We all have both good and bad memories, and how they can affect our health—including our mood—is nothing short of amazing. Interestingly, our mood can also affect our memories, but let’s talk about how memories affect mood.
Past studies have indicated that recalling certain memories, including good ones, bad ones and neutral ones can directly affect mood accordingly, with good memories gleaning the best mood; neutral memories precipitating a better mood; and bad memories resulting in the worst mood. Those results show that memory recall does directly affect mood and may even do so without a person being aware of it. Therefore, memory recall has been thought to be an effective mood regulation strategy.
More recently, research points toward an almost “curing” power of memory, including research published in Nature. More specifically, scientists have discovered that reactivating memories stored during a positive experience can hold off the effects of depression caused by stress.
Researchers at the RIKEN-MIT Center for Neural Circuit Genetics showed how both positive and negative memories affect mood disorders. The scientists, using study animals (mice), were focused on the dentate gyrus (DG) part of the brain where memory cells are located. The researchers were able to tag and reactivate certain memories, while also turning on memory cells created during past experiences.
The mice then were given a positive experience—male mice introduced to a female mouse—and formed a positive memory from it. Then the male mice were given a stressful event that formed a depression-like response in them. During their depressed state, light was used to stimulate the DG of some of the mice, reactivating the memory cells of the positive memory. What happened next was astounding: the mice recovered from the depressed condition.
The researchers mapped the brain circuitry for this response, and two other brain areas which cooperate with the DG were revealed. Those two areas are known as the BLA and the NAcc. The researchers then went on to determine whether this recovery from depression could persist in brain circuitry without light stimulation, and the mice were still resilient to the negative effects of stress-induced depression when the positive memory was reactivated.
This suggests that memory storage of positive experiences in the DG can suppress or overwrite unhealthy behavioral effects of stress. That is a new concept in mood control, implying that memory may be used to cope with stress and depression and that DG cells may play a role in supporting therapeutic approaches to mood disorders.
So, positive memories may very well lead to a positive mood.