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PubMed1988

Generalization of delayed identity matching in retarded children.

In an extension of prior research, four retarded children were trained under an identity matching-to-sample procedure containing features previously shown to produce controlled generalization to novel stimuli. They first were taught to relate a particular handsign to the sample shape, then to maintain the handsign over a delay interval, and then to select from an array the comparison shape that permitted the handsign to be maintained (i.e., the shape identical to the sample). An initial test revealed little generalization of matching to novel stimuli, but after handsigns were trained to these stimuli, accurate generalized matching appeared immediately. The results replicated prior findings and demonstrated particular features of stimulus control sufficient to enable generalized matching. A behavioral account of relational matching was supported. The technique used in this study was shown to be effective in teaching abstract relations to nonverbal retarded children.

Adolescent↗

PubMed1983

Painful sensation induced by a thermal cutaneous stimulus.

This review emphasizes how little we know about pain induced by a thermal stimulus. The study of the intensity of pain evoked by heat is relatively exhaustive: the influence of various local, stimulus-dependent or general factors upon threshold values has been well studied, as has the relation between pain and stimulus intensities. On the contrary, few studies have used very cold stimuli, since highly efficient stimulators allowing accurate control of the stimulus parameters have been obtainable only recently. Only the influence of stimulation area and stimulation rate on cold pain thresholds have been studied. Moreover, old results obtained on pain quality cannot be used since the conditions of stimulation were not specified or not controlled accurately. It is only known that stimulus duration and stimulation area are determinant for thermal pain quality. There is still much work to be done in this field. All the more so as this type of study is absolutely necessary for the understanding of pain mechanisms--it describes what must be explained by the function of the nervous system. We have seen that at the periphery the intensity of heat pain is coded by the response of polymodal nociceptors, mechanothermal nociceptors, thermal nociceptors and possibly by the paradoxical discharge of cold receptors. If the stimulus is lower than 45 degrees C the activity of certain heat receptors comes into play. Although we lack information which would allow confirmation of this as a fact it seems likely that the activity of polymodal nociceptors, cold mechanothermal nociceptors and possibly certain cold receptors sensitive to very low temperatures code cold pain. These nociceptive impulses carried by A delta and C fibers reach the dorsal horn of the spinal cord through the dorsal roots. They are notably at the origin of the activation of the neurons in Rexed's layers I, V and VIII which are to a large extent at the origin of the spinothalamic and spinoreticulothalamic tracks [21,115,168] moving in the anterolateral quadrant of the spinal cord. At supraspinal level, the thermal information reappears in the reticular formation; there it appears to be solely relative to the pain threshold and not to the intensity of a supraliminary stimulus [55]. In the posterior group of nuclei [134] and the ventroposterolateral nucleus of the thalamus [103], on the contrary, the activity of the neurons reflects the intensity of the stimulation. It has been proved that the neurons of the ventroposterolateral nucleus project onto the SI cortex [103].(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗

PubMed1994

Defeat engenders pentylenetetrazole-appropriate responding in rats: antagonism by midazolam.

Defeat and the threat of defeat by an aggressive conspecific is stressful and may engender an anxiety- or fear-like state in animals; the present experiment investigated whether defeat generalized to the discriminative stimulus properties of PTZ and how benzodiazepine receptors were involved in this generalization. Separate groups of male Long-Evans rats (Rattus norvegicus) were trained to discriminate 20 mg/kg pentylenetetrazole (PTZ) or 0.4 mg/kg midazolam (MDZ) from saline in a two-choice drug-discrimination task. After establishing stimulus control, PTZ- and MDZ-trained rats were exposed to an aggressive conspecific which resulted in defeat, as defined by the display of defensive and submissive postures as well as audible and ultrasonic vocalizations. Administration of saline after defeat resulted in greater than 80% PTZ lever selection in 15 out of 25 PTZ-trained rats; this effect was attenuated through pretreatment with MDZ (1 mg/kg). Furthermore, short-term defeat substitution for the PTZ discriminative stimulus was not accompanied by long-term changes in the post-defeat generalization curves for PTZ and MDZ when compared to pre-defeat generalization curves. Nor did defeat alter the antagonism of PTZ by diazepam (2.5 mg/kg) or MDZ by flumazenil (10 mg/kg). In order further to characterize the necessary features for defeat substitution for the PTZ discriminative stimulus, exposure to a threatening conspecific was also attempted by PTZ-trained rats protected from physical contact with a wire mesh cage. In these tests, saline continued to engender greater than 50% PTZ lever responding in 15 of 25 rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Agonistic Behavior↗

PubMed2001

Intentional and unintentional contributions to nonspecific preparation during reaction time foreperiods.

The nonspecific preparation that follows a warning stimulus (WS) to speed responding to an impending imperative stimulus (IS) is generally viewed as a strategic, intentional process. An alternative view holds that WS acts as a conditioned stimulus that unintentionally elicits a tendency to respond at the moment of IS presentation as a result of a process of trace conditioning. These views were contrasted as explanatory frameworks for classical effects on reaction time of the duration and intertrial variability of the foreperiod, the interval between WS and IS. It is shown that the conditioning view accounts for the available data at least as well as the strategic view. In addition, the results of 3 experiments provide support for the conditioning view by showing that unintentional contributions to nonspecific preparation can be dissociated from intentional contributions.

Adult↗

PubMed2005

The influence of training length on generalization of visual feature assemblies in honeybees.

Generalization is a fundamental cognitive ability that allows treating similar stimuli as equivalents, and thus responding to them in the same manner. Here, we show that after training free-flying bees with a single, constant pair of patterns made of four quadrants, each displaying different oriented gratings, bees extract the orientation information corresponding to each quadrant and integrate it in a generic layout that preserved the spatial relationship between oriented edges. Our results show that the amount of experience with the training patterns is critical to determine or not generalization to novel stimuli sharing the layout of the rewarded stimulus. Increasing experience results in higher generalization levels reflected in significant responding to novel stimuli. With ongoing training, redundant information seems to be eliminated and reduced to the minimum that is necessary and sufficient to solve the task. Controlling precisely the level of experience of individuals is therefore crucial in experiments on visual recognition.

Analysis of Variance↗

PubMed2006

Frequency of headache is related to sensitization: a population study.

Central sensitization is thought to play an important role in the chronification of tension-type headache and in the maintenance and exacerbation of the migraine attack. It has, however, almost exclusively been studied in highly selected patients from headache clinics. The aim of the present study was to evaluate pain perception in primary headaches in the general population. Stimulus-response functions for pressure versus pain, tenderness and pressure pain thresholds were studied in a random sample of 523 adults from the general population. All results were controlled for the effects of age and gender. The area under the stimulus-response function was increased in chronic- and frequent episodic tension-type headache compared with subjects without headache (p<0.001, p<0.001) and in chronic tension-type headache compared with migraine (p=0.01). Increasing slope (p<0.0001) and displacement towards lower pressures was found in the following order: no headache, migraine, frequent episodic tension-type headache, chronic tension-type headache. The displacement of the stimulus-response function was closely associated with frequency of headache. Finally, the stimulus-response function tended to be qualitatively altered in patients with frequent headache. The findings demonstrate, for the first time in a population-based study, a close relation between altered pain perception and chronification of headache, which most likely can be explained by central sensitization.

Adult↗

PubMed1996

Motor unit estimates obtained using the new "MUESA" method.

Motor unit number estimates were obtained from the extensor digitorum brevis and thenar muscles using a new method called MUESA. MUESA is distinguished from other estimation methods in the manner in which it deals with probabilistic motor unit activation, which is more commonly referred to as "alternation." Because of "alternation," incremental increases in the observed muscle potentials often cannot be interpreted in terms of the successive activation of single motor units. In the MUESA method, the nerve is subjected to a number of constant-intensity stimulus trains, and the resultant muscle response sequences are decomposed into their constituent motor unit action potentials. In general, if a stimulus train results in the probabilistic activation of n motor units, we can expect to see up to 2n different potentials, with each potential representing a unique combination of active and/or inactive motor units. If all 2n potentials are indeed observed, the decomposition of the observed potential sequence into its constituent motor unit action potentials is very straightforward. For the majority of the cases in which the number of observed potentials is not an integer power of 2, we have developed a novel decomposition method based on the analysis of the relative firing rates of the motor units.

Adolescent↗

PubMed1990

Potentiation of cocaine's discriminative effects by caffeine: a time-effect analysis.

The effects of caffeine upon the discriminative and rate-altering effects of cocaine were examined in rats. Using a food-reinforced two-lever operant procedure, 12 male Sprague-Dawley rats were trained to discriminate between 10 mg/kg cocaine and saline. Time-effect analysis of the training dose resulted in a median effective time interval (the duration of the discriminable effects of cocaine in producing 50% cocaine-appropriate responding), of 60.5 minutes postinjection. Caffeine partially generalized to the cocaine stimulus and, when administered with cocaine, produced a dose- and time-dependent increase in the percentage of drug-appropriate responding. Data are discussed with reference to our previous results with cocaine-caffeine interactions.

Animals↗

PubMed1991

Possible serotonergic and dopaminergic mediation of the N-ethyl-3,4-methylenedioxyamphetamine discriminative stimulus.

Eight male rats previously trained to discriminate 2.0 mg/kg N-ethyl-3,4-methylenedioxyamphetamine (MDE) from its vehicle in a two-lever, food motivated task were utilized to characterize the stimulus properties of MDE. The 5-HT receptor agonists 1-(m-trifluoromethylphenyl)piperazine (TFMPP), quipazine and 6-methoxy-1,2,3,4 tetrahydro-beta-carboline were able to generalize to the stimulus produced by MDE. However, the 5-HT receptor agonists m-chlorophenylpiperazine (mCPP), buspirone and norfenfluramine, the dopamine receptor agonist amphetamine, as well as the acetylcholine receptor agonist arecoline did not completely generalize. In addition, the simultaneous administration of norfenfluramine and amphetamine generalized to MDE. Pretreatment with the serotonin receptor antagonists cinanserin and metergoline or the dopamine receptor antagonist haloperidol failed to completely inhibit the discriminative stimulus produced by MDE. Multiple p-chlorophenylalanine (PCPA) pretreatments significantly reduced MDE discrimination, whereas vehicle discrimination was unaffected. Five days following cessation of PCPA pretreatment, MDE discrimination returned to criterion levels and remained at that level. These results suggest that the stimulus produced by MDE involve a complex interaction of various neurotransmitters, with both serotonergic and dopaminergic components.

3,4-Methylenedioxyamphetamine↗

PubMed2004

Focused analgesia and generalized relaxation produce differential hypnotic analgesia in response to ascending stimulus intensity.

This study was designed in order to examine the effects of different types of hypnotic suggestion on hypnotic analgesia. Generalized relaxation and focused analgesia were induced in seven high-hypnotizable (HH) and eight low-hypnotizable (LH) subjects. Subjects were not aware to which group they belonged. The two groups did not differ in their expectation rates to achieve analgesia under hypnosis. Pain intensity and unpleasantness were rated on visual analogue scales in response to painful electrical stimuli, delivered in random order in five ascending intensities. Both focused analgesia and generalized relaxation decreased pain intensity significantly (P < 0.01). However, stimulus-intensity response curves differed under the two hypnotic conditions. As stimulus intensity became higher pain reduction was enhanced under focused analgesia, while a constant reduction occurred under generalized relaxation. The interaction between hypnotic state and stimulus intensity was significant for focused analgesia (P < 0.05) but not for generalized relaxation (P > 0.07), difference became more pronounced when analyzed for HH subjects only (P < 0.002 for analgesia, P > 0.10 for relaxation). Pain reduction was significantly higher in HH than in LH subjects under focused analgesia (P < 0.02) but not under generalized relaxation (P > 0.5). We conclude that by utilizing two modes of hypnotic suggestions in response to ascending stimuli, we were able to discover two components of hypnotic analgesia. One shows a parallel shift in the stimulus-response function, has features similar to placebo and bears no clear relationship to hypnotic susceptibility. The other shows a slope change in the stimulus-response curve and has a positive relationship to hypnotic susceptibility.

Adult↗

PubMed1997

Generalization of D-, L- and DL-chlorpheniramine and zolantidine to the discriminative stimulus effects of cocaine and methamphetamine.

We recently demonstrated that some H-antagonists have cocaine or methamphetamine-like discriminative stimulus effects. In the present study, the effects of optical isomers of chlorpheniramine (D-, L- and DL-forms) on the discriminative stimulus effects of cocaine and methamphetamine were examined in rats trained to discriminate between cocaine (10.0 mg/kg) or methamphetamine (1.0 mg/kg) and saline, to determine whether these effects of H1-antagonists are mediated by the blockade of H-receptors. In generalization tests with optical isomers of chlorpheniramine, the D-, L- and DL-forms all completely generalized to the discriminative stimulus effects of cocaine, but did not generalize to those of methamphetamine. Dose-generalization by the optical isomers of chlorpheniramine to the discriminative stimulus effects of cocaine did not correlate with the H-antagonistic potency of these drugs. These results suggest that all of the optical isomers of chlorpheniramine have cocaine-like discriminative stimulus effects, but that these effects are not mediated by H1-receptor blockade. On the other hand, the H2-antagonist, zolantidine, generalized to the discriminative stimulus effects of methamphetamine, but not to those of cocaine, suggesting that zolantidine may have methamphetamine-like discriminative stimulus effects. In the present study, GBR12909 (dopamine uptake inhibitor) completely generalized to the discriminative stimulus effects of cocaine, but not to those of methamphetamine, whereas apomorphine (dopamine receptor agonist) generalized more potently to the discriminative stimulus effects of methamphetamine than to those of cocaine. These findings imply that although the dopaminergic system plays an important role in the discriminative stimulus effects of both cocaine and methamphetamine, there may be differences between their effects.

Animals↗

PubMed1979

Dark-adaptation in frog rods: changes in the stimulus-response function.

1. Aspartate-isolated photoresponses of the frog's rods to weak and strong flashes have been recorded during dark-adaptation after bleaching a fraction of rhodopsin (generally 4--30%). Stimulus--response functions were measured before the bleach and in the steady state after dark-adaptation. 2. The movements of the operating curve, i.e. the stimulus--response function plotted in a log-log diagram, are interpreted in terms of a model of outer segment adaptation, where the adaptation processes are associated with the transmitter release (Q-adaptation), the number of active sodium channels and leakage channels in the plasma membrane of the outer segment (M-adaptation), and the transmitter background (c1-adaptation). 3. A small bleach in a fully dark-adapted, non-bleached retina brings about a displacement of the operating curve predominantly to the right. The shift back to the left is approximately exponential, typical time constants being 6--12 min. 4. A strong exposure (bleaching 15--30% of rhodopsin) in a previously partially bleached retina brings about a nearly vertical displacement of the operating curve: after the bleach the maximum photoresponse is strongly reduced, and during intermediate adaptation the operating curve returns mainly upwards. 5. Cumulatively increasing permanent displacements of the operating curve are observed in the steady states after successive dark-adaptation transients. The permanent displacements are predominantly to the right and they increase with increasing temperature. 6. The experimental results, as interpreted according to the model, indicate that the Q-adaptation process is dominant in physiological conditions (small or moderate bleaches), whereas the M-adaptation becomes important only after rather large bleaches and especially after several successive bleaches in an isolated retina.

Animals↗

PubMed1988

Voiced calls evoked by hypothalamic stimulation in the cat.

Voiced vocalizations evoked by hypothalamic stimulation were studied in a series of six awake adult cats. Electrical stimulation was found to evoke vocalizations at numerous sites within the hypothalamus, ranging from A + 8 to A + 16. Regions showing the largest number of responsive sites were the preoptic region, the ventromedial area, the perifornical region, the lateral and the dorso-medial hypothalamus. The form of the evoked calls was generally similar to the spontaneous calls of the same animal. Call latency, duration, and intensity were not significantly affected by changes in stimulus intensity or duration but all three of these call parameters were significantly affected by changes in stimulus frequency. In general, call latency was longest at sites in the rostral hypothalamus and shortest at sites in the caudal hypothalamus. This study is the first to investigate systematically voiced call producing areas in the hypothalamus of awake cats and to document similarities between these calls and spontaneously produced voiced calls.

Animals↗

PubMed1997

Interactions between H1-antagonists and opioids: a drug discrimination study.

We previously demonstrated that combination of opioids, pentazocine and dihydrocodeine, with the histamine H1-receptor antagonists tripelennamine and chlorpheniramine could enhance their rewarding effects in rats. In the present study, the effects of combined treatment with opioids and H1-antagonists on discriminative stimulus effects were examined in rats trained to discriminate between cocaine (10 mg/kg) or morphine (3.0 mg/kg) and saline, since it is believed that discriminative stimulus effects of abused drugs are related to their rewarding effects. Tripelennamine and chlorpheniramine, but not pentazocine or dihydrocodeine, generalized to the discriminative stimulus effects of cocaine. Pentazocine (3.0 mg/kg) and dihydrocodeine (5.6 mg/kg) significantly potentiated the cocaine-like discriminative stimulus effects of low doses of tripelennamine and chlorpheniramine, respectively. On the other hand, pentazocine and dihydrocodeine, but not tripelennamine or chlorpheniramine, generalized to the discriminative stimulus effects of morphine. Neither 1.0 or 3.0 mg/kg tripelennamine nor chlorpheniramine affected the morphine-like discriminative stimulus effects of pentazocine and dihydrocodeine, respectively. These results suggest that the potentiation of the cocaine-like discriminative stimulus effects of H1-antagonists by opioids may be involved in the enhanced rewarding effects of combinations of opioids and H1-antagonists.

Analgesics, Opioid↗

PubMed1996

Training-to-testing intervals different from 24 h impair habituation in the crab Chasmagnathus.

A shadow moving overhead elicits an escape response in the crab Chasmagnathus that habituates promptly and for a long period. Experiments were done to test the effects of time of day (light-phase vs. dark-phase) on the acquisition and retention of the habituated response. The short-term habituation produced by the repetitive presentation of the stimulus does not differ between the two phases of the day though their reactivity during training seems to be higher during the dark phase than during the light, in agreement with the peak of circadian locomotor activity. The magnitude of the long-term habituated response, tested 24 or 72 h after training, does not appear to depend either on the time of day of training or on that of testing, but the retention is impaired when testing is conducted at a time of day that differs from that of the original training. Thus, results indicate a) that habituation of a response to a stimulus presented during the dark phase is not generalized to the same stimulus presented during the light phase, and vice versa; and b) that during training not only information regarding the target stimulus is stored but also information about the phase of the day.

Animals↗

PubMedDate not supplied

Spike correlation measures that eliminate stimulus effects in response to white noise.

When measured in response to non-repeating white noise, standard covariance measures of two neuronal spike trains contain components due simply to a shared stimulus. We argue that, without stimulus repeats, model-free measures cannot in general remove these stimulus-induced components. We present spike correlation measures that eliminate them when the neural response can be approximated by a linear-nonlinear system. One of these measures fully characterizes the correlations in the special case that all remaining correlations are due to small reciprocal connections between the neurons. In addition, we demonstrate that the proposed measures can give accurate results with a more realistic, integrate-and-fire model of neural response, provided that it is driven like a linear-nonlinear system.

Action Potentials↗

PubMed1983

Spinal motoneuronal excitability during wakefulness and non-REM sleep in hyperkinesis.

Variations in spinal motoneuronal excitability were assessed during wakefulness and non-REM sleep in hyperkinetic and normal children by determining the recovery cycle of the H-reflex following a conditioning stimulus. Reflex facilitation which generally occurs 100-300 msec after a conditioning stimulus was markedly reduced during sleep in both groups and during wakefulness as well in hyperkinetic subjects. Among possible mechanisms which might underlie the observed reductions in facilitation, emphasis is placed on decreased central excitability resulting from depressed fusimotor activity.

Attention Deficit Disorder with Hyperactivity↗

PubMed1992

Effects of methoxyflurane and flurothyl in mice trained to discriminate pentylenetetrazol from saline.

A procedure is described for training mice to discriminate 30mg/kg pentylenetetrazol (PTZ) from saline when lever pressing was maintained under a fixed-ratio 20 schedule of milk presentation. To define the pharmacological profile of the PTZ stimulus in mice, generalization testing was conducted with oxazepam and Ro 15-4513 (sarmazenil). Consistent with data obtained by others in rats, oxazepam (1mg/kg) blocked the PTZ stimulus whereas Ro 15-4513 substituted for PTZ, but only at a dose (2mg/kg) that also decreased rates of responding. The effects of both a depressant and excitatory vapor in this model were also determined. The volatile anesthetic methoxyflurane (1000-2000 ppm) blocked the discriminative stimulus effects of PTZ in a concentration-dependent manner, while the convulsant vapor flurothyl (900 ppm) produced greater than 90% PTZ-lever responding without disrupting rates of responding. The PTZ-like discriminative stimulus effects of flurothyl were dose-dependently blocked by oxazepam (0.03-1.0mg/kg). As has been shown in numerous previous studies in rats, PTZ could be established as a discriminative stimulus in mice. PTZ discrimination could be blocked by a benzodiazepine agonist and shares some properties with a benzodiazepine inverse agonist. Substitution and antagonism studies can also be performed with vapors, illustrating the utility of this model for comparing their behavioral effects to those of more widely studied drugs.

Journal Article↗