@@ -111,26 +111,28 @@ with Context("Model") as model:
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```
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Notice that the ` STPDenseSynapse ` has two important time constants to configure;
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- ` tau_f ` ($\tau_f$), the facilitation time constant, and ` tau_d ` ($\tau_d$, the
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+ ` tau_f ` ($\tau_f$), the facilitation time constant, and ` tau_d ` ($\tau_d$) , the
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depression time constant. In effect, it is these two constants that you will
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want to set to obtain different desired behavior from this in-built dynamic
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- synapse -- setting $\tau_f > \tau_d$ will result in STF-dominated behavior
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- whereas setting $\tauf < \tau_d$ will produce STD-dominated behavior. Note
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- that setting $\tau_d = 0$ will result in short-term depression being turned off
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- completely ($\tau_f 0$ disables STF).
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+ synapse:
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+ 1 . setting $\tau_f > \tau_d$ will result in STF-dominated behavior; whereas
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+ 2 . setting $\tau_f < \tau_d$ will produce STD-dominated behavior.
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+
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+ Note that setting $\tau_d = 0$ will result in short-term depression being turned off
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+ completely ($\tau_f = 0$ disables STF).
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Formally, given the time constants above the dynamics of the ` STPDenseSynapse `
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operate according to the following coupled ordinary differential equations (ODEs):
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$$
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- \tau_f \frac{\partial u_j(t)}{\partial t} &= -u_j(t) + N_R (1 - u_j(t)) s_j(t) \\
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+ \tau_f \frac{\partial u_j(t)}{\partial t} &= -u_j(t) + N_R \big (1 - u_j(t)\big ) s_j(t) \\
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\tau_d \frac{\partial x_j}{\partial t} &= (1 - x_j(t)) - u_j(t + \Delta t) x_j(t) s_j(t) \\
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$$
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and the resulting (short-term) synaptic efficacy:
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$$
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- W^{dyn}(t + \Delta t) = \Big( W^{max}_{ij} u_j(t + \Delta t) x_j(t) s_j(t) \Big)
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+ W^{dyn}_{ij} (t + \Delta t) = \Big( W^{max}_{ij} u_j(t + \Delta t) x_j(t) s_j(t) \Big)
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+ W^{dyn}_{ij} (1 - s_j(t))
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$$
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