First Direct Visualization of Memory Formation in the Brain

The phenomenon is called “synaptic plasticity,” and is the foundation for how we learn and remember. As we learn, the memories are stored in changes in the strength and/or number of synaptic connections between nerve cells in our brain.

Long lasting changes in synaptic connections are required for long-term memories, and the persistence of these changes requires new gene expression. This is the first study to use fluorescent imaging to directly visualize protein synthesis at individual synapses during learning related synaptic plasticity.

IMPACT: Understanding how synapses can change with experience is critical to understanding behavioral plasticity, and to understanding diseases in which learning and experience-dependent behaviors are impaired. Such diseases include mental retardation, Alzheimer’s disease, as well as anxiety and mood disorders. It also can elucidate potential strategies for improving normal cognition and behavioral plasticity.

JOURNAL: The research appears in the June 19 edition of the journal Science.

AUTHORS: Senior author Kelsey Martin, associate professor of psychiatry and biological chemistry; Dan Ohtan Wang, Sang Mok Kim, Yali Zhao, Hongik Hwang, Satoru K. Miura, all of UCLA; and Wayne S. Sossin, McGill University.

HOW: The researchers used sensory and motor neurons from the sea slug Aplysia Californica that can form connections in culture. The neurons were stimulated with serotonin, which strengthens the synapses, and allowed them to detect new protein synthesis—the making of a memory— using a “translational reporter,” a fluorescent protein that can be easily detected and tracked.

MORE: This is the first study to directly visualize protein synthesis at individual synapses during a long-lasting form of synaptic plasticity. The studies revealed an exquisite level of control over the specificity of regulation of new protein synthesis. “While this was not really surprising to us given the complexity of information processing in the brain,” said Martin, “visualizing the process of protein synthesis at individual synapses, and beginning to discern the elegance of its regulation, leaves us, as biologists, with a wonderful sense of awe.”

Funding: This study was funded by the National Institutes of Health, the WM Keck Foundation, and the Canadian Institutes of Health Research. The authors report no conflict of interest.