The role of the hippocampus in the formation of new memories has been well-documented, but the contribution of this structure to the representation and retrieval of long-term memories is less clear. In research published in the May 13 issue of Neuron, a team of scientists led by NYU Professor of Neural Science Wendy Suzuki recorded the activity of individual hippocampal neurons as animals retrieved well-learned information from memory.
Monkeys were first shown a complex image superimposed with four identical targets. Choice of one of the four targets would give them a reward for a particular image. Animals performed trials with very well-learned stimuli as well as with novel stimuli in which they learned the scene-target associations by trial and error. Suzuki's team found that the response of the hippocampal neurons differentiated between the well-learned stimuli significantly better than the novel stimuli. This differentiated response in the hippocampus provides strong evidence for a memory signal specific for the well-learned information.
"We know that the hippocampus is involved in transferring immediate or short-term memories into long-term memories, but its specific contribution to the representation of very well-learned information was not well-understood." said Suzuki. "These findings are exciting because they suggest that the hippocampus is involved in signaling even very well-learned information. This may be a way that well-learned information is incorporated into our memories of everyday episodes or events."
By demystifying the role of the hippocampus in both the acquisition and retrieval of everyday memories, this research forms the necessary first steps towards understanding and developing treatments for devastating memory-related diseases such as Alzheimer's Disease.
Suzuki's team that included NYU graduate student Marianna Yanike (lead author) and NYU post-doctoral fellow Sylvia Wirth.