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This study examined central inhibitory function in children with Tourette syndrome (TS; N = 46) and normally developing controls (N = 22) matched on age, gender, and IQ. A negative priming task measured the ability to inhibit processing of irrelevant distractor stimuli presented on a visual display. Initial analyses indicated that participants with Tourette syndrome did not differ significantly in inhibitory function from controls. However, when the large Tourette syndrome sample was separated into subgroups, one without evidence of comorbidity (N = 23) and the other meeting research criteria for either AD/HD, OCD, or both (N = 23), it became evident that individuals with Tourette syndrome with comorbid conditions tended to perform less well than the control group, whereas those without comorbidity performed much like controls. Similarly, when the large Tourette syndrome sample was divided into two subgroups on the basis of severity of symptomatology (N = 23 in each), those with more numerous and severe symptoms of Tourette syndrome, AD/HD, and OCD performed significantly less well than both controls and Tourette syndrome subjects with fewer and less severe symptoms. This suggests that neuropsychological impairment occurs as a function of comorbidity and symptom severity in Tourette syndrome. It also suggests that categorical diagnoses alone may be less useful than dimensional methods for predicting cognitive impairment in individuals with Tourette syndrome.

This research examined the processing demands imposed upon experienced pilots by two different communication formats, digital and verbal, in a high fidelity simulation of an advanced multi-function helicopter. The mental workload imposed by the type and magnitude of communications was assessed by a battery of subjective, performance, secondary, and physiological measures. The performance data indicated that the pilots had difficulty adhering to the Nap of the Earth altitude criterion with high communication demands, particularly with the digital communication system. This was presumably due to the requirement to spend more time scanning the multi-function displays with the digital than with the verbal communication system. On the other hand, the pilots were less prone to task shedding when they used the digital communication system possibly due to the provision of a permanent list of queries that was unavailable with the verbal system. Measures of heart rate variability and blink rate were larger with the verbal than with the digital system, presumably reflecting increased respiratory demands in the verbal condition as well as increased visual processing demands with the digital format. Finally, the probe evoked P300 component decreased in amplitude as a function of increases in the magnitude of communications. The results are discussed in terms of the structural and capacity demands of the communications systems that were proposed for the advanced multi-function helicopter.

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