Whether it's a first-time visit to a zoo or learning to ride a bicycle, childhood memories often stay with us well into adulthood. But what explains the persistence of these memories over a lifetime?
A study published in Science Advances by an international team of researchers sheds light on this question, uncovering a biological mechanism behind long-term memory retention. The study focuses on the molecule KIBRA, which acts as a “glue” to other molecules, thereby solidifying memory formation.
“Previous efforts to understand how molecules store long-term memory focused on the individual actions of single molecules,” explains André Fenton, a professor of neural science at New York University and one of the study's principal investigators. “Our study shows how they work together to ensure perpetual memory storage.”
Todd Sacktor, a professor at SUNY Downstate Health Sciences University and another principal investigator of the study, adds, “A firmer understanding of how we keep our memories will help guide efforts to illuminate and address memory-related afflictions in the future.”
Neurons store information in memory as patterns of strong and weak synapses, which determine the connectivity and function of neural networks. However, synaptic molecules are unstable, continually moving within neurons, and being replaced every few hours to days. This raises the question: how can memories remain stable for years to decades?
The researchers conducted a study using laboratory mice, focusing on KIBRA, a protein whose genetic variants in humans are associated with both good and poor memory. They examined KIBRA's interactions with other molecules crucial to memory formation, particularly protein kinase Mzeta (PKMzeta), an enzyme essential for strengthening synapses but which degrades after a few days.
Their experiments revealed that KIBRA serves as the “missing link” in long-term memory formation. It acts as a “persistent synaptic tag,” or glue, that attaches to strong synapses and PKMzeta while avoiding weak synapses.
“During memory formation, the synapses involved are activated, and KIBRA is selectively positioned in these synapses,” explains Sacktor, who is also a professor of physiology, pharmacology, anesthesiology, and neurology at SUNY Downstate. “PKMzeta then attaches to the KIBRA-synaptic tag and keeps those synapses strong. This allows the synapses to stick to newly made KIBRA, attracting more newly made PKMzeta.”
The study's experiments show that breaking the KIBRA-PKMzeta bond erases old memories, highlighting the crucial role of this molecular interaction in maintaining long-term memory. This discovery provides significant insights into how our brains store memories over extended periods and could pave the way for new approaches to treating memory-related disorders.
Source: New York University