Decades of research has shown that learning causes physical changes to our brain. But just how memory works and how it physically affects the brain is still under investigation and one of the most active fields of neuroscience.
Case in point, neuroscientists at New York University have found a vital link in the diminution of forgetting. They found that the better the coordination between two regions of the brain, the less likely we are to forget newly obtained information.
“When memories are supported by greater coordination between different parts of the brain, it’s a sign that they are going to last longer,” says Lila Davachi, an associate professor in NYU’s Department of Psychology and Center for Neural Science.
Cortical Area Distribution
Neuroscientists mostly agree that the key to memory consolidation (the permanent fixing of an experience or information in our brain) is signaling from the brain’s hippocampus across different cortical areas. It has also been theorized, though never proven, that the larger the distribution of signaling, the stronger the memory takes root in our brain.
Is there any scientific evidence for this theory? The researchers wanted to see how memories are formed at their earliest stages, and did a string of experiments over a three-day period.
On day one, researchers intended to encode, or create, new memories in the study subjects. So they showed participants a series of images. Objects and outdoor scenes were paired with words. Subjects were asked to form an association between the word and image on the screen.
The second day, study subjects came back and did another round of encoding tasks with new sets of visuals and words. The idea was to let the researchers compare two types of memory; the more consolidated, long duration (LD) memories encoded on day one with the less consolidated, short duration (SD) memories encoded on day two.
Following a small break, participants were put in an MRI machine to monitor neural activity. While in the MRI, they were shown the visual-word pairings they saw on days one and two plus a new round of visuals paired with words. They then took a memory test of around half of the visual-word pairings they’d seen so far. Finally, on day three, they returned for a memory test on the remaining visuals.
Hippocampus and Left Perirhinal Cortex
Testing over multiple days allowed the researchers to isolate memories that declined or were preserved over time. This way they could better understand the neurological features that contribute to preservation of memory.
They found that memories, in this case the visual-word associations, that were not forgotten were linked with more coordination between the hippocampus and left perirhinal cortex (LPRC). These are two parts of the brain previously associated with memory formation. On the other hand, they noted less connectivity between these regions for the visual-word associations that the study’s subjects tended to forget.
“These findings show the brain strengthens memories by distributing them across networks,” said Davachi. “However, this process takes time. Day-old memories show greater coordinated brain activity compared to recent ones. This suggests that coordinated brain activity increases with time after a memory is initially formed.”
Perirhinal-Hippocampal Connectivity during Reactivation Is a Marker for Object-Based Memory Consolidation
Kaia L. Vilberg, Lila Davachi
Neuron, 29 August 2013 10.1016/j.neuron.2013.07.013