Reaction time slowing in HIV-1-infected individuals: role of the preparatory interval

Psychomotor speed and directed attention were evaluated in 83 human immunodeficiency virus-1-infected individuals (HIV+) and 50 HIV-1 seronegative (HIV-) control participants using simple and choice reaction time (RT) tasks. The simple RT task included 1- and 3-s, irregularly varied preparatory intervals (PI) between the warning and target lights. Relative to the HIV- group, simple and choice RT were significantly slowed in the HIV+ group. Further, again relative to the HIV- controls, the HIV+ group did not show expected faster RT with increased response preparation time in the simple RT task. This also occurred in some HIV+ subjects who did not have psychomotor slowing. These findings suggest that RT performance in HIV-1-infected individuals may reflect separate processes associated with psychomotor slowing and impaired ability to direct attention. Possible neural mechanisms associated with control of these processes are discussed.