AAWSAP DIRD, Cognitive Limits on Simultaneous Control of Multiple Unmanned Spacecraft, December 2010

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The enteric system executes control of smooth muscle. Although the CNS and PNS are
anatomically distinct, they are functionally intertwined. When discussing the function of
the autonomic division, it is customary to refer to it as the Autonomic Nervous System,
or ANS.7
Changes in global arousal or activation through changing workload can result in
changes in physiological activity. These measures are advantageous as changes are
measurable continuously, in real-time, and usually unobtrusively in a naturalistic
setting. The drawback of using physiology alone is that there is no direct measure of
primary task performance.
Cardiac Function
Normal beating of the human heart produces a distinct and repeating pattern of
electrical activity measurable throughout the body for any two sample points that cross
the chest.c The typical electrocardiogram signal is shown in Figure 2.
R
T
p
Q
s
Figure 2. Typical EKG Signal for a Normal Heartbeat. Portions of the waveform are labeled P, Q,
R, S, and T.
Detection of the R-wave allows measurement of frequency, time,d and amplitude. For
continuous monitoring, heart rate measurements will vary considerably and in a non­
linear fashion; therefore, the measurement of inter-beat-interval (IBI), the time
between R peaks, is more normally distributed in the absence of signal, reducing noise
in the measurement. 8 Averaging the heart rate over minutes of task performance and
comparing to baseline yields a reliable estimate of increased metabolic function. 9 An
additional measure is the heart rate variability (HRV), calculated by dividing the
standard deviation of IBI by an average value of IBI within a sample period. Additional
measurements can be made by decomposing the spectra of HRV into low, mid, and
c In fact, a typical introductory physics course for life science students will include a laboratory experiment where
the heart rhythm is measured between electrodes located on the right wrist and left ankle.
d This time measurement is properly a phase measurement, with the phase relative to some reference event.
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