Figure 9. Subtractive inhibition, but not divisive inhibition can account for the improvement in sparsity, reproducibility, and temporal precision.
(A) In response to the RGS stimulus, the SBC output (blue) showed a consistent increase in sparsity (left), reproducibility (middle) and decreased temporal dispersion (right). The simulated subtractive inhibition (green) showed similar improvements as the experimental data, while divisive inhibition (purple) had no effect on sparsity, reproducibility, and temporal dispersion. (B) These relations are also reflected in the population data, with significant changes in both the experimental data and the simulated subtractive inhibition (p<0.001, one-way RM ANOVA).
DOI: http://dx.doi.org/10.7554/eLife.19295.020
Figure 9—source data 1. Simulation of divisive and subtractive inhibition.
Shown are the values of sparsity, reproducibility and temporal dispersion (in ms) obtained from the simulation of pure subtractive or pure divisive inhibition. The data set also contains the experimentally obtained data separately for ANF input and SBC output.
elife-19295-fig9-data1.mat (3.9KB, mat)
DOI: 10.7554/eLife.19295.021
Figure 9—figure supplement 1. Subtractive inhibition improves temporal precision and trial-to-trial reproducibility during SAM stimulation.
To test, if the subtractive or divisive effect of inhibition are sufficient to explain the observed increase in temporal precision and reproducibility of the SBC output, the ANF input was compared to the experimental SBC output data and simulated SBC outputs caused by either subtractive or divisive inhibition. For the simulated SBC output, the ANF input spikes were removed to match the experimentally observed failure fraction. (A) Vector strength, modulation depth, reproducibility stimulus reproduction (CorrNorm), and sparsity of the ANF input was compared to the experimental data (blue) and the simulated SBC output influenced by either divisive (purple) or subtractive (green) inhibition Pure divisive inhibition had no effect on temporal precision or reproducibility (dots on line of equality, gray). Pure subtractive inhibition matched the experimental data well and showed an increase in vector strength, modulation depths, reproducibility, and sparsity of the SBC output (dots above line of equality). (B) Population data showing the difference between ANF input and SBC output for the experimental (blue) and simulated divisive (purple) and subtractive inhibition (green) for different modulation frequencies. The experimental SBC output showed increased vector strength, modulation depth, reproducibility, and sparsity for all modulation frequencies. This change was also observed under simulated divisive inhibition, but absent for pure subtractive inhibition. Markers indicate mean ± standard deviation.
Figure 9—figure supplement 2. Subtractive inhibition, but not divisive inhibition can account for the improved temporal precision and reproducibility during SFM stimulation.
Similar to the SAM analysis, the effect of an increased failure fraction during SFM stimulation was simulated as purely divisive or subtractive inhibition and compared to the experimental data. (A) Pooled data across all modulation frequencies. The experimental data showed an increase in vector strength, modulation depths, reproducibility, and sparsity of the SBC output (blue dots above line of equality, gray). This change was present only for the simulated subtractive inhibition but absent for pure divisive inhibition. (B) Population data showing the difference between ANF input and SBC output for the experimental (blue) and simulated divisive (purple) and subtractive inhibition (green) for different modulation frequencies. The experimental SBC output showed increased vector strength, modulation depth and reproducibility for all modulation frequencies. This change was well matched by pure subtractive inhibition, but absent at pure divisive inhibition. The stimulus reproduction (CorrNorm) decreased in the experimental SBC output and the simulated subtractive inhibition but remained unchanged for pure divisive inhibition. Markers indicate mean ± standard deviation.