Conditioned Stimulus Duration Research Articles

Effects of inter-trial interval on sign-tracking and conditioned reinforcer efficacy in female rats

Previous nonhuman studies have reported that sign-tracking to a conditioned stimulus (CS) is increased when the intertrial interval (ITI) duration is increased. Separate studies indicate that individual differences in sign-tracking (vs. goal-tracking) at a fixed ITI (and CS duration) is predictive of the conditioned reinforcer efficacy of the CS. The present study evaluates, for the first time, if increasing the ITI increases rats’ sign-tracking and the conditioned reinforcing efficacy of the CS. Forty-five female rats were randomly assigned to one of three groups that completed appetitive Pavlovian training with ITIs of 14, 24, or 96 s. Subsequently, they completed tests of conditioned reinforcement. Replicating previous findings, longer ITIs increased sign-tracking to a lever-CS and, extending the literature, conditioned reinforcer efficacy of that CS was highest at the longest ITI used during Pavlovian training. Implications for behavioral interventions using conditioned reinforcement are discussed.

Effects of conditioned stimulus (CS) duration, intertrial interval, and I/T ratio on appetitive Pavlovian conditioning.

Pavlovian learning is influenced by at least 2 temporal variables: The time between the onset of the conditioned stimulus (CS) and presentation of the unconditioned stimulus (US), and the time between successive conditioning trials (the intertrial interval [ITI]). Wagner's Sometimes Opponent Process (SOP) model (e.g., 1981) provides a rich account of the effects of varying the absolute durations of CS and ITI. However, other theories have contrastingly emphasized the role of the relative durations of CS (T) and ITI (I). Three experiments with rats used an appetitive conditioning preparation to separate the two approaches. They manipulated absolute values of I and T over a factor of 6 and compared the effect of varying T and I/T by the same factor. Conditioning was indexed by the rate of foodcup entry during training, during common tests conducted later with different combinations of I and T, and with a reinforcers-to-criterion measure. Experiment 1 found that learning with a 10-s CS was superior to that with a 60-s CS when the I/T ratio was the same. There was little evidence of learning with the 60-s CS. Experiment 2 replicated that result and extended it to show that a 60-s CS still supported little conditioned responding when I/T was increased from 12 to 72. Experiment 3 then examined intermediate CS durations between 10-s and 60-s while I/T was controlled. The results support a role for absolute CS duration rather than the I/T ratio. Explanations based on SOP and behavior systems theory are explored. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Pavlovian conditioning under partial reinforcement: The effects of nonreinforced trials versus cumulative conditioned stimulus duration.

A core feature of associative models, such as those proposed by Allan Wagner (Rescorla & Wagner, 1972; Wagner, 1981), is that conditioning proceeds in a trial-by-trial fashion, with increments and decrements in associative strength occurring on each occasion that the conditioned stimulus (conditional stimulus, or CS) is present either with or without the unconditioned stimulus (US). A very different approach has been taken by theories that assume animals continuously accumulate information about the total length of time spent waiting for the US both during the CS and in the absence of the CS (e.g., Gallistel & Gibbon, 2000). Here we describe 3 experiments using within-subject designs that tested trial-based and time-accumulation accounts of the acquisition of conditioned responding using magazine approach conditioning in rats. We found that responding was affected by the total (cumulative) duration of exposure to the CS without the US rather than the number of trials on which the CS occurred without the US. We also found that exposure to the CS without the US had the same effect on conditioning whether that exposure occurred shortly (60 s) before each CS-US pairing or whether it occurred long (240 s) before each pairing. These findings are more consistent with time-accumulation models of conditioning than trial-based models like the Rescorla-Wagner model and Wagner's (1981) sometimes opponent process model. We discuss these findings in relation to other evidence that favors trial-based models rather than time-accumulation models. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Delay of reinforcement versus rate of reinforcement in Pavlovian conditioning.

Conditioned stimulus (CS) duration is a determinant of conditioned responding, with increases in duration leading to reductions in response rates. The CS duration effect has been proposed to reflect sensitivity to the reinforcement rate across cumulative exposure to the CS, suggesting that the delay of reinforcement from the onset of the cue is not crucial. Here, we compared the effects of delay and rate of reinforcement on Pavlovian appetitive conditioning in mice. In Experiment 1, the influence of reinforcement delay on the timing of responding was removed by making the duration of cues variable across trials. Mice trained with variable duration cues were sensitive to differences in the rate of reinforcement to a similar extent as mice trained with fixed duration cues. Experiments 2 and 3 tested the independent effects of delay and reinforcement rate. In Experiment 2, food was presented at either the termination of the CS or during the CS. In Experiment 3, food occurred during the CS for all cues. The latter experiment demonstrated an effect of delay, but not reinforcement rate. Experiment 4 ruled out the possibility that the lack of effect of reinforcement rate in Experiment 3 was due to mice failing to learn about the nonreinforced CS exposure after the presentation of food within a trial. These results demonstrate that although the CS duration effect is not simply a consequence of timing of conditioned responses, it is dependent on the delay of reinforcement. The results provide a challenge to current associative and nonassociative, time-accumulation models of learning.

Examining the influence of CS duration and US density on cue-potentiated feeding through analyses of licking microstructure

In the current study, groups of mice were trained with either short (20s) or long (120s) conditioned stimulus (CS) durations associated with different rates of sucrose unconditioned stimulus (US) delivery, to examine whether different behavioral forms of cue-potentiated feeding in sated mice would be evoked. In training mice received presentations of an auditory CS for 20s during which a sucrose US was delivered at a density of 1/9s (Group-20-s). A second group of mice received an auditory CS for 120s and a US density of 1/49s (Group-120-s). During training, a shorter CS duration and higher rate of US delivery resulted in greater acquisition of food cup responding, and during the test stage Group-20-s mice also displayed higher CS evoked lick rates, though all mice showed cue-potentiated feeding. An analysis of licking microstructure revealed that Group-120-s mice displayed CS evoked licking behavior that reflected an increase in the perceived palatability of the sucrose US. These findings are discussed with respect to the influence of CS duration and US density on associatively activated sensory and affective representations of a US, and contrast mediated effects resulting from presentation of excitatory and inhibitory conditioned stimuli.

Rescaling of temporal expectations during extinction.

Previous research suggests that extinction learning is temporally specific. Changing the conditioned stimulus (CS) duration between training and extinction can facilitate the loss of the conditioned response (CR) within the extinction session but impairs long-term retention of extinction. In 2 experiments using conditioned magazine approach with rats, we examined the relation between temporal specificity of extinction and CR timing. In Experiment 1, rats were trained on a 12-s, fixed CS-unconditional stimulus interval and then extinguished with CS presentations that were 6, 12, or 24 s in duration. The design of Experiment 2 was the same except rats were trained using partial rather than continuous reinforcement. In both experiments, extending the CS duration in extinction facilitated the diminution of CRs during the extinction session, but shortening the CS duration failed to slow extinction. In addition, extending (but not shortening) the CS duration caused temporal rescaling of the CR, in that the peak CR rate migrated later into the trial over the course of extinction training. This migration partially accounted for the faster loss of the CR when the CS duration was extended. Results are incompatible with the hypothesis that extinction is driven by cumulative CS exposure and suggest that temporally extended nonreinforced CS exposure reduces conditioned responding via temporal displacement rather than through extinction per se. (PsycINFO Database Record

Subliminal evaluative conditioning? Above-chance CS identification may be necessary and insufficient for attitude learning.

Previous research has claimed that evaluative conditioning (EC) effects may obtain in the absence of perceptual identification of conditioned stimuli (CSs). A recent meta-analysis suggested similar effect sizes for supra- and subliminal CSs, but this was based on a small body of evidence (k = 8 studies; Hofmann, De Houwer, Perugini, Baeyens, & Crombez, 2010). We critically discuss this prior evidence, and then report and discuss 6 experimental studies that investigate EC effects for briefly presented CSs using more stringent methods. Across these studies, we varied CS duration, the presence or absence of masking, the presence or absence of a CS identification check, CS material, and the instructions communicated to participants. EC effects for longer-duration CSs were modulated by attention to the CS-US pairing. Across studies, we were consistently unable to obtain EC for briefly presented CSs. In most studies, this pattern was observed despite above-chance perceptual identification of the CSs. A meta-analysis conducted across the 27 experimental conditions supported the null hypothesis of no EC for perceptually unidentified CSs. We conclude that EC effects for briefly presented and masked CSs are either not robust, are very small, or are limited to specific conditions that remain to be identified (or any combination of these). (PsycINFO Database Record

Individual trial analysis evidences clock and non-clock based conditioned suppression behaviors in rats

We analyzed the temporal pattern of conditioned suppression of lever-pressing for food in rats conditioned with tone-shock pairings using either a 10 or 15s conditioned stimulus (CS)-unconditioned stimulus (US) interval with a CS duration that was three times the CS-US interval. The analysis of average suppression and of individual trials was performed during Probe CS-alone trials and when a short gap was inserted during the CS. The pattern of suppression followed the classical temporal rules: (1) scalar property, (2) a shift in peak suppression due to a gap, compatible with a Stop rule, (3) a three-state pattern of lever-pressing in individual trials, with abrupt start and stop of suppression. The peak of the average suppression curve, but not the middle time, was anticipatory to the programmed US time. The pattern of lever-pressing in individual trials unraveled two types of start of suppression behavior: a clock-based biphasic responding, with a burst of lever-pressing before suppression, and a non-clock based monophasic reduction of lever-pressing close to the CS onset. The non-clock based type of behavior may be responsible for the anticipatory peak time, and the biphasic pattern of lever-pressing may reflect the decision stage described in clock models.

APRENDIZAGEM DA EXTENSÃO DA PROBÓSCIDE EM ZANGÕES AFRICANIZADOS (Apis mellifera L.) CONFINADOS

Estudos sobre a aprendizagem olfativa em abelhas (Apis mellifera L.) são predominantes nas operárias. Neste estudo, utilizou-se o condicionamento clássico da extensão da probóscide (PER) para avaliar o efeito de 5 odores como estímulos condicionantes (EC). Foram utilizados dez grupos de 20 zangões (A. mellifera L.) cada. Os estímulos condicionantes foram Citral, Hexanal, Geraniol, cera de abelha em favo e cera de abelha alveolada. Além da aquisição de aprendizagem, mediu-se a persistência do condicionamento quando o estímulo incondicional (EI) não foi mais oferecido (i.e. extinção). O intervalo entre testes, o tempo de apresentação de EC e EI foram10 minutos, 2 segundos e 3 segundos, respectivamente. Os zangões foram capazes de demonstrar condicionamento e armazenamento de informação. Citral, Hexanal e cera de abelha foram os estímulos mais eficientes no condicionamento clássico (CC) com zangões.

Temporal properties of fear extinction—Does time matter?

Fear extinction can be defined as the weakening of the expression of a conditioned response (CR) by extended experience of nonreinforcement. Conceptually, two distinct models have been invoked to account for extinction. R. A. Rescorla and A. R. Wagner (1972, A theory of Pavlovian conditioning: Variations in the effectiveness of reinforcement and nonreinforcement, in A. H. B. W. F. Prokasy (Ed.), Classical conditioning: II. Current research and theory, pp. 64-99, New York, NY, Appleton-Century-Crofts) postulated that the number of exposure trials is the primary determinant of CR decrement, whereas C. R. Gallistel and J. Gibbon (2000, Time, rate, and conditioning, Psychological Review, Vol. 107, pp. 289-344) proposed that the decisive event is the cumulated exposure time to the nonreinforced conditioned stimulus (CS) elapsed after the last CS reinforcement. We evaluated these two accounts in a human differential fear conditioning study in which CR was measured with the fear-potentiated startle response. Cumulated duration of nonreinforcement fails to explain our findings, whereas the number of trials appeared critical. In fact, many CS trials with a duration shorter than the acquisition CS duration facilitated within-session extinction, but this effect did not predict the recovery of fear.

Human fear conditioning and extinction: Timing is everything…or is it?

A differential fear conditioning paradigm was used with 107 healthy undergraduate participants to evaluate the effect of conditioned stimulus (CS) temporal properties on fear acquisition and extinction. Two minute duration CSs were used for Day 1 fear acquisition. Participants were randomized to receive either 1, 2, or 4min CS durations during Day 2 extinction. Extinction re-test was examined on Day 3 using the original acquisition CS duration (2min). Findings indicated that participants who were aware of the CS+/unconditioned stimulus (US) contingency (n=52) develop a temporal expectation about when the unconditioned stimulus will be delivered. Although the shorter duration CS resulted in greater fear reduction during extinction, cessation of fear responding at re-test was the same for CS extinction durations ranging from half the CS acquisition duration to twice the CS acquisition duration. Thus, extinction performance did not predict extinction at re-test, which could have important implications for optimizing exposure therapy for anxiety disorders.

Learning in intimate connections: Conditioned fertility and its role in sexual competition.

BackgroundStudies of sexual conditioning typically focus on the development of conditioned responses to a stimulus that precedes and has become associated with a sexual unconditioned stimulus (US). Such a sexually conditioned stimulus (CS) provides the opportunity for feed-forward regulation of sexual behavior, which improves the efficiency and effectiveness of the sexual activity.Objective and DesignThe present experiments were conducted to provide evidence of such feed-forward regulation of sexual behavior in laboratory studies with domesticated quail by measuring how many fertilized eggs were produced by the female after the sexual encounter. During the conditioning phase, male and female quail received a conditioned stimulus paired with the opportunity to copulate with each other.ResultsSexual conditioning increased the number of eggs that were fertilized as a consequence of copulation, especially if both the male and the female were exposed to the sexual CS. This conditioned fertility effect occurred with a range of CS durations and CS types. The conditioned fertility effect also occurred in situations involving sexual competition. When two males copulated with the same female, DNA fingerprinting showed that the male whose sexual encounter was signaled by a sexual CS was responsible for most of the resulting offspring. Sexual conditioning also reduced the first-male disadvantage in fertilization that occurs when two males copulate with the same female separated by several hours. Another significant finding was that sexual conditioning attenuated the usual drop in fertilization rate that occurs when the same male copulates with two females in succession.ConclusionThese results show that sexual conditioning increases the number of offspring that are produced in both isolated male-female encounters and in situations that involve two males copulating with the same female or one male copulating with more than one female. By increasing fertilization rates, sexual conditioning can alter genetic transmission across generations and shape evolutionary change.

The temporal pattern of responding in conditioned bar-press suppression: The role of the context switch and training mode

The present study examined the temporal pattern of responding in a conditioned bar-press suppression task in rats. Rats were exposed to either a 30-s or a 120-s conditioned stimulus (CS) followed by a footshock. Training took place either while the rats were lever-pressing for water (online), or with the lever removed from the box (offline). They were then exposed to the CS while they were lever-pressing for water, either in the training context or in a different context. Bar-press suppression during the CS was constant across the duration of the CS during training, but was restricted to the initial portion of the CS at the time of testing, especially when subjects were tested in a different context. Those results replicate the reactive (as opposed to anticipatory) pattern observed in a lick suppression procedure by Jozefowiez et al. (2011) and indicate that a change in context at the time of testing might be critical for its expression.

Ventrolateral prefrontal cortex is required for fear extinction in a modified delay conditioning paradigm in rats

Recent evidence has demonstrated that the ventromedial prefrontal cortex (vmPFC) is a critical site of the neural circuits underlying fear extinction memory. The ventrolateral prefrontal cortex (vlPFC) is not directly involved in extinction processes within the aversive domain. However, most of the current cumulated data on extinction is based on a classical delay fear conditioning paradigm in which the interval between the onset of the conditioned stimulus (CS) and the unconditioned stimulus (US) is consistent in a given protocol. In the present study, we developed a modified delay fear conditioning paradigm in which the temporal distribution of the footshock US during the duration of the tone CS is programmed to be pseudorandom. Here, we examined the effects of electrolytic vmPFC and vlPFC lesions made before training on conditioned fear response in the modified paradigm. The behavioral procedure involved four sessions with a 24-h interval: habituation, fear conditioning, extinction training, and extinction test. Percent freezing to tone was assessed as a measure of conditioned fear response. The results show that neither vmPFC nor vlPFC lesions affect acquisition or extinction of conditioned fear response during the fear conditioning and extinction training sessions, respectively. During the extinction test session, both vmPFC- and vlPFC-lesioned rats showed deficits in the recall of the between-session extinction memory. The deficits could not be attributed to altered nonspecific responses (footshock sensitivity, locomotor activity, and nonspecific freezing response). Furthermore, vlPFC lesions made before training had no effect on conditioned fear response in the classical fear conditioning paradigm. These data suggest a preserved role of the vmPFC in fear extinction and a selective involvement of the vlPFC in extinction process in certain fear conditioning tasks.

Total sleep deprivation impairs the encoding of trace-conditioned memory in the rat

Sleep may help consolidate the information of certain memories, though its benefits in the consolidation of trace-conditioned memory still remain elusive. We investigated the effect of sleep deprivation on trace learning in male wistar rats. Rats were trained for trace conditioning and the number of head entries into liquid dispenser was accounted as an outcome measure of trace-learning. For training and testing, 75 presentations of conditioned stimulus (CS) (light) and unconditioned stimulus (US) (juice) were offered in five sessions (15 presentations/session; with 5min inter-session gap). The duration of CS and US stimuli were 15 and 20s respectively, with 5s trace delay between stimuli and 20s condition delay between each presentation. The animals were divided randomly into three groups soon after training, sleep deprived (SD) (n=8), non-SD (NSD) (n=8) and stress control (n=5) groups. The animals of NSD and control groups were left undisturbed, while SD animals were sleep deprived for 6h after training. The learning of trace-conditioned task was examined on following days. We observed that SD rats poked approximately 63% less than NSD and control groups (p<0.001) to obtain juice on testing day. Also, the NSD rats exhibited significant positive correlation in number of head entries during the training and testing days; while the SD rats showed no significant correlation. The results demonstrate that SD animals had difficulties to associate CS with US and suggest that sleep deprivation soon after training impairs the encoding of trace memory.

A preliminary investigation of continuous and intermittent exposures in the treatment of public speaking anxiety.

INTRODUCTION Since the nascence of exposure-based interventions for the treatment of anxiety disorders in the mid 20th century, much research has been devoted to dismantling these interventions, investigating the manipulation of different parameters of the exposure, and determining which parameters are most essential. Numerous parameters have been investigated, such as the targeted modality of the exposure (i.e. imaginal vs. in vivo vs. analog stimuli), the presentation of these stimuli (i.e. graduated vs. immediate presentations), and the length of time between exposures (i.e. massed vs. spaced exposures). One variable that has been under-studied, however, is the optimal duration of exposure trials. It is commonly assumed that exposures must be delivered in a protracted, continuous fashion until a decrement in anxiety is achieved (Foa & Kozak, 1986). However, empirical findings to support this notion have been mixed. Extinction of Conditioned Avoidance The earliest work on the optimal duration of exposure trials came from research using animal models of anxiety using the conditioned avoidance paradigm. This design involves an avoidance-training phase, where subjects learn to run or jump to another area of a chamber in the presence of a conditioned stimulus (CS) (i.e. a light, a tone, or a buzzer) which has been paired with an unconditioned stimulus (US) (i.e. a footshock) until they become proficient at avoiding the US by responding in the presence of the CS alone. The avoidance-training phase is then followed by an extinction phase, involving the presentation of the CS in the absence of the US until the CS no longer elicits the avoidance response. Several studies have investigated the efficacy of differing exposure lengths on the extinction of conditioned avoidance, using this paradigm. Research by Polin (1959) found that one 100 sec trial of exposure produced more rapid extinction than twenty 5 sec exposures with response prevention. Though this provided evidence for prolonged trials over brief trials, the interpretation was confounded by the use of response prevention in only the brief exposure condition. To control for response prevention, Shearman (1970) compared 100 sec presentations of a CS with and without response prevention against twenty 5 sec trials, with and without response prevention. Shearman found no differences between the lengths of the exposure trials and concluded that response prevention, not CS duration, was the critical variable. A follow-up study by Berman and Katsev (1972) which replicated the methodology of Shearman (1970) found that shorter durations were actually more effective than one prolonged duration. And further research by Schiff, Smith, and Prochaska (1972) and Martasian, Smith, Neil, and Reig (1992), found that total duration time to the CS was the crucial variable in the extinction of conditioned avoidance, regardless of whether the individual exposures lasted 5 sec or 24 min in length. Extinction of Conditioned Fear While the conditioned avoidance paradigm offers a directly observable method for studying the reduction in physical avoidance, it does not permit an examination of extinction of the affective components of anxiety. When avoidance behaviors decrease in the presence of the CS after exposure training, it is assumed that the CS no longer elicits fear and no longer acts as a reflexive conditioned establishing operation (CEO-R) (see Michael, 1993) for the avoidance response. However, as Lang (1979) has argued, anxiety comprises three individual response systems (i.e. physiological, behavioral, and cognitive/affective) that are not always concordant. It has further been argued that fear in the presence of the CS often persists, despite the suppression of overt avoidance (Shipley, 1974). In order to examine the extinction of the private events/affective components of anxiety, the conditioned fear paradigm was developed. …

Relative temporal representations in Pavlovian conditioning

The transfer of relative temporal representations was assessed in a series of three experiments. In each experiment, rats (Rattus norvegicus) received one set of conditioned stimulus (CS) and intertrial interval (ITI) durations in Phase 1 and another set in Phase 2. The ratio between the CS and ITI intervals was either changed or maintained across phases. On the hypothesis that relative temporal representations are learned, groups receiving maintained temporal ratios across phases were expected to display greater change in responding upon encountering the new intervals. When the CS duration decreased across phases, maintaining the temporal ratio did lead to greater change in Day 1 of Phase 2 towards the final pattern of responding. However, when the CS increased across phases, maintaining the temporal ratio across phases did not facilitate adjustment to the new intervals, suggesting that extinction of previously reinforced times induced new learning. These results provide evidence that under some conditions, relative relationships in temporal maps may survive transformation-of-scale, like relative relationships in spatial maps.

Memory reconsolidation and extinction in the crab: Mutual exclusion or coexistence?

A conditioned stimulus (CS) exposure has the ability to induce two qualitatively different mnesic processes: memory reconsolidation and memory extinction. Previous work from our laboratory has shown that upon a single CS presentation the triggering of one or the other process depends on CS duration (short CS exposure triggers reconsolidation, whereas a long CS exposure triggers extinction), both being mutually exclusive processes. Here we show that either process is triggered only after CS offset, ruling out an interaction as the mechanism of this mutual exclusion. Also, we show here for the first time that reconsolidation and extinction can occur simultaneously without interfering with each other if they are serially triggered by respective short and long CS exposures. Thus, we conclude that (1) one single CS presentation triggers one single process, after CS offset, and (2) whether memory reconsolidation and extinction mutually exclude each other or whether they coexist depends only on whether they are triggered by single or multiple CS presentations.

Overshadowing and CS duration: counteraction and a reexamination of the role of within-compound associations in cue competition.

In the present experiments, we examined the role of within-compound associations in the interaction of the overshadowing procedure with conditioned stimulus (CS) duration, using a conditioned suppression procedure with rats. In Experiment 1, we found that, with elemental reinforced training, conditioned suppression to the target stimulus decreased as CS duration increased (i.e., the CS duration effect), whereas, with compound reinforced training (i.e., the overshadowing procedure), conditioned suppression to the target stimulus increased as CS duration increased. In subsequent experiments, we replicated these findings with sensory preconditioning and demonstrated that extinction of the overshadowing stimulus results in retrospective revaluation with short CSs and in mediated extinction with long CSs. These results highlight the role of the duration of the stimulus in behavioral control. Moreover, these results illuminate one cause (the CS duration) of whether retrospective revaluation or mediated extinction will be observed.

CS-duration and partial-reinforcement effects counteract overshadowing in select situations

Two experiments used rats in a conditioned lick suppression preparation to investigate how the conditioned stimulus (CS)-duration and partial-reinforcement effects (i.e., weakened responding due to conditioning with a CS of longer duration and presenting nonreinforced CSs intermingled with CS-unconditioned stimulus [US] pairings, respectively) interact with overshadowing. Experiment 1 found that when overshadowing treatment was combined with either extended CS duration or partial reinforcement, the response deficit was weaker than when either of these three treatments was administered alone. In Experiment 2, the generality of the findings in Experiment 1 was investigated by replicating it with various US-US intervals. This time counteraction was observed only when both the absolute duration of total CS exposure and the US-US interval were short. The results support neither the view that the ratio between the total CS exposure and total time in the context determines the CS-duration and the partial-reinforcement effects nor the view that these two effects arise from a loss of effectiveness of the excitatory CS-US association during CS-alone exposures in partial reinforcement or early periods of CS exposure with long CSs.