The variable response-stimulus interval effect and sleep deprivation: an unexplored aspect of psychomotor vigilance task performance.

STUDY OBJECTIVES

The Psychomotor Vigilance Task (PVT) contains variable response-stimulus intervals (RSI). Our goal is to investigate the effect of RSI on performance to determine whether sleep deprivation affects the ability to attend to events across seconds and whether this effect is independent of impairment in sustaining attention across minutes, as measured by time on task.

DESIGN

A control group following their normal sleep routines and 3 groups exposed to 54 hours of total sleep deprivation performed a 10-minute PVT every 6 hours for 9 total test runs.

SETTING

Sleep deprivation occurred in a sleep laboratory with continuous behavioral monitoring; the control group took the PVT at home.

SUBJECTS

Eighty-four healthy sleepers (68 sleep deprivation, 16 controls; 22 women; aged 18-35 years).

MEASUREMENTS AND RESULTS

Across groups, as the RSI increased from 2 to 10 seconds, mean RT was reduced by 69 milliseconds (main effect of RSI, P < 0.001). There was no interaction between the sleep deprivation and RSI effects. As expected, there was a significant interaction of sleep deprivation and time on task for mean RT (P = 0.002). Time on task and RSI effects were independent. Parallel analyses of percentage of lapses and percentage of false starts produced similar results.

CONCLUSIONS

We demonstrate that the cognitive mechanism of attention responsible for response preparation across seconds is distinct from that for maintaining attention to task performance across minutes. Of these, only vigilance across minutes is degraded by sleep deprivation. Theories of sleep deprivation should consider how this pattern of spared and impaired aspects of attention may affect real-world performance.