Noam Ziv (The Lorry I. Lokey Interdisciplinary Center for Life Sciences and Engineering, Technion, Israel Institute of Technology, Haifa, Israel) | Synaptic tenacity: When everything changes, do things really stay the same?

Abstract

Activity-dependent modifications to synaptic connections - synaptic plasticity – is widely believed to represent a fundamental mechanism for altering network function, giving rise to emergent phenomena commonly referred to as learning and memory. This belief also implies, however, that synapses, when not driven to change their properties by physiologically relevant stimuli, should retain these properties over time. Otherwise, physiologically relevant modifications would be gradually lost amidst spurious changes and spontaneous drift. We refer to the expected tendency of synapses to hold onto their properties as "synaptic tenacity". Imaging studies indicate that synapses can persist for long durations. However, at the same time, other imaging studies reveal that synapses are sites of intense molecular dynamics. Given these dynamics, the minute size of synaptic specializations, their remoteness from major biosynthetic centers, and the absence of obvious barriers to separate them from the neighboring axoplasm, axolemma and synapses, the tenacity exhibited by synaptic sites is by no means an obvious outcome. Yet, to date, not much is known on the degree to which synapses maintain their structure and function for long durations, nor are the principles that govern synaptic tenacity well understood. Our work on this topic and insights it has provided so far will be presented.