Robustness of neuronal tuning to binaural sound localization cues against age-related loss of inhibitory synaptic inputs
Fig 4
Simulated effects of inhibition loss on binaural tuning of LSO with amplitude overcompensation.
A. Total amount of inhibitory synaptic inputs normalized to the value for the default (Minh = 8 inputs). In the uncompensated case (gray dot-dashed line; data shown in Fig 2), the total inputs depended linearly on the number of inputs, while in the compensated case (thin gray line; data shown in Fig 3), the total inputs were kept constant. In the present overcompensation case (solid black line), the summed inhibitory conductance was a linear decreasing function of the number of inhibitory inputs. Namely, in comparison to the default condition, the LSO neuron model receives stronger inhibition in total, when the number of inhibitory inputs was reduced. B. Simulated ILD-tuning curves for different numbers of inhibitory inputs. C. (Thin lines) peak (max) and trough (min) rates of the ILD-tuning curves. (Thick solid line) Modulation depth defined as the difference between maximum and minimum rates. D. Neuronal discriminability of ILD tuning curves averaged over the range between -45 and +15 dB and normalized to the value for 8 inhibitory inputs. E. Simulated envelope phase-tuning curves at 300 Hz for different numbers of inhibitory inputs. F. (Thin lines) peak (max) and trough (min) rates of the envelope phase-tuning curves. (Thick solid line) Modulation depth defined as the difference between maximum and minimum rates. G. Neuronal discriminability of envelope phase-tuning curves averaged over the range between -180 and +180 degrees and normalized to the value for 8 inhibitory inputs. In panels C, D, F, and G, simulated results for the uncompensated case (gray dot-dashed lines; same data as in the corresponding panels in Fig 2) and for the perfectly compensated case (thin gray lines; same data as in the corresponding panels in Fig 3) are shown for comparison; the filled circles show the response for the default number of inputs (Minh = 8).