemen, but the tendency to remember negative memories remains. You may only have hazy memories of the excellent service you received from a fulfillment service, but have a clear recollection of the lousy service you received the last time you went out to lunch.
As for zolpidem’s ability to increase memory retention, the discovery could affect how we treat anxiety disorders. A PTSD sufferer may require sleep aids, for instance, but prescribing one which consolidates negative memories is unlikely to help his condition. It might actually worsen his symptoms by reinforcing memories he’d rather forget. In such cases, medication which doesn’t increase sleep spindle activity could prove more suitable.
