Figure 2.

Estimating the presynaptic membrane potential when the resting membrane potential randomly switches between two different values. (a) Presynaptic subthreshold membrane potential with action potentials (black), its optimal mean estimate ($\widehat{u}$, red line) with the associated s.d. (σ, red shading), and the postsynaptic membrane potential in a model synapse¹¹ with optimally tuned short-term plasticity (blue line). Inset, the (scaled) optimal estimator (red solid line) strongly depends on the estimated probability ρ of being in the up state (red dashed line). (b) EPSP amplitude in the optimal estimator depends on its uncertainty (horizontal axis, σ²) and the change in the estimated probability that the presynaptic cell is in its up state (color code, Δρ). (c) The estimated probability that the presynaptic cell is in its up state ρ (red) tracks the state of the presynaptic neuron (black) as it randomly switches between its up and down states. (d) EPSP magnitudes in the optimal estimator against EPSP magnitudes in the model synapse.