Neuroscientists are discovering striking similarities between the way the brain develops and the way it stores knowledge. In a special issue of the journal Learning & Memory, research groups from Caltech, Yale University, and other institutions explore this parallel, presenting new studies on how a family of proteins called growth factors help nerve cells not only to grow but to learn and accumulate a lifetime of memories.
Nerve cells signal one another at specialized connections called synapses, forming circuits that carry out specific functions like coordinating muscle activity or recognizing friends. Scientists widely believe that the brain can store newly learned facts and behaviors by increasing signal strength at the appropriate synapses. As they study this process, however, scientists are discovering the brain has more than one use for the same trick: circuits forming their connections at the beginning of life may use the same synaptic strengthening mechanisms as adult circuits use to learn. Standing out among the common elements are the neurotrophins, a family of proteins critical for cell survival and growth in the developing nervous system. The studies presented in the special issue of Learning & Memory continue a string of exciting indications that neurotrophins are also important for strengthening synapses in the adult brain.
In this issue, Benedikt Berninger, Alejandro Schinder, and Mu-ming Poo
(University of California, San Diego) show that neurotrophins have more effect
on weak synapses than strong ones. Measuring signal strength between pairs of
nerve cells, they find that applying neurotrophins increases synapse strength
dramatically if the initial signal is small. If the initial signal is already
large, neurotrophins do not increase it much further. This work suggests
neurotrophins strengthen nerve connections by "maturing" undeveloped synapses,
leaving strong or "mature" synapses relatively unaffected. So learning may
Contact: Peggy Calicchia
Cold Spring Harbor Laboratory