Figure 4.

Population analysis of stimulus information using different reference frames. A, Average information in the full spike train for each modulated neuron, when referenced to either a stereotyped another modulated neuron (large panel), and when referenced to the physical sound onset (small inset). Each dot corresponds to one neuron, information values were computed using the direct method, using 4 ms bins, and were averaged over all sliding window (T = 20 ms duration) positions. B, Time course of the stimulus information following stimulus (or reference neuron) onset (each aligned to t = 0) when using each reference frame. Lines denote the mean across all neurons (n = 48), shaded areas the standard error (SEM). Information was computed using the direct method, using 4 ms bins, and were averaged over all sliding window (T = 20 ms duration) positions. C, Fraction of stimulus information preserved by each type of reference (red, stereotyped; blue, modulated neurons) when stimulus information was computed using different bin sizes. The relative information was computed as the ratio of the information available using both types of reference neuron to the information available relative to the physical stimulus onset. Box plots display the median (central bar), 25th and 75th percentiles (box). D, Distribution (across the population of all modulated neurons when aligned to stimulus onset) of the ratio between the information provided by the spike train of a hypothetical Poisson neuron with the same time-dependent rate as the one under analysis (I_PSTH(S;R), Eq. 2) and the information carried by the actual spike train (I(S;R), Eq. 1). I_PSTH accounted for a large fraction of the total information for most of the neurons. Information was calculated using 4 ms bins (T = 20 ms windows). E, Stimulus information obtained from a linear decoder applied to response epochs of increasing duration. Left, Information obtained when using the response in progressively longer time windows for decoding (starting at t = 0 and ending at each indicated time point). Lines denote the mean across neurons, shaded areas the standard error (SEM). Right, Information obtained when using the full 300 ms of the response for each modulated latency neuron, when referenced to either a stereotyped or another modulated neuron (large panel), and when referenced to the physical sound onset (small inset). Each dot corresponds to one neuron. F, Stimulus information in the response onset latency for each neuron, when referenced to either a stereotyped or a modulated reference neuron. Information was calculated using the direct approach and by considering only the onset latency as response variable.