Motor and nonmotor event-related potentials during a complex processing task.

Identification of the necessary stimulus properties to elicit the stimulus preceding negativity (SPN) has been the impetus for numerous research studies. The current study was conducted to explore the possibility that the SPN is an index of cognitive resource allocation. An auditory warning stimulus (S1) indicated whether an easy or difficult discrimination would occur at S2. The SPN was collected before a nonmotor discrimination task (S2) that consisted of identifying the higher of two bars. To eliminate the influence of motor processing prior to S2, a button press on the side of the higher bar was held until perception of a response cue (S3). Additionally, P3, contingent negative variation (CNV), and behavioral measures were collected to assist in assessing the SPN. Results indicated that although the SPN exhibited increased negativity, no differences were observed based on task difficulty. However, task difficulty did affect P3 data for both the warning tone and the discrimination task, an effect not observed for the CNV. Overall, the data did not support that hypothesis that the SPN provides an index of cognitive demand.

An electrocortical comparison of executed and rejected shots in skilled marksmen.

Electroencephalographic (EEG) activity during the preshot period was investigated in seven skilled marksmen. Specifically, alpha and beta spectral power were obtained for the 4-s period prior to the execution or rejection of shots. Rejected shots were defined as those that resulted in the marksman's self-initiated decision to withdraw their rifle from the target rather than execute the shot. EEG activity during the preparatory period was contrasted between the executed and rejected shots to better understand the involved attentional processes associated with the preshot state. Results for rejected compared with executed shots revealed a progressive increase in alpha and beta power for rejected compared with executed shots, which increased across the preparatory period. Furthermore, increased spectral power was found in the left compared with the right hemisphere for both executed and rejected shots, and in the different regions of the scalp. Therefore, the decision to reject a shot seems to be characterized by inappropriate allocation of the neural resources associated with task execution.

A psychophysiological investigation of the effects of driving longer-combination vehicles.

Fatigue contributes to driving-related accidents and fatalities. Cardiovascular measures such as heart rate and heart rate variability may serve as early indicators of fatigue. In the current investigation, 24 professional truck drivers drove three truck configurations: single trailer, triple trailer A-dolly, and triple trailer C-dolly on a standard route that lasted between 8 and 10 h. During the driving session, continuous measures of heart rate were quantified on-line. In addition to heart rate, two measures of heart rate variability (i.e. respiratory sinus arrhythmia and the Traube-Hering-Mayer wave or 0.1 Hz oscillation) were derived from the beat-to-beat heart rate. Independent of configuration, heart rate increased and the measures of heart rate variability decreased during the driving route. Only heart rate statistically differed among the configurations. Since heart rate is physiologically linked to metabolic output, the results suggest that the observed effect may be due to the physical demands required to drive each truck configuration. In support of this conclusion, the heart rate effect was consistent with the subjective report of task demand. The slowest heart rates were observed while driving the least demanding configuration (i.e. single trailer). The fastest heart rates were observed while driving the most demanding configuration (i.e. triple trailer A-dolly).