Varying the temporal placement of a signal within a constant response-independent food cycle on the activity of rats

Abstract

The temporal distribution of stabilimeter-activity in rats across a constant 128 s response-independent food cycle was examined. Four rats participated in two different phases of the experiment. In the first phase or baseline, the pattern of activity was simply recorded across eight 16-s subintervals of the food cycle. Following baseline, the second phase, consisting of intruding a sound on a fixed location within the food cycle was initiated. The sound was co-terminal with a given bin and on successive conditions, it was first placed on the last bin, in contiguity with the subsequent food. On the second condition, the sound was placed on the penultimate bin before food. On the third condition of the second phase the sound was intruded on the antepenultimate bin before food and so on until the sound was placed on the first bin, in contiguity with the preceding food. The baseline activity pattern consisted in a sudden post-food increase followed by a gradual decline until the subsequent food. Intruding the 16-s sound on a given bin changed the baseline patterns in, complex but orderly new patterns. Although with minor variations, such stimulus-controlled patterns of activity resembled the time-course of fixed-interval operant responding interrupted by stimuli intruded on selected locations of the inter-reinforcement interval. The parallels between the results of the current experiment and those from previous studies involving fixed-interval responding with added stimuli suggest the possibility of reducing schedule-induced activity to operant responding.