Fringe boundaries coincide with Notch-dependent patterning centres in mammals and alter Notch-dependent development in Drosophila.

In both vertebrate and invertebrate development, cells are often programmed to adopt fates distinct from their neighbors. Genetic analyses in Drosophila melanogaster have highlighted the importance of cell surface and secreted proteins in these cell fate decisions. Homologues of these proteins have been identified and shown to play similar roles in vertebrate development. Fringe, a novel signalling protein, has been shown to induce wing margin formation in Drosophila. Fringe shares significant sequence homology and predicted secondary structure similarity with bacterial glycosyltransferases. Thus fringe may control wing development by altering glycosylation of cell surface and/or secreted molecules. Recently, two fringe genes were isolated from Xenopus laevis. We report here the cloning and characterization of three murine fringe genes (lunatic fringe, manic fringe and radical fringe). We find in several tissues that fringe expression boundaries coincide with Notch-dependent patterning centres and with Notch-ligand expression boundaries. Ectopic expression of murine manic fringe or radical fringe in Drosophila results in phenotypes that resemble those seen in Notch mutants.

Reciprocal effects of hyper- and hypoactivity mutations in the Drosophila pattern gene torso.

In Drosophila, five "terminal" polarity genes must be active in females in order for them to produce embryos with normal anterior and posterior ends. Hypoactivity mutations in one such gene, torso, result in the loss of the most posterior domain of fushi tarazu expression and the terminal cuticular structures. In contrast, a torso hyperactivity mutation causes the loss of central fushi tarazu expression and central cuticular structures. Cytoplasmic leakage, transplantation, and temperature-shift experiments suggest that the latter effect is caused by abnormal persistence of the torso product in the central region of the embryo during early development. Thus, the amount and timing of torso activity is key to distinguishing the central and terminal regions of the embryo. Mutations in the tailless terminal gene act as dominant maternal suppressors of the hyperactive torso allele, indicating that the torso product acts through, or in concert with, the tailless product.

Automating fruit fly Drosophila embryo injection for high throughput transgenic studies.

To decipher and manipulate the 14 000 identified Drosophila genes, there is a need to inject a large number of embryos with transgenes. We have developed an automated instrument for high throughput injection of Drosophila embryos. It was built on an inverted microscope, equipped with a motorized xy stage, autofocus, a charge coupled device camera, and an injection needle mounted on a high speed vertical stage. A novel, micromachined embryo alignment device was developed to facilitate the arrangement of a large number of eggs. The control system included intelligent and dynamic imaging and analysis software and an embryo injection algorithm imitating a human operator. Once the injection needle and embryo slide are loaded, the software automatically images and characterizes each embryo and subsequently injects DNA into all suitable embryos. The ability to program needle flushing and monitor needle status after each injection ensures reliable delivery of biomaterials. Using this instrument, we performed a set of transformation injection experiments. The robot achieved injection speeds and transformation efficiencies comparable to those of a skilled human injector. Because it can be programed to allow injection at various locations in the embryo, such as the anterior pole or along the dorsal or ventral axes, this system is also suitable for injection of general biochemicals, including drugs and RNAi.

Integrating caregiver report with systematic choice assessment to enhance reinforcer identification.

To determine client preferences, we asked caregivers to rank-order, according to predicted client preference, a standard list of items and a list generated using a structured interview for caregivers, the Reinforcer Assessment for Individuals with Severe Disabilities. Systematic choice assessments were then conducted with both sets of stimuli. A concurrent operants paradigm was used to compare the reinforcing effects of the highest preference stimulus identified from each list. Results indicated that caregiver predictions of client preferences were slightly better for the set of stimuli they generated than for the standard set, and the choice assessment identified more potent reinforcers from the set of stimuli generated by the caregivers than from the standard set.

Using chronotherapy to treat severe sleep problems: a case study.

Chronotherapy was used to treat severe sleep problems (irregular sleep onset times, frequent night and early wakings, and short total sleep times) in a girl with mental retardation. Chronotherapy involved systematically delaying the child's bedtime each night while maintaining a regular schedule during waking hours until an age-appropriate bedtime was achieved. Immediate improvements in the child's sleep pattern were observed with the introduction of treatment, and an age-appropriate bedtime was achieved in 11 days. Four months of follow-up data indicated that improvements maintained in the home. Although chronotherapy was developed specifically for adults with delayed sleep phase insomnia, the current results suggest that the treatment may be useful for other populations and problems.

Bedtime fading in the treatment of pediatric insomnia.

In this paper, the sleep-wake cycles of two children with severe sleep problems were regulated by delaying bedtimes, thus increasing the probability of short latency to sleep onset. A fading procedure was then utilized to advance the bedtimes and gradually increase duration of sleep. Several treatments had previously been attempted with both of these patients without success. The advantages of this treatment over other interventions for pediatric sleep disorders are discussed.

Enhancing child compliance with nebulized respiratory treatment. A case study.

A 2.7-year-old developmentally delayed boy diagnosed as having chronic lung disease, severe hyaline membrane disease, and persistent pulmonary hypertension with interstitial emphysema was referred in hopes of modifying his refusal to wear a mask during nebulized administrations of Chromolyn. The child was prescribed four 20-minute nebulized treatments daily but resisted treatment and removed the mask by turning his head and pushing the mask away with his hands. A procedure was implemented to gradually teach the child that turning his head and pushing the mask would not result in mask removal, and that by wearing the mask he would receive positive attention. By the end of treatment, the child was consistently wearing his mask for the required 20-minute intervals. Follow-up at 3 months confirmed maintenance of treatment effects.

The effects of noncontingent and contingent attention for self-injury, manding, and collateral responses.

To date, most functional analysis studies have focused on the effects of treatment contingencies on specific targeted aberrant and alternative responses. In the current investigation, the main and collateral effects of the assessment and treatment of attention-maintained self-injury were assessed. Specifically, we evaluated the effects of noncontingent and contingent social attention on four categories of behavior: self-injury, a novel mand, preexisting prosocial responses (e.g., babbling and reaching out), and other aberrant responses (i.e., aggression and destruction). Results suggested that self-injury, prosocial responses, and other aberrant behaviors were within the same functional response class. Possible impact of these results when selecting mands for functional communication training is discussed.

Facilitating tolerance of delayed reinforcement during functional communication training.

Few clinical investigations have addressed the problem of delayed reinforcement. In this investigation, three individuals whose destructive behavior was maintained by positive reinforcement were treated using functional communication training (FCT) with extinction (EXT). Next, procedures used in the basic literature on delayed reinforcement and self-control (reinforcer delay fading, punishment of impulsive responding, and provision of an alternative activity during reinforcer delay) were used to teach participants to tolerate delayed reinforcement. With the first case, reinforcer delay fading alone was effective at maintaining low rates of destructive behavior while introducing delayed reinforcement. In the second case, the addition of a punishment component reduced destructive behavior to near-zero levels and facilitated reinforcer delay fading. With the third case, reinforcer delay fading was associated with increases in masturbation and head rolling, but prompting and praising the individual for completing work during the delay interval reduced all problem behaviors and facilitated reinforcer delay fading.

Evaluating the reinforcing effects of choice in comparison to reinforcement rate.

A concurrent-operants arrangement was used to evaluate a boy's preference for a choice condition (in which he chose the reinforcement) over a no-choice condition (in which the therapist selected the reinforcement for him) when (a) these conditions produced equal rates of reinforcement and (b) lower rates of reinforcement were associated with the choice condition. The boy preferred the choice condition even when it resulted in a much less favorable rate of reinforcement than the no-choice condition (up to 4000% less).

Stimulus control and resistance to extinction in attention-maintained SIB.

A functional analysis of the self-injurious behavior (SIB) of a young man diagnosed with severe mental retardation demonstrated that SIB was sensitive to social attention as reinforcement. In addition, lower but consistent rates of SIB occurred in sessions where a person was present (Demand and Toy Play), and a gradual decrease in SIB was observed across sessions where a person was not present (Alone). Evaluation of the within-session trends of SIB during the functional analysis demonstrated that SIB maintained throughout each Social Attention session and declined within and across Alone sessions. This pattern of responding suggested that the presence of a person may have differentially affected rates of SIB independent of the programmed consequences for SIB. In a subsequent analysis, SIB was reduced to near-zero levels in the absence of a person, but maintained in the presence of a person even when attention was withheld, suggesting that the response was highly resistant to extinction. The results of these assessments then were used to develop a treatment to reduce the client's SIB. During treatment, a person was present and delivered attention only when the client appropriately communicated. SIB resulted in the removal of the antecedent stimulus that exerted control over the response (i.e., the person left the room). The findings of this investigation are discussed in terms of the differential effects of stimuli on interpretation of functional analysis results and the subsequent development of treatment.

The establishing effects of client location on self-injurious behavior.

Three functional assessments were conducted with a client with self-injurious behavior (SIB), which indicated that SIB appeared to be sensitive to attention as reinforcement. In addition, levels of SIB were much higher when the client was seated in his wheelchair. An additional analysis was conducted in which client location (in and out of wheelchair) was altered while reinforcement contingencies (attention) for SIB were held constant. Levels of SIB again were higher when the client was positioned in his wheelchair, even though the consequences for SIB were identical. The results of this final analysis suggested that the wheelchair functioned as an establishing stimulus altering the efficacy of social positive reinforcement.

On the establishing and reinforcing effects of termination of demands for destructive behavior maintained by positive and negative reinforcement.

The results of functional analyses suggested that the destructive behavior of two individuals was sensitive to escape and attention as reinforcement. In an instructional context, we evaluated the effects of reinforcing compliance with functional reinforcers when destructive behavior produced a break. For one participant we also evaluated the effects of reinforcing compliance with functional reinforcers when destructive behavior produced no differential consequence (escape extinction). We hypothesized that destructive behavior failed to decrease in an instructional context when compliance resulted in a break because presentation of a break evoked attention-maintained destructive behavior. The results of a reinforcer assessment supported this hypothesis by demonstrating that demands functioned as positive reinforcement when no alternative activities were available. These results are discussed in terms of the importance of establishing operations in determining the appetitive or aversive properties of stimuli when destructive behavior is multiply controlled.

Operative mechanisms of noncontingent reinforcement at varying magnitudes and schedules.

In order to examine the mechanism(s) responsible for response reductions from noncontingent reinforcement (NCR), multiple magnitudes and densities of NCR were superimposed on a variable ratio (VR) 3 schedule of contingent reinforcement for the performance of an arbitrary manual response. Data were collected on responding that occurred during access to the reinforcer separately from responding that occurred between reinforcer access intervals (i.e.. when the participant did not have access to the reinforcer). Higher magnitudes and denser schedules of NCR produced greater reductions in responding than did lower magnitudes and leaner schedules. Within-session response patterns suggested that decrements in responding were primarily a function of the increased amount of reinforcer access time associated with higher magnitudes and denser schedules of NCR. That is, it appeared that the participant consumed reinforcers (regardless of whether they were delivered contingently or noncontingently) when they were available and responded for contingent reinforcers primarily when reinforcers were absent.

A brief method for conducting a negative-reinforcement assessment.

A brief negative-reinforcement assessment was conducted with developmentally disabled children with severe destructive behavior. Five children were trained to engage in a simple escape response (e.g., a hand clap). Then each child was presented with a variety of stimuli or tasks that ranged on a scale from preferred to nonpreferred, based on parent ranking. The participant received a brief break from the stimuli or task, contingent on each escape response. For one child, an avoidance contingency was also implemented in which he could engage in the response to avoid the presentation of stimuli. Results showed that for each child, several stimuli were identified that may serve as effective negative reinforcers. Results also indicated that the procedure did not elicit any negative side effects for four children and low rates of destructive behavior for the fifth child. For one child, the results of the negative-reinforcement assessment were used to develop an effective treatment for destructive behavior. Additional applications of the reinforcement assessment to treatment interventions is discussed, as well as limitations to the procedure.

Noncontingent reinforcement: effects of satiation versus choice responding.

Recent research findings suggest that the initial reductive effects of noncontingent reinforcement (NCR) schedules on destructive behavior result from the establishing effects of an antecedent stimulus (i.e., the availability of "free" reinforcement) rather than extinction. A number of authors have suggested that these antecedent effects result primarily from reinforcer satiation, but an alternative hypothesis is that the individual attempts to access contingent reinforcement primarily when noncontingent reinforcement is unavailable, but chooses not to access contingent reinforcement when noncontingent reinforcement is available. If the satiation hypothesis is more accurate, then the reductive effects of NCR should increase over the course of a session, especially for denser schedules of NCR, and should occur during both NCR delivery and the NCR inter-reinforcement interval (NCR IRI). If the choice hypothesis is more accurate, then the reductive effects of NCR should be relatively constant over the course of a session for both denser and leaner schedules of NCR and should occur almost exclusively during the NCR interval (rather than the NCR IRI). To evaluate these hypotheses, we examined within-session trends of destructive behavior with denser and leaner schedules of NCR (without extinction), and also measured responding in the NCR interval separate from responding in the NCR IRI. Reductions in destructive behavior were mostly due to the participants choosing not to access contingent reinforcement when NCR was being delivered and only minimally due to reinforcer satiation.

Basic and applied research on choice responding.

Choice responding refers to the manner in which individuals allocate their time or responding among available response options. In this article, we first review basic investigations that have identified and examined variables that influence choice responding, such as response effort and reinforcement rate, immediacy, and quality. We then describe recent bridge and applied studies that illustrate how the results of basic research on choice responding can help to account for human behavior in natural environments and improve clinical assessments and interventions.

Behavioral economic influences on treatments designed to decrease destructive behavior.

In behavioral economics terms, response allocation is viewed as an exchange between the price of and the demand for reinforcers associated with various responses. In this study, behavioral economics principles were used to develop and evaluate a treatment package that reduced destructive behavior to zero while communication and compliance were increased.

The treatment of covert self-injury through contingencies on response products.

Assessment and treatment of covert self-injurious behavior are complicated because it is difficult to quantify and apply differential consequences to covert responses. In this study, both tangible and social reinforcers were identified using reinforcer assessment methods. These reinforcers were then provided contingent upon the absence of tissue damage identified during physical examinations, resulting in near 100% success in physical assessment checks that was maintained over 10 months.

Achieving and maintaining compliance with the ketogenic diet.

The ketogenic diet, a treatment for intractable epilepsy, is rarely initiated because it requires strict compliance with a diet that is perceived to be unpalatable. In a case study of a 15-year-old girl with uncontrolled epilepsy, we used a stimulus-choice procedure to assess relative preferences of 33 foods from the diet and to develop two treatments based on Premack's principle. The results of a multielement analysis showed that both treatments increased dietary compliance. Compliance was maintained with generalization of treatment across settings, and was associated with a 40% reduction in seizures.