A team of researchers from the Mediterranean Institute of Neurobiology in France claims to have witnessed the process by which the brain constructs memories. Reporting their discovery in the journal Science, the study authors reveal how they used fluorescent proteins to track the brain activity of mice, observing how neurons interacted with one another in groups that form the “building blocks” of these memories.
In their study, the team explain it has long been hypothesized that major cognitive processes are supported by the “activation of neuronal assemblies,” whereby clusters of neurons fire in a specific pattern in order to reproduce a certain memory. This new study provides evidence that these assemblies are broken down into smaller segments that interact with one another to form a larger chain, within which an entire memory is encoded.
To conduct their work, the team injected the brains of mice with a fluorescent protein that causes neurons to glow when calcium ions flow across their membranes, as occurs when they become active. They then watched how assemblies of neurons in the hippocampus – a brain region associated with memory – began to fire in sequence as the mice ran on a treadmill, enabling them to form new memories relating to how far they had run.
When the mice later rested, these memories were replayed in their brains, resulting in their consolidation. However, rather than repeating the entire sequence at once, the animals’ brains replayed individual sections of these assemblies, which the study authors believe correspond to different parts of the run.
Speaking to New Scientist, study co-author Rosa Cossart explained that “we've been able to image the individual building-blocks of memory.” Though much more work will be needed before this discovery can be put to practical use, understanding the mechanisms underlying the formation of memories could one day prove crucial in the treatment of disorders like Alzheimer’s and other forms of dementia.