Showing papers in "International Journal of Comparative Psychology in 2005"

Consummatory Successive Negative Contrast Induces Hypoalgesia

Abstract: Rats received training in the consummatory successive negative contrast (cSNC) situation in which access to 32% sucrose solution during ten daily trials is followed by a downshift to 4% sucrose. Separate groups were exposed to the hot plate test for pain sensitivity immediately after either the first or the second downshift trial (Trials 11 and 12, respectively). Rats exhibited hypoalgesia after Trial 12 downshift, but not after Trial 11. These results suggest that cSNC induces the release of endogenous opioids that cause hypoalgesia, but only after some experience with the downshifted solution. This interpretation is supported by experiments demonstrating that opioid agonists reduce cSNC, whereas opioid antagonists enhance it.

Interaction of Extinguished Cocaine-Conditioned Stimuli and Footshock on Reinstatement in Rats

Abstract: The reinstatement paradigm has been proposed as an animal model of human drug relapse. In most reinstatement studies, conditioned stimuli accompany drug infusions during self-administration, re- sponding in extinction, as well as responding during reinstatement tests. The importance of these extinguished drug-paired stimuli during stress-induced reinstatement has not been examined. In this study, rats were trained to self-administer 0.5 mg/kg/infusion cocaine during daily, 2-h sessions until behavior stabilized. Each cocaine infusion was accompanied by a 6-s flashing light + tone condi- tioned stimulus (CS). In two groups of rats, responding during subsequent extinction and reinstate- ment had no scheduled consequences (CS Omitted). In two other groups of rats, responding produced the light + tone but no cocaine injections (CS Present). Footshock did not significantly reinstate co- caine seeking behavior in CS Omitted rats. Footshock significantly reinstated cocaine-seeking behav- ior over multiple test sessions in both CS Present groups, regardless of whether footshock reinstate- ment was examined on consecutive days or with trials spaced two days apart. These data show that environmental stimuli and stressors which are ineffective by themselves to occasion reinstatement of cocaine-seeking behavior can do so if concurrently present. Relapse is a major impediment to successful substance abuse treatment (O'Brien 1997). The vast majority of drug abusers relapse on multiple occasions (Haynes, 1998; Hunt, Barnett, & Branch, 1971) and relapse may be particularly problematic in cocaine abusers (Washton & Stone-Washton, 1990). At least three major classes of relapse-promoting events have been hypothesized, although other factors may clearly be involved. These classes include brief exposure to the previ- ously abused drug or a related drug, exposure to environmental or other stimuli that had been paired with drug self-administration, and exposure to stressors (Jaffe, Cascella, Kumor, & Sherer, 1989; Kreek & Koob, 1998; Robbins, Ehrman, Chil- dress, & O'Brien, 1997). Understanding how these events trigger relapse may be extremely important for designing successful behavioral and pharmacological re- lapse prevention strategies. The drug reinstatement paradigm in experimental animals has been used extensively over the past decade and is thought to model some aspects of human drug relapse (Koob, 2000; Meil & See, 1996; Shaham, Shalev, Lu, De Wit, & Stewart, 2002). In the reinstatement procedure, animals are trained to self- administer a drug until some stability criteria are reached. Subsequently, over a period of hours to sometimes many days responding is extinguished by discontinu- ing drug reinforcement. Noncontingent drug administration, exposure to previously drug-paired environmental stimuli and experimental stressors all can produce re-

The Modern Role of Morgan's Canon in Comparative Psychology.

Abstract: C. Lloyd Morgan is widely credited as the “father of comparative psychology” due to his contribution of guidelines for the psychological interpretation of animal behavior. Many modern comparative psychologists believe that constraints encouraged by Morgan are now obsolete and some assert that adherence to the canon restricts further progress in the field. Nonetheless, Morgan’s guidance continues to be important in comparative psychology. A review of Morgan’s canon, its historical misuse, and consideration of popular alternatives reinforce Morgan’s role in comparative psychology. A recent model of cognitive evolution highlights the importance of Morgan’s guidelines and an illustration of the continued usefulness of the canon is given in the context of investigations of theory of mind in chimpanzees.

A Within-trial Contrast Effect and its Implications for Several Social Psychological Phenomena.

Abstract: Contrast refers to a comparison between two conditions of reward such that the relation between them is magnified (relative to an appropriate control condition). It is an effect that is opposite in direction from generalization (which is a form of averaging). Three kinds of contrast have received substantial empirical attention: Incentive contrast in which a sudden change in reward (either an increase or a decrease) results in an overreaction to the change, relative to a control condition; anticipatory contrast in which an anticipated improvement in reward results in less consumption of an initial reward; and differential or behavioral contrast in which a change in reward associated with one stimulus results in a change in behavior associated with a second stimulus in the opposite direction. Here I discuss a fourth kind of contrast that I call within-trial contrast. In this form of contrast a discriminative stimulus is preferred when it follows a less appetitive event (effort, delay, or the absence of reward). A model of this kind of contrast is proposed that is based on a presumed change in the hedonic state of the organism between the end of the less appetitive event and the reward (or stimulus signaling the reward). It is distinguished from an account based on the relative reduction in delay to reinforcement. Finally, I suggest that a general form of this within-trial contrast may help to explain various complex human social phenomena including cognitive dissonance, justification of effort, the effect of extrinsic rewards on behavior that is maintained by intrinsic rewards, and learned industriousness.

The Reference-Dose Place Conditioning Procedure Yields a Graded Dose-Effect Function

Abstract: A major criticism of the place conditioning procedure for studying conditioned drug reward is that it is relatively insensitive to large quantitative shifts in drug dose (i.e., dose effects are all or none). Experiment 1 demonstrated this lack of sensitivity using a wide range of intravenous (IV) cocaine doses (0.1, 0.3, 0.45, 0.6, 0.9, or 1.2 mg/kg). Rats had cocaine repeatedly paired with one distinct end compartment of a 3 compartment apparatus; vehicle was administered in the other end compartment. In a subsequent drug-free choice test, the 0.45 to 1.2 mg/kg doses of cocaine conditioned a place preference. The magnitude of the effect did not differ. Experiment 2 used a modified version of this standard place conditioning method. In this alternative method termed reference-dose procedure, a fixed dose of cocaine (reference dose) was repeatedly paired with one end compartment (i.e., 0.45 mg/kg); the comparison dose of cocaine was administered in the other end compartment (vehicle, 0.6, or 1.2 mg/kg). Preference for the comparison-dose compartment increased with dose—a graded doseeffect curve. In contrast to the standard procedure, the reference-dose procedure revealed that the conditioned rewarding effect of 1.2 mg/kg of cocaine was greater than that of 0.45 mg/kg. This increase in sensitivity to conditioned reward with the reference-dose procedure will likely increase the utility of the place conditioning method as a preclinical model, as well as a procedure for studying processes mediating associatively-motivated choice behavior.

Effects of outcome devaluation on the performance of a heterogeneous instrumental chain

Abstract: Two experiments investigated the effects of outcome devaluation induced by conditioned taste aversion on the performance of the components of a heterogeneous chain of instrumental actions. In Experiment 1, thirsty rats were trained to perform two actions, R1 and R2, i.e., chain pulling and lever pressing counterbalanced, in sequence to gain access to a sucrose outcome in a single session; i.e., R1→R2→O. Immediately after this session or after a delay the rats were injected with lithium chloride and given an extinction test on the two actions the next day. Although the immediate and delayed groups did not differ in the incidence of R1 on test, the immediate group reduced their performance of R2 relative to the delayed group. Experiment 2 assessed the effect of incentive learning after outcome devaluation. All rats were given an injection of lithium chloride immediately after training on the heterogeneous chain for sucrose reward after which half of the rats were reexposed to the sucrose whereas the remainder were reexposed to water prior to the extinction test. Although reexposure had no effect on the test performance of the R2 component in the chain, it significantly reduced performance of R1. These data are consistent with previous claims that responses proximal to outcome delivery are influenced by a Pavlovian incentive process whereas those more distal are controlled by the experienced incentive value of the outcome; i.e., by an instrumental incentive process.

A Neural-Functionalist Approach to Learning

Abstract: Researchers within the field of learning have traditionally divided their empirical world according to methodology, with phenomena classified as single stimulus learning, Pavlovian conditioning, or in- strumental learning. This trichotomy, a vestige of our behaviorist past, continues to influence the field, both in the classroom and in the laboratory. Relying on data collected using a simple model system (learning within the mammalian spinal cord), evidence is presented that organisms can learn about an environmental relationship in multiple ways, an observation that argues against a simple isomorphism between methodology and mechanism. It is suggested that a new classification system is needed that focuses on mechanism rather than methodology, subdividing our empirical world along lines that make sense given commonalties in the neural-functional mechanisms involved. For over a century, learning has remained a central force within psychol- ogy. Introductory students hear of Thorndike (1898), Pavlov (1927), and Skinner (1938), and advanced students routinely take a course on learning to fulfill their core requirements. It was learning theorists (e.g., Hull, 1943; Watson, 1913; also see Boakes, 1984) who sold psychologists on the value of studying animal behav- ior, providing evidence that we and our evolutionary brethren often adjust to new situations in a similar fashion. This proof of principle laid the foundation for the study of the neurobiology of learning and memory, an enterprise that relies primar- ily on infrahuman creatures, from simple invertebrates (Kandel & Schwartz, 1982) to primates (Mishkin, 1982). The field of learning has remained a central focus of investigation primar- ily because many endorse its core assumptions. The first core assumption is that learning is essential. Natural selection cannot prepare a response for every situa- tion that an organism might encounter. The range of environmental situations is simply too great and biologically relevant stimuli often occur in an unpredictable

Failure to Obtain Instrumental Successive Negative Contrast in Tasks that Support Consummatory Successive Negative Contrast

Abstract: In four experiments (three in operant chambers, one in a runway) with food-deprived rats, we sought to obtain instrumental successive negative contrast (iSNC) and consummatory successive negative contrast (cSNC) following shifts in the value of liquid rewards. Despite finding robust cSNC in each of the four experiments, there was no indication of iSNC in any of the measured instrumental re- sponses (pressing a lever, licking an empty spout, or time to traverse a runway). Consistent with the literature, these results might be taken to suggest that iSNC cannot be obtained following a downshift in liquid reward value. However, behaviors observed in the downshifted rats suggests that the ab- sence of iSNC might be due to the occurrence of competing responses or nonoptimal test conditions. Thus, the failure to observe iSNC in rats that show cSNC is interpreted as a failure of performance. Animals experiencing an unexpected shift from a high to a low value re- ward exhibit a decrease in performance to a level significantly below that of ani- mals accustomed to the low value reward throughout the experiment. The behav- ioral effect caused by a surprising reward reduction is termed successive negative

Negative Incentive Contrast Induces Economic Choice Behavior by Bumble Bees

Abstract: A negative incentive contrast experiment was conducted to determine whether responses to a reward reduction facilitate adaptive decisions by bumble bee (Bombus impatiens) foragers. In the acquisition phase of the experiment subjects were trained on blue targets (artificial flowers) that contained 50% (weight percent) or 20% sucrose solution and in the test phase subjects were given a choice between familiar targets and yellow targets that had either an economic profitability lower than, equal to, or higher than blue targets, where all targets contained 20% sucrose solution. Subjects trained to a low reward concentration showed a consistent preference for blue targets in the test phase of the experiment, while subjects that experienced a reward reduction exhibited a temporary disruption of consummatory behavior and developed preferences that reflected the profitability of targets. These results support a functional interpretation of responses to a reward reduction: incentive contrast induces foragers to visit alternative sources of nectar and, thereby, facilitates economical decisions. The choice behavior observed over the test phase suggests that associative processes then direct the formation of flower choices.

Interactions Between Ethanol Experiences During LateGestation and Nursing: Effects upon Infantile and Maternal Responsiveness to Ethanol

Abstract: Responsiveness to ethanol is markedly affected by fetal or infantile experiences with the drug. Yet, there is minimal information available relative to the interaction of these experiences. This study focused on such interaction and on the impact of ethanol intoxication on maternal care. Water or subnarcoleptic doses of ethanol were administered to pregnant rats during late gestation (2.0 g/kg) and/or while nursing (2.5 g/kg). Infantile intake of a low concentrated ethanol solution (0.22% v/v) was assessed during postpartum days (PPDs) 15 and 16. Following the first intake test, infantile intake was explicitly paired with water or varying ethanol doses (0.5, 1.0, or 2.0 g/kg) to assess possible associative learning comprising ethanol’s sensory and unconditioned properties. The interaction between ethanol pre- and postnatal treatment resulted in heightened ethanol reactivity as assessed through intake scores, particularly during PPD 16. Maternal treatments failed to affect associative learning mediated by ethanol. Ethanol was also found to disrupt both maternal retrieval and crouching latencies. This effect was markedly reduced when females had experienced ethanol during gestation, a phenomenon indicative of tolerance. Sequential experience with ethanol during gestation and nursing facilitates subsequent responsiveness to minimal ethanol concentrations, without affecting the sensitivity to the unconditioned effects of the drug as evaluated through associative learning procedures.

Effects of Absolute Proximity Between Landmark and Platform in a Virtual Morris Pool Task with Humans

Abstract: In two experiments in a virtual pool the participants were trained to find a hidden platform placed in a specific position in relation to one (Experiment 1) or two (Experiment 2) objects; then, all the participants received a test trial, without the platform, and the time spent in the segment where the platform should have been was measured. In Experiment 1, groups differed in the distance between the landmark and the hidden platform. Test results showed that the control acquired by the landmark was different depending on its relative distance from the platform: Closer landmarks acquired a better control than distant ones. In Experiment 2, two objects, B and F, were simultaneously present during acquisition. Object B was just above the hidden platform (i.e., a beacon for the platform) while object F was above the edge of the pool (i.e., a frame of reference). On the test, the spatial location of B in relation to F was manipulated in the different groups and a generalization gradient was found: Participants spent more time in the segment where B was when B was in front of F (training position), and this time decreased symmetrically with distance of B from F. The two experiments provide convergent evidence of spatial learning effects in a virtual task with humans.

Single neurons in the nucleus accumbens track relative reward

Abstract: A within subjects simultaneous contrast experiment evaluated nucleus accumbens (NAc) neural responses to a low (0.05 M) and high (0.5 M) concentration of sucrose in 6 rats. During continuous trials, rats were given repeated brief intraoral infusions of the low and then the high concentration of sucrose while electrophysiological activity of NAc neurons and oromotor behavior (EMG) were measured. Following the continuous phase of testing, the two concentrations were infused in an alternating manner. The results showed that rats reduced oromotor behavior when infused with the low concentration of sucrose when alternated with the high concentration (i.e., during alternating trials) relative to the infusion during the continuous low condition (negative contrast). Rats also increased oromotor behavior for the high concentration when presented during alternating relative to continuous trials (positive contrast). Of 137 NAc neurons, 35 exhibited brief inhibitions or excitations to tastant delivery during baseline testing that were correlated with oromotor output. Some NAc neuronal activity reflected negative or positive contrast effects while other neurons encoded alternating testing in general and still other neurons encoded sucrose concentration. These data demonstrate that neuronal activity in the NAc is altered in coincidence with the expression of contrast in consummatory behavior.

Animal Cognition and the New Anthropomorphism

Abstract: Animal behavior studies of the 19th century were characterized by an appeal to anthropomorphic attitudes, which were resolutely challenged beginning with the start of the 20th century, particularly by the forerunners of what became the behaviorist school. The ethological school founded by Tinbergen and Lorenz also rejected appeals to human-like cognitive abilities. In the l970s, under the leadership of the physiologist, Donald Griffin, animal cognition was again admitted into “respectable” ethological company, leading to a strong critique by another eminent physiologist, John Kennedy. (The influence of Tolman had previously made many comparative psychologists receptive to this possibility). Recent studies based upon developments on direct recordings of brain activity now suggest that Tolman and Griffin’s prescience will carry the day.

Palaeoanthropology and the Evolutionary Place of Humans in Nature

Abstract: Palaeoanthropology, the study of the fossil evidence for human evolution, remains a highly contested field. New discoveries are continuously being used to promote alternative models as well as to propose new candidates for our ultimate ancestor. The fossil evidence has increased over the years, and has been supplemented (and often challenged) by molecular data drawn from living people and the great apes. As recently as the 1980s, palaeoanthropologists proposed that human roots stretched back into the Middle Miocene, between 17 and 8 million years ago. Then the earliest true hominids or human ancestors became the South African australopithecines, who are less than 5 million years old. Now there appears to be a tremendous variety of early humans at all stages of their evolution. Along with this new research on the basal hominids has been a renewed interest about what it means to be Homo sapiens. Molecular and fossil data shows that Africa was also our homeland, and that all people today are descended from a small founder population in existence there between 50,000 and 200,000 years ago.

Inhibition of Successive Positive Contrast in Rats Withdrawn from an Escalating Dose Schedule of D-amphetamine

Abstract: Rats in a vehicle treated control condition when shifted from 4% to 32% sucrose displayed successive positive contrast by responding at a significantly higher lick rate in a 5 min trial than rats maintained on 32% sucrose throughout the experiment. In contrast, rats treated with an escalating dose regimen of D-amphetamine (1-10 mg/kg) over a 4 day interval failed to display successive positive contrast. Withdrawal from drug treatment had no effect on lick rate or response latency in rats maintained on 32% sucrose. These data are consistent with many previous reports that withdrawal from a binge-like regimen of psychostimulant drug administration disrupts responding for natural reward stimuli. These findings support the use of psychostimulant withdrawal as a model of drug-induced dysphoria and suggest that incentive contrast is a particularly sensitive measure of these changes in motivation and emotion.

Extensive interference attenuates reinstatement in human predictive judgments

Abstract: An experiment assessed the impact of varying levels of interference on reinstatement in human causal learning. Participants studied fictitious customer files to learn relationships between foods and gastric illness in acquisition. During interference training, a new relationship was learned between the same foods and a different illness over 12, 15, or 18 trials. Prior to the test, presentations of either outcome in the absence of information about the food led to losses of the second-learned information and recovery of that learned first. This effect was reduced as the number of interference trials increased. Results are discussed in terms of their implications for theories of reinstatement and of the parallels with animal studies on renewal.

Alcohol Ataxia Tolerance: Extinction Cues, Spontaneous Recovery, and Relapse

Abstract: This article reviews ethanol ataxic tolerance experiments with rats that investigate spontaneous recovery after extinction and how extinction-related cues reduce this recovery. Tolerance to the effects of many drugs including ethanol is partly the result of Pavlovian conditioning. Tolerance to the ataxic (and other) effects of ethanol depends critically upon the circumstances in which the drug is administered. Tolerance shows other characteristics common in Pavlovian conditioning, e.g.,. it can be extinguished and is subject to spontaneous recovery. The analogy of spontaneous recovery to instances of relapse in humans potentially makes such spontaneous recovery relevant to both researchers and clinicians. Recently, extinction cues have been found to reduce spontaneous recovery and other relapse- like effects in the animal conditioning laboratory. These cues may work in part by activating an association formed during the extinction process, and thus they may serve as memory retrieval cues. Research assessing spontaneous recovery using an ethanol ataxia method, as well as other Pavlovian conditioning methods, has contributed to an understanding of the properties and utility of extinction cues. These topics are addressed and the potential implications of this research for treating substance abusers is considered.

Posttrial Administration of Cholinergic Drugs does not Affect Consummatory Successive Negative Contrast in Rats

Abstract: Posttraining administration of cholinergic drugs modulates the consolidation of memory processes in several learning tasks. We studied the effect of the administration of atropine (cholinergic antagonist, Experiment 1) and physostigmine (acetylcholinesterase inhibitor, Experiment 2) immediately after the first session of reward downshift, and immediately after the last preshift session (Experiment 3) on a consummatory successive negative contrast procedure. Animals were given access to a high-value reward (32% sucrose solution), and surprisingly shifted to a low-value reward (4% sucrose solution) in a second phase. The results indicate that atropine and physostigmine have no effects on contrast. The role of cholinergic neurotransmission in the memory of surprising reward changes is discussed.

Lesions of the ventral tegmental area disrupt drug-induced appetite stimulating effects but spare reward comparison

Abstract: Dopamine neurons in the ventral tegmental area (VTA) - nucleus accumbens (NAC) pathway track both absolute and relative properties of reward. The present study used 6-hydroxydopamine lesions of the VTA to test the obligate role of this nucleus in morphine- and cocaine-induced suppression of conditioned stimulus (CS) intake and in chlordiazepoxide- and morphine-induced appetite stimulating effects. The results showed that an 80% reduction in accumbens DA fully prevented drug-induced appetite stimulating effects, augmented a latent inhibition-like effect, but failed to disrupt druginduced suppression of CS intake. These data demonstrate that, while the VTA is essential for responding to the reward-enhancing effects of chlordiazepoxide and morphine, it does not contribute to cocaine- or morphine-induced devaluation of the lesser saccharin reward cue.

Effects of age on pavlovian autoshaping of ethanol drinking in non-deprived rats

Abstract: Previous studies of autoshaping of drinking report a positive relationship between experience with autoshaping procedures and drinking, but this effect was confounded with age, as the rats were older when they drank more. The present experiment evaluated the effects of the age of male Long-Evans hooded rats [90-days old (Younger group) vs. 135 days old (Older group)], at the beginning of the study, on drinking induced by Pavlovian autoshaping procedures. Autoshaping procedures consisted of pairings of sipper conditioned stimulus (CS) with food unconditioned stimulus (US). Rats were deprived of neither food or fluid, and sweeteners were not employed at any time during the study. For all rats (n = 32), during sessions 1-10, the sipper CS contained water. Thereafter, for rats in the Ethanol groups (n = 20), the sipper CS contained ethanol, with the concentration (1, 2, 3, 4, 5, 6%, v/v) increasing across autoshaping sessions. For rats in the Water groups (n = 12), throughout the experiment the sipper CS contained tap water (0% ethanol). Rats in the Younger group drank more ethanol and more water from the sipper CS than rats in the Older group, and across age groups there was more ethanol drinking than water drinking, an effect unlikely due to foraging for calories. Data support the hypothesis that ethanol’s pharmacological effect was to enhance autoshaping, resulting in a positive feedback loop inducing still more ethanol drinking. The younger rats were more vulnerable to autoshaping effects. Implications for models of addiction are discussed.

Neurofunctionalism Revisited: Learning is More Than You Think It Is

Abstract: Studies of learning in simple systems (invertebrates and spinal cord) have revealed that organisms can encode stimulus-stimulus (Pavlovian) and response-outcome (instrumental) relations in multiple ways. It is suggested that nonassociative mechanisms contribute to learning and that there is value in adopting an approach that details the neural-functional mechanisms involved.

Behavioral Contrast in a Group Foraging Paradigm

Abstract: Two experiments examined multiple schedule behavioral contrast in a group foraging paradigm. Groups of five rats foraged simultaneously in a large open field apparatus with two feeding stations. Food pellets were delivered at each of the feeding stations on multiple Variable Time schedules. As predicted by both the matching law and the ideal free distribution, the relative distribution of behavior between the two feeding stations roughly matched the relative rate of food delivery at the feeding stations. These differences were reflected in both the behavior of individual animals and in the behavior of the group. Positive behavioral contrast was found in Experiment 1, evidenced by an increase in the frequency of response in one component produced by a decreased rate of food delivery in the other component. Negative behavioral contrast was found in Experiment 2, evidenced by a decreased frequency of response in one component produced by an increased rate of food delivery in the other component. Interestingly, there was virtually no correlation between the behavior of an individual animal and the number of pellets consumed by that animal. The present results support other attempts to compare the matching law to the ideal free distribution. The data also show that behavioral contrast is predicted by both models and in fact occurs in ways consistent with both models.

Experimental Methods and Conceptual Confusion

Abstract: According to Grau and Joynes (2005), (1) the current classification of types of learning is based on methodology and assumes a correspondence between types of learning and distinct neural-functional mechanisms; (2) this assumption is wrong because experiments show that different mechanisms may underlie the same type of learning; consequently, (3) we should change the teaching of the psychology of learning. I argue that because Grau and Joynes misunderstood the nature of the classification of learning phenomena and cloaked their research findings with a garb of conceptual errors and infelicities, their recommendations concerning the teaching of learning should be rejected.

Pavlovian Conditioning Requires Ruling Out Nonassociative Factors to Claim Conditioning Occurred

Abstract: In a thought provoking article based on their studies concerning the behavioral capacities of spinallytransected rats, Grau and Joynes (2005) claim that protection-from-habituation and pairing-specific enhanced sensitization are learned phenomena that occur during pairings between a conditioned stimulus and an unconditioned stimulus. Our commentary questions whether such effects: (1) should be put in the same category as associative learning; (2) necessitate or warrant a new neurofunctionalism; (3) suggest that the field should have less emphasis on the methods of Pavlov and Skinner and more focus on function and neuroscience; (4) suggest that our textbooks be revised. Grau and Joynes (2005) propose a new approach to the study of learning, labeled "neural-functionalism," stemming from their critique of perceived problems involving the practice (i.e., methodological issues) and image management (for our students and for colleagues in other disciplines) of the field of animal learning and conditioning. We discuss these critiques and this new approach by focusing on these two problems in turn. Although some important, if primarily familiar, issues are raised, we are unconvinced by Grau and Joynes's arguments. Methodological Issues The views articulated by Grau and Joynes developed out of their research into the learning capacities of a reduced animal preparation, spinally-transected rats. This work, involving the analysis of behavior produced by pairing a conditioned stimulus (CS) with an unconditioned stimulus (US), appears to be amenable to explanation in terms of one of three factors: Pavlovian conditioning as it is conventionally viewed, protection from habituation (PH), or pairing-specific enhanced sensitization (PSES). Most researchers would ask whether the change in behavior observed is due to associative learning or an artifact (PH or PSES). Grau and Joynes concluded that the behavioral effects obtained in their spinal rats were not due to the former factor and, rather than accepting an artifactual interpretation, the authors took a much bolder step by declaring that PH and PSES should be considered

Associative Mechanisms and Drug-Related Behavior

Abstract: Author(s): Weiss, Stanley J.; Reilly, Mark P.; Kearns, David N. | Abstract: This special issue of the International Journal of Comparative Psychology is based on presentations delivered at the Focus Session of the 2004 Winter Conference on Animal Learning and Behavior (WCALB) held in Winter Park, Colorado. The Associative Mechanisms and Drug-Related Behavior Focus Session began with an invited address by Shepard Siegel titled The Ghost in the Addict: Drug Anticipation and Drug Addiction. He described an impressive body of research showing that conditioning mechanisms underlie drug tolerance and withdrawal. Siegel's address underscored the important contribution of associative mechanisms to drug-related behavior and set the stage for the six papers presented in this issue. Siegel began by describing his landmark study that first demonstrated the "situational specificity of tolerance" (Siegel, 1975). In that study, tolerance to morphine was only observed when rats were injected with morphine in an environment where they had previously experienced morphine. In contrast, no tolerance to morphine was observed when rats were injected in a novel environment. This result demonstrated that environmental factors might be as important, or even more important, than pharmacological factors in the expression of tolerance to drugs. Siegel pointed out that these results were anticipated by Subkov and Zilov (1937) who demonstrated conditioned tolerance of epinephrine-induced tachycardia. Siegel hypothesized that this situational specificity of tolerance was mediated by conditioned compensatory responses (CCRs) that counteracted the analgesic effects of morphine. According to this conditioning account of tolerance, the environmental stimuli present before and during morphine (the unconditioned stimulus or US) administration should act as Pavlovian conditioned stimuli (CSs). Through these pairings, the CSs come to elicit a conditioned response (CR) that opposes the direct effects of morphine. Therefore, since morphine itself produces analgesia, the environmental CSs that are paired with morphine come to elicit hyperalgesia. These oppositional processes then summate to produce a zero net effect, which manifests itself as tolerance, when morphine is administered in the presence of cues previously paired with morphine.A critical prediction of the CCR analysis of tolerance is that an effect opposite to the direct effects of morphine (e.g., hyperalgesia) should be observed if the morphine-paired CSs are presented without the morphine (e.g., saline injection substituted for morphine). This is because the full expression of the CCR should be elicited with nothing to counteract them. Siegel (1975) showed that hyperalgesia is indeed observed when previously morphine-paired stimuli are presented in the absence of morphine to morphine-tolerant rats. He has called these unopposed CCRs "withdrawal symptoms" (Siegel, 1999). Thus, for Siegel, tolerance and withdrawal are both manifestations of a CCR—tolerance is observed when the CCR is elicited in the presence of the drug and withdrawal symptoms are observed when the CCR is elicited in the absence of the drug (Siegel, 1999; 2002). Siegel proceeded to review numerous studies conducted over the past 30 years supporting the view that drug tolerance reflects the processes of classical conditioning. Principally, this evidence comes from studies showing that tolerance is affected by learning contingencies in the same way that other nondrug Pavlovian CRs are affected by these contingencies. This reveals generality of process through "functional contiguity" (Sidman, 1960). These learning phenomena include, but are not limited to, extinction, external inhibition, latent inhibition, partial reinforcement effects, blocking, sensory preconditioning as well as electrophysiological and pharmacological manipulations (Siegel, 1975, 1989, 1991; Siegel a Larson, 1996; Dafters et al., 1983; Siegel et al., 2000). So where is the ghost in Siegel's address? In describing his experience with opium addiction, Jean Cocteau wrote "the dead drug leaves a ghost behind. At certain hours it haunts the house" (Cocteau, 1958, p. 60). Siegel materializes the ghost by reframing it in terms of Pavlovian conditioning. For Siegel, the 'ghost' refers to the CRs elicited by drug-associated CSs resulting from extended drug experiences. The candidates for conditioned stimuli can be numerous and include the complex of stimuli present when drugs are taken, such as people, places, sounds and smells. He also posited that the CSs may be interoceptive in nature. Siegel presented his recent research on interoceptive drug-associated cues that logically extend his research on Pavlovian conditioning of exteroceptive cues. This work essentially shows that interoceptive cues can indeed acquire CS functions in ways similar to exteroceptive cues. He considered two types of interoceptive cues, those associated with self-administration and drug onset cues. Self administration cues are stimuli arising from the active administration of the drug (such as movement of the body and other proprioceptive stimuli). Evidence was presented that self-administration cues contribute to tolerance and symptoms of withdrawal (Weise-Kelly a Siegel, 2001; MacRae a Siegel, 1997). Siegel then described research demonstrating the CS function of drug onset cues. In a prototypical experiment, rats receive chronic injections of a large dose of morphine (50 mg/kg). On test days, a much smaller dose (e.g., 5 mg/kg) is given. The small dose of morphine precipitated opiate withdrawal as evidenced by the behavioral and thermic data. This finding is expected if the interoceptive stimulation produced by the small dose was similar to the early drug-onset cues associated with the administration of the large dose. In other words, the early drug-onset cues are analogous to exteroceptive morphine-paired stimuli and elicit CCRs (i.e., precipitate withdrawal) when presented without the US (see Sokolowska, Siegel, a Kim, 2002). Siegel's keynote address provided convincing evidence that drugassociated stimuli, environmental and internal, play a critical role in drug tolerance and withdrawal. The six papers presented in this issue are concerned with a variety of effects of drug-related stimuli, including place conditioning (Bevins), selective associations produced by cocaine-associated stimuli (Weiss, Kearns, Cohn, Panlilio a Schindler), conditioned tolerance to the ataxic effects of alcohol (Brooks), the drug as a CS (Tomie, Mohamed, a Poherecky), and the conditioned reinforcing properties of drug-paired stimuli (Shelton a Beardsley, Newman a Beardsley, and Bevins). Siegel's address and the spectrum of learning paradigms represented by these six articles confirm the central role learning and associative mechanisms play in drug-related behavior. They also illustrate that this is an active area of research that needs people with diverse backgrounds and interests including classical and operant conditioning, behavioral pharmacology and drug abuse. Clearly, people other than metaphysicians acknowledge that the "ghost" is alive and well, and worthy of study.

Cocaine and selective associations : Investigations into a biological constraint on learning with drug self-administration and shock avoidance as reinforcers

Abstract: When a tone-light compound was a discriminative stimulus for cocaine-reinforced responding, the light gained most of the control over responding. In contrast, when the compound was an aversive SD for shock-avoidance, tone control increased. In previous studies, tone control also increased when the tone-light compound was made aversive by signaling food-absence. However, that was not the case in Experiment 2 where tone-light signaled cocaine-absence. Experiment 1 produced an interincentive (cocaine vs. shock) selective association with drug self-administration maintained behavior for the first time. This extends the generality of the selective association biological constraint on learning to self-administered drugs.

A Continuum of Learning and Memory Research

Abstract: History has revealed time and time again that science is moved forward by revolutions that pit one point of view, theory, or methodology, against an opposing view. During calmer times, however, we as researchers are left to our own devices and settle into our work with little thought to the world around us. The field of learning and memory has been privy to many such revolutions in the past but has yet to form a cohesive, modern message. Grau and Joynes suggest that our strong ties to the past are to blame for a lack of progression in the field. We agree and add that the focus of the field on two extreme ends of a continuum has also held us back; suggesting that research that goes on in the middle of the continuum may be the key to leading the field out of its rut.

Unexpected post-CS events during extinction and the slow reacquisition effect

Abstract: Rats were used to examine the effects of a surprising post-CS event on reacquisition of an extinguished conditioned taste aversion. One flavor CS was paired with LiCl and then followed by many CS-alone extinction trials. Following these extinction trials, subjects received the CS paired again with LiCl to assess the extent of reacquisition. For some subjects, the final extinction exposure was immediately followed by a surprising second flavor CS. The surprising event did not influence the degree of reacquisition. Additional results found that the second flavor did influence habituation of neophobia to a flavor showing that the event does influence consumption in some circumstances. These results are discussed with respect to the role of attention on extinction and reacquisition of a conditioned taste aversion.

Dose history and occurrence of conditional stimuli determine the strength of cocaine-seeking behavior of rhesus monkeys

Abstract: Four adult male rhesus monkeys were trained to lever press for cocaine under a daily two-component MIX PR (progressive ratio) schedule. During the first 10 min of experimental sessions, completion of progressive ratios resulted in 1-s presentations of brief visual stimuli (BS; colored lights) associated with cocaine infusions during the second component. Stimulus lights of different colors were associated with doses of 3, 30, and 300 μg/kg cocaine as the available self-administered infusate. A 5-min time out period followed the first component, which in turn was followed by a 60-min component during which completion of progressive ratios resulted in cocaine infusions and the associated visual stimuli. Once reinforcer rates had stabilized under each dosing condition in both components, break point tests were conducted separately for BS as the reinforcer and with cocaine + stimuli as the reinforcer. Break points for lever pressing maintained by BS alone increased as they were paired with increasing doses of cocaine. Break points maintained by actual cocaine delivery, however, demonstrated an inverted U-shaped function to cocaine dose. The results of this study suggest that the strength of cocaine-seeking behavior varies monotonically with the self-administered dose of cocaine and that the level of motivation to obtain cocaine may not be directly revealed by levels of actual cocaine self-administration.

Mechanism Through Methodology: No Madness to the Method

Abstract: Grau and Joynes (2005) assess the current state of the field of animal learning and behavior, with particular emphasis on pedagogical and curricular issues. They suggest that the conventional framework which organizes lecture material around methodology is flawed and that an organization around mechanism should be used instead. They also advocate a shift from a purely behavioral approach to research on learning and behavior to a neural-functionalist approach more akin to contemporary behavioral neuroscience. While I support many of the suggestions for improving instruction, I disagree with their proposed shift away from purely behavioral investigations of animal behavior. Behavioral research continues to be a thriving and productive source of empirical and theoretical discoveries. The diverse array of specialized methodologies that have been developed to pursue this work are still paying dividends by illuminating the nature of behavioral mechanisms. Banishing purely behavioral approaches to learning and behavior, such as those used to study associative learning, animal cognition, and comparative psychology, would severely hamper our knowledge of behavioral mechanism. “A complete theory of learning must speak to all of the ways in which experience can alter behavior….” (Grau & Joynes, 2005, p. 15). This statement resonates the views espoused by most contemporary researchers of learning and behavior. Grau and his students have published excellent work on the neural basis of learning in spinal rats. This research is exemplary in its use of rigorous methodology and the nuanced appreciation of the theoretical issues it raises. Thus, they are in an excellent position to comment on the state of the field of learning. Grau and Joynes (2005) address a number of important issues that are germane to the study of learning and behavior. Most importantly, they provide a timely critique of the current state of pedagogy and curriculum. They delineate inherent problems with the manner in which theory and research are portrayed in standard textbooks for academic courses on learning. The conventional view, as Grau and Joynes see it, adopted by textbooks organizes information around the methodologies used to understand learning rather than around the mechanisms of learning. One problem with a methodological approach is that it fails to provide a coherent theme or framework in which to connect all of the disparate findings and theories. Thus, issues relevant to both Pavlovian and instrumental learning, for example, are presented in separate chapters with little integration into a larger, coherent framework. This disconnection between facts and framework probably contributes significantly to the tendency for students to perceive courses on learning as difficult or uninteresting. The conventional framework produces another negative consequence: neuroscientists who wish to study the neural mechanisms of learning often receive an antiquated (at best) or misguided (at worst) understanding of