Insights into How & Why the Brain Sorts Information

The NMDA receptor in the brain's hippocampus is like a switch for regulating learning and memory, working through subunits called NR2A and NR2B. NR2B is expressed in higher percentages in children, enabling neurons to talk a fraction of a second longer; make stronger bonds, called synapses; and optimize learning and memory. This formation of strong bonds is called long-term potentiation. The ratio shifts after puberty, so there is more NR2A and slightly reduced communication time between neurons.  Joe Z. Tsien, from the Medical College of Georgia at Georgia Regents University (Georgia, USA), and colleagues genetically modified mice to mimic the adult ratio – that is, more NR2A and less NR2B, the team found that the rodents were still good at making strong connections and short-term memories but had an impaired ability to weaken existing connections, called long-term depression, and to make new long-term memories as a result. Such information sculpting is not an attribute of adult ratios of NMDA receptor subunits, suggesting a critical weakening that appears hampered in the older brain.