We investigated the influence of extended wakefulness on automatic and nonautomatic processes in memory and visual search tasks. Subjects were trained in consistently mapped and variably mapped versions of each task, attaining automatic performance in the consistently mapped versions. We then recorded performance measures and event-related brain potentials for a 14-h period that began during the evening of the last day of training. Overall performance declined with extended wakefulness, but the benefits of consistently mapped training were retained throughout the night. Performance decrements consisted of an increase in nonresponses, increased response latencies, and decreased accuracies. P300 latencies increased, and P300 amplitudes decreased with extended wakefulness. When viewed together, reaction time and event-related brain potentials measures suggest that the locus of extended wakefulness effects was during early perceptual processes.

We examined the effects of both 5- and 10-mg/7O kg body weight of d-methamphetamine HCl on high event rate vigilance and tracking performance in a 13.5-hr sustained-performance session during one night of sleep loss. At 0116 hours participants were administered either a 5 mg/70 kg oral dose of d-methamphetamine (n=10), 10 mg/70 kg d-methamphetamine (n=10), or a placebo (n=10) using standard double-blind procedures. Performance on all measures degraded markedly during the night in the placebo group. Both the 5- and 10-mg methamphetamines treatment reversed an initial decline in d', and reversed increases in nonresponses (lapses) and tracking error within approximately 3 hr of administration. No evidence that amphetamine treatment increased impulsive responding (fast guesses) was observed. The magnitude of the performance effects of the methamphetamine treatments was similar at 3 hr postadministration. However, the effects of the 5-mg dose were shorter-lived, disappearing by the last testing session (6.5 hr postadministration), whereas effects of the 10-mg dose tended to remain throughout testing. Both amphetamine treatments decreased subjective sleepiness during the night and tended to increase subjective sleep latencies during a post-testing sleep period.

The nature of error detection as manifested by the error-related negativity was examined in both a Sternberg memory search task and a visual search task. Both tasks were performed in conditions with consistent or varied stimulus-response mapping and loads of three or six letters. After subjects were trained extensively in all conditions, they performed the tasks throughout the night without sleeping. The data suggest that the effectiveness of error detection decreases over time because of a decrease in the quality of perceptual processing. Error detection also suffers when performance requires more search-related resources. In both cases, the representation of the correct response is compromised. These results indicate that error detection depends on the same perceptual and cognitive processes that are required for correct performance.

Approved for public release; distribution is unlimited.Navy Personnel Rese-,. 6 and Development Uenter San Diego, California 92152-6800REPORT DOCUMENTATION PAGE Oo.070rov18Public reporng burden for this collction of i wfr wan is stana to avrage I hour per rpone mcuing the tine for reviewmg uitsuccoes, searting easting data souc. gaidng and maintaiing the dats needed, and crmnplaeng and reviewing thecoflcuion of infornsaum. Sed oannuis regarding this burden sui nste or my other Approved for public release; distribution is unlimited. ABSTRACT (Maximum 200 words)The auditory evoked potential in a signal classification task using rare and frequent tones was measured by four independent laboratories, to assess the test-retest reliability and interlaboratory consistency of the P300 component. Across laboratories, 61 male subjects (three samples of military subjects, n = 25, n = 18, and n = 8; one sample of college students, n = 10), ranging between 18 and 49 years of age were tested. With few exceptions, all experimental and subject factors were controlled. At each of three electrode sites (Fz, Cz, and Pz), peak amplitude, peak latency, and root-mean-square amplitude (RMS), of the P300 were computed for each subject in test and retest conditions. Statistical analyses of the data supported three strong inferences: (1) test-retest reliability and interlaboratory consistency of P300 measures is high for RMS amplitude, lower for peak amplitude, and lowest for peak latency; (2) recordings from site Pz provide higher reliability and consistency than sites Fz or Cz; (3) the RMS amplitude of P300 is negatively correlated with reaction time to correctly classify rare tones. The data support the notion that ERP components, such as P300, can be reliably measured by different laboratories, with a test-retest correlation coefficient of 0.8 or higher. SUBJECT TERMS NUMBER OF PAGESPhysiological metrics -yrchnnhy,,',-,-q7y -vr-rlanttM rntentinl'c PW.0 c,:,PCrnt. FOREWORDThis report describes experiments performed under the project Biopsychometric Assessment of Combat Operations or BIOPS (PE 0602234N, Task RS34H21), in order to verify procedural uniformity of the laboratories that are performing electrophysiological recording of event-related potentials (ERPs). The experiments involved the presentation of sequences of auditory stimuli (tone bursts of two frequencies) that elicit a positive-going wave in the ERP known as the P300 component. The laboratories were the Navy Personnel Research and Development Center (NPRDC), the Naval Aerospace Medical Research Laboratory (NAMRL), the Naval Health Research Center (NHRC), and the ERP laboratory of the Neurosciences Department at the University of California, San Diego (UCSD). The research was sponsored by the Office of Naval Technology.The results of the experiments show that, with minor exceptions, the laboratories involved in the BIOPS project have achieved the level of procedural uniformity required to allow for independent advanced investigations in later phases of the project. Further...

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