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. Author manuscript; available in PMC: 2016 Jun 20.
Published in final edited form as: Neuron. 2014 Sep 11;84(1):214–226. doi: 10.1016/j.neuron.2014.08.019

Figure 6. Computational model II: Gain modulation of units inside the inhibitory feedback loop robustly reproduces the experimental effects of AGF microstimulation.

Figure 6

The AGF modulates the gain of Imc units in a space-specific manner. Same conventions as in Figure 5. (A-D). Effects of aligned AGF stimulation (red icons and data). (A) Inset: Visual mnemonic illustrating multiplicative gain modulation of Imc responses by AGF microstimulation. Shown are schematic responses of an Imc unit to a single stimulus inside the RF, without (black) and with (red) microstimulation. X-axis, strength of RF stimulus; y-axis, firing rate. (B) AGF→Imc input gain parameter = 0.325, response gain parameter = 1.22 (same values as AGF→OTid gain parameters in Figure 5b, and correspond to the white ‘x’ in C; top panels). (C) Top panels: Shift in s50 (%; left) and change in transition range (%; right). Red arrow: average % change from experiments (Fig. 1). Bottom panels: Plot (“mask”) showing whether or not the value of % change in the simulated CRP's s50 (left panel) and transition range (right panel) due to AGF microstimulation was within the range of experimentally observed values of % change. Ranges for experimentally observed values were estimated to be the mean ± 2*std, where mean and std were calculated from recordings (Fig. 1E). “Good” (black): simulated values that lie within the range of experimentally observed values; “bad” (white): simulated values that lie outside the range of experimentally observed values. (D) Top panels: Change in minimum response rate (%; left) and maximum response rate (%; right) of simulated CRPs. Bottom panels: Masks; same conventions as in (C). Range of values of the parameters that yielded results that were consistent with experiments is determined by the area of the intersection of the “good” (black) portions of the four masks from C and D. (E-H) Effects of non-aligned stimulation (AGF RF non-aligned with OTid RF, but aligned with location of the competitor; blue icons and data). Same conventions as in (A-D). (F) AGF→Imc input gain parameter = 0.325, response gain parameter = 1.22. (G) Top panels: Blue arrow: average % change from experiments (Fig. 2). Top-right panel: No effect of non-aligned AGF microstimulation on the CRP maximum response rate.

See also Figure S4.