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The Read-Out Layer

During dynamical coherence detection, the total output current of the coherence layer is composed of a small random component plus an oscillatory component coming from the synchronous coherence cluster. The oscillatory component has to be detected by the read-out layer \( \mathcal{R}(i,j) \).

In the simulations, the read-out neurons \( r\in \mathcal{R}(i,j) \) are driven by the total output current of the coherence layer (the first term in equation (13)), plus a synchronizing interaction term:

\begin{displaymath}
I_{r}(t)=w_{\mathcal{CR}}/N_{\mathcal{C}}\cdot \sum _{s\in \...
...mathcal{R}}_{r\bar{r}}\cdot i_{\bar{r}}(t;\tau _{\mathcal{R}})
\end{displaymath} (13)

The interlayer connections,
\begin{displaymath}
w^{\mathcal{R}}_{r\bar{r}}=\left\{ \begin{array}{cc}
w_{\mat...
...f}\, \, r\neq \bar{r}\\
0 & \mbox {else}
\end{array},\right.
\end{displaymath} (14)

include no self-interaction term, as in the coherence layer.

The number of read-out neurons \( N_{\mathcal{R}} \) ranges between 2 and 16, and the synaptic decay time constant \( \tau _{\mathcal{R}} \) is chosen to equal \( \tau _{\mathcal{C}} \) in the simulations. Network performance turns out to be insensitive to the precise value of \( w_{\mathcal{RR}} \), and \( w_{\mathcal{RR}} \) was set to \( w_{\mathcal{RR}}=0.85 \) in all simulations.

The coupling between coherence- and read-out layer, \( w_{\mathcal{CR}} \), modifies the capture range of the read-out neurons; in the simulations, it was fixed to \( w_{\mathcal{CR}}=4.4 \), and the synaptic time constant to \( \tau _{\mathcal{CR}}=0.01. \) The results displayed in the maps of the main text were obtained by measuring the spike frequencies \( f_{r} \) of the neurons in the read-out layer \( \mathcal{R}(i,j) \) and averaging: \( \overline{f_{(i,j)}}=1/N_{\mathcal{R}}\sum _{r\in \mathcal{R}(i,j)}\, f_{r} \).


next up previous
Next: Bibliography Up: The Coherence Network Previous: The Coherence Layer

2000-11-20