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PubMed1985

Motivation in childhood autism: can they or won't they?

Research in the area of motivation in autistic and other children suggests that autistic children may be capable of performing at a higher level than they typically function. This article describes research in the area of 'learned helplessness' which suggests that autistic children's handicaps may expose them to frequent failure and to an unusual level of non-contingent reinforcement which may produce a 'learned helplessness' state of extremely low motivation, with a consequent abnormally low overall functioning level. The present article also discusses research on strategies which might be employed to improve autistic children's exposure to favourable response-reinforcer contingencies. This would be expected to improve the general level of motivation in such children, with related gains in the acquisition, generalization maintenance of a broad array of target behaviours.

Autistic Disorder↗
PubMed1964

NOTE OF CHANGES IN RESPONSE LATENCY FOLLOWING DISCRIMINATION TRAINING IN THE MONKEY.

Two monkeys were trained to press and hold down a telegraph key in the presence of a red light. Subsequent release of the key in response to a white cross superimposed on the red background was followed by reinforcement. Key release in response to a white circle on the red background was never reinforced. Latencies for the key release response to the reinforced stimulus (cross) were considerably shorter and less variable than those to the unreinforced stimulus (circle).

Animals↗
PubMed2004

Extinction deficit and fear reinstatement after electrical stimulation of the amygdala: implications for kindling-associated fear and anxiety.

Generalized seizures produced by electrical kindling of the amygdala in laboratory rats are a widely used animal model of temporal lobe epilepsy. In addition to seizure evolution amygdala kindling enhances emotionality. The relative roles of electrical stimulation and seizure induction in fear responding are unclear. Here we investigate this issue using extinction and reinstatement of fear-potentiated startle. After classical conditioning (light+footshock pairings) laboratory rats were fear extinguished with each light presentation followed by nonepileptogenic amygdala stimulation. In contrast to the normal extinction learning of control subjects, amygdala stimulated animals exhibited conditioned fear after 120 presentations of the nonreinforced conditioned stimulus (CS). In a second experiment electrical stimulation of the amygdala restored extinguished fear responding and the fear reinstatement was specific to extinction context. The reinstatement effect did not involve sensitized fear to the CS produced by amygdala stimulation. The possibility that electrical activation of the amygdala produces unconditioned fear was considered. Animals uniformly failed to demonstrate fear-potentiated startle using electrical stimulation of the amygdala as the unconditioned stimulus. This was the case with a subthreshold afterdischarge stimulus and a stimulation schedule that produced kindled seizures. The extinction deficit and fear reinstatement results were interpreted to suggest that amygdala stimulation activates acquired excitatory stimulus-affect neural connections formed during Pavlovian fear conditioning. Our data supports a model in which excitation of an amygdala-based memory-retrieval system reinforces the expression of learned fear behaviors.

Acoustic Stimulation↗
PubMed1992

Behavioural and neurohistological changes in aging Sepia.

The life cycle of the cuttlefish in the English Channel is characterized by a succession of homogeneous population cohorts. These conditions provide an excellent opportunity for the study of aging in this cephalopod. In a first longitudinal study, we considered the oldest animals and compared their success rates at the first capture attempt. During the first weeks of the study, the results remained constant and then, during the weeks immediately preceding the natural death, a dramatic drop was observed. This deterioration may be due to defects of visuomotor coordination. In a second study, we used an associative learning protocol with negative reinforcement and the performances of young and old animals were compared. The most striking results showed that the performances of the oldest animals during the retention test were very mediocre. Such results suggest that the long-term memory process is affected. Finally, a modification of the Fink-Heimer silver stain enabled us to draw a map of spontaneous terminal degeneration in the central nervous system of the oldest animals. The structures which are characterized by the presence of multimodal inputs (the spine of the peduncle lobe and the basal lobes) present the most obvious signs of degeneration.

Aging↗
PubMedDate not supplied

Is dopamine important in nicotine dependence?

Nicotine, like other drugs when abused, can produce a wide array of behaviours, some of which collectively propel 'drug-seeking behaviour'. This review focuses on three stimulus properties of nicotine and examines the role of dopamine in mediating each effect with respect to D1 and D2 receptor subtypes. Dopamine appears to be critical in mediating the reinforcing effects of nicotine, which is in line with other commonly abused psychomotor stimulants. However, evidence derived from studies with local microinjections of nicotine suggests that the origin of nicotine action to produce its other stimulus properties may be via multiple neuroanatomical substrates. The aversive stimulus effects are resistant to dopamine receptor antagonists. The discriminative stimulus effects of nicotine, despite showing some modification with dopaminergic compounds, appear not to be solely mediated via the mesolimbic dopamine system. Taken together, the neurobiology of nicotine dependence remains complex. Nonetheless, such dissociation between stimulus properties may permit the development of more effective therapies in combating tobacco dependence.

Animals↗
PubMed1986

Response patterning in goldfish: single alternation in a Pavlovian aversive paradigm.

Single alternation behavior was studied in a Pavlovian aversive shuttle-response situation using goldfish. Independent groups of fish were given either a fixed interval between alternating reinforced (R) and nonreinforced (N) trials or were given differential temporal information between trials. Although all groups exhibited higher response probabilities on reinforced than on nonreinforced trials, goldfish receiving a short interval (10 s) following R trials and a long interval (60 s) following N trials (R10N60) demonstrated significantly superior alternation performance compared with subjects receiving a fixed intertrial interval (R35N35) or a long interval following R trials and a short interval following N trials (R60N10). The alternation performance exhibited by the R10N60 group was shown to be equivalent to that of subjects receiving standard color discrimination training. However, the alternation performance in group R35N35 showed a great deal of within-subject variability and raises questions concerning the elusive nature of alternation using Pavlovian conditioning procedures.

Animals↗
PubMed1979

ACTH self-administration in rats.

The ability of rats to learn a lever pressing response reinforced by a contingent intravenous delivery of ACTH 1--24 and 4--10, was investigated. About 60% of the rats tested learned to press the lever for the two analogues that were infused at a rate of 2.08 microgram per second via a chronically implanted intrajugular catheter. Most of the animals exhibited sustained daily self-injections of 250 to 375 microgram of ACTH 1--24 and more variable amounts of ACTH 4--10. Comparisons with the self-administration of saline and altered responses following a change in the concentration of ACTH 1--24 solution indicated a positively reinforcing effect for the neuropeptide. The self-administration of the ACTH 4--10 analogue demonstrates that this reinforcing property of ACTH is not due to its adrenal stimulating activity. Brain targets possibly involved in the self-administration of ACTH are discussed.

Adrenocorticotropic Hormone↗
PubMed1994

Duration comparison: relative stimulus differences stimulus age, and stimulus predictiveness.

Under a psychophysical trials procedure, pigeons were presented with a red light of one duration followed by a green light of a second duration. Eight geometrically spaced base durations were paired with one of four shorter and four longer durations as the alternate member of a duration pair, with different pairs randomly intermixed. One choice was reinforced if red had lasted longer than green, and a second choice was reinforced if green had lasted longer. Performance was compared when all the base durations and their pair members were included (entire-range condition) or when only the four longest base durations and their comparison durations (restricted-range condition) were used. Discrimination sensitivity decreased for longer duration pairs under both conditions, supporting a memory-based account. Sensitivity was lower under the restricted-range condition. Under both conditions, a bias to report "green as longer" increased as the second green duration increased. Bias changed as a matching function of the green-duration predictiveness of the correct choice. The results are related to a quantitative model of timing and remembering proposed by Staddon.

Animals↗
PubMed1986

Transplants of purified astrocytes promote behavioral recovery after frontal cortex ablation.

Ablation of the medial frontal cortex produces a learning deficit on a reinforced alternation task. Recovery from this deficit was significantly accelerated in rats by transplantation of either cultured purified astrocytes or Gelfoam that had remained the previous 5 days in a brain wound in another animal (wound-Gelfoam). Cell-free extracts of wound-Gelfoam did not enhance behavioral recovery. Embryonic frontal cortex was effective only if transplanted with a delay after ablation. It appears from these results that transplants can facilitate functional recovery by more than one mechanism, including promotion of survival and reactive synaptogenesis of host neurons, stabilization of the damaged environment and replacement of lost neurons. In this study, glial cells were capable of facilitating recovery from central nervous system damage to the same extent as neuronal transplants.

Animals↗
PubMed1983

Bisection of temporal intervals by pigeons.

Two experiments investigated temporal bisection in pigeons using a procedure similar to that of Stubbs (1976). This procedure measures the point in time at which the bird switches from the shorter to the longer valued of two fixed-interval reinforcement schedules with a common starting point. The first experiment substantiated previous findings of switching at the geometric mean of the two interval values and strengthened identification of this switching with bisection by eliminating the possibility that the birds simply switched to the longer interval when the shorter one was perceived to have expired. The experiment also extended the range of values for which temporal intervals have been found to be bisected at their geometric mean. A second experiment demonstrated that the usefulness of the present procedure for determining temporal bisection points is limited to cases in which the longer interval is no more than four times the duration of the shorter interval. Greater separation of the two interval durations produced a period of nonresponding during which the location of the switching or bisection point was totally ambiguous.

Animals↗
PubMed1994

On the relationship between differential outcomes and differential sample responding in matching-to-sample.

Four experiments examined control over choice by differential sample responding in matching-to-sample with differential outcomes. In Experiment 1, pigeons initially learned to match with food versus no-food outcomes. Their performances later transferred to other samples to which responding versus not responding had been explicitly reinforced with a single outcome (food). In Experiment 2, pigeons initially learned to produce the comparisons by pecking one sample but not the other. Transfer was then observed to new samples associated with food versus no food (and thus often vs. seldomly pecked). Experiments 3 and 4 showed that transfer of matching required differential behavior to each sample set and did not depend on explicit conditioning of that behavior prior to acquisition. Together, these results show that differential sample behaviour provides a redundant cue for choice in differential outcome matching-to-sample.

Animals↗
PubMed1964

ESCAPE FROM SD ASSOCIATED WITH FIXED-RATIO REINFORCEMENT.

Throughout ascending and descending fixed-ratio (FR) sequences, rats were allowed to terminate the FR stimulus control by pressing a time-out (TO) lever. To minimize chance or accidental responses on this second lever, three presses were required to produce the 30-sec S(Delta) period. As FR performance became more "strained," there was an increased predisposition to escape from the time-in stimulus complex. The generality of this finding was extended by obtaining recoverability (independent of the direction of stimulus change) of the FR-TO function in the descending series. Typically, escapes were produced only during the post-reinforcement pause; however, under a mixed FR FR schedule, their occurrence shifted to a point within the inter-reinforcement interval corresponding to the unreinforced completion of the lower ratio component. It appears that the point where the rat can discriminate the size of the ratio requirement will be the place where TOs are imposed. This inference was supported by a substantial increase in TO frequency accompanying a shift from CRF to extinction on the FR lever. Finally, the escape lever was placed on a progressively increasing FR schedule and later extinguished to demonstrate that the TO condition was in fact reinforcing.

Avoidance Learning↗
PubMed1997

Presession noise increases sensitivity to chlordiazepoxide's discriminative stimulus in pigeons.

1. Pigeons were trained to discriminate chlordiazepoxide (CDP) from saline using two-key food reinforced drug discrimination procedures. Discriminative control by CDP was maintained despite extended training with vehicle-like doses of CDP, by using a modified "fading" procedure that provided for a mixture of drug discrimination training sessions preceded by an i.m. injection of either 8.0 mg/kg CDP, or a lower training dose of CDP (4.0, 2.8, 2.0, 1.4, 1.0, 0.7, or 0.5 mg/kg CDP), or saline. The lower training dose was decreased across blocks of sessions. 2. Four lower training doses (1.4, 1.0, 0.7, and 0.5 mg/kg CDP) were retrained, with 10 min of 98 dB of noise administered 75 min prior to each drug discrimination training session. Presession exposure to noise increased percent CDP-appropriate choices for each of the four lower training doses by 15-20% over those obtained previously. 3. It is concluded that brief presession exposure to loud noise increases sensitivity to the discriminative stimulus effects of low training doses of CDP.

Animals↗
PubMed1998

Applying learning theory to the management of the horse: the difference between getting it right and getting it wrong.

Horses constantly modify their behaviour as a result of experience. This involves the creation of an association between events or stimuli. The influence of people on the modification and generation of certain behaviour patterns extends beyond the intentional training of the horse. The impact of any action depends on how it is perceived by the horse, rather than the motive of the handler. Negative and positive reinforcement increase the probability of specific behaviours recurring i.e. strengthen the association between events, whereas punishment reduces the probable recurrence of a behaviour without providing specific information about the desired alternative. In this paper the term 'punishers' is used to refer to the physical aids, such as a whip or crop, which may be used to bring about the process of punishment. However, if their application ceases when a specific behaviour occurs they may negatively reinforce that action. Intended 'punishers' may also be rewarding (e.g. for attention seeking behaviour). Therefore, contingency factors (which define the relationship between stimuli, such as the level of reinforcement), contiguity factors (which describe the proximity of events in space or time) and choice of reinforcing stimuli are critical in determining the rate of learning. The many problems associated with the application of punishment in practice lead to confusion by both horse and handler and, possibly, abuse of the former. Most behaviour problems relate to handling and management of the horse and can be avoided or treated with a proper analysis of the factors influencing the behaviour.

Animals↗
PubMed2001

Second-order schedules of token reinforcement with pigeons: effects of fixed- and variable-ratio exchange schedules.

Pigeons' key pecks produced food under second-order schedules of token reinforcement, with light-emitting diodes serving as token reinforcers. In Experiment 1, tokens were earned according to a fixed-ratio 50 schedule and were exchanged for food according to either fixed-ratio or variable-ratio exchange schedules, with schedule type varied across conditions. In Experiment 2, schedule type was varied within sessions using a multiple schedule. In one component, tokens were earned according to a fixed-ratio 50 schedule and exchanged according to a variable-ratio schedule. In the other component, tokens were earned according to a variable-ratio 50 schedule and exchanged according to a fixed-ratio schedule. In both experiments, the number of responses per exchange was varied parametrically across conditions, ranging from 50 to 400 responses. Response rates decreased systematically with increases in the fixed-ratio exchange schedules, but were much less affected by changes in the variable-ratio exchange schedules. Response rates were consistently higher under variable-ratio exchange schedules than tinder comparable fixed-ratio exchange schedules, especially at higher exchange ratios. These response-rate differences were due both to greater pre-ratio pausing and to lower local rates tinder the fixed-ratio exchange schedules. Local response rates increased with proximity to food under the higher fixed-ratio exchange schedules, indicative of discriminative control by the tokens.

Animals↗