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PubMed1991

Habituation of the ultrasound-induced acoustic startle response in flying crickets.

The ultrasound-induced negative phonotactic response of tethered, flying Australian field crickets habituates to repeated stimuli. Using the magnitude of the metathoracic leg's swing during a series of ultrasonic stimuli as a measure of habituation, we show that: (1) the response declines exponentially; (2) the response recovers spontaneously; (3) repeated trials produce more rapid and stronger habituation; (4) successive stimuli presented more rapidly produce more rapid and stronger habituation; (5) a weaker stimulus intensity produces more rapid and stronger habituation; (6) the habituation shows stimulus generalization (i.e. the response is similar for different ultrasonic frequencies); (7) a novel stimulus produces dishabituation; and (8) the effect of the dishabituating stimulus habituates after repeated trials. These findings place habituation of cricket negative phonotaxis in the context described for habituation in mammals.

Animals↗
PubMed1975

Some effects of response-independent reinforcement on auditory generalization gradients.

Two groups of six rats received discrimination training with two auditory stimuli differing in intensity. During one stimulus, the schedule was variable interval; during the other, it was either variable time or extinction. Both the variable time and extinction schedules resulted in differential rates of responding in the presence of the two stimuli. Extinction resulted in an earlier and more stable difference. Stimulus generalization gradients obtained along the noise-intensity dimension revealed peak shift with both procedures. In addition, a secondary peak to stimuli in between the two training stimuli occurred with the variable-time schedule.

Acoustic Stimulation↗
PubMed1989

Functional equivalence of autistic leading and communicative pointing: analysis and treatment.

Several studies have demonstrated that behavior problems can be reduced by teaching new, socially desirable responses that serve the same function as the undesirable behaviors being replaced. The present study was undertaken to extend this strategy systematically to a different area of child development, specifically, language disorder. A less desirable form of requesting, autistic leading, was treated by strengthening a more desirable form of requesting, pointing. The study was conducted using a multiple baseline design across four children with autism. Intervention included verbal and physical prompting of the pointing response as well as tangible reinforcement for child-initiated instances of that response. In a later phase, verbal requesting was also taught to accompany the pointing. Following intervention, response generalization was observed; that is, as pointing became frequent, leading became rare. In addition, stimulus generalization was observed; that is, pointing was exhibited in the presence of new adults, new settings, and new tangible objects. Results are discussed with respect to the principle that functional equivalence and response efficiency can be combined procedurally to treat a variety of undesirable behaviors in an educationally constructive manner.

Autistic Disorder↗
PubMed1978

Discriminative effects of cyclazocine in the squirrel monkey.

In order to characterize the discriminative stimulus properties of cyclazocine squirrel monkeys were trained to discriminate between intramuscular injections of 0.1 mg/kg of cyclazocine and drug vehicle in a discrete-trial avoidance paradigm in which a response on one of two levers would prevent or terminate the delivery of a mild electric shock to the tail. Behavior was considered to be under stimulus control when the monkeys completed at least 22 trials of a 25-trial session on the appropriate choice lever after they received cyclazocine or vehicle. Stimulus generalization (i.e., dose-response) curves were then determined for a variety of drugs over a broad range of doses. The following analgesics with narcotic antagonist properties produced stimulus control of behavior comparable to that produced by 0.1 mg/kg of cyclazocine: ketocyclazocine (0.1 mg/kg), butorphanol (1.0 mg/kg), oxilorphan (3.0 mg/kg) and levallorphan (3.0 mg/kg). Time course experiments revealed that the duration of complete stimulus control was relatively short: 1 hour after 0.1 mg/kg of cyclazocine and 3.0 mg/kg of oxilorphan and 0.5 hour after 0.1 mg/kg of ketocyclazocine. Naloxone produced a dose-related antagonism of the stimulus control by cyclazocine and butorphanol which was complete at 1.0 mg/kg. In contrast, as much as 10 mg/kg of naloxone only partially blocked stimulus control by ketocyclazocine and failed to modify stimulus control by oxilorphan and levallorphan. The monkeys showed partial generalization to other drugs with activity as narcotic agonists, antagonists or both (e.g., morphine, naloxone, pentazocine, nalbuphine, nalmexone and nalorphine), but little or no generalization to the nonopioid psychoactive drugs, d-amphetamine, mescaline, pentobarbital and scopolamine. This discrimination paradigm appears to have potential as a model for the quantitative assessment of the discriminative stimulus properties of narcotic antagonist analgesics.

Animals↗
PubMed1981

Morphine-like stimulus effects in the monkey: opioids with antagonist properties.

The discriminative stimulus properties of opioids with a wide spectrum of agonist and antagonist properties were evaluated in squirrel monkeys trained to discriminate between morphine and saline in a two-choice discrete-trial avoidance task. Stimulus control was considered to be established when the monkeys reliably completed at least 22 trials of a 25-trial session on the lever appropriate for the drug state. Tests of stimulus generalization were conducted with compounds that were previously shown in the rat to produce discriminative stimulus effects that are: (a) morphine-like (profadol, WY-16,225, pentazocine, butorphanol, nalmexone); (b) cyclazocine-like (cyclazocine, ketocyclazocine, levallorphan); (c) neither morphine-like nor cyclazocine-like (nalbuphine and nalorphine). Profadol and WY-16,225 were equipotent with morphine in producing morphine-like stimulus effects. Naloxone antagonized the morphine-appropriate responding produced by all three compounds, but 10 times more naloxone was needed to block the stimulus effects of WY-16,225 than to block those of either morphine or profadol consistent with the known antagonist properties of WY-16,225. None of the other drugs produced complete morphine-like stimulus control of behavior but, with the exception of nalorphine, the highest dose of each resulted in about half of the trials being completed on the morphine-appropriate choice lever. These results confirm the heterogeneous nature of the discriminative stimulus effects of opioids with mixed agonist and antagonist properties and indicate the importance of interspecies comparisons.

Animals↗
PubMed2006

Pitch cue learning in chinchillas: the role of spectral region in the training stimulus.

Chinchillas were trained to discriminate a cosine-phase harmonic tone complex (COS) from wideband noise (WBN) and tested in a stimulus generalization paradigm with tone complexes in which phase differed between frequency regions. In this split-phase condition, responses to complexes made of random-phase low frequencies, cosine-phase high frequencies were similar to responses to the COS-training stimulus. However, responses to complexes made of cosine-phase low frequencies, random-phase high frequencies were generally lower than their responses to the COS-training stimulus. When tested with sine-phase (SIN) and random-phase (RND) tone complexes, responses were large for SIN, but were small for RND. Chinchillas were then trained to discriminate infinitely-iterated rippled noise (IIRN) from WBN and tested with noises in which the spectral ripple differed between frequency regions. In this split-spectrum condition, responses were large to noises made of rippled-spectrum low frequencies, flat-spectrum high frequencies, whereas responses were generally lower to noises made of flat-spectrum low frequencies, rippled-spectrum high frequencies. The results suggest that chinchillas listen across all frequencies, but attend to high frequencies when discriminating COS from WBN and attend to low frequencies when discriminating IIRN from WBN.

Animals↗
PubMed1984

Cross generalization with LSD and yohimbine in the rat.

Rats trained to discriminate intraperitoneal injections of 0.16 mg/kg LSD from saline injections were found to show stimulus generalization with 0.31-5 mg/kg of yohimbine. Partial generalization also occurred with clonidine and xylazine. Rats discriminating intraperitoneal injections of 5 mg/kg of yohimbine from saline generalized LSD at doses of 0.08-0.63 mg/kg. The data establish an equivalence between LSD and yohimbine as to discriminative effects in rats. This equivalence is consistent with LSD and yohimbine producing at least partly similar subjective effects in humans.

Animals↗
PubMed1976

The reduced responsiveness of neurones in nucleus reticularis gigantocellularis following their excitation by peripheral nerve stimulation.

1. Post-stimulus histograms of neuronal activity, constructed from extracellular recordings in decerebrate, decerebellate cats, have been used to investigate the responsiveness of neurons in nucleus reticularis gigantocellularis following their excitation by a peripheral nerve stimulus. 2. The response to a testing stimulus applied to a peripheral nerve was depressed following the response to a conditioning stimulus applied to the same or a different peripheral nerve. This reduction in responsiveness was maximal within 50 msec of the peak of the response to the conditioning stimulus. Response latencies to the testing stimulus were increased during the period of reduced responsiveness. 3. Responsiveness to a peripheral nerve stimulus was also reduced following a spontaneous or an antidromically evoked spike, but this effect was weaker and much shorter-lasting than that following a nerve-evoked spike. Thus, the reduced responsiveness cannot be solely due to phenomena which are an inevitable consequence of an action potential in the neurone. 4. In spontaneously firing neurones, the duration of the reduced responsiveness to a testing stimulus generally outlasted the depression of spontaneous activity which often followed an excitation evoked by a peripheral nerve conditioning stimulus. 5. The reduction in responsiveness to a testing stimulus applied to the same nerve as the conditioning stimulus was greater and longer-lasting than that to a testing stimulus applied to a different nerve. 6. When stimuli were applied to one nerve at a relatively high rate, the neurone became much less responsive to that input, but simultaneously became more responsive to low rate stimulation of other nerves. 7. It is concluded that the greater part of the reduced responsiveness is due to events occurring on the input pathway to a reticular neurone, or possibly in the region of the afferent endings on its dendrites. These processes may allow selective changes in responsiveness to different inputs, and enable the units to act as novelty detectors.

Action Potentials↗
PubMed1999

Stimulus amplification, efficacy, and the operational model. Part II--ternary complex occupancy mechanisms.

To understand how deviations from simple binary occupancy affect measures of efficacy, the generalized stimulus function developed in Part I was used to examine the actions of drugs in systems where occupation of the receptor was modeled using a two-state, ternary complex, or combination of mechanisms. Amplification of drug responses can occur during formation of an active agonist-receptor complex, during generation of the initial stimulus, and during signal transduction. Expressions were derived to characterize the separate contributions of these three phases. Ideally, comparison of relative intrinsic efficacy measures differences in the ability of the agonists to convert active complex into an active stimulus. In practice, differences in the ability of the drugs to form the stimulus-generating complex may also contribute to the efficacy ratio and must be taken into consideration. Failure to adequately account for differences in occupancy can result in overestimation of the efficacy ratio. The magnitude of the difference between true and experimental measures of intrinsic efficacy may be affected by G protein concentration, by the affinity between the G protein and receptor, and (in some models) by the receptor activation constant. Provided that the dissociation constant between the G protein and receptor is of the same order of magnitude as, or lower than the receptor concentration, however, experimental estimates should provide reasonably accurate estimates of the true efficacy ratio. In agreement with previously published experimental data, total G protein level was found capable of influencing agonist maximal response, Emax, and EC50 values in all four ternary complex models. The magnitude of the changes in Emax and EC50 appear to be dependent upon the efficacy of the agonist as well as characteristics of the post-receptor stimulus sequence.Additionally, the concentration-response relations for all four ternary complex models could be reduced to a modified operational format in which the apparent dissociation constant Kapp replaced the true KA, and an apparent operational efficacy, tauapp, replaced tau. tauapp can be estimated experimentally from measurements of the Kapp and EC50, while the operational maximum, Em, may be found from the calculated tauapp and the measured Emax of the response curve. These findings support the use of direct operational model-fitting in a variety of systems, regardless of the mechanisms underlying occupancy. Values of Kapp calculated using the exact formula for [ARG] displayed an anomalous rise or discontinuity where the concentrations of total G protein equaled that of the receptor protein. This discontinuity is not observed in the estimates based on approximations to [ARG], and may explain practical difficulties in evaluating the dissociation constant under these conditions.

Animals↗
PubMed1982

Parametric effects in the discrimination of intracranial stimulation: some methodological and analytical issues.

Rats were implanted with electrodes in the medial forebrain bundle at the level of the lateral hypothalamus. Electrical stimulation was established as a conditioned stimulus for responding in a modified two-way active shock avoidance procedure. Stimulus generalization experiments were conducted to determine the effects of pulse frequency, current intensity, pulse duration, and of train duration. It was found that the discriminative stimulus properties of the electrical stimulation co-varied in an orderly manner with variations in each of the parameters. The generalization data sets of frequency, intensity, and train duration could be fitted by linear functions in log-linear coordinates; the effects of pulse duration generated a biphasic gradient. An analysis in terms of charge revealed that train duration had the lowest slope, whereas frequency and intensity generated equally steep functions. The most striking differences occurred among conditions which were similar in terms of current intensity, pulse duration and number of pulses, but which differed in the temporal patterning of pulses. Some methodological and analytical aspects of discrimination and generalization with intracranial stimulation are discussed.

Animals↗
PubMed2000

Stimulus control and generalization of point-loss punishment with humans.

Two experiments demonstrated stimulus control and generalization of conditioned punishment with humans. In both studies, responses first were reinforced with points exchangeable for money on a variable-interval schedule in the presence of one line length (S(D)). Next, a second line length was introduced, and point loss followed every response in the presence of that line (S(D)p). In the final training condition, points were deducted at session end. Response rate was lower in the presence of the S(D)p despite equal rates of points for money in the presence of both stimuli. In generalization testing for Experiment 1, the two lines were included in a 10-line continuum; S(D)p fell in the middle and the trained SD was at one end. Lines were presented randomly, and point delivery and loss contingencies were as in training but with points available in the presence of all lines. For all subjects, response rates were lowest around S(D)p and increased towards the SD end of the continuum. Because testing included only one or two lines beyond S(D), this pattern did not rule out S(D) generalization. Thus, in Experiment 2, stimuli beyond S(D) were added to generalization tests. Response rates did not decrease as a function of distance from S(D), clarifying the demonstration of punishment generalization.

Adult↗
PubMed2002

Perception of the periodicity strength of complex sounds by the chinchilla.

The perception of periodicity strength was studied in chinchillas using a stimulus generalization paradigm in an operant-conditioning, positive reinforcement behavioral task. Stimuli consisted of cosine-phase and random-phase harmonic complex tones, infinitely iterated rippled noises, and wideband noise. These stimuli vary in periodicity strength as measured by autocorrelation functions and are known to generate a continuum in the perception of pitch strength in human listeners. Chinchillas were trained to discriminate a cosine-phase harmonic tone complex from wideband noise and tested in the generalization paradigm using random-phase tone complexes and iterated rippled noises as probe stimuli. Chinchillas were tested in three different conditions in which the periods of the fundamental frequencies of the tone complexes were fixed at 2 ms, 4 ms, or 8 ms. Behavioral responses obtained from chinchillas were related to stimulus periodicity strength. For most animals, the behavioral responses to random-phase tone complexes were smaller than those to cosine-phase tone complexes. The behavioral responses were analyzed in terms of the Auditory Image Model of Patterson et al. [Patterson, R.D., Allerhand, M.H., Giguère, C., J. Acoust. Soc. Am. 98 (1995) 1890-1894], and the results suggest that the periodicity information in the stimulus envelope has a large influence in controlling the behavioral response of the chinchilla. Comparison of the generalization data obtained in the present study to magnitude estimation data obtained previously in human subjects suggests a greater influence of stimulus envelope for the perception of periodicity strength in chinchillas than for the perception of pitch strength in human listeners.

Animals↗
PubMed1978

Neuroleptic interference with the cocaine cue: internal stimulus control of behavior and psychosis.

The ability of cocaine to exert internal stimulus control of behavior was investigated by training rats to discriminate 10 mg/kg cocaine from saline in a discrete-trial, two-lever, food-reward procedure. Acquisition of response control by cocaine (1) succeeded in all animals tested, (2) proceeded rapidly, and (3) was associated with a high Commission Error: Omission Error ratio. These findings support the hypothesis that cocaine, a prototype of drugs inducing a psychotic condition in humans, can act as a powerful internal stimulus in rats. The cocaine cue was also responsive to the action of the dopamine-receptor-blocking agents spiperone (ED50: 0.06 mg/kg), haloperidol (0.24 mg/kg), and pimozide (1.90 mg/kg). d, l-Amphetamine (1.25 mg/kg) induced stimulus generalization with cocaine, and this generalization was blocked by dosages of the same neuroleptics comparable to those of cocaine antagonism. The results are discussed in terms of internal stimulus control of behavior and its relevance to the psychophysiology of schizophrenia.

Amphetamine↗
PubMed2000

The Ornstein-Uhlenbeck model for decision time in cognitive tasks: an example of control of nonlinear network dynamics.

The Ornstein-Uhlenbeck (OU) model for human decision-making has been successfully applied to account for response accuracy and response time (RT) data in recent two-choice decision models. A variant of the OU model is shown to arise from the response dynamics of a nonlinear network consisting of randomly connected neural processing units. When feedback control of the network is effected by the stimulus onset, the average network response is an autocorrelated random signal satisfying the stochastic differential equation for the OU process. An alternative, more general, stimulus detection procedure is proposed which involves the use of an adaptive Kalman filter process to track any temporal change in autoregressive parameters. The predicted decision time distributions suggest that both the OU and the Kalman filter processes can serve as alternative models for RT data in experimental tasks.

Cognition↗
PubMed2006

Attentional modulation of repetition attenuation is anatomically dissociable for scenes and faces.

Repeating a stimulus generally leads to a decreased response in neural activity compared to that for novel items. This neural attenuation provides a marker for stimulus-specific perceptual encoding and memory that can be detected using functional magnetic resonance imaging (fMRI). Although previously assumed to occur automatically whenever a stimulus is repeated, recent studies have begun to show that the repetition attenuation effect is task-specific and modulated by attention. Here, we demonstrate that attention is crucial for obtaining neural attenuation even after extensive stimulus repetitions. Furthermore, the effect of attention on attenuation is anatomically dissociable for stimuli that have relatively segregated neural representations in high-level perceptual cortex. To manipulate attention, we used overlapping scene and face images, and asked subjects to attend to either category. In a scene-sensitive cortical region known as the parahippocampal place area (PPA), significant attenuation in the fMRI BOLD signal was observed for the attended repeated scenes (relative to attended novel scenes), while no attenuation was observed for ignored repeated scenes or attended repeated faces against their respective novel image baselines. Conversely, in the face-sensitive region known as the fusiform face area (FFA), significant attenuation was observed for attended repeated faces, but not for ignored repeated faces or attended repeated scenes. An additional control experiment ruled out alternative explanations based on global signal level reductions due to inattention. Thus, attention actively governed when neuronal activity was attenuated to repeated perceptual input, and such attenuation was specific to the cortical regions that actively represent the attended category of stimuli.

Adaptation, Physiological↗
PubMed1986

Discriminative stimulus effects of atypical anxiolytics in baboons and rats.

Baboons and rats were trained to discriminate lorazepam and pentobarbital in a food-maintained two-lever drug vs. no-drug discrimination procedure. Previous research showed that benzodiazepines, but not barbiturates, occasioned drug lever responding in the lorazepam-trained animals. Lorazepam and six nonbenzodiazepines that have been proposed as anxiolytics (CGS 9896, CL 218,872, PK 9084, zopiclone, buspirone and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) were studied in test sessions in which responding on either level produced food. Of the nonbenzodiazepine compounds studied that displace 3H-benzodiazepines in vitro, CL 218,872 and zopiclone occasioned drug lever responding in all animals; PK 9084 did not occasion drug lever responding in any animal; and CGS 9896 did not occasion drug lever responding in lorazepam- or pentobarbital-trained baboons or in lorazepam-trained rats, but did so in the pentobarbital-trained rats. Buspirone, a nonbenzodiazepine anxiolytic with prominent dopaminergic activity, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol, a gamma-aminobutyric acid agonist, also did not occasion drug lever responding in either baboons or rats, regardless of training drug. Time course studies in baboons with CGS 9896, PK 9084, 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol and buspirone did not reveal delayed onset of drug stimulus generalization. Some differences in potency as a function of route of administration were found with CL 218,872, zopiclone and buspirone. The discriminative stimulus effects of lorazepam, CL 218,872 and zopiclone were antagonized by the benzodiazepine receptor antagonist Ro 15-1788. It is concluded that the discriminative stimulus properties of these nonbenzodiazepine compounds thus do not co-vary with their antipunishment effects, with their clinical efficacy as anxiolytics or with benzodiazepine receptor binding.

Animals↗
PubMed1982

Effects of septal lesion on go, no-go differentiation and reversal learning in rats.

Experiments were done on 24 Sprague-Dawley male albino rats. Acquisition of go, no-go differentiation and its reversal were compared between normal and septal animals. Rats were trained in Skinner boxes on a 30-s VI food reinforcement schedule. Differentiation sessions consisted of periods with flashing and steady light on, randomly distributed. In half the subjects of each group reinforcement was available only during the flashing light (CS+ periods) while during the steady light no reinforcement was delivered (CS- periods). For the remaining subjects the allocation of stimuli as CS+ or CS- was reversed. During reversal training the signalling properties of the stimuli were reversed. The experiments confirmed that there is lesion-induced increment in base-line response rate. During differentiation training septal damage had no significant effect on the proportion of total responses emitted during CS-, although it increased the overall rate of CS- responding when the flashing light was used as CS-. During reversal training when the flashing light was used as CS- septal animals both responded at a higher rate during CS-, and emitted a higher proportion of their responses during CS-, relative to controls. There were no lesion effects on CS- responding when the steady light was used as CS-. Thus the septal deficit appeared when the to-be-extinguished habit was fairly strong and only under conditions of greater stimulus generalization. These results indicate that septal effects depend on a variety of experimental factors determining performance in any given test situation, among which stimulus intensity dynamism is one of particular importance.

Analysis of Variance↗
PubMed1997

Modulatory effects of morphine, U-50488H and 1,3-di-(2-tolyl)guanidine on cocaine-like discriminative stimulus in the rat using two-choice discrete-trial avoidance paradigm.

The present study was designed to investigate the effects of the mu-opioid morphine, trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)- cyclohexyl]-benzene acetamide, methane sulfonate hydrate (U-50488H), a kappa-selective opioid receptor agonist, and 1,3-di-(2-tolyl)guanidine (DTG), sigma-receptor agonist, on the discriminative stimulus properties of cocaine in the rat trained to discriminate 10 mg/kg of cocaine from its vehicle in a shock avoidance paradigm. Morphine (1-5.6 mg/kg), U-50488H (1-10 mg/kg) or 1,3-di-(2-tolyl) guanidine (1 and 10 mg/kg) alone did not produce any stimulus effects in common with cocaine. In contrast, morphine (5.6 mg/kg) and DTG (10 mg/kg), unlike U-50488H (10 mg/kg), significantly shifted the stimulus-generalization curve for cocaine to the left. These results suggest that agonists for mu-opioid- and sigma-receptors augment the discriminative stimulus properties of cocaine.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗