Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Generalization, Stimulus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMedDate not supplied

Desflurane, enflurane, isoflurane and ether produce ethanol-like discriminative stimulus effects in mice.

In the present studies, drug discrimination procedures were used to compare the discriminative stimulus effects of ethanol (ETOH) and several volatile anesthetics. Male albino mice were trained to discriminate between IP injections of ETOH (1.25 g/kg) and saline in a two-lever operant task in which responding was under the control of a fixed-ratio 20 (FR20) schedule of food presentation. Stimulus generalization was examined after 20-min inhalation exposures to desflurane (4,000-32,000 ppm), enflurane (3,000-12,000 ppm), isoflurane (1,000-8,000 ppm) and ether (4,000-32,000 ppm). Concentration-related increases in ETOH-lever responding were observed for all four volatile anesthetics. For enflurane and ether, maximal levels of > 85% ETOH-lever responding were obtained at one or more concentrations. For desflurane and isoflurane, the maximal mean percentages of ETOH-lever responding were somewhat lower, but 6 out of 7 mice showed full substitution with desflurane and 5 out of 7 for isoflurane. The shared discriminative properties of these compounds with ETOH suggest that these anesthetics may share some of ETOH's pharmacological properties. These results are similar to previous research results showing ETOH-like discriminative stimulus effects in mice with other anesthetics and abused volatile inhalants (i.e. halothane, toluene and 1.1,1-trichloroethane) and may reflect the CNS-depressant drug-like effects of inhaled anesthetics and abused solvents.

Anesthetics, Inhalation↗
PubMed1993

Pharmacological specificity of the discriminative stimulus properties of 2-amino-4,5-(1,2-cyclohexyl)-7-phosphono-heptanoic acid (NPC 12626), a competitive N-methyl-D-aspartate receptor antagonist.

A drug discrimination based upon the competitive N-methyl-D-aspartate (NMDA) antagonist 2-amino-4,5-(1,2-cyclohexyl)-7-phosphonoheptanoic acid (NPC 12626) was assessed for pharmacological specificity. Adult male Sprague-Dawley rats were trained to discriminate 20 mg/kg i.p. of NPC 12626 from saline under a standard two-lever fixed ratio 32 schedule of food reinforcement. Stimulus generalization tests were conducted to examine the similarities and differences between NPC 12626, its active (2R,4R,5S) enantiomer NPC 17742, other competitive and noncompetitive NMDA antagonists and a number of drugs representative of other classes. During test sessions, the competitive NMDA antagonists NPC 12626, CGS 19755, [1-(cis-2-carboxypiperidine-4-yl)- methyl-1-phosphonic acid], NPC 17742, CSP 37849 [DL-(E)-2-amino-4-methyl-5-phosphono-3-pen-tenoic acid] and CPPene [D-3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphonic acid] all completely substituted for the training dose of NPC 12626 with ED50 values of 18.1, 2.3, 2.1, 0.8 and 0.8 mg/kg, respectively. In contrast, drugs that failed to substitute for NPC 12626 included (+)-amphetamine, baclofen, chlorpromazine, dextromethorphan, diazepam, dizocilpine (MK-801), imipramine, (-)-ketocyclazocine, L-N6-phenylisopropyladenosine, methocarbamol, morphine, muscimol, phenytoin, physostigmine and valproate. These results provide evidence that the NPC 12626 discriminative stimulus is unique and specific, shared fully only by its active enantiomer NPC 17742 and other competitive NMDA antagonists. This specificity provides further support for the hypothesis of NMDA receptor mediation of NPC 12626 discrimination, and suggests that this is a useful model to evaluate behavioral effects of competitive NMDA antagonists.

Amino Acids↗
PubMed1966

Some effects on generalization gradients of tandem schedules.

The relationship between training conditions and stimulus generalization gradients was examined using tandem schedules of reinforcement. Schedules were selected so that frequency of reinforcement and rate of responding were varied somewhat independently of each other. A peak-shift in the generalization gradient was obtained when extinction had been associated with one of the stimuli. No comparable peak shift was obtained when there were equal response rates in the training stimuli even with dissimilar frequencies of reinforcement. The data imply that response rates at the end of training, rather than reinforcement frequency per se, determine the characteristics of the generalization gradient.

Animals↗
PubMed1993

Antagonism of a (+)N-allylnormetazocine stimulus by (-)PPAP and several structurally related analogs.

Employing rats trained to discriminate 5 mg/kg of the benzomorphan opioid (+)N-allylnormetazocine [(+)NANM] from vehicle, tests of stimulus generalization and antagonism were conducted to determine the influence of several potential sigma-receptor ligands. It has been previously suggested that the (+)NANM stimulus may involve concurrent action at sigma- and phencyclidine (PCP) receptors. Although the low-affinity sigma-antagonist rimcazole was without stimulus-attenuating effect, three novel sigma-ligands--(-)PPAP, CNS 3018, and CNS 3093 (ID50 doses = 3.2, 6.7, and 4.5 mg/kg, respectively)--antagonized the (+)NANM stimulus in a dose-related fashion. The nonselective serotonergic agent 1-(3-trifluoromethyl)phenylpiperazine (TFMPP) produced partial generalization in (+)NANM-trained animals whereas buspirone, a 5-hydroxytryptamine1A (5-HT1A) agonist, attenuated (to 27% drug-appropriate responding) the (+)NANM stimulus. Because the prototypic 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) failed to attenuate the (+)NANM stimulus at pharmacologically relevant doses, it seems unlikely that the (+)NANM stimulus involves a 5-HT1A mechanism. TFMPP and buspirone display modest affinity for sigma-receptors and this may account for the present findings with these agents. The present results neither establish a role for sigma involvement in the stimulus properties of (+)NANM nor eliminate a role for PCP receptors. They do, however, demonstrate that sigma-ligands with little to no affinity for PCP receptors are capable of antagonizing the (+)NANM stimulus.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1979

Discriminative stimulus properties of psychomotor stimulants in the cat.

Cats were trained to choose between two levels or an operant chamber using interoceptive cues provided by d-amphetamine or saline as the discriminative stimuli. Following training, stimulus generalization was observed to additional doses of d-amphetamine and cocaine. but not to morphine. Clozapine blocked the generalization of the drug discrimination response to d-amphetamine, but had no effect on generalization to cocaine. These data indicate that discriminative stimulus properties of psychomotor stimulants, previously described in rats, are similar in cats.

Animals↗
PubMed2006

Modulation of a (+)amphetamine discriminative stimulus in rats by 8-hydroxy-2-(N,N-di-n-propylamino)tetralin (8-OH DPAT).

It is well established that the discriminative stimulus (DS) effect of amphetamine involves a dopaminergic and/or noradrenergic mechanism. These catecholamines can be modulated by the 5-HT(1A) serotonin receptor agonist 8-hydroxy-2-(N,N-di-n-propylamino)tetralin (8-OH DPAT). The present study was conducted to determine whether 8-OH DPAT could influence the DS effects of (+)amphetamine. Administration of 8-OH DPAT doses to Sprague-Dawley rats trained to discriminate 1 mg/kg of (+)amphetamine (ED(50)=0.33 mg/kg) using a two-lever operant paradigm (VI-15 s schedule of reinforcement for appetitive reward) failed to result in stimulus generalization when administered alone, and failed to antagonize the stimulus effect when administered in combination with the training dose of (+)amphetamine. However, administration of 8-OH DPAT doses that produced saline-like responding (i.e., 0.01-0.1 mg/kg; <20% amphetamine-appropriate responding) in combination with the ED(50) dose of (+)amphetamine resulted in the animals' making a progressively greater number of responses on the drug-appropriate lever such that a combination of 0.1 mg/kg of 8-OH DPAT plus (+)amphetamine (0.33 mg/kg) elicited 91% (+)amphetamine-appropriate responding. In a separate study, administration of (+)amphetamine doses in combination with fixed doses of 8-OH DPAT (either 0.01 or 0.1 mg/kg) resulted in an apparent leftward shift of the dose-response curve. The results indicate that (+)amphetamine can be more effective as a discriminative stimulus in the presence of 8-OH DPAT than in its absence.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1986

Adaptation level as an explanation of the peak shift in generalization with movement stimuli.

Two experiments examine the value of adaptation level theory as an explanation of the peak shift phenomenon in stimulus generalization using linear arm movements. The first experiment manipulates the differences in adaptation levels during training by varying the frequency of experience of the training stimulus. Significant shifts in the peaks of generalization gradients were subsequently identified. The peak shifts were in the direction predicted by adaptation level theory. The second experiment manipulates testing adaptation levels by biasing the generalization test movements. Three groups of subjects performed differentially weighted test sequences in which the relative number of short, medium, or long movements was manipulated. Significant peak shifts of generalization gradients were observed in the direction predicted by adaptation level theory.

Journal Article↗
PubMed1999

Nalorphine's ability to substitute for morphine in a drug discrimination procedure is a function of training dose.

Rats trained to discriminate the mu agonists fentanyl or morphine from their respective vehicles generalize to the partial mu agonist nalorphine incompletely and inconsistently. Any number of factors may influence the generalization patterns obtained, one of which being the specific dose of the full opioid agonist used during training, a factor reported to influence generalization with other partial opioid agonists. To assess if training dose influences stimulus generalization to nalorphine and to support its role in the aforementioned variability across studies, in the present experiments rats were trained to discriminate either a low (5.6 mg/kg) or a high (10 mg/kg) dose of morphine from distilled water within the taste aversion baseline of drug discrimination learning. Subjects were then given a range of doses of morphine, nalorphine, methadone, or naloxone to assess the degree of substitution (if any) of these compounds for the training dose of morphine. For all subjects, morphine fully substituted for itself, and the opioid antagonist naloxone failed to substitute for the morphine cue. Rats generalized the morphine cue to nalorphine in subjects trained at the lower dose but not in subjects trained at the higher dose. Rats generalized the morphine cue to methadone in the latter group (the high dose group), indicating that the failure to generalize to nalorphine in this group was not a general inability of an opioid agonist to substitute for morphine. Naloxone blocked morphine stimulus control in all subjects and nalorphine control in the low-dose group for which nalorphine substituted for morphine, suggesting that morphine control (and the nalorphine substitution) was based on opioid activity. These results indicate that the substitution patterns of nalorphine in morphine-trained subjects are a function in part of the dose of morphine used in training and support the position that nalorphine is a partial opioid agonist with intermediate efficacy.

Animals↗
PubMed1983

Behavioral effects of 5-methoxy-N,N-dimethyltryptamine and dose-dependent antagonism by BC-105.

The discriminative effects of 5-methoxy-N,N-dimethyltryptamine (5-OMeDMT) were studied in rats trained to discriminate 1.5 mg/kg or 3.0 mg/kg 5-OMeDMT from saline. A series of antagonist and generalization tests revealed that (1) antagonism of the 5-OMeDMT stimulus response by the presumed serotonin antagonist BC-105 depended on the dose of 5-OMeDMT, (2) the 5-OMeDMT stimulus generalized to LSD, and (3) like 5-OMeDMT, antagonism of the LSD generalization response by BC-105 depended on the dose of LSD. In a second study, with rats responding under a variable-interval (VI) 15-s schedule of reinforcement, doses of 1.0-3.0 mg/kg 5-OMeDMT significantly decreased response rate. Furthermore, the decrease in responding produced by the administration of 1.5 mg/kg (but not by 3.0 mg/kg) 5-OMeDMT was blocked by BC-105. This dose-dependent antagonism was of particular interest since the 1.5 mg/kg and 3.0 mg/kg dose of 5-O-MeDMT had essentially the same effect on responding when given alone. The results of both studies emphasize the importance of 5-OMeDMT dose in antagonism experiments.

Animals↗
PubMed1978

Chronic effects of methadone on a line tilt generalization gradient in the pigeon.

Using an adjusting interval schedule, pigeons were trained to key peck at a relatively constant rate during 45 degrees line tilt presentations and at an extremely low rate in the presence of 0 degrees and 90 degrees line angles. Subsequently, the birds received intramuscular injections of methadone hydrochloride every 8 hr in doses beginning at 3 mg/kg/day and increasing progressively to 90 mg/kg/day. Stimulus generalization tests were run on the first day and on the last day a given dose was administered to assess the development of tolerance. Although chronic methadone treatment was associated with an overall decrement in key peck rate, the gradients of line tilt generalization were indistinguishable from saline control gradients at doses as high as 90 mg/kg/day. Though the birds exhibited gross behavioral incoordination, visual stimulus control appeared unaffected.

Animals↗
PubMed1989

Characterization of the discriminative stimulus effects of physostigmine in the rat.

Rats were trained to discriminate physostigmine (0.1 mg/kg s.c.) from saline in a two-choice, discrete-trial avoidance paradigm. Stimulus generalization curves for physostigmine were steep; complete generalization with physostigmine occurred only at the 0.1 mg/kg training dose. The muscarinic cholinergic agonists oxotremorine, pilocarpine and arecoline were evaluated for physostigmine-like discriminative effects. Oxotremorine generalized with physostigmine at a dose of 0.1 mg/kg in four of six rats tested; partial generalization was engendered by this dose in the remaining two animals. Complete generalization with physostigmine was produced in only one of six rats treated with pilocarpine. However, pilocarpine (3.0-10 mg/kg) did engender some physostigmine-appropriate responding in all rats tested. Arecoline (1.0 mg/kg) produced primarily saline-appropriate responding in all animals tested. Neostigmine, eseroline and nicotine were tested for physostigmine-like discriminative effects in order to assess the specificity of the physostigmine cue. Eseroline (1.0 mg/kg), an opioid-like derivative of physostigmine, and neostigmine (0.1 mg/kg) engendered saline-appropriate responding. Similarly, nicotine failed to generalize with physostigmine at doses up to 1.0 mg/kg. The discriminative stimulus effects of physostigmine were sensitive to antagonism by atropine. Complete blockade of the stimulus effects of the training dose of physostigmine was produced by 1.0 to 3.0 mg/kg of atropine. In contrast, a 10-fold higher dose of the quaternary antagonist homatropine methylbromide was necessary to block the discriminative effects of physostigmine. The discriminative effects of physostigmine were not blocked or were only partially blocked by mecamylamine at doses up to 10 mg/kg. The results of these experiments suggest that the discriminative stimulus effects of physostigmine are selective and probably centrally mediated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Effect of a stimulus intervening between CS and US in autoshaping.

Five experiments explored the effect of placing a stimulus between the termination of a key light CS and the onset of a food US in an autoshaping preparation with pigeon subjects. Whether that stimulus was itself a key light evoking pecking or an auditory event failing to evoke pecking, it facilitated performance to the key light CS. The use of a within-subjects design made differential conditioning of background cues and stimulus generalization unlikely accounts. Experiment 3 found that extinction of the intervening stimulus did not remove the facilitative effect. Experiment 4 found that pairing the CS with food and the intervening stimulus did not produce the effect unless both occurred on the same trial. Together, these experiments rule out an account in terms of second-order conditioning of the CS by the intervening stimulus. Experiment 5 used an intervening stimulus in a second-order conditioning design to demonstrate that the stimulus acted to improve the association between the CS and the reinforcer. That experiment found the intervening stimulus to make responding to the CS more vulnerable to subsequent extinction of its reinforcer. Together, these experiments document a kind of catalytic effect of the intervening stimulus on the CS-reinforcer association.

Animals↗
PubMed2000

Shepard's universal law supported by honeybees in spatial generalization.

An animal that is rewarded for a response in one situation (the S+) is likely to respond to similar but recognizably different stimuli, the ubiquitous phenomenon of stimulus generalization. On the basis of functional analyses of the probabilistic structure of the world, Shepard formulated a universal law of generalization, claiming that generalization gradients, as a function of the appropriately scaled distance of a stimulus from S+, should be exponential in shape. This law was tested in spatial generalization in honeybees. Based on theoretically derived scales, generalization along both the dimensions of the distance from a landmark and the direction to a landmark followed Shepard's law. Support in an invertebrate animal increases the scope of the law, and suggests that the ecological structure of the world may have driven the evolution of cognitive structures in diverse animals.

Adaptation, Physiological↗
PubMed1997

Discriminative characteristics of high and low cocaine administration: effect of other psychostimulants.

Two groups of N/Nih male rats were trained to discriminate saline vehicle from either 2.0 mg/kg (n = 10) or 10.0 mg/kg (n = 10) cocaine in a food-motivated, two-lever operant paradigm. The rats trained at the low-dose cocaine took a significantly longer training period to reach criterion performance than did the high-dose cocaine group. In addition, the ED50 value for the 2.0 mg/kg cocaine-trained animals (0.465 mg/kg) was significantly lower than the ED50 value (2.105 mg/kg) for those animals trained at the 10.0 mg/kg dose of cocaine. This correlation of ED50 values for stimulus generalization decreasing with reduction in training dose was in contrast to the time-course of the two groups when tested from 15 to 240 min post-injection; this experimentation indicated that there was a non-significant difference in half-life for the 2.0 mg/kg (t1/2: 97.1 min) vs. that of the 10.0 mg/kg cocaine-trained group (t1/2: 83.4 min). Generalization tests with other purportedly dopaminergically-active drugs of abuse including 0.05-0.8 mg/kg d-amphetamine, 0.125-1.5 mg/kg methamphetamine and 0.125-1.0 mg/kg methcathinone indicated that the highest doses of each produced generalization and, with the exception of methcathinone, the ED50 values were significantly lower in the low-cocaine trained group. The stimulus properties of cocaine, as they generalize to amphetamine, methamphetamine and methcathinone, can be explained by effects upon central dopaminergic neurons and may be qualitatively different in low-and high-dose trained rats.

Amphetamine↗
PubMed1978

Discriminated response and incentive processes in operant conditioning: a two-factor model of stimulus control.

Understanding stimulus control generated in instrumental learning requires the direct investigation of discriminated response and reinforcer (incentive) processes acquired exclusively through the response-reinforcer contingencies operating on complex (multicomponent) baselines. Two series of stimulus-compounding studies accomplished this direct investigation. In one series, the independent variable was the relative reinforcement between schedule components; in the second series, it was relative response rate between components. Stimulus-compounding tests revealed that response and incentive processes enhanced each other when in agreement, counteracted each other when in opposition, and produced intermediate results when only one factor was operating. This pattern of results led to the conclusion that these factors were algebraically combining and to the development of a response/incentive matrix reflecting these dynamics. This two-factor analysis was extended to the peak-shift effect in stimulus generalization experiments and to the generation of inhibitory control. Two decades of stimulus compounding and peak-shift research were organized within this two-factor framework, extending this traditional approach to learning to active research areas heretofore not systematically considered in these terms.

Journal Article↗
PubMed1983

Discriminative stimulus properties of nalorphine in the rhesus monkeys.

The discriminative stimulus properties of nalorphine were studied in rhesus monkeys trained to discriminate i.m. injections of nalorphine (1 mg/kg) from saline. During training, a two-lever paradigm was employed where a single, 3-min extinction schedule was followed by fixed-ratio-20 schedules of food presentation. During the fixed-rate schedules, responses on one of the two levers produced food when nalorphine had been administered and responses on the other lever produced food when saline had been administered. During stimulus generalization tests, responses on either lever produced food under the fixed-ratio schedule. The discriminative stimulus effects of nalorphine were antagonized by naloxone which, by itself, did not generalize to nalorphine. The kappa opiate agonists, ethylketocyclazocine, U-50,488, bremazocine, tifluadom, as well as two mixed kappa-sigma agonists, dl-cyclazocine and dl-N-allylnormetazocine (SKF-10047), generalized to nalorphine with the following potency ranking order: bremazocine greater than ethylketocyclazocine greater than tifluadom greater than cyclazocine greater than U-50,488 greater than N-allylnormetazocine greater than nalorphine. The levo-isomers of cyclazocine, N-allylnormetazocine or U-50,488 generalized to nalorphine whereas the dextroisomers did not. Generalization to nalorphine did not occur with the mu opiate agonists, morphine, methadone and meperidine, or the nonopiate compounds, phencyclidine, ketamine and chlorpromazine. The results suggest that a kappa opiate receptor mechanism mediates the discriminative effects of nalorphine in the rhesus monkey, which may also be involved with the naloxone-sensitive, sedative and dysphoric effects of nalorphine in humans.

Animals↗
PubMed1980

An investigation of peak shift and behavioral contrast for autoshaped and operant behavior.

Instrumental treadle press and nonreinforced key peck responses were monitored during discrimination training and generalization testing in pigeons on positive and negative reinforcement schedules. In Experiment 1, six pigeons pressed a treadle for food on a multiple variable-interval extinction schedule. In Experiment 2, three pigeons pressed a treadle to avoid shock on a multiple free-operant avoidance extinction schedule. Different color keylights signaled S+ and S- components. Some positive behavioral contrast occurred during discrimination training, but the effect was small. Pecking occurred to the S+ keylight in Experiment 1 but not in Experiment 2. On stimulus generalization tests, all subjects displayed a positive peak shift when pressing the treadle for food or to avoid shock. However, peak shift was not found for nonreinforced "autopecks" on the stimulus key, although an area shift was observed in Experiment 1. This is the first demonstration of peak shift for pigeons pressing treadles and the only reliable demonstration of peak shift when negative reinforcement maintained responding. These results, in combination with previous demonstrations of peak shift for rats pressing levers and pigeons pecking keys, indicate that peak shift is a general by-product of operant discrimination learning, since it occurs across a variety of the organisms, responses, and reinforcers.

Animals↗
PubMed2003

Covariation of alternative measures of responding in rabbit (Oryctolagus cuniculus) eyeblink conditioning during acquisition training and tone generalization.

The likelihood, size, and speed of eyelid movements are thought to covary during the acquisition and expression of conditioning in rabbits (Oryctolagus cuniculus) and are generally accepted as interchangeable measures of the associative strength activated by the conditioned stimulus (CS). To test this assumption, the authors examined the patterns of covariation in these eyelid movement measures in acquisition and stimulus generalization in the upper eyelid and nictitating membrane. Rather than the expected covariation among these measures, eyelid movement magnitudes during the CS were distributed in approximately a bimodal manner. That is, eyelid activity consisted largely of a mixture of very small (< 0.125 mm) baseline measurements and larger (> 1 mm) movements. The results are discussed with respect to their implications for real-time models of eyelid conditioning.

Acoustic Stimulation↗