The goal of the proposed research is to determine the effect of induced sleep loss on attentional processes simple auditory reaction time and event-related brain potentials. A spatio-temporal model of cortical function before and after sleep deprivation will be developed using recent advances in brain electric source analysis. It is hypothesized that sleep loss will result in a more rapid transition to deteriorated states of auditory reaction time performance across time-on-task, which will be reflected in amplitude decreases and latency shifts in the N100 and P300 waveform components of the auditory event-related potential. It is further hypothesized that cortical dipole sources will be derived from primary auditory cortex (N100) and pre-frontal association cortex (P300), resulting in a model of activity that will reveal the effects of sleep loss to be initiated in basic attentional mechanisms.