A report presents additional information about the Impairscope — an instrument for noninvasive meas- urement of fine neuromuscular control and, more particularly, for quantifying the degradation of neuromuscular performance under psychological stress. The instrument, previously called the “Neuroskill device,” was described in “Biometric Instrument Measuring Neuromuscular Disorder/Performance Degradation (MFS-26449), NASA Tech Briefs, Vol. 21, No. 11 (November 1997), page 40. To recapitulate: The instrument includes an instrumented pen that measures motions along the two axes perpendicular to its long axis and the axial force with which the pen is pressed against a writing surface. The measurements are digitized 200 times per second and processed by software that implements an advanced method of correlation-function analysis to generate measures of the stability, smoothness, and synchronization of handwriting movements. The instant report reiterates information from the cited previous article, discusses the shortcomings of prior techniques for assessing effects of stress on motor control, briefly describes an underlying theory of the granular stationarity of the statistical properties of handwriting dynamics, and summarizes results of an experiment in which Impairscope measurements showed a degradation of handwriting performance in a group of students under the stress of final examinations.

This work was done by Ruth Shrairman and Alexander Landau of VeriFax Corp. for Johnson Space Center.