Professor Noam Ziv
Synapses are sites of cell-cell contact specialized for transmitting signals between nerve cells. It is widely believed that modifications to synaptic connections – synaptic plasticity – represent a fundamental mechanism for altering network function, giving rise to phenomena collectively referred to as learning and memory. This belief also implies, however, that synapses, when not driven to change their properties, should retain these properties over time.
Synapses are composed of proteins, complex molecules with finite lifetimes, and therefore, for synapses to persist and maintain their individual characteristics they must be replenished continuously and precisely. Moreover, imaging studies indicate that synaptic proteins exhibit remarkable dynamics, moving in, out and between synapses at high rates. Given these dynamics, and the challenges of maintaining synapses in face of numerous “erosive forces,” the persistence of synapses, and in particular, their capacity to maintain their unique characteristics over behaviorally relevant time scales (a capacity we refer to as synaptic tenacity) is by no means obvious. Indeed, very recent studies indicate that aging, at least in mice, is associated with significantly reduced synaptic tenacity. Moreover, synaptic loss seems to be an early hallmark of several neurodegenerative diseases, most notably Alzheimer’s disease, pointing to the importance of understanding the basis of synaptic tenacity and the processes involved in synaptic maintenance.