Sugar affects brain 'plasticity', helping with learning and memory
Complex sugar molecules control the formation of perineuronal networks that surround neurons, helping to stabilize connections in the brain.Members of Linda Hsieh-Wilson's lab have found that complex sugar molecules control the formation of perineuronal networks. They surround neurons, helping to stabilize connections in the brain.
A person may recognize an acquaintance they haven't seen in years, but forget what they had for breakfast yesterday. This is because the brain is constantly reorganizing itself to learn new skills, but the molecular basis of this process is not well understood. Scientists have found that the sulfate groups of complex sugar molecules known as glycosaminoglycans (GAGs) affect the "plasticity" of the brains of mice. Understanding how GAGs function will help elucidate how memory and learning work in humans. There will also be ways to restore neural connectivity after injury.
In the brain, the most common form of GAG is chondroitin sulfate, which is found in the extracellular matrix. It surrounds many brain cells. Chondroitin sulfate also forms structures known as "perineuronal networks." These wrap around individual neurons and stabilize the synaptic connections between them.
When the scientists deleted the Chst11 gene responsible for generating the two major patterns of chondroitin sulfation in mice, defects formed in their perineuronal networks. However, the number of networks actually increased in the absence of sulfation motifs, altering the types of synaptic connections between neurons. In addition, the mice did not recognize the mice they were familiar with. Therefore, the scientists hypothesized that these patterns affect social memory.
Interestingly, these networks may be more dynamic than previously thought. When the researchers targeted Chst11 specifically in the brains of adult mice, they found the same effects on perineuronal networks and social memory.
In other recent experiments, the team wanted to understand how GAGs and their sulfation patterns might affect axon regeneration, or the ability of neurons to recover from damage. The researchers are now working to identify protein receptors that bind specific sulfation motifs.