The ecological validity of delay aversion and response inhibition as measures of impulsivity in AD/HD: a supplement to the NIMH multimodal treatment study of AD/HD.

Impulsivity is a primary symptom of the combined type of Attention Deficit/Hyperactivity Disorder (AD/HD). The Stop Signal Paradigm is premised upon a primary deficit in inhibitory control in AD/HD, whereas the Delay Aversion Hypothesis, by contrast, conceptualizes impulsivity in AD/HD, not as an inability to inhibit a response, but rather as a choice to avoid delay. This study compared the ecological validity of the Stop Signal Task (SST) and Choice-Delay Task (C-DT) measure of delay aversion, with respect to their relative utility in discriminating AD/HD children from normal control participants, and their correlations with classroom observations and with ratings of impulsivity and other core AD/HD symptoms on the Conners and SNAP-IV checklists. The tasks exhibited modest discriminant validity when used individually and excellent discriminant validity when used in combination. The C-DT correlated with teacher ratings of impulsivity, hyperactivity, and conduct problems, and with observations of gross motor activity, physical aggression, and an AD/HD composite score. The SST correlated with the observations only. These results suggest that delay aversion is associated with a broad range of AD/HD characteristics whereas inhibitory failure seems to tap a more discrete dimension of executive control.

Antipsychotic medication effects on neuropsychological functions.

The investigator of antipsychotic drug effects on neuropsychological functions faces a range of conceptual, methodological, and technical obstacles. Some of these hurdles are pointed out in a brief review of existing literature, and a more detailed consideration of instrumentation issues is presented. The need for hypothesis-driven assessment strategies is highlighted. Interpretive difficulties are posed by the polyfactorial nature of the most widely used neuropsychological tests, and emphasis is placed on the use and development of methods that enable isolation of specific neuropsychological constructs. Examples of this strategy are drawn from ongoing work in the Neuropsychology Unit of the Clinical Research Center for the Study of Schizophrenia at Hillside Hospital, where hypotheses about the behavioral site of action of dopamine agonists and antagonists are used to guide the construction of novel computerized tests.

A microcomputer based portable hemodialysis system.

A microprocessor controlled portable hemodialysis system (The Suitcase Kidney) has been designed and 18 dialyses have been successfully completed. The microprocessor is shown to be an improvement and simplification over the conventional discrete control mechanisms presently used to monitor and control system functions. The microprocessor is shown to reduce development time, complexity and size of the system while improving patient safety. A description of the system is presented emphasizing the functioning of the microcomputer.