The computer-assisted Neurobehavioral Evaluation System (NES) test battery was developed for the purpose of detecting brain dysfunction resulting from exposure to neurotoxicants. The NES tests are derived from standard neuropsychological tests that have been well characterized in terms of brain-behavior relationships. However, as the NES tests are designed for administration via a computer, they differ in the administration and response modalities from the traditional tests. Previous studies have shown that NES tests provide an efficient method of measuring neurobehavioral effects in epidemiological studies and that a number of the tests are sensitive to exposure to neurotoxicants. A recent study by has examined the validity of NES2 tests in patients with known brain damage (i.e., patients with multiple sclerosis (MS), Parkinson's Disease (PD), and focal cortical lesions (FL)) and found that the test battery was good at identifying behavioral impairment in subjects with neuropathology involving the white matter of the brain (subjects with MS), but not the basal ganglia (subjects with PD). The researchers suggested that the NES2 test battery lacked in tasks that were sensitive to deficits in complex attention, visuospatial function, verbal encoding known to be associated with PD and they concluded that an expansion of the NES battery be initiated to improve its effectiveness in detecting brain damage in patients with clinical disease. For this reason, additional computer-based tasks that more closely approximate the stimulus and response characteristics of traditional neuropsychological tests with known sensitivity to basal ganglia and other types of cerebral dysfunction have been developed. These newer NES3 tests included List Learning, Visual Spans, Sequences, Digit Symbol, and List Learning Delayed Recognition. These new tasks were designed for administration via a pen-based laptop computer and available for test administration in the fall of 1996. The purpose of this study was to assess the validity of the updated NES test battery in patients diagnosed with toxicant encephalopathy (TE) either due to exposure to lead or to mixed solvents to improve the interpretation of NES test performance in research studies and clinical evaluations examining central nervous system (CNS) function and neurotoxicant exposure. Performance on a hybrid NES2/3 test battery, consisting of several NES2 and the above listed five NES3 tests, by persons diagnosed with toxicant encephalopathy (TE) was compared to that of controls to determine if performance differences reflect a priori hypothesized brain-behavior relationships. Performance on the NES tests also was correlated with performance on the analogous traditional tests. Significant performance differences between the TE case groups and controls were observed in the predicted domains on the NES test battery, thus confirming the sensitivity of the NES2/3 test battery to CNS dysfunction. The results indicating differences between TE cases and controls were observed to be more robust for solvent TE cases with predicted deficits observed in tasks involving motor, attention and tracking, visuospatial, and memory abilities, as well as mood. Overall, moderate correlations between standard and NES tests from the same functional domains were observed. In conclusion, these results suggest that the updated NES2/3 test battery does identify clinically significant performance deficits in the functional domains found to be impaired in diagnosed TE patients via traditional clinical neuropsychological tests. Expansion of the NES battery has continued; currently a complete NES3 battery (made up of 17 tests) is available. Further research is either planned or is ongoing to validate the complete NES3 battery in a clinical neurological population and to examine is effectiveness as a screening battery for the assessment of toxicant-induced cognitive impairments.
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