According to Charan Ranganath, a professor at the UC Davis Centre for Neuroscience and the Department of Psychology, the brain puts together different items, the what, who, where and when, to form a complete memory.
It was previously believed that this association process occurred entirely in a brain structure called the hippocampus, but this appears not to be the case.
"We want to know how the brain areas that encode memory are organized," said Ranganath.
"If your memory is affected by aging or Alzheimer's disease, is there a way to learn that can capitalize on the brain structures that may still be working well?" he added.
During the study, Ranganath and his team used functional magnetic resonance imaging (fMRI) to see which parts of the brain were active when volunteers memorized pairs of words such as "motor/bear" or "liver/tree."
The volunteers either learned the pairs as separate words that could be fitted into a sentence, or as a new compound word, for example "motorbear," defined as a motorized stuffed toy.
"It's a sort of memory trick," he said.
The team found that when volunteers memorized word pairs as a compound word, the perirhinal cortex lit up, and this activity predicted whether the volunteers would be able to successfully remember the pairs in the future.
The results suggest that the perirhinal cortex probably can form simple associations, such as between the parts of a complex object.
This information is probably passed up to the hippocampus, which may create more complex memories, such as the place and time a specific object was seen.
The findings are published Aug. 28 in the journal Neuron.