Selectivity and sparseness generation mechanism.

<p>A) On top is response to stimuli of an example neuron and on the bottom are time-averaged synaptic currents for corresponding stimuli. B) Scatter plot of neuron selectivity vs. voltage modulation index (VMI). Shown on left is the excitatory population and inhibitory population is on the right. C) Histogram of the similarity between peak current (excitatory current in red and inhibitory current in blue) and preferred stimulus for excitatory population. Similarity is defined as follows. For each neuron stimuli are ordered based on magnitude of response they elicit. Similarity is the difference in ranks of the stimulus that elicits peak excitatory or inhibitory current and the preferred stimulus, which is ranked 1. D) Dependence of connection modulation index (CMI, see Methods) on mean number of synapses a neuron receives from a particular population. Only E-to-E, I-to-E and 0-to-E type connections are shown. Lines are fits to the function where is the fitted parameter. Solid lines show CMI for our default parameters. Dotted lines correspond to a parameter set where . Excitatory network firing rate is kept at 10 Hz by adjusting the input mean firing rate at default input SPI = 0.75.