**Correlation between the input signal
and the mean firing rate under different intensities of white and red noise.
The input signal, with frequency 0.2 (arbitrary unit), was the same for
all the simulations. Coefficient of correlation was calculated for each
trial (using different seeds to generate the noise for each trial). Points
and bars correspond to the average and standard error of 50 trials, respectively,
for each of the noise intensities.
a) Gaussian white noise.
b) Red noise.
Note that the peak for SR is lower when the system is driven by red noise.
Also, the peak is shifted to higher noise intensities.**