Electrocortical responses to ecologically relevant visual stimuli among professional drivers with and without...

Electrocortical responses were assessed using two simulated aspects of visual signals encountered in traffic: the Glare Pressor Test (GPT) and Event-Related Potential Avoidance Task (ERPAT) among four groups of male professional drivers: 12 with ischemic heart disease (IHD), 12 hypertensives, 10 borderline hypertensives, 34 who were apparently healthy and 23 nonprofessional driver healthy control subjects. The blood pressure (BP) responses immediately after the ERPAT were also measured. There was a significant between groups effect for the amplitude of the target N2 component in the ERPAT (p = 0.02), with the lowest means among the drivers with IHD and the highest among those with hypertension. Drivers with IHD also showed the highest diastolic BP reactivity to the ERPAT. Significantly more than the expected number of drivers with IHD failed to recover alpha activity after the first glare impulse of the GPT. Professional drivers who failed to recover baseline levels of alpha activity after the GPT showed a significantly smaller N2 amplitude compared to those who recovered (p = 0.01). There was a positive correlation between abundance of alpha activity at rest with P300 amplitude (p = 0.02). An inverse relation was found between number of work hours behind the wheel and the amplitude of the target P300 (p = 0.04). Results are interpreted in light of recent advances concerning integrative mechanisms of defence versus vigilance response patterns. The findings in this study justify further applications of these psychophysiologic methods to assess the relationship between simulated signals of the work environment and mechanisms of cardiac risk in this occupational group.