Temporal coding affects transfer of serial and simultaneous inhibitors

In three experiments with rats, the temporal relationships under which a conditioned inhibitor would transfer its inhibitory potential to an independently trained excitor in a summation test were investigated. Each experiment varied the temporal relationship between the inhibitor and the transfer excitor at test (serial or simultaneous) and, in addition, manipulated either the inhibitor-training excitor (serial or simultaneous), training excitor-unconditioned stimulus (US) (trace or delay), or the transfer excitor-US (trace or delay) temporal relationships. Conditioned inhibition was found only when the no-US expectation evoked by the conditioned inhibitor was temporally aligned with the US expectation evoked by the transfer excitor, independent of whether the inhibitor was trained as a serial or simultaneous signal for US omission. Results are discussed in terms of the temporal coding hypothesis and the comparator hypothesis.