A new brain imaging study illustrates what happens to memories as time goes by.
The study, in the January 28 issue of The Journal of Neuroscience , shows that distinct brain structures are involved in recalling recent and older events.
The findings support earlier studies of memory-impaired patients with damage limited to the hippocampus. These patients show deficits in learning new information and in recalling events that occurred just prior to their injuries. However, they are able to recall older events, which are thought to involve other regions of the brain, particularly the cortex.
"It has long been known that older memories are more resistant to hippocampal damage than newer memories, and this was thought to reflect the fact that the hippocampus becomes less involved in remembering as a memory gets older," said Russell Poldrack, PhD, an expert on the cognitive and neural mechanisms of memory at the University of California, Los Angeles, who was not involved in the study. "However, there has been a recent debate over whether the hippocampus ever really stops being involved, even for older memories," Poldrack said.