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PubMedDate not supplied

Histidine-decarboxylase knockout mice show deficient nonreinforced episodic object memory, improved negatively reinforced water-maze performance, and increased neo- and ventro-striatal dopamine turnover.

The brain's histaminergic system has been implicated in hippocampal synaptic plasticity, learning, and memory, as well as brain reward and reinforcement. Our past pharmacological and lesion studies indicated that the brain's histamine system exerts inhibitory effects on the brain's reinforcement respective reward system reciprocal to mesolimbic dopamine systems, thereby modulating learning and memory performance. Given the close functional relationship between brain reinforcement and memory processes, the total disruption of brain histamine synthesis via genetic disruption of its synthesizing enzyme, histidine decarboxylase (HDC), in the mouse might have differential effects on learning dependent on the task-inherent reinforcement contingencies. Here, we investigated the effects of an HDC gene disruption in the mouse in a nonreinforced object exploration task and a negatively reinforced water-maze task as well as on neo- and ventro-striatal dopamine systems known to be involved in brain reward and reinforcement. Histidine decarboxylase knockout (HDC-KO) mice had higher dihydrophenylacetic acid concentrations and a higher dihydrophenylacetic acid/dopamine ratio in the neostriatum. In the ventral striatum, dihydrophenylacetic acid/dopamine and 3-methoxytyramine/dopamine ratios were higher in HDC-KO mice. Furthermore, the HDC-KO mice showed improved water-maze performance during both hidden and cued platform tasks, but deficient object discrimination based on temporal relationships. Our data imply that disruption of brain histamine synthesis can have both memory promoting and suppressive effects via distinct and independent mechanisms and further indicate that these opposed effects are related to the task-inherent reinforcement contingencies.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2001

Lack of reinforcing effect of the benzodiazepine and tricyclic antidepressant combination of diazepam and dothiepin.

Fixed combinations of a tricyclic antidepressant (TCA) with a benzodiazepine (BZD) for the treatment of depressive syndromes enjoy remarkable acceptance among patients and prescribing physicians. In order to investigate if the widespread use of one such fixed TCA-BZD combination might be due to its high positive reinforcing effect, we tested each drug alone and in combination in an operant conditioning paradigm (fixed ratio 1 time-out 150 s) of intravenous self-administration in rats and compared their reinforcing effects to that of cocaine. Diazepam proved to be of only moderate reinforcing strength. Dothiepin alone was ineffective as a reinforcer but essentially abolished the reinforcing effect of diazepam when given in combination with it. These data indicate that the widespread acceptance of the fixed diazepam-dothiepin combination by the therapeutic community is not due to an increase in the positive reinforcing effect of diazepam by dothiepin but that, in contrast, addition of dothiepin might even decrease diazepam's moderately positive reinforcing effect.

Animals↗
PubMed1985

Surface of the shoot apex: a reinforcement-field theory for phyllotaxis.

Theory for leaf patterning, phyllotaxis, is usually expressed in terms of interactions in the surface of the apical dome of the shoot. Mechanisms for leaf formation, however, usually relate to phenomena in the longitudinal section, e.g. periclinal divisions. Studying epidermal cell file patterns and the directionality of cellulose in the outer walls of the dome we have found distinct patterns of cells and reinforcing cellulose on the surface. Changes in the epidermal pattern correlate with the phyllotactic sequence to suggest that: Recently established leaves are associated with fields of tangential cellulose reinforcement which extend toward the apical dome. Where such aligned fields come into contact so as to generate relatively abrupt angular changes in reinforcement pattern, a new leaf will appear. As this region of discontinuity develops into a hoop-reinforced structure, the visible primordium, a new single field of tangentially aligned reinforcement is generated. The new field interacts with other fields to continue the cycle. In whorled phyllotaxis two angular discontinuities appear to be involved with each new leaf; the pertinent older leaves are just one plastochron older than the leaf being initiated. In spiral phyllotaxis (3:2) a single angular discontinuity appears to be involved initially; the pertinent older leaves are three and five plastochrons older than the leaf being formed. There are two major differences from previous theories of phyllotaxis. First, the cyclic changes in leaf initiation are thought to be based on the constructive involvement of new leaves in modifying the dome's reinforcement pattern. Many theories assume that leaf formation is spontaneous and the role of nearby leaves is inhibitory. Second, the pattern sequence can explain the concurrent appearance of reinforced stem tissue along with leaves.

Cell Division↗
PubMed1968

Reinforcer sampling: a technique for increasing the behavior of mental patients.

Mental hospital patients in a motivating ward environment were using the available reinforcers less than was desired. A procedure for increasing the frequency of using reinforcers was developed: all patients were required to engage in the reinforcing event each time it was available but the duration of this required participation was limited so that the event was merely sampled. The effect of this required sampling was experimentally evaluated for three different reinforcers: going for a walk, watching a movie, and attending a music session. More patients used each of the three reinforcers and to a greater extent when the sampling procedure was used. Participation was increased even for those patients who had already been using the reinforcers, demonstrating that the technique did more than provide simple familiarization. Some familiarization was involved since the participation was slightly increased even after the sampling procedure was discontinued. The technique appears to be especially applicable when reinforcers are being delivered infrequently.

Journal Article↗
PubMed1969

Application of timeout from positive reinforcement for increasing the efficiency of speech training.

Language training procedures, which involved positive reinforcement for verbal imitation, were applied to increase the appropriate verbal behavior of an almost non-verbal, brain damaged, 5-yr-old boy. Two experiments assessed the effectiveness of timeout from positive reinforcement as a training procedure viewed as having potential punishing and negatively reinforcing functions. In both experiments, timein, termination of timeout and resumption of training, was arranged to have reinforcing properties in that it presented an opportunity to receive positive reinforcers. In Exp. I, the procedure consisted of temporarily halting language training (timeout) following verbal jargon and resuming it (timein) contingent upon the boy sitting quietly in his chair for approximately 30 sec. The jargon declined to almost zero for an extended period each time the procedure was employed. In Exp. II, the procedure consisted of halting language training (timeout) after emission of undesired verbal responses which previously had been reinforced as the desired approximation to the target verbal behavior. Resumption of training (timein) was made contingent upon the emission of the then-desired approximation of the target verbal behavior. In each experiment, the contingent timeout and timein of the language training that involved positive reinforcement effectively reduced the undesired and increased the desired responses.

Journal Article↗
PubMed1971

Instructions and group versus individual reinforcement in modifying disruptive group behavior.

Head Start children were matched into two groups on the basis of rates of disruptive behavior during rest periods. Attempts were made to modify their behavior using either individual or group token reinforcement procedures. While the reinforcement procedures reduced inappropriate behavior somewhat, the addition of instructions to the reinforcement reduced the inappropriate behavior to near zero for both groups. Instructions alone, however, were ineffective in controlling behavior. Type of reinforcement (group or individual) did not produce differential effects. While experimental control over the target behavior was demonstrated, there was little carryover from the experimental room to the regular classroom. Even when treatment was introduced into the regular class, follow-up results showed that with time the target behavior approximated pretreatment levels. The results suggest that (a) the combination of instructions and reinforcement is much more effective than either one of these alone, (b) behavior change is specific to the environmental contingencies, and (c) the group reinforcement technique, which is much more easily implemented, was at least as effective as individual reinforcement in the present study.

Journal Article↗
PubMed1971

Systematic reinforcement: academic performance of underachieving students.

The effect of contingent tangible and social reinforcement on academic performance was investigated in an experimental classroom of 25 selected underachieving students. Measures were taken of both teacher and child behavior during a baseline and two experimental treatment periods. During Treatment I, a point system with tangible backup reinforcers was combined with contingent social reinforcers dispensed by the teaching staff to assess the effects on three measures of academic performance (i.e., per cent of time at work, work output per minute, and accuracy). During Treatment II, the contingencies for the tangible reinforcers were terminated while social reinforcement was continued to see if the positive effects of Treatment I on academic performance would persist. The results show that with combined tangible and social reinforcers, students' work time, rate of output per hour, and accuracy in all activities substantially increased. After termination of the tangible reinforcers, the students maintained their high rates of output per hour and accuracy for the remaining period of the study while the total amount of time at work returned to the baseline level.

Journal Article↗
PubMed1995

Effects of subject- versus experimenter-selected reinforcers on the behavior of individuals with profound developmental disabilities.

Results from a number of studies have shown that individuals with profound developmental disabilities often show differential approach behavior to stimuli presented in a variety of formats, and that such behavior is a reasonably good predictor of reinforcement effects when these "preferred" stimuli are used subsequently in a contingent arrangement. Recent data suggest that reinforcement effects may be enhanced further by allowing individuals to select, just prior to training sessions, which (of several) preferred stimuli would be used as reinforcers, but whether this method is superior to one based on selection by a teacher or therapist has not been adequately addressed. We compared the effects of these two methods of reinforcer selection on rates of responding on a free-operant task, using stimuli previously identified as potential reinforcers. Results obtained with 4 subjects indicated little or no difference in reinforcement effects when stimuli were selected by subjects rather than experimenters. Implications of these results with respect to choice and its relation to reinforcement are discussed.

Adult↗
PubMed1969

Concurrent responding with fixed relative rate of reinforcement.

Responding by pigeons on one key of a two-key chamber alternated the color of the second key, on which responding produced food according to a variable-interval schedule of reinforcement. From time to time, reinforcement would be available for a response, but in the presence of a particular stimulus, either red or green light on the key. Red or green was chosen irregularly from reinforcement to reinforcement, so that a proportion of the total number of reinforcements could be specified for each color. Experimental manipulations involved variations of (1) the proportions for each color, (2) changeover delay, or, alternatively, (3) a fixed-ratio changeover requirement. The main findings were: (1) relative overall rates of responding and relative times in the presence of a key color approximated the proportions of reinforcements obtained in the presence of that color, while relative local rates of responding changed little; (2) changeover rate decreased as the proportions diverged from 0.50; (3) relative overall rate of responding and relative time remained constant as the changeover delay was increased from 2 to 32 sec, with reinforcement proportions for red and green of 0.75 and 0.25, but they increased above 0.90 when a fixed-ratio changeover of 20 responses replaced the changeover delay; (4) changeover rate decreased as the delay or fixed-ratio was increased.

Journal Article↗
PubMed1971

Differential reinforcement of other behavior (DRO): a yoked-control comparison.

After training to press a lever on a variable-interval 30-sec schedule, one group of rats was shifted to a differential-reinforcement-of-other-behavior 10-sec schedule, while a second group was shifted to a noncontingent yoked-control schedule that provided the same frequency and distribution of reinforcement. Then, both groups were extensively retrained on the variable-interval schedule, after which the first group was shifted to a series of differential-reinforcement-of-other-behavior 30-sec sessions alternating daily with variable-interval 30-sec sessions, while the second group was treated like the first on variable-interval days and yoked with the first as before on differential-reinforcement-of-other-behavior days. In both phases, response-decrement was more rapid and more marked in the differential-reinforcement-of-other-behavior animals than in the controls. The difference was due, at least in large measure, to sustainment of response in the control animals by adventitious reinforcement. All the differential-reinforcement-of-other-behavior animals developed "other" behavior-the same distinctive pattern of waiting at the foodcup-but there was no direct evidence that it contributed in any way to the decrement in lever pressing.

Journal Article↗
PubMed1971

Delayed reinforcement in a multiple schedule.

Three rats and a pigeon were first trained on a two-component multiple schedule in which reinforcement in the two components occurred immediately after a response. Later, reinforcement in one component was delayed by a few seconds. During both stages of the experiment, reinforcement was scheduled by equal variable- (pigeon) or random-interval (rats) schedules in the two components. The main effect of the delayed reinforcement was to increase the rate of responding in the unchanged (non-delay) component. This behavioral contrast effect did not appear in all cases to be dependent upon a reduction in the rate of responding or the frequency of reinforcement in the delay component. This finding suggests that a reduction in response rate and/or reinforcement frequency in one component of a multiple schedule may not be a necessary prerequisite for the occurrence of behavioral contrast. This finding is, however, consistent with an explanation that suggests that behavioral contrast results from the introduction of a less-preferred condition in one component of a multiple schedule, since it is known that animals "prefer" immediate to delayed reinforcement.

Journal Article↗
PubMed1971

Rates and patterns of responding with concurrent fixed-interval and variable-interval reinforcement.

Pigeons were exposed to concurrent fixed-interval and variable-interval schedules of food reinforcement on two keys. The times between reinforcement were varied systematically on both keys. The overall relative frequency of responding on the fixed-interval key depended on the relative frequency of reinforcement, but did not match it. Instead, the ratio of responses on the fixed-interval key to responses on the variable-interval key was a power function of the ratio of reinforcements, with an exponent of 0.5. Patterns of responding between reinforcements on the fixed-interval key depended on both relative and absolute values of the reinforcement schedules. Similar overall relative responding was obtained at different absolute schedule values with equal relative reinforcement, despite some differences in patterns of responding.

Journal Article↗
PubMed1972

Reinforcement delay: some effects on behavioral contrast.

Thirty five White Carneaux pigeons first received 20 sessions of non-delayed reinforcement according to a multiple variable-interval 1-min variable-interval 1-min schedule. For the remaining 15 sessions, subjects were assigned to one of five groups, with seven subjects per group. Four of these groups involved reinforcement according to the same multiple schedule as before, but reinforcement during one of the components was delayed for either 2.5, 5, 10, or 120 sec. The schedule for the fifth group was changed to multiple variable-interval 1-min extinction schedule of reinforcement. While some subjects in all groups showed behavioral contrast, it occurred more consistently in the groups involving extinction or the longer delays of reinforcement. Groups involving the various durations of delayed reinforcement or even extinction during the altered component did not, however, show a statistically significant difference in the amount of behavioral contrast. It was suggested that neither a reduction in reinforcement frequency nor response rate during the altered component is necessary to the production of behavioral contrast.

Journal Article↗
PubMed1975

Behavioral similarity as a reinforcer for preschool children.

Three experiments evaluated whether behavioral similarity provided by an adult could serve as a reinforcer for the modelling behavior of four preschoolers. In each experiment, sessions consisted of two kinds of trials: (1) experimenter-modelled trials, when the child's imitation of modelled motor responses was reinforced with praise and tokens, and (2) child-modelled trials when experimenter imitation of child-modelled responses was contingent upon the child's modelling one of three alternative responses: operation of a ball, horn, or clicker. Experiment I showed that the children consistently modelled whichever responses the experimenter imitated. Experiment II determined whether that performance was due to differences in the amount of experimenter behavior following imitated versus nonimitated child models or to experimenter imitation. Neither reducing nor increasing the amount of experimenter behavior following the children's nonimitated models altered their modelling of imitated responses. Experiment III evaluated whether experimenter imitation of child models was a reinforcer because the child's imitative responses were reinforced on experimenter-modelled trials. In Experiment III, the children's nonimitation of experimenter-models was reinforced with praise and tokens on a schedule of differential reinforcement of other behavior, yet they continued to model experimenter-imitated responses on child-modelled trials. These results indicate behavioral similarity was reinforcing, though no conditioning history through which it acquired that function was demonstrated.

Journal Article↗
PubMed1976

Preference for mixed versus constant delay of reinforcement.

Preference for constant and mixed delay of reinforcement was studied using concurrent equal variable-interval schedules. For four pigeons, pecking one key was reinforced following constant delays of 8 sec and mixed delays of 6 or 10 and 2 or 14 sec. Pecking a second key was reinforced following constant delays of 0, 8, 16, and 32 sec. For two additional pigeons, pecking one key was reinforced following delays of 30, 15 or 45, 5 or 55, and 0 or 60 sec. Reinforcements on the other key were delayed 30 sec. It was found that (a) pigeons preferred mixed relative to constant delay of reinforcement, and (b) preference for mixed delay of reinforcement increased as the range of delay interval variability increased.

Journal Article↗
PubMed1976

Behavior of humans in variable-interval schedules of reinforcement.

During Phase I, human subjects pressed a button for monetary reinforcement in five variable-interval schedules, each of which specified a different frequency of reinforcement. The rate of responding was an increasing, negatively accelerated function of reinforcement frequency; the data conformed closely to Herrnstein's equation. During Phase II, the same five schedules were in operation, but in addition a concurrent variable-interval schedule (B) was introduced, responses on which were always reinforced at the same frequency. Response rate in component A increased while the response rate in B decreased, as a function of the reinforcement frequency in component A. Relative response rates in the two component schedules matched the relative frequencies of reinforcement. Comparing the absolute response rates in component A during Phase I and Phase II it was found that introduction of the concurrent schedule did not affect the value of the theoretical maximum response rate, but did increase the value of the reinforcement frequency needed to obtain any particular submaximal response rate.

Journal Article↗
PubMed1976

Signalled reinforcement and multiple schedules.

The responses of four pigeons were first reinforced in the presence of two different wave-lengths (green and red) on a two-ply multiple schedule with identical variable-interval 3-min schedules of reinforcement associated with each component. While the constant-component reinforcement schedule remained unchanged during the experiment, the schedule associated with the variable component was changed to (1) signalled variable time, (2) unsignalled variable time, or (3) signalled variable interval. The probability with which the availability of the reinforcer was signalled in the variable-interval schedules was either 0.5 or 1.0. Positive contrast occurred in both signalled variable-interval and variable-time schedules, but only when the availability of all the variable-component reinforcers was signalled. Signalling the availability of only 50% of the reinforcers in signalled variable-interval schedules resulted in negative induction. The present data suggest that positive behavioral contrast resulting from signalled reinforcer availability is due to the presence of an extinction-correlated stimulus.

Journal Article↗
PubMed1977

The effect of reinforcement differences on choice and response distribution during stimulus compounding.

In Experiments I and II, rats were trained to respond on one lever during light and another during tone. The absence of tone and light controlled response cessation. In the multiple schedule of Experiment I, all reinforcements were received for responding in tone or light; in the chain schedule of Experiment II, all reinforcements were received in no tone + no light for not responding. Experiment I subjects, for which tone and light were associated with response and reinforcement increase, responded significantly more to tone-plus-light than to tone or light alone (additive summation). Experiment II subjects, for which tone and light were associated with response increase and reinforcement decrease, responded comparably to tone, light, and tone + light. Thus, additive summation was observed when stimulus-response and stimulus-reinforcer associations in tone and light were both positive, but not when they were conflicting. All subjects in both experiments responded predominantly on the light-correlated lever during tone + light, even when light intensity was reduced in testing. Furthermore, when a light was presented to a subject engaged in tone-associated responding, all subjects immediately switched the locus of responding to the light-correlated lever. No change in locus occurred when a tone was presented to a subject engaged in light-associated responding, irrespective of the stimulus-reinforcer association conditioned to tone. The light-lever preference in tone + light indicates that the heightened responding observed in Experiment I was not the summation of tone-associated behavior with light-associated behavior. Rather, it appears to be the result of a facilitation of one operant (light-associated responding) by the reinforcement-associated cue for the other.

Journal Article↗