Mechanisms of schedule entrainment

Abstract

Abstract If hungry rats are placed on a fixed-time (FT) schedule of food delivery in which food pellets are delivered every, say, 60 seconds independent of the rat’s behaviour, and if supporting apparatus such as a running wheel and a water dispenser are available, the sequence of the activities between food deliveries becomes strikingly stereotyped. Fig. 8.1 shows a second-by-second summary of an entire 45-min session for a rat on an FT 60-s schedule. Each row represents a single interfood interval, and each character or space represents one second of an activity. ‘F’ corresponds to ‘head-in-feeder’, ‘D’ to drinking, ‘R’ to wheel running, ‘C’ to chewing an oak block, blank spaces to unmeasured activities, and the lower case letters correspond to various inoperative levers in the apparatus. The ‘l’ in the first column is the number of food pellets beginning the interval, and the ‘60’ in the last column represents the duration of the interfood interval.When data are depicted in this format, the most striking aspect is the temporal entrainment of the various activities by food presentation. With few exceptions most interfood intervals contained a relatively stereotyped temporal pattern of activities: eating the food pellet, then drinking from the water spout, running in the wheel, and finally returning to the feeder area in anticipation of the next food delivery. But there is another striking aspect of these data.