Synapses with short-term plasticity are optimal estimators of presynaptic membrane potentials.

The trajectory of the somatic membrane potential of a cortical neuron exactly reflects the computations performed on its afferent inputs. However, the spikes of such a neuron are a very low-dimensional and discrete projection of this continually evolving signal. We explored the possibility that the neuron's efferent synapses perform the critical computational step of estimating the membrane potential trajectory from the spikes. We found that short-term changes in synaptic efficacy can be interpreted as implementing an optimal estimator of this trajectory. Short-term depression arose when presynaptic spiking was sufficiently intense as to reduce the uncertainty associated with the estimate; short-term facilitation reflected structural features of the statistics of the presynaptic neuron such as up and down states. Our analysis provides a unifying account of a powerful, but puzzling, form of plasticity.

Small-diameter membrane reflector wrinkling

This study concerns the wrinkling performance of thin membranes for use as novel reflectors in space-based telescopes. We introduce small-scale experiments for inducing and interrogating wrinkling patterns in at membranes, and we capture these details computationally by performing a range of finite element analysis. The overall aim is to assess the sophistication of modelling, to verify the feasibility of a small-diameter reector concept proposed in accompanying work. © 2009 by the American Institute of Aeronautics and Astronautics, Inc.