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At least 937 records · Page 52Linked to original sources
PubMed1993

D-amphetamine-like stimulus properties are produced by morphine injections into the ventral tegmental area but not into the nucleus accumbens.

We investigated whether injections of morphine into the ventral tegmental area (VTA) or the nucleus accumbens (NAS) could produce amphetamine-like stimulus properties and locomotor stimulant effects. Rats were trained to discriminate 1.0 mg/kg D-amphetamine from saline using both VI-30 and FR-16 reinforcement schedules and they were then tested following bilateral injections of morphine sulfate (2.5, 5.0 and 10.0 micrograms/side) either into the VTA or the NAS. Intra-VTA injections of morphine produced significant increases in amphetamine-lever responding that were comparable to increases observed following intra-NAS D-amphetamine (2.5, 5.0 and 10.0 micrograms/side). Such increases were not observed, however, following intra-NAS injections of morphine. Tests for the effects of intracerebral morphine and D-amphetamine on locomotor activity produced a similar pattern of results. Locomotor activity was increased following intra-VTA morphine and intra-NAS D-amphetamine injections, but not after intra-NAS morphine injections. Together, these findings indicate that activation of opioid receptors within the VTA, but not the NAS, can produce a behavioral state which mimics to some degree the state produced by systemic and intra-NAS injections of D-amphetamine.

Animals↗
PubMed2002

Ability of honeybee, Apis mellifera, to detect and discriminate odors of varieties of canola (Brassica rapa and Brassica napus) and snapdragon flowers (Antirrhinum majus).

Honeybees (Apis mellifera) use odors to identify and discriminate among flowers during foraging. This series of experiments examined the ability of bees to detect and discriminate among the floral odors of different varieties of two species of canola (Brassica rapa and Brassica napus) and also among three varieties of snapdragons (Antirhinnum majus). Individual worker honeybees were trained using a proboscis extension assay. The ability of bees to distinguish a floral odor from an air stimulus during training increased as the number of flowers used during training increased. Bees conditioned to the odor of one variety of flower were asked to discriminate it from the odors of other flowers in two different training assays. Bees were unable to discriminate among flowers at the level of variety in a randomized presentation of a reinforced floral odor and an unreinforced floral odor. In the second type of assay, bees were trained with one floral variety for 40 trials without reinforcement and then tested with the same variety or with other varieties and species. If a bee had been trained with a variety of canola, it was unable to differentiate the odor of one canola flower from the odor of other canola flowers, but it could differentiate canola from the odor of a snapdragon flower. Bees trained with the odor of snapdragon flowers readily differentiated the odor of one variety of a snapdragon from the odor of other varieties of snapdragons and also canola flowers. Our study suggests that both intensity and odor quality affect the ability of honeybees to differentiate among floral perfumes.

Animals↗
PubMed1996

Pharmacologic evaluation of the discriminative stimulus of metachlorophenylpiperazine.

A pharmacologic analysis of the discriminative stimulus of metachlorophenylpiperazine (mCPP) is reported. mCPP and m-trifluoromethylphenylpiperazine generalised, whereas 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole, 6-chloro-2-(1-piperazinyl)-pyrazine, and mesulergine partially generalised to the mCPP discriminative cue. However, although mianserin, methiothepin, ritanserin, mesulergine and N-(1-methyl-5'-indolyl)-N'-(3-pyridyl)urea hydrochloride (SB 200646) all antagonised the effect of 5-hydroxytryptamine (5-HT) on IP3 formation in the rat choroid plexus, they failed to antagonise the mCPP response in the drug discrimination studies. The 5-HT3 receptor antagonist MDL 72222 neither generalised nor antagonised the mCPP cue. These data suggest that neither the 5-HT1A, 5-HT1B, 5-HT1D, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT3, 5-HT5, 5-HT6, nor 5-HT7 receptors are involved. The response does appear to be mediated by a postsynaptic 5-HT receptor, however, because fenfluramine generalised to the cue. Haloperidol generalises, and amphetamine partially antagonises the mCPP discriminative cue and low doses of apomorphine partially generalises to the mCPP cue, which suggests that a decrease in dopamine neurotransmission may also be involved.

Amphetamine↗
PubMed2004

The role of context specificity in learning: the effects of training context on explosives detection in dogs.

Various experiments revealed that if an animal learns a stimulus-response-reinforcer relationship in one context and is then tested in another context there is usually a lessening of stimulus control, and the same discriminative stimuli that reliably controlled the behavior in the first context will have less effect in the new context. This reduction in performance is known as the "context shift effect." The effect of changing context on the probability of detecting explosives was investigated in seven highly trained explosives detection dogs (EDDs). In experiment 1 the dogs were trained alternately on path A, which always had five hidden explosives, and on a very similar path B, which never had any explosives. Within a few sessions the dogs showed a significant decrease in search behavior on path B, but not on path A. In experiment 2 the same dogs were trained only on path B with a target density of one explosive hidden every 4th day. The probability of the dogs now detecting the explosive was found to be significantly lower than in experiment 1. In experiment 3 the effect of the low target density as used in experiment 2 was investigated on a new but very similar path C. Both the detection probability for the one explosive every 4th day on the new path and the motivation to search were significantly higher than found in experiment 2. Finally, in experiment 4, an attempt was made to recondition the dogs to search on path B. Although trained for 12 daily sessions with one explosive hidden every session, the dogs failed to regain the normal levels of motivation they had shown on both new paths and on the paths that they knew usually contained explosives. The findings reveal that even a very intensively trained EDD will rapidly learn that a specific stretch of path does not contain explosives. The dog will then be less motivated to search and will miss newly placed targets. This learning is specific to the formerly always-clean path and is to some extent irreversible. However, the dog will search and detect normally on new paths even if they are very similar to the always-clean path. The data are discussed in terms of variables affecting renewal. The results suggest that following training designed to make a behavior "context independent," any extinction training will not generalize beyond that specific context used during the extinction training. In addition, if the behavior is extinguished in a specific context, it will be very difficult to restore that behavior in that context. These conclusions should be considered by anyone attempting to extinguish well-established trans-context behaviors.

Animals↗
PubMed2003

Stimulus and response representations underlying orthogonal stimulus-response compatibility effects.

One of the most important findings in recent years regarding response selection is that stimulus-response compatibility (SRC) effects occur for situations in which stimulus and response sets vary along orthogonal dimensions. For two-choice tasks, two types of orthogonal SRC effects are found: an overall advantage for the up-right/down-left mapping, and mapping preferences that vary as a function of position of the response apparatus and responding hand. We review evidence regarding the nature of both types of orthogonal SRC effects. Only asymmetric coding accounts have been proposed for the up-right/down-left advantage, and the evidence indicates that this asymmetry is a property of both verbal and spatial codes. Motoric and coding accounts, as well as a hybrid account based on end-state comfort, have been proposed for the second type of orthogonal SRC effect. In this case, the effects of response-apparatus position, hand, and hand posture conform more closely to predictions of the asymmetric coding accounts than to those of the motoric accounts. We also evaluate the mechanisms proposed by the alternative accounts in terms of related literature on the properties of spatial and verbal codes. Evidence indicates that spatial information is represented in categorical and coordinate codes, and both categorical spatial codes and verbal codes are asymmetric. Experiments on mental rotation suggest that it is unlikely that the direction of rotation is determined automatically by movement constraints, as the end-state comfort hypothesis suggests. An explanation in terms of salient features and referential coding can accommodate the range of orthogonal SRC effects.

Functional Laterality↗
PubMed1992

Drug discrimination studies in rats with caffeine and phenylpropanolamine administered separately and as mixtures.

The discriminative stimulus effects of mixtures of caffeine and phenylpropanolamine (PPA) have been investigated because these drugs have been abused together. Rats were trained to discriminate caffeine (20 mg/kg), PPA (20 mg/kg), or a mixture of both drugs, from saline in a two-bar operant conditioning procedure with food reinforcers presented on a tandem VI-FR schedule. Discriminations of mixture, caffeine alone and PPA alone were 90% accurate after 40 sessions. Generalisation to both PPA and caffeine was weak (25-47%) at the doses used in the training mixture, although there was almost complete generalisation to larger doses of PPA. Under these conditions, there was a possible synergistic interaction between caffeine and PPA because the discriminative effect of the mixture could not be fully explained by the combined effects of its component drugs. However, in rats trained on caffeine, PPA had no effect on the dose-response relationship for caffeine; similarly, in rats trained on PPA, caffeine had no effect on the dose-response relationship for PPA (no synergism or antagonism). Generalisation to (+)-amphetamine and cocaine was weakest in rats trained on caffeine, was partial in rats trained on the mixture, and was complete in rats trained on PPA; thus, the mixture of caffeine and PPA was not more like cocaine or amphetamine than PPA alone. The results are in agreement with reports that caffeine and PPA may interact in a complex manner, but do not support the view that the interaction enhances their resemblance to highly abused stimulants such as amphetamine and cocaine.

Animals↗
PubMed1975

The ontogeny of auditory frequency generalization in the chicken.

To determine if there is an ontogenetic change in stimulus coding, chickens between the day of hatching and 9-10 days old were tested using a habituation-generalization paradigm. Experiment 1 indicated that 1 day-old and 3--4-day-old chicks show similar habituation of an eye-opening response to auditory stimuli in the 800--1,200-Hz range. In Experiment 2 the eye-opening response to a 1,000-Hz stimulus was habituated and then immediately tested using stimuli which varied between 800 and 1,200 Hz. Each age-group (1 day, 3--4 days, and 9--10 days) showed a symmetrical stimulus generalization gradient around the 1,000-Hz stimulus and the 1-day-old chicks displayed a reliably flatter gradient than either of the older groups, which did not differ. In a third experiment, the position of the gradients relative to the baseline was shifted without altering the relative shapes. These results allow general arousal, general auditory responsiveness, overall error rate, and metric characteristics of the independent and dependent variables to be eliminated as possible sources of the age differences in gradient shape. The changes in stimulus generalization, therefore, support the view that during normal development there is a sharpening of perceptual coding processes.

Acoustic Stimulation↗
PubMed1979

Hereditary myoclonus and progressive distal muscular atrophy.

Myoclonus occurs in a variety of pathological conditions, some inherited. We recently evaluated 3 members of a Louisiana-Texas family with an autosomal dominant disorder manifested by adult-onset, generalized, stimulus-sensitive myoclonus and slowly progressive distal muscle weakness and wasting. The analyses of cerebrospinal fluid homovanillic acid and 5-hydroxyindoleacetic acid before and after probenecid provided some evidence of impaired turnover of central dopamine and serotonin. Treatment with clonazepam resulted in complete and lasting improvement of the myoclonus. A postmortem examination in 1 member of the family revealed chiefly neuronal degeneration of the anterior horn cells, Clark's nucleus, and the lower cranial nerve nuclei. A similar syndrome has not previously been reported.

Adult↗
PubMed1980

Topographic organization of the orientation column system in the striate cortex of the tree shrew (Tupaia glis). I. Microelectrode recording.

Microelectrode recordings were made in the binocular portion of the tree shrew striate cortex to determine how orientation selective cells are distributed topographically in area 17 of this species. Seventy-five percent of the cells sampled were activated well by elongated visual stimuli and were quite selective for stimulus orientation. Ninety-five percent of the orientation-selective cells had orientation tuning ranges (Wilson and Sherman, '76) between +/- 5 degrees and +/- 40 degrees from their optimal orientation. Orientation-selective cells with the same or similar optimal orientations were distributed in cortex in a columnar manner (Hubel and Wiesel, '62), as determined from electrode penetrations nearly normal to the cortical surface. Penetrations parallel to the cortical surface revealed a highly ordered representation of optimal stimulus orientation, generally characterized by sequential changes in optimal orientation with electrode movement across the striate cortex. In addition, relatively consistent differences were observed in the rates and patterns of orientation shift on these penetrations depending on the direction of electrode movement across the cortex. Penetrations parallel to the 17--18 border yielded moderate-to-high rates of orientation change (mean slope = 434 degrees/mm), with the changes generally progressing through a complete clockwise or counterclockwise cycle of 180 degrees or more before a major reversal in the direction of orientation shift was encountered. In contrast, penetrations perpendicular to the border yielded low-to-moderate slopes (mean slope = 239 degrees/mm). On these penetrations a more limited range of optimal orientations (< 180 degrees) was usually encountered, due to frequent reversals in the direction of orientation shift. Also, extended regions (100--200) micrometers long) of constant optimal orientation were observed in these penetrations. The different patterns of orientation change found on these orthogonal penetrations across the striate cortex indicate that the orientation column system in this species is anisotropically organized with respect to the 17--18 border. Further, the regions of constant optimal orientation frequently encountered on penetrations perpendicular to the 17--18 border suggest that the anisotropy is subserved by a system of elongated zones of iso-orientation arranged approximately perpendicular to the 17--18 border.

Animals↗
PubMed1982

Generalization after form discrimination in light-reared and dark-reared rats.

In 2 experiments the performance of 90- and 150-day-old light-reared and dark-reared rats was compared under appetitive reinforcement conditions on rigorous tests of form discriminative abilities. Although early stimulatory history had little impact on either the ability to discriminate shapes on the basis of contour orientation or to generalize from that initial experience to lines in other orientations lack of visual experience did have significant consequences with respect to a comparable task in which the relationship between lines was the significant feature. Little change in the initial deficits was observed with exposure to a normal light environment for 60 days following the period of early visual deprivation in the case of this 2nd complex pattern discrimination task.

Animals↗
PubMed1993

Increasing the naming speed of poor readers: representations formed across repetitions.

In three experiments we examined the effect of repetition practice on the acquisition, retention, and generalization of children's skill in rapidly naming visually presented words. Experiment 1 showed that naming times decrease rapidly with practice. Retention of this newly acquired skill in rapid naming was a function of the degree of learning during training. "Overlearning" was necessary to prevent forgetting of the skill. Experiment 2 indicated that the rate at which the naming gains were acquired, and the amount of forgetting, was unrelated to the specific orthographic to phonological correspondences among the trained words. Experiment 3 suggested that even when the spelling/sound regularities were used to facilitate learning, there was no generalization of the naming time skill to new words that share the same spelling/sound relations. The results were discussed in terms of the nature of the representation that underlies rapid naming.

Child↗
PubMed1993

Feature-based versus exemplar-based strategies in preschoolers' category learning.

Five experiments examined whether preschool children learn categories by formulating a categorization rule based on attention to one or two features, or by memorizing the category assignment for whole exemplars. Using fictitious animals as stimuli, children were taught a two-category discrimination at the basic level and were tested for their category learning using a procedure that required them to categorize from memory, rather than perform perceptual matching. Transfer stimuli manipulated the retention of features encountered in the training instances, and children were instructed to classify only the items about whose category membership they were certain. By measuring the extent of generalization, in addition to categorization accuracy, it was possible to assess whether children were applying a feature-based rule in making their categorization decisions. The studies found little evidence that children were employing rules. Analyses of the individual response patterns identified few children who categorized by attending to a single attribute such as shape, or else who used a two-feature disjunctive rule. In addition, a recognition memory test given after category gaining produced strong evidence that children had encoded the training examples as wholes, rather than focusing on individual features. Despite clear evidence that children had encoded the training examples, however, examplar information was not used successfully in categorization when subjects were trained on only a single instance per category. The implication of these results for theories of early categorization are discussed.

Attention↗
PubMed2001

Temporal generalization in 3- to 8-year-old children.

Children aged 3, 5, and 8 years were tested on temporal generalization with visual stimuli. Different groups received 4- and 8-s standards. Gradients at all ages superimposed when plotted on the same relative scale, indicating underlying scalar timing. The principal developmental changes were (i) increasing sharpness of the generalization gradient with increasing age and (ii) a change from symmetrical (3 and 5 years) to adultlike asymmetrical generalization gradients in the oldest children. Theoretical modeling attributed these changes to increasing precision of the reference memory of the standard with increasing age, as well as a decreased tendency to "misremember" the standard as being shorter than it actually was, as the children developed.

Child↗
PubMed1996

Parametric features of habituation of swim cycle number in the marine mollusc tritonia diomedea.

When repeatedly elicited, the oscillatory escape swim of the marine mollusc Tritonia diomedea undergoes habituation of the number of cycles per swim. Because the neural circuit for this behavior is reasonably well understood, a cellular analyses of habituation in Tritonia is feasible. Since such a study must ultimately relate cellular correlates to behavioral modifications, we have sought to increase our understanding of the parametric features of cycle number habituation in Tritonia. Habituation was compared when using different intertrial intervals, repeated training sessions, and different stimulus locations. Stimulus site generalization of habituation was demonstrated, suggesting that at least one site of plasticity underlying habitation is located postsynaptic to the sensory neurons for the response. Dishabituation from an above-zero baseline response level was not obtained. An isolated brain preparation was tested as a potential simplified system for cellular studies of habituation mechanisms. Repeated stimulation of a nerve containing sensory afferent processes resulted in a progressive reduction of swim motor program cycle number, with a rate similar to that seen in the behavior. Together, these findings: (1) establish a set of parametric features of cycle numbers habituation to be explained by physiological studies; (2) suggest that at least one circuit modification underlying the habituation is located among the circuit interneurons; and (3) indicate that the isolated brain preparation may serve as a useful neural analogue for studies of the cellular mechanisms of cycle number habituation in Tritonia.

Animals↗