Human biovibrations: assessment of human life signs, motor activity, and cognitive performance using wrist-mounted actigraphy.

The application of miniature motion sensors (accelerometers) to study the macro- (gross) and micro- (barely discernible) activities associated with human motion has been termed actigraphy. In countless human sleep studies, actigraphy has mostly been applied to distinguish between when a person is asleep or awake. Use of sleep/wake information has been applied to the development of mathematical models that aim to predict aspects of cognitive performance. However, wrist-mounted actigraphy potentially has many more applications to cognitive and physical assessment beyond sleep/wake discrimination. For example, studies reveal that micro-miniature accelerometric sensors can discriminate heart rate, breathing, and life cessation (death) via actigraphically measured biovibration signals. This paper briefly reviews the development of wrist-mounted actigraphy; presents the data showing wrist-monitored ballistocardioimpulses, respirations, and life-signs signals; discusses the application of sophisticated signal processing for new clinical, operational, and cognitive-assessment-related applications; and concludes with recommendations for further research for demodulating the complex actigram signal.