A study led by University of Pennsylvania researchers has identified key molecules that help convert short-term memories into long-term ones.
These molecules are part of a group of proteins called nuclear receptors, which could offer a target for memory-enhancing drugs, thereby alleviating some of the cognitive symptoms of conditions including schizophrenia and Alzheimer's disease.
In the study, published in the Journal of Clinical Investigation, mice were trained to create memories of a place and event by associating a specific experience with a particular context or tone.
The scientists examined expression patterns of all 49 nuclear receptor genes. They found 13 that increased in expression in the hippocampus in the first two hours after training, including all three members of a class of nuclear receptors called Nr4a. The scientists next created transgenic mice in which they could selectively block the activity of the three Nr4a genes.
The mice showed reduced memory of the location where the training took place, but their tone-associated memories remained intact.
"The mice had impairment for contextual memory," says Ted Abel, one of the researchers. "That is the type of memory that goes away in Alzheimer's and schizophrenia."