Fixed-interval Procedure Research Articles

In a daily time-place learning task, time is only used as a discriminative stimulus if each daily session is associated with a distinct spatial location.

It is difficult for rats to acquire daily time-place (TP) learning tasks. One theory suggests that rats do not use time of day as a stimulus signaling a specific response. In the present study, we tested rats' ability to use time of day as a discriminative stimulus. A fixed-interval procedure was used in which one lever provided reinforcement on a FI-5-s schedule in morning sessions, and the same lever provided reinforcement on a FI-30-s schedule in afternoon sessions. Because only one place was used in this paradigm, the rats could only use time of day to acquire the task. Mean responses during the first 5 s of the first trial in each session indicated that the rats did not discriminate between the two sessions. In Phase II, a different lever location was used for each of the two daily sessions, which meant that both spatial and temporal information could be used to acquire the task. The rats readily acquired the task in this phase, and probe trials indicated that the rats were using a combination of spatial and temporal information to discriminate between the two different trial types. When the spatial cue was removed in Phase III, rats no longer discriminated the two sessions, suggesting that time can only be used as a discriminative stimulus when each daily session is associated with a distinct spatial location.

Interval timing behavior in Pallas’s long-tongued bat (Glossophaga soricina).

Timing behavior in animals and its underlying mechanisms have been investigated extensively in the peak procedure, a variant of fixed interval procedures. In such experiments, individuals typically start responding with high frequency after an initial inactive time interval and continue their responses after peak time if rewards are omitted. This begs the so far unexplored question as to how timing behavior is influenced when such continuous responses are suppressed. Here, we present results from a nectar-feeding bat species, Glossophaga soricina, that was tested in a modified version of the peak procedure at three fixed time intervals (5 s, 11 s, 20 s). In contrast to standard peak procedures we imposed metabolic costs on individual responses which effectively suppressed trains of rapid responses during trials. Under this manipulation, bats' aggregated responses showed clear peaks around the peak time in the 5-s and 11-s schedules. Bats' responses in the 20-s schedule, however, did not peak around the fixed interval time. Crucially, an analysis of time intervals between successive revisits in all schedules revealed that bats revisited feeders at accurately timed intervals in all three conditions. The individual within trial behavioral responses showed clear oscillatory patterns throughout nonrewarded trials. These findings follow predictions from mechanistic timing models, like the striatal beat frequency model, and are discussed with regard to these models.

Time Is Everywhere: Review of H. Helfrich, (Ed.), Time and Mind II: Information Processing Perspectives.

Is Everywhere: Review of H. Helfrich, (Ed.), and Mind II: Information Perspectives has been a topic of intense interest to psychologists from very beginnings of field, and it continues to be focus of much experimental and theoretical work. The reason for this continued interest is that time is everywhere in psychological landscape. Temporal phenomena represent a core clement of virtually all psychological processes. All behaviour, from macro level of actions, perceptions, and thoughts, to micro level of brain function, neurological networks, and responses of individual neurons, occurs in time. These processes have their own temporal dynamics, they operate on their own time scales, and they affect timing of other processes and mechanisms. This wide-ranging character of time has drawn attention of many different specialists, and Helfrich's book represents a sampling of some of these perspectives. The book is based on symposium Time and Mind 02, held at University of Hildesheim in September 2002. The contributions represent a mixed format, ranging from straight experimental reports to literature reviews to descriptions of elaborate theoretical models. The 12 chapters are divided evenly into two parts, Time as an Object of Information Processing and Time as a Constituent of Information Processing. Part 1: as an Object of Information Researchers in time perception probably will find first part of book to be of greater interest and relevance. The first three chapters relate to Scalar Expectancy Theory of timing. Scalar Expectancy Theory (SET), originally derived from animal timing literature, describes a multicomponent timing model involving a biologically driven pacemaker-accumulator mechanism, a memory component, and a decision-making component. Chapter 1 (Simultaneous Temporal Processing by Russell M. Church, Paulo Guilhardi, Richard Keen, Mika Maclnnis, & Kimberly Kirkpatrick) consists of a review of work on simultaneous timing in laboratory animals. The authors describe segmented fixed-interval procedure, in which fixed interval includes stimulus events that serve to subdivide interval into smaller parts. Although procedure has been used to test hypotheses related to chaining of responses and secondary reinforcers, its major impact is that the fixed-interval procedure makes it clear that they (animals) are able to time two intervals simultaneously (p. 12). The authors argue that simultaneous timing is also evident in numerous conditioning procedures, including Pavlovian delay and trace conditioning, and in effects of variations in trial and intertriai intervals. They suggest that modifications to SET, such as incorporating another set of independent pacemaker-memory-decision components, may be required to account for results. However, human research on multiple timing (not discussed by Church et al.) may require more substantial changes to SET than those envisioned here. Indeed, researchers in recent years have adapted some of standard animal research paradigms used to test SET in an effort to evaluate theory in terms of human timing. In Chapter 2 Applying Scalar Timing Model to Human Psychology: Progress and Challenges, John H. Wearden provides a well-organized review of this work. Wearden points out that theory faces certain challenges when applied to human timing, especially memory and decision components of model. Other compatibility issues arise with shift from animal to human experimentation, including role of attention in timing and implementation of different time judgment methodologies. One of chief benefits of application of SET to human studies, in Wearden's view, is that it brings back emphasis of an internal timer/clock mechanism to human timing. Richard A. Block's contribution (Chapter 3, Psychological Timing Without a Timer: The Roles of Attention and Memory) is a good companion piece to Wearden's paper. …

The effects of concurrent task and gap events on peak time in the peak procedure.

The effect of a concurrent task on timing performance of pigeons was investigated with the peak interval procedure. Birds were trained to peck a side key on a discrete-trial schedule that included reinforced fixed-interval (FI) 30-s trials and nonreinforced extended probe trials. Then, in separate sessions, birds were trained to peck a 6-s center key for food. In a subsequent test phase, the FI procedure was in effect along with dual-task probe test trials. On those test trials, the 6-s center key (task cue) was presented at 3, 9, or 15s after probe trial onset. During another test phase, a 6-s gap (the FI keylight was extinguished) was presented at 3, 9, or 15s after probe trial onset. Peak time increased with center key time of onset, and was greater under task than gap conditions. Moreover, peak time under task conditions exceeded values predicted by stop and reset clock mechanisms. These results are at variance with current attentional accounts of timing behavior in dual-task conditions, and suggest a role of nontemporal factors in the control of timing behavior.

Chronic bretazenil produces tolerance to chlordiazepoxide, midazolam, and abecarnil

The purpose of the present study was to determine if chronic treatment with a nonsedative benzodiazepine partial agonist would confer tolerance to the rate-decreasing effects of other benzodiazepine ligands in a fixed-interval procedure in rats. A separate group of rats was treated chronically with the sedative benzodiazepine full agonist, chlordiazepoxide, for comparison. It was hypothesized that tolerance would develop rapidly to chlordiazepoxide due to loss of reinforcement density at rate-decreasing doses and that there would probably be cross-tolerance to other rate-decreasing benzodiazepine ligands such as midazolam and abecarnil. Because bretazenil does not produce rate decreases, however, it was not expected that tolerance would be found to chlordiazepoxide, midazolam, or abecarnil. After 8–12 weeks of chronic treatment with either chlordiazepoxide or bretazenil, however (final dose of benzodiazepine = 30 mg/kg/day), tolerance was found to the rate-decreasing effects of chlordiazepoxide, midazolam, and abecarnil in both groups. It is concluded that such tolerance was most likely due to a saturation of benzodiazepine receptors by this high-affinity partial agonist.

TEMPORAL CONTROL ON INTERVAL SCHEDULES: WHAT DETERMINES THE POSTREINFORCEMENT PAUSE?

On fixed-interval or response-initiated delay schedules of reinforcement, the average pause following food presentation is proportional to the interfood interval. Moreover, when a number of intervals of different durations occur in a programmed cyclic series, postreinforcement pauses track the changes in interval value. What controls the duration of postreinforcement pauses under these conditions? Staddon, Wynne, and Higa (1991), in their linear waiting model, propose control by the preceding interfood interval. Another possibility is that delay to reinforcement, signaled by a key peck and/or stimulus change, determines the subsequent pause. The experiments reported here examined the role of these two possible time markers by studying the performance of pigeons under a chained cyclic fixed-interval procedure. The data support the linear waiting model, but suggest that more than the immediately preceding interfood interval plays a role in temporal control.

Variable sampling intervals for multiparameter shewhart charts

This paper considers the problem of using control charts to simultaneously monitor more than one parameter with emphasis on simultaneously monitoring the mean and variance. Fixed sampling interval control charts are modified to use variable sampling intervals depending on what is being observed from the data. Two basic strategies are investigated. One strategy uses separate control charts for each parameter, A second strategy uses a proposed single combined statistic which is sensitive to shifts in both the mean and variance. Each procedure is compared to corresponding fixed interval procedures. It is seen that for both strategies the variable sampling interval approach is substantially more efficient than fixed interval procedures.

Comparison of timing and classical conditioning.

Four experiments with rats investigated if the timing of a stimulus (sound) correlated with the strength of a conditioned response (CR) to the stimulus. The timing (effective duration) of the stimulus was measured using the peak procedure, similar to a discrete-trials fixed-interval procedure. The rats were trained so that their response rate reached a maximum about 40 s or 60 s after the onset of a light; the time of the maximum measured from the start of the light (peak time) was the measure of timing. On some trials, the light was preceded by a short (5 s) or long (20 s or 30 s) interval of sound. We assumed that the difference in peak time after long and short sounds reflected the timing of the sound--if the sound was timed, the longer sound would produce a lower peak time; if the sound was not timed, the two durations of sound would produce the same peak time. The CR was lever-pressing during the sound. The sound was treated in various ways: presented alone (Experiments 1, 3, and 4), followed by food (Experiments 1, 3, and 4), preceded by food (Experiment 3), and followed by food after 20 s (Experiment 4). Treatments that produced no timing of sound produced no CR, and treatments that increased (or diseased) timing also increased (or decreased) the CR. The results suggest that there is overlap between the mechanisms that produce time discrimination and the mechanisms that produce classical conditioning.

Cross-modal use of an internal clock.

Four experiments used time-discrimination procedures with rats to ask if light and sound are timed by the same internal clock and if measured durations of light and sound are stored in the same memory. Experiment 1 used a choice procedure and a cross-modal transfer-of-training design. Rats were trained to press one lever after a 1-sec signal, another lever after a 4-sec signal. At first, the signal was light (or sound); when performance was accurate, the signal was changed ot sound (or light). There was transfer of the time discrimination across modalities: To some extent, the rats treated the new signal (sound) as if it were the old signal (light). The rest of the experiments used the peak procedure, which is similar to a discrete-trials fixed-interval procedure. With the peak procedure, response rate reaches a maximum in the middle of the trial; the time of the maximum (peak time) is a measure of the clock and temporal memory. Experiment 2 found that changing the time of food during light (or sound) changed peak time during sound (or light). In Experiments 3 and 4, intervals of light (or sound) were followed by intervals of sound (or light). The interval of light decreased the peak time measured from the start to the interval of sound, whether the two intervals were adjacent (Experiment 3) or separated by 5 sec (Experiment 3). Experiments 1 and 2 suggest that measured durations of light and sound are stored by the same memory; Experiments 3 and 4 suggest that light and sound are timed by the same clock.

Sniffing and motivated behavior in the rat

The effect of rewarding brain stimulation on inspiration rate in the rat was investigated using a temporal conditioning and a fixed-interval lever-pressing procedure. In early temporal conditioning trials, inspiration frequency was most pronounced following brain stimulation. With conditioning, inspiration frequency became most pronounced preceding brain stimulation. Inspiration frequency in the sniffing range remained part of the unconditional response to rewarding brain stimulation throughout both experiments of this study. In the fixed-interval procedure, inspiration frequency increased just prior to the first lever-press of an interval, and continued to increase until reinforcement was delivered. These results suggest that measurement of respiration/sniffing frequency may have relevance to classical conditioning interpretations of motivated behavior.

PARAMETERS AFFECTING THE ACQUISITION OF SIDMAN AVOIDANCE.

Four studies were conducted to investigate the source of reinforcement of Sidman avoidance. First it was found that the acquisition of avoidance was seriously impaired if there was no immediate stimulus consequence of responding, i.e., proprioceptive and auditory feedback. The second study showed that if the shock-shock interval was split so that only responses occurring in one half of the interval were effective in postponing shock, then learning was impaired. It made little difference which half of the interval was used. The third study demonstrated that Ss learn Sidman avoidance more quickly with a variable shock-shock interval than with the usual fixed-interval procedure. The results of the second and third experiments argue against the view that avoidance is reinforced by the decrease in conditioned aversiveness that occurs at long post-shock times. The final experiment indicated that Ss do not learn Sidman avoidance if the response-produced delay of shock is preceded by a shock, hence it seems unlikely that the crucial source of reinforcement is merely an overall reduction in shock density. All of the findings are consistent with the hypothesis that the avoidance response is reinforced by the decrease in conditioned aversiveness of stimuli at short post-response times. This seems to be the case even at the beginning of acquisition.

Behavioral effects of caffeine, methamphetamine, and methylphenidate in the rat.

It was possible to distinguish three closely-related psychomotor stimulants, caffeine, methamphetamine, and methylphenidate, by means of two operant behavior procedures, fixed interval and fixed number. Under the fixed interval procedure, the percentage change in the number of R(B)s per reinforcement was significantly smaller with caffeine than with methamphetamine or methylphenidate (p < .001). Under the fixed number procedure, the percentage change was significantly smaller with methamphetamine than with caffeine or methylphenidate (p < .001). Thus, methylphenidate had a methamphetamine-like effect under fixed interval and a caffeine-like effect under fixed number.