Genetic Studies of Autism: From the 1970s into the Millennium

Reviewers in the 1960s and early 1970s were skeptical about any substantial role for genetic factors in the etiology of autism. A realization that the 2% rate of autism in siblings (as estimated at that time) was far above the general population base rate, and that this suggested a possible high genetic liability, led to the first small-scale twin study of autism. The replicated evidence from both twin and family studies undertaken in the 1970s and 1980s indicated both strong genetic influences and the likelihood that they applied to a phenotype that was much broader than the traditional diagnostic category of autism. Medical and chromosomal findings also indicated genetic heterogeneity. Advances in molecular genetics led to genome-wide scans of affected relative pair samples with a positive log of the odds to base 10 score for a location on chromosome 7. The major remaining research challenges and the likely clinical benefits that should derive from genetic research are considered in relation to both current knowledge and that anticipated to emerge from research over the next decade.     

Right hemisphere semantic processing of visual words in an aphasic patient: an fMRI study

This study was designed to identify the neural network supporting the semantic processing of visual words in a patient with large-scale damage to left-hemisphere (LH) language structures. Patient GP, and a control subject, RT, performed semantic and orthographic tasks while brain-activation patterns were recorded using functional magnetic resonance imaging. In RT, the semantic-orthographic comparison activated LH perisylvian and extrasylvian temporal regions comparable to the network of areas activated by non-brain-damaged subjects in other neuroimaging studies of semantic discrimination. In GP, the same comparison activated homologous right-hemisphere regions, demonstrating the ability of the right hemisphere to subserve visual lexicosemantic processes. The results are discussed within the context of the normal right hemisphere's capacity for semantic processing of visual words. Examining results from functional neuroimaging studies on recovery in the context of innate hemispheric abilities may enable reconciliation of disparate claims about mechanisms supporting recovery from aphasia.     

Transcranial Doppler Ultrasonography Monitoring of Cerebral Hemodynamics During Performance of Cognitive Tasks: A Review

The examination of blood flow velocity (BFV) changes during the performance of mental tasks is one of the applications of transcranial Doppler (TCD) ultrasonography. The purpose of this review is to summarize the results of the functional TCD literature, to investigate the effects of methodological differences between studies, and to provide guidelines for future research. It is concluded that larger series of more homogeneous groups concerning age and handedness, and stricter criteria for subject selection and laboratory setting are required. The implication of quantitative and qualitative performance measures and psychological parameters (motivation, anxiety, and task anticipation) could also yield important information. We recommend future agreement upon a more standardized methodology. TCD promises to be a useful tool to provide further insight into the cerebral organization and temporal reactivity of the human brain.     

On aims and methods in the neuroimaging of derived relations

Ingenious and seemingly powerful technologies have been developed recently that enable the visualization in some detail of events in the brain concomitant upon the ongoing behavioral performance of a human participant. Measurement of such brain events offers at the very least a new set of dependent variables in relation to which the independent variables familiarly manipulated in the operant laboratory may be explored. Two related paradigms in which a start has been made in such research concern the derivation of novel or emergent relations from a baseline set of trained relations, and include the phenomenon of transitive inference (TI), observed in studies of stimulus equivalence (SE) and serial learning (SL) or seriation. This paper reviews some published and forthcoming neuroimaging studies of these and related phenomena, and considers how this line of research both demands and represents a welcome synthesis between types of question and levels of explanation in behavioral science that often have been seen as antithetical.     

Relationships of Functional Flexibility with Individual and Work Factors

To investigate how functional flexibility is related to demographics, personality traits, and work perceptions, 250 employees of a large Dutch passenger transport firm filled out a written questionnaire. Two dimensions of functional flexibility were discerned: willingness and ability to be flexible. Analysis of variance showed the support staff and managers were higher on willingness and ability to be flexible than workers. Hierarchic regression analysis showed that willingness to be flexible was positively related to initiative and trust in management, and was negatively related to age and task formalization. Ability to be flexible was positively related to general self-efficacy and initiative, and was negatively related to task formalization. It was concluded that willingness to be flexible depends on fair treatment and freedom provided by their organization and that ability to be flexible is part of the development of general self-efficacy.     

On the effectiveness of and preference for punishment and extinction components of function-based interventions

The current study describes an assessment sequence that may be used to identify individualized, effective, and preferred interventions for severe problem behavior in lieu of relying on a restricted set of treatment options that are assumed to be in the best interest of consumers. The relative effectiveness of functional communication training (FCT) with and without a punishment component was evaluated with 2 children for whom functional analyses demonstrated behavioral maintenance via social positive reinforcement. The results showed that FCT plus punishment was more effective than FCT in reducing problem behavior. Subsequently, participants' relative preference for each treatment was evaluated in a concurrent-chains arrangement, and both participants demonstrated a dear preference for FCT with punishment. These findings suggest that the treatment-selection process may be guided by person-centered and evidence-based values.     

A methodology for assessing the functions of emerging speech in children with developmental disabilities

An approach based on Skinner's (1957) theory of verbal behavior has been developed to understand and teach elementary communication skills to children with autism and developmental disabilities (Sundberg & Partington, 1998). However, few studies have directly examined the characteristics of emerging language in children with developmental disabilities. The purpose of this study was to develop and evaluate an assessment for identifying the elementary functions of vocal speech in children. Participants were 4 children with developmental disabilities, aged 6 years to 12 years, who exhibited at least one distinguishable vocal response (word or phrase) frequently in the natural environment. The assessment focused on three verbal operants delineated by Skinner (mand, tact, and intraverbal). One or more functions were identified for at least one vocal response of each child. Results suggested that this assessment would be useful for (a) evaluating Skinner's theory, (b) guiding decisions about language training for individual children, and (c) studying the nature of expressive language development in children with developmental disabilities.     

The effects of directive and nondirective prompts on noncompliant vocal behavior exhibited by a child with autism

Results of an analogue functional analysis indicated that noncompliant vocal behavior exhibited by a young girl with autism was maintained by negative reinforcement. Follow-up analyses suggested that the immediate escape contingency assessed in the demand condition did not appear to maintain the behavior. Instead, noncompliant vocal behavior occurred in response to directive prompts. Nondirective prompts reduced noncompliant vocal behavior to near zero.     

Treatment efficacy of noncontingent reinforcement during brief and extended application

We evaluated the long-term therapeutic effects of noncontingent reinforcement (NCR). In Experiment 1, NCR effects were examined with 2 participants' arbitrary responses; in Experiment 2, NCR was used as treatment with 3 participants whose self-injurious behavior (SIB) was maintained by automatic reinforcement. In both experiments, NCR consisted of continuous access to a highly preferred leisure item and was implemented initially during 10-min and later during 120-min sessions. Varied reinforcers (leisure items) were subsequently introduced during 120-min sessions to determine if treatment effects might be extended. Finally (Experiment 2 only), NCR was implemented throughout the day in participants' homes. Results of Experiments 1 and 2 showed that reinforcers obtained through object manipulation can compete with those obtained automatically by engaging in SIB during brief NCR sessions. However, data from the 120-min sessions indicated that satiation to a specific leisure item might occur over periods of time more typical of those during which treatment would be implemented. Access to a variety of highly preferred leisure items extended the effectiveness of NCR for some individuals. When NCR was implemented throughout the day (Experiment 2), therapeutic effects were shown to be maintained for up to 1 year.