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At least 721 records · Page 40Linked to original sources
PubMed1990

Generalized reflex myoclonus in a patient with alcohol-sensitive spontaneous myoclonus and an abnormal gait.

A patient with alcohol-sensitive spontaneous, action- and stimulus-sensitive generalized reflex myoclonus is reported. Gait was abnormal but could not be clearly classified as dystonic. No other neurological abnormality was present. The possible relationship between alcohol-sensitive myoclonic dystonia and this case is discussed. Reflex myoclonus may serve as an additional clinical marker in the study of families with alcohol-sensitive myoclonus, dystonia, or both.

Adult↗
PubMed1978

Generalization study with some narcotic and nonnarcotic drugs in rats trained for morphine-saline discrimination.

Rats were trained to lever-press on an FR-10 schedule for food reinforcement, and to respond differentially on two levers while discriminating the effects of morphine (10 mg/kg) injection from those of saline (1 ml/kg). Following discrimination training, the morphine stimulus was generalized to propoxyphene, methadone, fentanyl, and sulfentanyl in a dose-dependent manner, and saline was generalized to alcohol, pentobarbital, azaperone, clonidine, naloxone, and p-chloroamphetamine. p-Chloroamphetamine failed to block the morphine stimulus.

Animals↗
PubMed1993

Directional sensitivity of tuberous electroreceptors: polarity preferences and frequency tuning.

This paper examines the directionality of tuberous electroreceptor responses and relates them to a polarity bias seen for passive electrolocation by electric fish (Hypopomus). We recorded from Burst Duration Coders (BDCs) while stimulating with 1 kHz single period sine waves with electric fields oriented horizontally in different directions. Electroreceptors have figure-8 directional sensitivity profiles with two, usually unequal lobes of sensitivity separated by 180 degrees. For most units the larger lobe points inward, while for a few, the lobes are symmetrical or the larger lobe points outward. The differences correlate with differences in frequency tuning of the receptors. We can alter, and even reverse, the directional asymmetry of a single unit by changing the frequency of the stimulus. Two general response profiles results, with two corresponding classes of tuning curves. The degree of asymmetries and the effects of stimulus frequency and of tuning can be modeled with a linear/non-linear/linear cascade filter. The behavioral preference for approaching the head end (+) of an electrode is difficult to understand in light of the asymmetry of responses we report for amplitude-coding BDCs but can be understood by reference to the time-coding Pulse Marker (PM) receptors.

Animals↗
PubMed1976

Fixed versus variable sequences of food and stimulus presentation in second-order schedules.

Three pigeons were exposed to a second-order schedule in which the behavior specified by a fixed-interval component schedule was reinforced according to a ratio overall schedule. The completion of components not followed by food was signalled by a brief stimulus never paired with food. Food and the stimulus occurred in a random sequence or in fixed alternation, but the overall schedules (variable ratio 2 or fixed ratio 2) ensured that an equal number of food and brief-stimulus presentations occurred in each session. The control exerted by the food and by the brief stimulus was measured by overall response rates, mean pauses, frequency distributions of pauses, and response patterning across components. In general, the stimulus controlled patterns of behavior more similar to those controlled by food when food and the stimulus occurred in a random sequence than when they occurred in fixed alternation.

Journal Article↗
PubMed1982

Acquisition and maintenance of autoshaped key pecking as a function of food stimulus and key stimulus similarity.

The results of a number of recent studies suggest that acquisitions of autoshaped key pecking in pigeons is affected by the similarity of the grain-hopper stimulus and response-key stimulus. In Experiment 1 this hypothesis was tested by training independent groups of pigeons to key peck under six different hopper-stimulus and key-stimulus similarity conditions, and three procedures containing either immediate reinforcement, variable delay of reinforcement, or omission of reinforcement for key pecking. Number of trials to acquisition was found to be related to the similarity variable. Maintained responding was affected by the response-reinforcer contingency. This effect was found both within and between subjects. Under two of the contingencies (automaintenance and omission), maintained responding continued to be affected by the similarity of the hopper stimulus and key stimulus. In Experiment 2 pigeons were given omission training with a hopper light on or off. Both acquisition and maintenance of key pecking were facilitated by the presence of the hopper light. The present findings suggest that much of the responding reported in various automatic shaping and training procedures may reflect the effects of key stimulus/food stimulus similarity.

Animals↗
PubMed1981

Associations to contextual stimuli as a determinant of long-term habituation.

A series of experiments was performed to determine whether long-term habituation of the acoustic startle response in rats is mediated by conditioned associations between contextual cues and the test stimulus. Experiment 1 established parameters yielding demonstrable long-term habituation of the startle response. Experiment 2 attempted to overshadow the hypothesized associations to contextual cues by providing a more reliable predictor of the acoustic stimulus. Experiment 3 investigated the effect of changes in contextual cues on long-term habituation. Experiment 4 provided treatments designed to extinguish the hypothesized associations between the context and the habituated stimulus. Experiment 5 sought latent inhibition of the hypothesized association between the contextual cues and the acoustic stimulus. The results of these experiments uniformly failed to support an associative model of long-term habituation of the startle response, but they are consistent with a nonassociative model emphasizing habituation to the entire experimental situation rather than exclusively to the iterated stimulus.

Animals↗
PubMed1988

Rapid discrimination of the stimulus properties of 5-hydroxytryptamine agonists using conditioned taste aversion.

Separate groups of rats were trained to discriminate the stimulus properties of selective agonists at 5-HT receptors using a conditioned taste aversion procedure. Fluid-restricted rats were injected with drug or saline and then given access to a 0.25% saccharin solution for 30 min. When rats received a drug trial, saccharin consumption was followed by an injection of LiCl (1.8 mEq/kg i.p.), whereas on saline trials saccharin consumption was followed by a second injection of saline instead of LiCl. Rats were trained using injections of either 8-hydroxy-2-(di-n-propylamino)tetralin (0.4 mg/kg i.p.), an agonist selective for the 5-HT1A receptor, or 1-(m-trifluoromethylphenyl)piperazine (0.8 mg/kg i.p.), an agonist selective for 5-HT1B and 5-HT1C receptors, as the drug stimuli. Acquisition of the discriminated taste aversion, as measured by the differential effects on saccharin drinking between drug and saline trials, required only two to three pairings of either drug stimulus with LiCl injections. The 8-hydroxy-2-(di-n-propylamino)tetralin discriminative stimulus cue generalized to other drugs that are selective for the 5-HT1A receptor, such as ipsapirone (8-16 mg/kg i.p.) or buspirone (4 mg/kg i.p.), but not to agonists that are selective for the 5-HT1B/1C receptor, such as 1-(m-trifluoromethylphenyl)piperazine or 1-(m-chlorophenyl)piperazine. The discriminative stimulus properties of 1-(m-trifluoromethylphenyl)piperazine generalized to 1-(m-chlorophenyl)piperazine (0.2-0.8 mg/kg i.p.) but not to the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (0.4 mg/kg i.p.).(ABSTRACT TRUNCATED AT 250 WORDS)

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Facilitating prelinguistic communication skills in young children with developmental delay.

Very little research has focused on the development and evaluation of intervention strategies designed to facilitate the acquisition of prelinguistic communication skills. We conducted two experiments to determine the effects of a milieu teaching approach on the acquisition and generalization of specific prelinguistic communication skills. In the first experiment, we utilized this intervention approach within a multiple baseline design to teach prelinguistic requesting, commenting, and vocal imitation to a single subject with Down syndrome and language delay. The results indicated that the intervention approach was effective at facilitating the child's use of these skills within the treatment setting. Therefore, in the second experiment we conducted a more comprehensive analysis of this approach with 4 subjects with mental retardation. Three of these subjects were taught to request, and 1 subject was taught both to request and to comment. The effects were experimentally evaluated with multiple baseline across subjects design. The results indicated that the intervention was effective in eliciting the intervention targets within the training setting for all 4 subjects. All 4 subjects showed evidence of generalization across stimulus materials, setting, teachers, and interaction style. There was also evidence of reciprocal effects on how classroom teachers in the generalization setting interacted with the subjects as a result of changes in the child's communication behavior.

Child, Preschool↗
PubMed2005

Gender differences in response to lorazepam in a human drug discrimination study.

Gender differences in the discriminative stimulus properties of drugs of abuse have sometimes been reported, although we have previously found no differences in subjective or discriminative responses in human subjects acquiring an alcohol discrimination. The aim of the present work was to determine if there were gender differences in the effects of lorazepam, a benzodiazepine-receptor agonist which substituted for the alcohol stimulus in trained social drinkers. Volunteers who had already acquired an alcohol (0.2g/kg) placebo discrimination were administered (double-blind) either placebo (nine females, nine males) or lorazepam 2mg (six females, six males). They then sampled a series of five drinks and rated each one for likeness to the training stimulus (the generalization response). In addition they completed rating scales for subjective effects and the Digit Symbol Substitution Test (DSST). Lorazepam substituted for the alcohol stimulus equally in both sexes and increased associated scores for lightheadedness. Females however, showed a much greater DSST performance impairment following lorazepam, compared with males. This effect was independent of body weight differences and sedation. These results are discussed in the light of current knowledge of gender differences in response to drugs of abuse and suggest that the stimulus and cognitive effects of benzodiazepine-receptor agonists are modulated by different brain mechanisms.

Adolescent↗
PubMed1995

The nucleus accumbens in monkeys (Macaca fascicularis). III. Reversal learning.

The nucleus accumbens (NA), which receives inputs from limbic structures and projects to the motor system, may be important for the association of reinforcement with action. There are projections to the NA from the amygdala and hippocampus. Discrimination and reversal learning tasks which are known to be disrupted by lesions to these areas in monkeys were given to monkeys with lesions of the NA. Twelve monkeys (Macaca fascicularis) were used in the present study. Six of these received ibotenic acid lesions which resulted in considerable cell loss in the NA; the remaining six acted as controls. The first group of six monkeys were taught a visual discrimination task pre-operatively. Post-operatively, these monkeys were tested on visual and spatial discrimination and reversal tasks. A second group of six monkeys were tested on a motor reversal task. The results indicate that ibotenic acid lesions of the NA transiently impair spatial but not visual reversal learning in monkeys. The NA lesions did not impair a monkey's ability to perform visual or spatial discriminations, or the ability to perform the motor learning or motor reversal tasks. Our results suggest that bilateral lesions of the NA in monkeys do not disrupt the ability to discriminate basic properties of reward-related stimuli or the formation of visual stimulus-reward associations. In addition, our results argue against theories which suggest that the NA is important for behavioural switching or general behavioural flexibility. We conclude that the NA may play a more specific role in the association of temporal and spatial cues with movement and reward.

Animals↗
PubMed1984

Stimulus control and associative learning.

Interest in operant research on stimulus control has declined at the same time that much interest has burgeoned in nonoperant areas. Several examples of this shift toward traditional learning theory are considered, all of which have sponsored theoretical approaches that attempt to characterize the underlying associative units. These theoretical approaches are defended on the grounds that they have generated a deeper understanding of a variety of often puzzling phenomena. My projection is that future research will be determined even more strongly by theories about the structure of associations. Particular issues for which such discussion will have major impact include (1) whether conditional stimulus control is qualitatively different than simpler forms of stimulus control, (2) whether stimulus control is organized hierarchically, and (3) the origin of categories of stimulus equivalence.

Animals↗
PubMed1996

Brainstem encephalopathy with stimulus-sensitive myoclonus leading to respiratory arrest, but with recovery: a description of two cases and review of the literature.

Two unrelated patients developed bulbar symptoms, followed within several weeks by spontaneous myoclonus and painful, generalized, stimulus-sensitive jerks triggered by unexpected noises and cutaneous stimuli. They progressed to respiratory arrest and required mechanical ventilation, but both patients subsequently made an almost full recovery. These cases stress the importance of persevering with supportive treatment despite rapid progression of this severe generalized movement disorder. The relationship of brainstem reflex myoclonus to hyperekplexia, progressive encephalomyelitis with rigidity, and the stiff-man syndrome is discussed.

Adult↗