[stim_reconstruction] slightly different explanaition of sta

projects/project_stimulus_reconstruction/stimulus_reconstruction.tex

@@ -13,13 +13,16 @@
 \section*{Reverse reconstruction of the stimulus that evoked a neuronal response.}
 To analyse encoding properties of a neuron one often calculates the
 Spike-Triggered-Average (STA). The STA is the average stimulus that
-led to a spike in the neuron and is calculated by cutting out snippets
-form the stimulus centered on the respective spike time:
+led to a spike in the neuron:
 \[ STA(\tau) = \frac{1}{n} \displaystyle\sum_{i=1}^{n}{s(t_i - \tau)} \]
-where $n$ is the number of trials and $t_i$ is the time of the
-$i_{th}$ spike. The Spike-Triggered-Average can be used to reconstruct
-the stimulus from the neuronal response. The reconstructed stimulus
-can then be compared to the original stimulus.
+where $n$ is the number of spikes and $t_i$ is the time of the
+$i_{th}$ spike. $\tau$ is a temporal shift relative to the spike
+time. For the beginning let $\tau$ assume values in the range
+$\pm50$\,ms. It can be estimated by cutting out snippets form the
+stimulus centered on the respective spike time and averaging them. The
+Spike-Triggered-Average can be used to reconstruct the stimulus from
+the neuronal response. The reconstructed stimulus can then be compared
+to the original stimulus.
 
 \begin{questions}
   \question In the accompanying data files you find the spike responses of