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ago109 committed Jun 27, 2024
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Expand Up @@ -111,26 +111,28 @@ with Context("Model") as model:
```

Notice that the `STPDenseSynapse` has two important time constants to configure;
`tau_f` ($\tau_f$), the facilitation time constant, and `tau_d` ($\tau_d$, the
`tau_f` ($\tau_f$), the facilitation time constant, and `tau_d` ($\tau_d$), the
depression time constant. In effect, it is these two constants that you will
want to set to obtain different desired behavior from this in-built dynamic
synapse -- setting $\tau_f > \tau_d$ will result in STF-dominated behavior
whereas setting $\tauf < \tau_d$ will produce STD-dominated behavior. Note
that setting $\tau_d = 0$ will result in short-term depression being turned off
completely ($\tau_f 0$ disables STF).
synapse:
1. setting $\tau_f > \tau_d$ will result in STF-dominated behavior; whereas
2. setting $\tau_f < \tau_d$ will produce STD-dominated behavior.

Note that setting $\tau_d = 0$ will result in short-term depression being turned off
completely ($\tau_f = 0$ disables STF).

Formally, given the time constants above the dynamics of the `STPDenseSynapse`
operate according to the following coupled ordinary differential equations (ODEs):

$$
\tau_f \frac{\partial u_j(t)}{\partial t} &= -u_j(t) + N_R (1 - u_j(t)) s_j(t) \\
\tau_f \frac{\partial u_j(t)}{\partial t} &= -u_j(t) + N_R \big(1 - u_j(t)\big) s_j(t) \\
\tau_d \frac{\partial x_j}{\partial t} &= (1 - x_j(t)) - u_j(t + \Delta t) x_j(t) s_j(t) \\
$$

and the resulting (short-term) synaptic efficacy:

$$
W^{dyn}(t + \Delta t) = \Big( W^{max}_{ij} u_j(t + \Delta t) x_j(t) s_j(t) \Big)
W^{dyn}_{ij}(t + \Delta t) = \Big( W^{max}_{ij} u_j(t + \Delta t) x_j(t) s_j(t) \Big)
+ W^{dyn}_{ij} (1 - s_j(t))
$$

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