Scientists Develop New Model Explaining How Memories are Formed

Amy Taylor April 22, 2014

Scientists at Salk Institute have created a new model that describes how the brain retains select memories a few hours after an event. The new findings can give more light on how memory works and deepen the understanding of related illnesses like Parkinson’s, Alzheimer’s, post-traumatic stress, and learning disabilities.

Much about how the brain stores long-term memories has been discussed in previous studies. In the case of significant events, for instance, like being bitten by a dog – a number of proteins are quickly made in activated brain cells to create the new memories. Some of these proteins linger for a few hours at specific places on specific neurons before breaking down. Such series of biological events allow a person to remember important details about the said event, such as which dog, where it was located, and so on.

But one problem scientists have had with modelling memory storage is explaining why only selective details and not everything in that 1-2 hour window is strongly remembered. By incorporating data from previous literature, Terry Sejnowski, a Howard Hughes Medical Institute Investigator, and Cian O’Donnell, a Salk postdoctoral researcher, developed a model that bridges findings from both molecular and systems observations of memory to explain how this 1-2 hour memory window works. The work is detailed in the latest issue of Neuron.

"Previous models of memory were based on fast activity patterns," Sejnowski, a holder of Salk’s Francis Crick Chair, said. "Our new model of memory makes it possible to integrate experiences over hours rather than moments."

Using computational modelling, despite the proteins being available to a number of neurons in a given circuit, Sejnowski and O’Donnell showed that memories are retained when subsequent events activate the same neurons as the original event. They found that the spatial positioning of proteins at both specific neurons and at specific areas around these neurons predicts which memories are recorded. This spatial patterning framework successfully predicts memory retention as a mathematical function of time and location overlap.

"One thing this study does is link what’s happing in memory formation at the cellular level to the systems level," says O’Donnell. "That the time window is important was already established; we worked out how the content could also determine whether memories were remembered or not. We prove that a set of ideas are consistent and sufficient to explain something in the real world."

The new model also suggests that some memory retention does happen during dreams. For instance, during sleep, there’s a reorganising of memory, in which you strengthen some memories and lose ones you don’t need any more, O’Donnell explained. “In addition, people learn abstractions as they sleep, but there was no idea how generalization processes happen at a neural level.”

Source of this article:

Modelling the Cellular Basis of Memory