Interval timing with gaps and distracters: evaluation of the ambiguity, switch, and time-sharing hypotheses.

Gaps and distracters were presented during the timed signal to examine whether the stop/reset mechanism is activated by (a) changes in the timed signal (switch hypothesis), (b) ITI-like events (ambiguity hypothesis), or (c) processes concurrent with the timing process (time-sharing hypothesis). While the switch and ambiguity hypotheses predict that rats should time through (ignore) distracters, the time-sharing hypothesis predicts that extraneous events (e.g., gaps and distracters) delay timing by causing working memory to decay in proportion to the events' salience. The authors found that response functions were displaced by both gaps and distracters, in accord with the time-sharing hypothesis. Computer simulations show that the time-sharing and memory-decay hypotheses can mechanistically address present data, and reflect different levels of the same model.