Cognitive processing speed in Lyme disease

Objective: The goal of this study was to more precisely define the nature o f the cognitive processing deficits in the patients with Lyme disease. Back ground: Lyme disease has been associated with cognitive disturbances. Metho d: Sixteen patients who met the Centers for Disease Control's case definiti on for Lyme disease and 15 age- and education-matched control subjects comp leted two computerized assessments. The first was a matching procedure that assessed perceptual/motor speed. The second task was an alphabet-arithmeti c (AA) test that measured the speed of mental arithmetic. On the matching t ask, subjects judged as true or false simple identity equations (e.g., B O = 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 arithmet ic (e.g., A + 3 = D). The use of this paradigm permits sensory or motor slo wing to be distinguished from slowed cognitive processing speed. Also, the tests do not involve automated or overlearned responses. Results: Lyme dise ase patients and healthy controls did not differ in perceptual/motor speed. However, Lyme disease patients' response times were significantly longer t han those of healthy controls during the AA task, demonstrating specific im pairments in mental activation speed. Conclusions: These results suggest th at Lyme disease patients show specific deficits when initiating a cognitive process. These impairments are independent of sensory, perceptual, or moto r deficits.