Ever wonder why we remember some events, places and things but forget others? A new study from scientists at the University of California, Davis suggests that our brains prioritize rewarding memories over others by replaying them while we rest in order to reinforce them.
"Rewards help you remember things, because you want future rewards," Charan Ranganath, senior author on the paper, said in a press release. "The brain prioritizes memories that are going to be useful for future decisions."
Ranganath claims that we only retain detailed memories for a small percentage of daily events, and people with detailed memories in particular can become overwhelmed by the amount of information that we take in on a regular basis. To combat this, the brain filters out information that we need to remember in order to obtain future rewards.
The study used functional magnetic resonance (fMRI) imaging to scan the brains of subjects as they answered yes-no questions regarding a short series of objects, including questions regarding their weight in comparison to each other. Each series was shown on a background image to give them context and the subjects were offered rewards, either large (in dollars) or small (in cents) for giving correct answers.
After the tests, the subjects were scanned during a resting period and afterwards, there was a surprise memory test for all of the objects shown during the initial experiment. The findings revealed that individuals were better at remembering objects with a higher reward.
"Also, when an object was associated with high reward, people remembered better the particular background scene that was on the screen during scanning," said Matthias Gruber, first author of the study.
Furthermore, the brain activity observed during the fMRI scans during rest was able to predict memory performance - the brain scans of subjects at rest after the initial test was the same pattern of activity that was observed during the high-reward task. This implies that their brain's were replaying the rewarding memories in order to strengthen neural connections to consolidate the memory.
"It speaks to a memory process that is normally hidden from us," Ranganath said. "Are you remembering what you really need to know? It could depend on what your brain does while you are at rest."
The findings were published in the Feb. 11 issue of Neuron.
