A simultaneous procedure facilitates acquisition under an optimal interstimulus interval in artificial neural networks and rats

In a computer simulation, a neural network first received a simultaneous procedure, where the interstimulus interval (ISI) was 0 time-steps (ts). Output activations were near zero under this procedure. The network then received a forward-delay procedure where the ISI was 8 ts. Output activations increased to the near-maximum level faster than those of a control network that first received an explicitly unpaired procedure. Comparable results were obtained with rats that first received trials where a retractable lever was presented for 3 s concurrently with access to water. Low-lever pressing was observed under this procedure. The rats then received trials where the lever was followed 15 s after by water. Lever pressing appeared faster than a control group that received the 15-s ISI after an explicitly unpaired procedure. The model used in the simulation explains these results as connection–weight increments that promote little output activations in a simultaneous procedure, but facilitate acquisition in an optimal ISI.