Sparse Codes for Speech Predict Spectrotemporal Receptive Fields in the Inferior Colliculus
Modulation spectra of half-complete cochleogram-trained dictionary and four-times overcomplete spectroram-trained dictionary are shown. The four-times overcomplete spectrogram-trained dictionary elements (red dots; same dictionary as in Fig. 4) display a clear tradeoff between spectral and temporal modulations, similar to what has been reported for Inferior Colliculus (IC) . By contrast, the half-complete cochleogram-trained dictionary (blue circles; same dictionary as in Fig. 2) exhibits a much more limited range of temporal modulations, with no such tradeoff in spectrotemporal resolution. Each data point represents the centroid of the modulation spectrum of the corresponding element. The elements shown in Fig. 4 are indicated on the graph with the same symbols as before.