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 919 records · Page 51Linked to original sources
PubMed1984

Phencyclidine-like behavioral effects of 2-methyl-3,3-diphenyl-3-propanolamine (2-MDP).

2-Methyl-3,3-diphenyl-3-propanolamine (2-MDP) produced effects in animals similar to those produced by the dissociative anesthetics such as phencyclidine (PCP). Specifically, it shared the discriminative stimulus properties of PCP in rats trained to discriminate PCP (1 mg/kg) from saline; at higher doses, it disrupted brightness discrimination and stimulated locomotor activities in rats trained to avoid shocks in an automated Y-maze; and it produced surgical anesthesia when injected IV to rhesus monkeys. These pharmacological activities were observed only with the levo-isomer of 2-MDP. The dextro-isomer was either inactive or produced opposite effects, depending on the tests. Among several related diphenylpropylamines, 2-MDP represents the optimal structure for potency of PCP-like effects since changes in the amino, 2-methyl and 3-hydroxy groups reduced the potencies of the PCP-like discriminative properties.

Anesthesia↗
PubMed2006

Associative activation of stimulus representations restores lost salience: implications for perceptual learning.

In 3 experiments, rats received preexposure to presentations of a compound flavor BX. The effective salience of B was then tested by assessing its ability to interfere with the aversion controlled by another flavor or the tendency to drink a saline solution after the induction of a salt need. It was found that the effective salience of B was maintained when during preexposure, presentations of BX alternated with presentations of X alone. This was true both when BX was presented as a simultaneous compound (Experiment 1) and as a serial compound (X-->B; Experiments 2 and 3); salience was not maintained when the serial compound took the form B-->X (Experiments 2 and 3a). It was argued that the salience of B declines during preexposure but is restored when presentations of X are able to activate the representation of B by way of the associative X-B link.

Animals↗
PubMed1992

Using stimulus equivalence procedures to teach name-face matching to adults with brain injuries.

On pretests, 3 men with brain injuries matched dictated names of three therapists to written names, but did not match dictated or written names to photos, produce correct names in response to photos, locate offices given written names, or name therapists on sight. Match-to-sample training established conditional relations between dictated names and photos. Posttests showed the emergence of untrained conditional relations involving photos and written names, indicating development of three classes of equivalent stimuli (each containing a dictated name, photo, and written name). For 1 participant, conditional relations involving photos of office nameplates were also examined, but did not emerge pre- or posttraining. Two participants produced names orally when given photos and sorted written names and faces together after training; the 3rd participant was unavailable for these posttests. After training, 1 participant located and named all three therapists in their offices.

Adult↗
PubMed2006

Familiarization and cross-familiarization of wheel running and LiCl in conditioned taste aversion.

Familiarization with an unconditioned stimulus (US) interferes with the learning of subsequent Pavlovian conditioned associations. We conducted a series of experiments exploiting this US preexposure effect to elucidate the underlying mechanism of conditioned taste aversion in rats induced by voluntary wheel running. Experiment 1 demonstrated that running-induced taste aversion was alleviated if rats had sufficient experience of running in advance. In Experiments 2A and 2B, preexposure to wheel running had no effect on subsequent taste aversion conditioning by lithium chloride (LiCl) injection. In Experiment 3, however, we observed a weak partial interference from the LiCl injection pretreatment to the subsequent conditioning by wheel running US. This US crossover effect suggests the possibility that wheel running and LiCl injection share a common or similar physiological mechanism in inducing taste aversion.

Analysis of Variance↗
PubMed1990

Three-choice discrimination among (+)-amphetamine, fenfluramine and saline in pigeons.

Five pigeons were trained to discriminate among (+)-amphetamine (AMPH; 1.7 or 3.0 mg/kg), fenfluramine (FEN; 5.6 or 10 mg/kg), and saline using a three-choice drug discrimination procedure. The results of the study demonstrated that a reliable discrimination between AMPH and FEN could be obtained and the discriminative stimulus (DS) effects of these two drugs did not overlap, i.e., were mutually exclusive. Phenmetrazine produced a dose-related increase in AMPH-appropriate responding with no responding occurring on the FEN-appropriate key. Two serotonin agonists, quipazine (5-HT2) and MK 212 (5-HT1), produced FEN-appropriate responding in two of three pigeons, while a third pigeon responded predominantly on the AMPH-appropriate key following their administration. In contrast, phencyclidine produced predominantly (greater than 50%) saline-appropriate responding, indicating that the DS effect of phencyclidine was unlike either AMPH or FEN. Finally, compounds known to have multiple DS properties such as MDA and MDMA were tested. The results with these compounds confirmed that these drugs have complex DS effects both within and across individual pigeons.

3,4-Methylenedioxyamphetamine↗
PubMed2005

Can chimpanzee infants (Pan troglodytes) form categorical representations in the same manner as human infants (Homo sapiens)?

We directly compared chimpanzee infants and human infants for categorical representations of three global-like categories (mammals, furniture and vehicles), using the familiarization-novelty preference technique. Neither species received any training during the experiments. We used the time that participants spent looking at the stimulus object while touching it as a measure. During the familiarization phase, participants were presented with four familiarization objects from one of three categories (e.g. mammals). Then, they were tested with a pair of novel objects, one was a familiar-category object and another was a novel-category object (e.g. vehicle) in the test phase. The chimpanzee infants did not show significant habituation, whereas human infants did. However, most important, both species showed significant novelty-preference in the test phase. This indicates that not only human infants, but also chimpanzee infants formed categorical representations of a global-like level. Implications for the shared origins and species-specificity of categorization abilities, and the cognitive operations underlying categorization, are discussed.

Age Factors↗
PubMed2004

The US-preexposure effect in lithium-induced flavor-aversion conditioning is a consequence of blocking by injection cues.

In 2 experiments, rats received flavor-aversion conditioning in which the unconditioned stimulus (US) was an orally consumed solution of lithium chloride (LiCl). The resulting aversion was not attenuated by giving preexposure to injections of LiCl, although such preexposure did attenuate aversions established using injected LiCl as the US (Experiment 1). This outcome suggests that blocking by injection-related cues is responsible for the US-preexposure effect observed in this situation. Experiment 2 confirmed this interpretation by showing that presenting such cues (by giving an injection of saline) at the time that the LiCl was drunk resulted in an attenuation of conditioning in animals preexposed to injections of LiCl. The US-preexposure effect obtained in these experiments can be explained solely in terms of blocking by injection cues, although other mechanisms may contribute to the effect seen in other flavor-aversion paradigms.

Administration, Oral↗
PubMed1984

Effects of stimulus representation and cue category level on exposure (flooding) therapy.

The present study was an attempt to examine the role of cue category level (symptom-contingent vs. hypothesized cues) and mode of stimulus presentation (in vivo vs. imaginal) in exposure (flooding) therapy. Sixty-four speech phobics were randomly assigned to one of eight conditions. Exposed to either one of the two cue category conditions, subjects received either two sessions of in vivo exposure, two sessions of imaginal exposure, or two sessions consisting of either an imaginal followed by an in vivo exposure or vice versa. Results support the predictions of Levis & Hare (1977) that the inclusion of hypothesized cues is not necessary in the treatment of analogue phobias or simple clinical cases. These data also support and extend several previous findings that in vivo exposure produces more rapid anxiety decrement than imaginal exposure. Finally, a variant of the usual in vivo procedure is described which apparently is effective, yet does not require the assemblage of a large audience for each in vivo exposure.

Adolescent↗
PubMed1989

Nicotine as a discriminative stimulus: a neurobehavioral approach to studying central cholinergic mechanisms.

A major goal of basic nicotine research is to obtain information useful to the clinician in determining why and how people become dependent on this substance via the use of tobacco products. To accomplish this, the basic scientist must first develop an animal model of nicotine action that is parallel to its effects in humans. This review describes such a model, based on the ability of nicotine to exert discriminative stimulus (DS) control over behavior. The nicotine DS, as studied in the rat, mouse, or subhuman primate, appears to provide information analogous to human subjective reports concerning the effects of smoking. Findings indicate that nicotine is specific and selective in its actions, explaining, in part, why tobacco is dependence-producing. The nicotine DS effect is stereoselective and appears to be the result of an action at specific central nicotinic cholinergic (N-Ch) receptors located in at least two brain areas, the hippocampus and midbrain reticular formation. Whether acetylcholine is the mediator of nicotine's effects at these receptor sites, as was once thought, has yet to be clearly determined. Finally, these N-Ch receptors appear to have a wide distribution and may also sit on presynaptic dopamine neurons, helping to explain some of nicotine's additional behavioral and/or rewarding effects.

Animals↗
PubMedDate not supplied

Parallel neural systems for classical conditioning: support from computational modeling.

Classical conditioning has been explained by two main types of theories that postulate different learning mechanisms. Rescorla and Wagner (1972) put forth a theory in which conditioning is based on the ability of the US to drive learning through error correction. Alternatively, Mackintosh (1973) put forth a theory in which the ability of the CS to be associated with the unconditioned stimulus is modulated. We have proposed a reconciliation of these two mechanisms as working in parallel within different neural systems: a cerebellar system for US modulation and a hippocampal system for CS modulation. We developed a computational model of cerebellar function in eyeblink conditioning based on the error correction mechanism of the Rescorla-Wagner rule in which learning-related activity from the cerebellum inhibits the inferior olive, which is the US input pathway to the cerebellum (Gluck et al., 1994). We developed a computational model of the hippocampal region that forms altered representations of conditioned stimuli based on their behavioral outcomes (Gluck & Myers, 1993; Myers et al., 1995). Overall, computational modeling and empirical findings support the idea that, at least in the case of eyeblink conditioning, there may be two different neural systems: the cerebellum which mediates US-based error correction and hippocampus which alters representations of CSs.

Animals↗
PubMed1990

Postconditioning effects of magnesium on cocaine conditioned place preference in mice.

Magnesium chloride (MgCl2) has recently been shown to have stimulant-like properties. Because stimulants are known to induce conditioned place preference (CPP), the CPP procedure was used to test the hypothesis that cocaine and MgCl2 share similar stimulus properties. This would be shown if cocaine-induced CPP could be enhanced in a postconditioning preference test by MgCl2 and other stimulants. Mice were conditioned with 5.0 mg/kg cocaine to the nonpreferred end of a three-compartment straight shuttle box. All groups showed significant shifts in preference from the preconditioning test to the postconditioning test. There were no changes in place preference over test days in mice that were injected only with saline and therefore not conditioned. When animals were given acute injections of either saline, 5.0 mg/kg cocaine, 1.0 mg/kg amphetamine, 30 mg/kg MgCl2, 10 mg/kg pentobarbital, or 0.25 mg/kg haloperidol following conditioning with cocaine, amphetamine and MgCl2 elevated the conditioned cocaine effect, and pentobarbital and haloperidol decreased the conditioned cocaine effect compared to saline. In addition, there was a dose-dependent influence of MgCl2, with 30 mg/kg producing the maximum effect on the conditioned cocaine effect.

Animals↗
PubMed1992

Hemispheric specialization for categorical and coordinate spatial representations: a reappraisal.

The purpose of the present study was to examine Kosslyn's (1987) claim that the left hemisphere (LH) is specialized for the computation of categorical spatial representations and that the right hemisphere (RH) is specialized for the computation of coordinate spatial representations. Categorical representations involve making judgements about the relative position of the components of a visual stimulus (e.g., whether one component is above/below another). Coordinate representations involve calibrating absolute distances between the components of a visual stimulus (e.g., whether one component is within 5 mm of another). Thirty-two male and 32 female undergraduates were administered two versions of a categorical or a coordinate task over three blocks of 36 trials. Within each block, items were presented to the right visual field-left hemisphere (RVF-LH), the left visual field-right hemisphere (LVF-RH), or a centralized position. Overall, results were more supportive of Kosslyn's assertions concerning the role played by the RH in the computation of spatial representations. Specifically, subjects displayed an LVF-RH advantage when performing both versions of the coordinate task. The LVF-RH advantage on the coordinate task, however, was confirmed to the first block of trials. Finally, it was found that males were more likely than females to display faster reaction times (RTs) on coordinate tasks, slower RTs on categorical tasks, and an LVF-RH advantage in computing coordinate tasks.

Adult↗
PubMed1979

Discriminative stimulus effects of naltrexone in the morphine-dependent rat.

Rats maintained physically dependent upon morphine by scheduled access to drinking water containing morphine were trained to discriminate between s.c. injections of saline and 0.1 mg/kg of naltrexone in a discrete trial avoidance procedure in which a response on one of two choice levers would prevent or terminate the delivery of mild electric shocks to the floor of the test chember. Stimulus control of behavior by naltrexone in the morphine-dependent rat (defined as the reliable completion of at least 18 trials of a 20-trial session on the appropriate choice lever) had many of the features previously described for the stimulus control of behavior by morphine in the nondependent rat: long-term stability and reproducibility, orderly dose- and time-effect relationships and pharmacologic specificity. Stimulus control by naltrexone was blocked in a dose-related manner by morphine, an effect completely surmounted by a 10-fold increase in the dose of naltrexone suggesting a competitive antagonism. The naltrexone-induced discriminative stimuli appeared to be related to precipitated morphine withdrawal phenomena: following the abrupt withdrawal of morphine the amount and time course of naltrexone-appropriate responding were directly related to the degree of physical dependence; loss of body weight, a reliable index of morphine withdrawal in the rat, paralleled changes in naltrexone-appropriate responding; the maximum level of naltrexone-appropriate responding produced by a total of eight narcotic antagonists with agonist activity of differing prominence was a function of the extent of separation of the agonist and antagonist components of action of the drugs. Control of behavior by stimuli associated with morphine withdrawal may afford a specific animal model for studying factors relevant to the perpetuation of chronic drug use by human addicts.

Animals↗
PubMed1979

Evidence supporting lack of discriminative stimulus properties of a combination of naltrexone and morphine.

The aim of the present experiment was to study the potentially discriminable effects of combinations of morphine and naltrexone during long-term treatment. Three groups of gerbils had to discriminate the effects of morphine (12 mg/kg) and those of either saline (4 ml/kg), naltrexone (2 mg/kg), or a combination of this dose of morphine plus naltrexone injected IP 60 min prior to the start of the discriminative training in a T-shaped maze. Rapid development of drug discriminative control of choice behavior (left or right turn in the maze) was evident in these 3 groups which is in marked contrast to the performance of gerbils trained with morphine-naltrexone combination vs. saline or gerbils trained with naltrexone only vs. saline. Neither of these latter groups reached the criterion of performing 8 correct first-trial choices in 10 consecutive training sessions during the 60 training sessions allowed, while the 3 other groups began their criterion performance after only 7--8 training sessions. Thus the discriminative properties of certain combinations of morphine and naltrexone are weak and therfore are not easily discriminable from the effects induced by saline.

Animals↗
PubMed2005

Functional MRI reveals the existence of modality and coordination-dependent timing networks.

Growing evidence suggests that interval timing in humans is supported by distributed brain networks. Recently, we demonstrated that the specific network recruited for the performance of rhythmic timing is not static but is influenced by the coordination pattern employed during interval acquisition. Here we expand on this previous work to investigate the role of stimulus modality and coordination pattern in determining the brain areas recruited for performance of a self-paced rhythmic timing task. Subjects were paced with either a visual or an auditory metronome in either a synchronized (on the beat) or syncopated (off the beat) coordination pattern. The pacing stimulus was then removed and subjects continued to move based on the required interval. When compared with networks recruited for auditory pacing and continuation, the visual-specific activity was observed in the classic dorsal visual stream that included bilateral MT/V5, bilateral superior parietal lobe, and right ventral premotor cortex. Activity in these regions was present not only during pacing, when visual information is used to guide motor behavior, but also during continuation, when visual information specifying the temporal interval was no longer present. These results suggest a role for modality-specific areas in processing and representing temporal information. The cognitive demands imposed by syncopated coordination resulted in increased activity in a broad network that included supplementary motor area, lateral pre-motor cortex, bilateral insula, and cerebellum. This coordination-dependent activity persisted during the subsequent continuation period, when stimuli were removed and no coordination constraints were imposed. Taken together, the present results provide additional evidence that time and timing are served by a context-dependent distributed network rooted in basic sensorimotor processes.

Acoustic Stimulation↗
PubMed2003

Is it an animal? Is it a human face? Fast processing in upright and inverted natural scenes.

Object categorization can be extremely fast. But among all objects, human faces might hold a special status that could depend on a specialized module. Visual processing could thus be faster for faces than for any other kind of object. Moreover, because face processing might rely on facial configuration, it could be more disrupted by stimulus inversion. Here we report two experiments that compared the rapid categorization of human faces and animals or animal faces in the context of upright and inverted natural scenes. In Experiment 1, the natural scenes contained human faces and animals in a full range of scales from close-up to far views. In Experiment 2, targets were restricted to close-ups of human faces and animal faces. Both experiments revealed the remarkable object processing efficiency of our visual system and further showed (1) virtually no advantage for faces over animals; (2) very little performance impairment with inversion; and (3) greater sensitivity of faces to inversion. These results are interpreted within the framework of a unique system for object processing in the ventral pathway. In this system, evidence would accumulate very quickly and efficiently to categorize visual objects, without involving a face module or a mental rotation mechanism. It is further suggested that rapid object categorization in natural scenes might not rely on high-level features but rather on features of intermediate complexity.

Adult↗
PubMed1989

Risperidone (R 64 766), a potent and complete LSD antagonist in drug discrimination by rats.

Risperidone was studied in a 0.16 mg/kg LSD-saline drug discrimination test procedure. At doses varying from 0.0025 to 0.63 mg/kg, no LSD-like agonist effects were observed. Studies on the antagonism of the LSD-cue indicated that risperidone was able to completely block the discriminative stimulus properties of LSD with a minimum ED50-value of 0.028 mg/kg. Risperidone was also very active over time with reference to LSD antagonism, the ED50S after 2, 4 and 8 h pretreatment being 0.028, 0.064 and 0.44 mg/kg. Response rate reductions were only observed at doses greater than or equal to 0.16 mg/kg after 1 h and at 0.63 mg/kg after 2 h pretreatment. Four and 8 h after treatment, no rate-reducing effects were apparent at doses up to 2.50 mg/kg. Thus at pretreatment intervals ranging between 2 and 8 h, complete antagonism of LSD without any rate effects was obtained. As compared to other LSD antagonists, risperidone was quantitatively better than setoperone and ritanserin and longer acting than pirenperone. Based on the pharmacological profile of risperidone and the other LSD antagonists, it was concluded that a potent central 5-HT2 and catecholamine antagonism is needed for a potent and complete antagonism of the 0.16 mg/kg LSD-cue. The potential clinical effect of risperidone in the positive and negative symptoms of schizophrenia is discussed.

Animals↗
PubMed1979

Role of conditioned contextual stimuli in reinstatement of extinguished fear.

If the unconditioned stimulus (US) is presented independently of the conditioned stimulus (CS) following extinction, the conditioned response may be reinstated to the CS. Three experiments are reported that suggest that reinstatement is mediated by conditioning to contextual stimuli that are present during both US presentation and testing. Shocks presented to rats following the extinction of conditioned suppression reliably reinstated suppression to the CS, but only when they were presented in the context in which testing was later to occur. Reinstatement was also reversed by extinguishing fear to the context through nonreinforced exposure to the context between shock presentation and testing. Reinstatement was obtained in these experiments in spite of procedures that have been used in the past to minimize the influence of context conditioning. Moreover, fear of the context was never detected directly by depressed bar-press rates in the absence of the CS. The results do not support the hypothesis that reinstatement results from an increment in the strength of a memory of the US that has been weakened during extinction. Problems inherent in controlling and detecting levels of context conditioning that may influence behavior toward nominal CSs are discussed.

Animals↗