Figure 6.

Extra wake, potentiation in sleep, and down-selection in wake degrade Matching. (A) The same neuron shown in Figure 5C is allowed to undergo an extended period of training. The constraint on the total synaptic weight is relaxed. As a result, the neuron continues to potentiate synapses D/D′, E/E′, and F/F′. While the firing rate in response to the World increases slightly, the firing rate in response to Chance increases more significantly, thus degrading Matching (B) The same neuron shown in Figure 5C is allowed to undergo synaptic potentiation during sleep, using the correlated inputs generated internally (shown in the green boxes). Since synapses A/A′, B/B′, and C/C′ are saturated before this sleep period, the synapses D/D′ corresponding to the spurious activations (A and D 0.1%, B and D 0.1%) become further potentiated. Afterward, all synapses are linearly depressed so the total synaptic weight after sleep is comparable to the neuron shown in Figure 5D. As a result, Matching is degraded. (C) The neuron from Figure 5B is allowed to undergo both synaptic potentiation as well as activity-dependent down-selection in wake. Since the Training of this particular day does not include correlations on inputs A and B (but they are still present in the Long-Term statistics of the World), synapses A/A′ become depressed. Thus, Matching is degraded.