Fig. 4.

Rate modulation. (A) Distribution of synaptic efficacies of nine postsynaptic neurons after 60 min of stimulation with identical inputs for all neurons. Synapses 1 ≤ j ≤ 40 (red symbols) received Poisson input with common rate modulation; the input at synapses 41 ≤ j ≤ 80 (blue symbols) was also rate-modulated but phase-shifted; and the input at the remaining 20 synapses was uncorrelated (green symbols). Four postsynaptic neurons (numbers 1, 3, 5, and 8) develop a spontaneous specialization for the first group of modulated input (red symbols close to the maximum efficacy of one) and five (numbers 2, 4, 6, 7, and 9) specialized for the second group. (B) Modulation of the output rate of the nine postsynaptic neurons before (Left) and after (Right) learning. Red/blue bars, neurons responding to the first/second group of input; Red/blue lines, modulation of the input of groups 1 and 2.