ObjectiveThe goal of this study was to more precisely define the nature of the cognitive processing deficits in the patients with Lyme disease.BackgroundLyme disease has been associated with cognitive disturbances.MethodSixteen patients who met the Centers for Disease Control's case definition for Lyme disease and 15 age-and education-matched control subjects completed two computerized assessments. The first was a matching procedure that assessed perceptual/motor speed. The second task was an alphabet-arithmetic (AA) test that measured the speed of mental arithmetic. On the matching task, subjects judged as true or false simple identity equations (e.g., B + 0 = B). On the AA task, subjects indicated the veracity of equations of the same form as those of the matching task but which required mental arithmetic (e.g., A + 3 = D). The use of this paradigm permits sensory or motor slowing to be distinguished from slowed cognitive processing speed. Also, the tests do not involve automated or overlearned responses.ResultsLyme disease patients and healthy controls did not differ in perceptual/motor speed. However, Lyme disease patients' response times were significantly longer than those of healthy controls during the AA task, demonstrating specific impairments in mental activation speed.ConclusionsThese results suggest that Lyme disease patients show specific deficits when initiating a cognitive process. These impairments are independent of sensory, perceptual, or motor deficits.