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PubMedDate not supplied

Stimulus properties of some analogues of 4-methylaminorex.

The stimulus properties of aminorex and analogues of 4-methylaminorex, namely (4S,5S)-4-methylaminorex, N-methyl-(4S,5S)-4-methylaminorex, and the regioisomeric (R)- and (S)-2-amino-4-phenyl-2-oxazoline (rexamino) were compared in rats trained to distinguish (S)-amphetamine (1 mg/kg) from saline. The first three compounds, aminorex, (4S,5S)-4-methylaminorex, and N-methyl-(4S,5S)-4-methylaminorex shared discriminative stimulus effects with amphetamine, although the stimulus properties for racemic aminorex were less than those of the other two compounds. The two regioisomers, (R)- and (S)-rexamino, produced only partial generalisation to the amphetamine.

Amphetamine↗
PubMed2005

Unsupervised categorization and category learning.

When people categorize a set of items in a certain way they often change their perceptions for these items so that they become more compatible with the learned categorization. In two experiments we examined whether such changes are extensive enough to change the unsupervised categorization for the items-that is, the categorization of the items that is considered more intuitive or natural without any learning. In Experiment 1 we directly employed an unsupervised categorization task; in Experiment 2 we collected similarity ratings for the items and inferred unsupervised categorizations using Pothos and Chater's (2002) model of unsupervised categorization. The unsupervised categorization for the items changed to resemble more the learned one when this was specified by the suppression of a stimulus dimension (both experiments), but less so when it was almost specified by the suppression of a stimulus dimension (Experiment 1, nonsignificant trend in Experiment 2). By contrast, no changes in the unsupervised categorization were observed when participants were taught a classification that was specified by a more fine tuning of the relative salience of the two dimensions.

Association Learning↗
PubMed1985

Potentiation and overshadowing in preweanling and adult rats.

Four experiments compared the aversion acquired by 18-day-old and 60-day-old rats to a flavor that was either tasted alone or in combination, simultaneously or successively, with another flavor when paired with illness. The purpose was to study temporal variables and theoretical issues pertinent to potentiation and overshadowing while investigating ontogenetic differences in these phenomena. When either the preweanlings or the adults were presented a simultaneous compound flavor (sucrose/coffee) followed by lithium chloride-induced illness, greater sucrose aversions were found than for animals conditioned on sucrose alone--that is, potentiation. Preweanlings demonstrated greater potentiation than did adults, whether the conditioned stimulus-unconditioned stimulus (CS-US) delay was 0 or 1 hr. This potentiation was eliminated by nonreinforced presentations of the alternative CS element. Potentiation was not seen when the two flavors were presented successively as the CS; instead, overshadowing occurred. Tests of configuring by extinction procedures indicated a tendency for these animals to form a configured representation of the simultaneous compound solution. This disposition for configuring tended to be more pronounced for preweanlings than for adults. Ontogenetic differences in response to configuration, CS saliency, and generalization decrement seem consistent with at least one model of potentiation and the ontogenetic differences in potentiation seen in the present experiments.

Animals↗
PubMed2000

Correspondence effects with manual gestures and postures: a study of imitation.

In this study, the authors applied methods and theories from research of stimulus-response compatibility (SRC) to action imitation. In 6 experiments, they adopted the logic of the Simon paradigm (B. Hommel & W. Prinz, 1996) to explore interference between task-relevant symbolic stimulus features (color) and task-irrelevant iconic stimulus features (2 hand gestures and 2 postures). The same 2 hand gestures served as responses. Pronounced correspondence effects for both gestures and postures showed up throughout. In line with theories of SRC, the authors account for these correspondence effects in terms of overlap arising between stimulus and response features in a common representational domain. As a specific extension of this approach, they propose 2 functionally independent mechanisms: One operates movement-based when dynamic information is provided, and the other operates state-based with static postures as stimuli. Implications for theories of both SRC and action imitation are discussed.

Adult↗
PubMed1998

Effects of d-amphetamine and caffeine in humans under a cocaine discrimination procedure.

This study examined further the pharmacological specificity of an oral cocaine discriminative stimulus in humans. Five male cocaine-abusing volunteers (two African-American/three Caucasian) were trained to discriminate between a low dose of cocaine hydrochloride (80 mg/70 kg, p.o.) and placebo. Once the criterion for discrimination was met (i.e. > or = 80% correct responding for four consecutive sessions), dose-effect curves were determined for the dopamine reuptake inhibitor cocaine (20, 40, 80, 120 mg/70 kg, p.o.), the indirect dopamine agonist d-amphetamine (5, 10, 20 mg/70 kg, p.o.) and the adenosine antagonist caffeine (150, 300, 600 mg/70 kg, p.o.). Cocaine, d-amphetamine and caffeine each produced dose-related increases in cocaine-appropriate responding. Each compound produced at least a trend towards increases in a few stimulant-like self-reports and vital signs. When the relationship between cocaine-appropriate responding and self-reports were examined, cocaine and d-amphetamine, but not caffeine, had a similar profile of significant associations between discriminative performance and stimulant-like self-reports. These results suggest that, although the cocaine discriminative stimulus (80 mg/70 kg) is not specific only to stimulants with primarily dopaminergic actions, its pharmacological specificity may be more clearly defined when the relationship between discrimination and self-reports is examined.

Adult↗
PubMed2003

Signalization and stimulus-substitution in Pavlov's theory of conditioning.

The concept of conditioning as signalization proposed by Ivan P. Pavlov (1927, 1928) is studied in relation to the theory of stimulus-substitution, which is also attributed to him. In the so-called theory of stimulus-substitution a distinction must be made between an empirical principle of substitution and an actual theory of substitution, which can adopt different forms. The Pavlovian theory of substitution--which conceives substitution as a substitution of the unconditioned stimulus (US) by the conditioned stimulus (CS) in the activation of the representation of the former--can be understood as an explanation or model of signalization. Signalization and substitution are answers to different questions, and the level of analysis to which signalization corresponds, is that which concerns the nature of conditioning as an operation of the animal in the environment.

Animals↗
PubMed1980

Brightness contrast: a reinterpretation of compound cue and combined cue experiments with pigeons.

A group of three pigeons was trained on a 4-ply multiple schedule: a green color and a vertical line superimposed upon an achromatic background as positive stimuli, and a red color and a horizontal line on an achromatic background as negative stimuli. The pigeons were tested with the vertical line superimposed upon different achromatic background intensities, then with the vertical line superimposed upon different green background intensities, and finally with the vertical line and its training achromatic backgfound attenuated (and unattenuated) by a neutral density filter. The gradients peaked at the luminance of the achromatic background used during training and at the equivalent luminance for the green background when it was substituted for the achromatic background. The brightness contrast, not the background luminance, was the critical variable as the neutral density filter attenuated both the line and the background equally, leaving brightness contrast unchanged; there was no response decrement to this attenuated stimulus. Two other groups of three pigeons showed that they attended to line orientation as well as to brightness contrast. The brightness contrast hypothesis was extended to explain results of attention experiments and combined cue experiments which have used line stimuli in combinations with different backgrounds.

Animals↗
PubMed1981

Further definition of history and observation variables in assessing febrile children.

The experienced clinician makes a judgment (hereafter called overall assessment [OA]) about the degree of illness of a febrile child prior to physical examination. In order to define the history and observation variables on which OA is based, 262 febrile children less than or equal to 24 months of age were evaluated simultaneously by multiple observers including attending pediatricians, practicing pediatricians, pediatric house officers, and nurses. The observer listed history and observation variables he/she thought most important in making an OA on a blank, lined form and then scored those variables and OA as normal, or mildly, moderately, or severely impaired. Scoring for observation rather than history variables was better correlated with scoring for OA and serious illness. The observation variables most frequently mentioned by all observers were the child's "looking at the observer" and "looking around the room." There were 20 observation variables frequently mentioned, the scoring of which significantly correlated with scoring for OA; four of these 20 variables related to eye function. The child's response to a stimulus was noted in 105/186 different observation variables listed; both the attending pediatrician and the house officer scored these stimulus-response variables significantly different in children with, vs those without, serious illnesses. For attending pediatricians, house officers, and nurses, serious illness was five to seven times as likely if an OA of moderate or severe impairment was made than if it were not made. OA is a key skill in evaluating febrile children; these data identify variables on which OA is based, document the importance of assessing eye function in young, febrile children, and demonstrate that eye function is one key type of stimulus-response behavior on which the pediatrician as clinician and developmentalist relies to make judgments about febrile children.

Child Development↗
PubMed1996

Visual stability across saccades while viewing complex pictures.

As people examine their world, the proximal stimulus changes position on their retinae with every saccade, but they perceive the world as being stable. This phenomenon of visual stability was explored by making changes in natural, full-color pictures during selected saccades as observers examined them in preparation for a recognition test. In Experiment 1, the pictures were displaced up, down, left, or right by 0.3, 0.4, or 1.2 degrees. In Experiment 2, the pictures were expanded or contracted by 10% or 20%. As a secondary task, subjects pressed a button when a change was detected. Three results from previous studies with simpler stimuli did not generalize. Evidence suggests that subjects' detection of image changes primarily involves the use of local information in the region of the eyes' landing position. A saccade target theory of visual stability is proposed.

Attention↗
PubMed1976

Theoretical and methodological considerations on drug discrimination learning.

A method is described which allows the assessment of discriminative stimulus properties of drugs, and the ability of amphetamine (0.16 mg/kg s.c.), chlordiazepoxide (5 mg/kg p.o.), desipramine (5 mg/kg s.c.), and haloperidol (0.02 mg/kg s.c.) to produce a discriminative stimulus complex (DSC) is evidenced. The method is found to yield clear-cut data that are specifically related to drug discrimination learning without being possibly confounded by state dependent effects. In addition, the experimental procedure is designed so as to provide an appropriate measurement of operant response modulating drug effects.

Amphetamine↗
PubMed1981

Discriminative stimulus properties of cocaine, norcocaine, and N-allylnorcocaine.

A discriminative stimulus paradigm was employed to train eight male and female Wistar rats to discriminate 5.0 mg/kg cocaine HCl from 2.0 ml/kg saline. Subjects responded in a two bar operant chamber on an FR 30 schedule for food reinforcement. All sessions followed a 10 minute pretreatment with either saline, the training dose of cocaine, four probe doses of cocaine HCl (1.0, 2.5, 7.5, 10 mg/kg), four probe doses of norcocaine (1.0, 2.5, 5.0, 7.5 mg/kg) or four probe doses of N-allylnorcocaine (5.0, 7.5, 10, 20 mg/kg). All probe doses were treated using an extinction procedure. The three highest doses of cocaine generalized to cocaine while the 1.0 mg/kg dose of cocaine generalized to saline. The two highest doses of norcocaine generalized to cocaine while the 2.5 mg/kg dose of norcocaine resulted in 57% responding on the cocaine lever with the 1.0 mg/kg dose generalizing to saline. Only the highest dose of N-allylnorcocaine was found to generalize to cocaine with the intermediate doses resulting in an intermediate level of responding occurring on the cocaine lever. The 5.0 mg/kg dose of N-allylnorcocaine generalized to saline.

Animals↗
PubMed1982

Amino acids as taste stimuli. II. Quality coding.

Two experiments were performed in rats to evaluate the relative taste qualities of 12 L-amino acids, each at a concentration which evoked half the maximum response for that chemical. The first study involved recording the activity of 40 individual chorda tympani fibers to the stimulus series. Only 34% of the evoked responses resembled the short latency phasic-tonic activity which characterizes gustatory responses to inorganic salts and acids. 32% had latencies exceeding 1 s; another 27% consisted of only a phasic burst lasting less than 1 s. The remaining 7% were inhibitory. Both long latency and purely phasic activity were stimulus selective: 61% of the former were in response to Gly or Pro while 69% of the latter were evoked by Cys-HCl, Lys-HCl or His. Response inhibition was not associated with either specific fibers or stimuli. Thus amino acids, which to humans represent a class of perceptually complex stimuli, show a corresponding complexity of evoked neural properties in the rat. The second study employed a conditioned taste aversion paradigm to assess the qualitative similarity of each amino acid to the others and to the 4 prototypical taste stimuli; NaCl, HCl, quinine-HCl and sucrose. Some amino acids showed strong generalization to a single gustatory prototype (Pro and Gly to sucrose; Cys-HCl to HCl); others generalized well to multiple prototypes (e.g. Arg to sucrose and NaCl). Several showed poor generalization to all 4 prototypical tastes, calling into question the assumption that these 4 totally encompass the gustatory domain.

Animals↗
PubMed1986

5-HT1 and 5-HT2 binding characteristics of some quipazine analogues.

Arylpiperazines, such as 1-(3-trifluoromethylphenyl)piperazine (TFMPP) and its chloro analogue mCPP, are 5-HT1 agonists, whereas quipazine, i.e., 2-(1-piperazino)quinoline, appears to be a 5-HT2 agonist. Radioligand binding studies using rat cortical membrane homogenates and drug discrimination studies using rats trained to discriminate a 5-HT1 agonist (i.e., TFMPP) or a 5-HT2 agonist (i.e., 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM)) from saline reveal that quipazine and its 1-deaza analogue 2-naphthylpiperazine (2-NP) bind at 5-HT1 and 5-HT2 sites but produce stimulus effects similar to those of DOM. A structurally related compound, 1-naphthylpiperazine (1-NP), possesses a high affinity for 5-HT1 (Ki = 5 nM) and 5-HT2 (Ki = 18 nM) sites. 1-NP produces stimulus effects similar to those of TFMPP and is able to antagonize the stimulus effects produced by DOM. The present results suggest that the unsubstituted benzene ring of quipazine, and of its 1-deaza analogue 2-naphthylpiperazine, makes a significant contribution to the binding of these agents to 5-HT2 sites and, more importantly, may account for their 5-HT2 agonist properties.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed2004

Different thresholds for detection and discrimination of odors in the honey bee (Apis mellifera).

Naturally occurring odors used by animals for mate recognition, food identification and other purposes must be detected at concentrations that vary across several orders of magnitude. Olfactory systems must therefore have the capacity to represent odors over a large range of concentrations regardless of dramatic changes in the salience, or perceived intensity, of a stimulus. The stability of the representation of an odor relative to other odors across concentration has not been extensively evaluated. We tested the ability of honey bees to discriminate pure odorants across a range of concentrations at and above their detection threshold. Our study showed that pure odorant compounds became progressively easier for honey bees to discriminate with increasing concentration. Discrimination is, therefore, a function of odorant concentration. We hypothesize that the recruitment of sensory cell populations across a range of concentrations may be important for odor coding, perhaps by changing its perceptual qualities or by increasing its salience against background stimuli, and that this mechanism is a general property of olfactory systems.

Animals↗
PubMed1999

Stimulus amplification, efficacy, and the operational model. Part I--binary complex occupancy mechanisms.

A simple function, developed to represent the stimulus produced at the n -th step of a multistep signaling sequence, is applied to the classic model of agonist-receptor interaction. The model indicates that the relative efficacy of two agonists can be easily estimated from three experimental measures: maximal response, EC50, and apparent dissociation constant. Efficacy ratios obtained in this manner appear statistically and mathematically equivalent to those estimated with null-based methods. Enhancement of both maximal response (vertical amplification) and potency (horizontal amplification) are demonstrated to result from the interaction between highly efficacious agonists and signal transduction mechanisms. Both properties, not just relative maxima, must therefore be examined when comparing relative efficacy. Three additional generalized stimulus-response models are developed and shown to be functionally equivalent. Increasing the complexity of the function used to represent stimulus amplification does not appear to alter the conclusions derived based on the simple model of stimulus amplification. Analysis of the results also reveals a close relationship between mechanistic and operational modes of drug action, and allows operational parameters to be given mechanistic interpretation.

Animals↗
PubMed1999

Influencing the specificity of drug mixture discriminations by varying the training procedure.

Studies of the discriminative stimulus effects of drug mixtures provide an approach to polydrug abuse and to studies on single drugs with multiple effects. The experiments described here investigated whether the use of the AND-OR procedure increases the specificity of drug mixture discriminations. Rats were trained to discriminate a mixture of nicotine (0.4 mg/ kg) plus midazolam (0.2 mg/kg) from saline (AND-discrimination, n = 10) or to discriminate the same mixture from its component drugs alone (AND-OR discrimination, n = 10). The studies used two-lever operant procedures with a tandem variable interval 1 min fixed ratio 10 (FR 10) schedule of food reinforcement. Under AND-discrimination conditions, there was partial generalization to amphetamine and pentobarbitone when each drug was administered singly. With the AND-OR-discrimination, there was no generalization to amphetamine and partial generalization to pentobarbitone. In 'single substitution' tests, pentobarbitone or amphetamine was co-administered with the training doses of nicotine and midazolam, respectively; there was full generalization in the AND-discrimination and no generalization under AND-OR conditions. In 'dual substitution' tests, mixtures of amphetamine plus pentobarbitone produced full generalization under AND-discrimination conditions, and partial generalization in the AND-OR procedure. Wherever comparisons were made, generalization was less under AND-OR- than under the AND-discrimination procedure, confirming that the AND-OR procedure can increase the specificity of discriminations based on drug mixtures. The similarity with findings reported previously for training with mixtures of amphetamine plus pentobarbitone suggests that this may reflect a general principle rather than a phenomenon restricted to particular training drugs.

Animals↗
PubMed1987

Oddity performance in preschool children at risk for mental retardation: transfer and maintenance.

The oddity performance of five preschool children at risk for mental retardation was facilitated by increasing the number of nonodd elements in a visual array. A combination intrasubject reversal and multiple baseline across subjects design indicated the internal validity of interventions designed to enhance the perceptual salience and consequent stimulus control of the odd stimulus. Results demonstrate that transfer and maintenance of oddity learning can be obtained even with individuals for whom correct oddity responding is uncommon. The typically poor performance of young and developmentally delayed children as compared to nondelayed children on tasks such as the oddity task may be attributable to a lower sensitivity to relational information.

Attention↗
PubMedDate not supplied

A comparison of static and dynamic presentation procedures on discrimination learning of individuals with severe or moderate mental retardation.

A dynamic presentation of stimulus materials may be more effective than a static presentation. To test this hypothesis, we taught 16 individuals with moderate or severe mental retardation to identify two comparative discriminations (more, longer) by each of two different procedures. In the static, or traditional, presentation procedure the stimuli were positioned before a trial began and not manipulated by the experimenter during the trial. In the dynamic presentation procedure the individual watched the experimenter manipulate the relevant dimension of the stimuli during a series of trials. Both procedures were used in combination with a procedure that relied on fading and on many examples of both the correct and incorrect stimuli across trials. Data were presented in four phases: training, generalization, 1-week maintenance, and 1-month maintenance. No differences in percentage of unprompted correct responses were found between the two procedures in training, generalization, or any of the four maintenance tests. Discussion included possible reasons these results differed from those of prior studies as well as the need for further investigation of the dynamic presentation procedure used with more traditional teaching procedures that rely on extrastimulus prompts.

Adolescent↗