The Variable Response-Stimulus Interval Effect and Sleep Deprivation: An Unexplored Aspect of Psychomotor Vigilance Task Performance

THE PSYCHOMOTOR VIGILANCE TASK (PVT)1 HAS EMERGED AS THE GOLD-STANDARD METHOD OF ASSESSING CHANGES TO VIGILANT ATTENTION STEMMING from sleep deprivation in both applied and basic research. The standard PVT consists of a 10-minute speeded detection task with stimuli presented randomly 2 to 10 seconds after each response. During sleep deprivation, there is a time on task (ToT) effect for PVT performance as, for example, mean reaction time (RT) increases across minutes of the task.2 The variable (2 -10 s) response-stimulus interval (RSI) of the PVT is a manipulation that can directly address the relationship between sleep deprivation and the ability to sustain attention and readiness to respond across the seconds before the stimulus is presented. On experimenter-paced choice RT tests using RSIs in the range of milliseconds, longer RSI values have been documented to give rise to shorter RTs and an increased rate of errors.3,4 That is, subjects respond faster and less accurately on those trials with longer intervals before stimulus presentation. Two previous studies found that the RSI effect was unchanged after a single night of sleep deprivation.4,5 The current study is the first to test whether the RSI effect is present within the PVT, an instrument known to be highly sensitive to sleep loss.2 Specifically, we hypothesize that mean RT will decrease at the relatively longer RSIs, and we explore whether the percentage of either false starts or lapses changes with RSI. Next, we want to see if the RSI effect is altered when performance is tested after a second night of sleep deprivation, allowing more homeostatic pressure for sleep to accrue than was present in previous studies. Third, our main goal is to replicate the ToT effect on mean RT and to compare this with the RSI effect during sleep deprivation. Dissociation between the two effects during sleep deprivation would imply both that the cognitive mechanism of attention responsible for response preparation across seconds is distinct from that maintaining task performance across minutes and that not all forms of attention are degraded with sleep deprivation.