Abstract
Objectives
At FISITA 2012 we proposed a new concept for active driver safety, which uses human body’s endogenous pain-processing mechanism to automatically trigger vigilance enhancement on-demand. In this paper we present preliminary results from a pilot study designed to test the hypothesis that, as one becomes drowsy, his/her pain threshold declines, in order to use it as a trigger for the automatic vigilance enhancer concept.
Methodology
We recruited six healthy male subjects to test their pain threshold movements over a time period when their vigilance would be under stress. By employing a custom steering wheel with an peltier-array which provide a profile of thermal stimulation through a subject’s palm, we collected subject’s pain-response as we change the peltier temperature settings, while monitoring changes in his vigilance, using pre- and post-session psychomotor vigilance test (PVT), in-session Perclos (camera on eyes, objectively), and the Karolinska Sleep Scale (KSS, subjective rating) to establish the sought-after correlation between vigilance change and pain sensation response in a subject.
Results
Our measure of pain threshold movements over time, as indexed by declining vigilance at various time scales, in terms of the number of painful events recorded, shows a complex pain threshold control in our body. The findings suggest that on top of a stable, constant pain threshold control that is in effect when a person is vigilant, moderately sleepy, or totally asleep, there is a secondary mechanism that engages only when one becomes extremely drowsy while wanting to stay awake, in which his/her pain threshold would move down transiently to trigger noxious-like responses as if hyper-sensitively, when in fact the presenting stimulus is still innocuous, perhaps in a last resort attempt to stifle an unwanted entry into a state of the body and the mind.
Limitations
While the dataset is too small to afford statistical trends, the two-layer model was the outcome of observational data analysis, and our pilot protocol was limited in teasing apart these two layers (e.g., our test environment easily allows subjects to fall asleep without them eliciting such extreme efforts to stay awake as would in a vehicle piloting task), the observational insights offered in this paper may lend to new and more powerful study design in the future. Further, important as they are, individual susceptibility to sensitization and adaptation artifacts (which most likely would exert confounding pressure to pain threshold) are not normalized due to limitations in protocol design and dataset size.
What is New
In this framework we propose that, through a unique mechanism inside our body, driver vigilance can be actively maintained in situations when other detector-based interventions are rendered ineffective. By using our approach a user can leverage his/her body’s own danger-detection system to elevate his/her own vigilance, when and only when his/her body would beneficially require so, especially in a driving setting.
Conclusion
We are excited to present these first results from this research. With insights offered herein and future investigations, we are hopeful that a new path can be forged to lead to totally new, game-changing advanced technology for safe driving.
KEY WORDS : vigilance, arousal, pain threshold, pain mechanisms, active safety