Influence of the response sparseness of the units in the model.

To obtain the curve for one layer, a total of 16 values were chosen non-uniformly between 0.001 and 100 for λ in that layer, while keeping λ = 1 in lower layers. (a) Relationship between F-ratio and lifetime sparseness in layers S5, C5, S6, and C6. (b) Relationship between the decoding accuracy of different acoustic parameters and lifetime sparseness in layer C6. SP, spectral peak. (c) PSI vectors of phonemes in C6 with λ = 0.01. The order of rows is the same as in Fig 5A. (d) PSI vectors of phonemes in C6 with λ = 1 (exactly the same as Fig 5A).