Figure 8. Modeling dopamine and NO mediated plasticity (A) Summary of plasticity model for independent dopaminergic (DA) and NO pathways.

Synaptic weight w_i from KC_i to an MBON is increased or decreased depending on the pairing protocol. A and B determine the magnitude of the depression or potentiation induced by pairing, and τ determines the timescale over which weight changes occur. (B) Illustration of the effects of the model in (A), for only DA (left) or only NO (right) dependent plasticity. In each plot, KC and DANs are first co-activated, followed by a later DA activation without KC activation. (C) Top: Model performance index (PI) for different pairing protocols. In (C)-(F), crosses represent the means of data from Figure 7. Bottom: Dynamics of D(t) and N(t) in the model. (D) Modeling effects of combined DA and NO dependent plasticity. Gray curve: synaptic weights w(t) are modeled as an additive function of DA and NO dependent effects D(t) and N(t), w(t) ∝ N(t) – D(t). Blue curve: a multiplicative interaction with w(t) ∝ (1 + N(t)) (1 – D(t)). (E) Modeling 24 hr memory decay following 1 × 1 min odor pairing. We assume a low level of spontaneous DAN activity and choose B_DA and B_NO to fit the data. Top: Performance index in model and data. Blue curve: control. Purple curve: only DA-dependent plasticity (compared to data from NOS-RNAi experiment). Bottom: Dynamics of D(t) and N(t) in the model. (F) Modeling effects of DAN activation and reversal learning. B_DA and B_NO are chosen to fit the effects of DAN activation (top). The model qualitatively reproduces the effects of reversal learning (bottom) with no free parameters.

Figure 8—figure supplement 1. Parameters for modeling dopamine and NO mediated plasticity.

Values of N(t), D(t), and synaptic weight w(t) for the model of DAN-activation and reversal protocols in Figure 8F.

Plots of ‘A-selective KCs’ show N(t) and D(t)for KCs that represent the odor paired with DAN activation in the first two pairings, whereas ‘B-selective KCs’ show N(t) and D(t) for KCs that represent the corresponding odor for the second two pairings (Figure 7A).

Figure 8—figure supplement 2. Performance of additive model on DAN activation and reversal paradigms.

(A) Same as Figure 7F, but for a model in which DA and NO effects are additive, w(t) ∝ N(t) – D(t).

The model produces a worse fit than the multiplicative model (Figure 7F). (B) Same as Figure 8—figure supplement 1, but for the additive model.