Why bad memories last so long
Scientists have theorized as to why painful memories can be hard to shake. Now, research by an international team of scientists confirms what scientists have long thought--that bad memories linger because neurons in the brain make stronger connections to each other during traumatic experiences.
Researchers at New York University and Japan’s RIKEN Brain Science Institute have found evidence supporting what's known as the Hebbian plasticity hypothesis, which holds that during trauma more neurons in the brainn fire impulses in unison and that causes them to make better connections than under normal situations.This hypothesis also suggests when the amygdala--the region of the brain that plays a key role in processing emotions-- allows sensory stimuli to become associated with either rewarding or aversive outcomes, emotional memories are produced.
To test how this brain functioning worked, the researchers conditioned rats to associate an auditory tone with a mild shock to their feet, while tracking the path of electrical impulses in the rats’ amygdalas. When researchers weakened or blocked the signaling among neurons, the memory that linked the sound to the shock didn't form. That was in line with the Hebbian plasticity hypothesis.
"Our results not only show that we are able to artificially manipulate memory, but also that the manipulation is correlated with long-lasting changes in the brain," said Lorenzo Diaz-Mataix, the lead author of the study.
These findings open a new door of memory modification as a potential treatment for PTSD or for other patients suffering from painful memories.