Educing Information: Interrogation - National Intelligence University

limitations and the few laboratory studies of fNIRS and deception conducted to
date, this technology is not ready to be deployed.
Transcranial Magnetic Stimulation (TMS)
Transcranial magnetic stimulation (TMS) was introduced in 1985. It
involves placing an electromagnetic coil on the scalp. A high-intensity current
is then rapidly turned on and off in the coil. This produces a powerful magnetic
field, with a strength of about 2T, that lasts for about 100 to 200 microseconds.
The magnetic field passes through the skin, soft tissue, and skull, and induces
an electrical current in neurons. This, in turn, causes a neuronal depolarization
that can have observable behavioral effects, such as body movement and speech
production difficulties, as well as unobservable effects, such as producing
temporary scotomas (blind spots) and phosphenes (perceptual flashes of light).
The area of depolarization is limited to a depth of about two centimeters below the
brain’s surface, because the magnetic field declines logarithmically with distance
from the electromagnetic coil.
TMS has primarily been studied in conjunction with mood disorders,
neurological disorders, and a variety of cognitive processes (such as language,
memory, and emotion). To date there appears to have been only one study using
TMS in a deception paradigm (Lo et al., 2003). In this study, subjects were to
respond in their imagination (i.e., not verbally) to four sets of questions during
TMS. These four sets of questions were divided into two types of response
conditions: “Yes” or “No” (to questions such as “Are you a man”) and short,
free-form responses (to questions such as “How old are you”). The subjects were
asked to respond truthfully to two sets of questions and untruthfully to the other
two sets. Motor-evoked potentials (i.e., contractions of contralateral muscles)
were also recorded. The results showed increased cortical excitability when
subjects were generating deceptive responses. This was found in both types of
response conditions (i.e., Yes/No and free-form). These results support the results
of previous fMRI studies on deception (Spence et al., 2001; Lee et al., 2002;
Langleben et al., 2002), which showed increased cortical activity, commonly in
the premotor areas.
Potential
TMS is a non-invasive, portable technique. There are usually no adverse
effects from TMS, though some subjects have reported mild headaches and
discomfort at the site of the stimulation. This pain is most likely due to the
repetitive stimulation of peripheral facial and scalp muscles, and responds well to
treatment with aspirin or acetaminophen. Another known adverse effect is a highfrequency
noise artifact that can cause short-term changes in hearing threshold.
This can be avoided with the use of ear plugs. The most serious adverse effect
has been seizure. Although the number of individuals who have received TMS is
unknown, it is likely in the thousands. Seizures during TMS are known to have
occurred in seven individuals, including six normal subjects (Wasserman et al.,
1996a; Pascual-Leone et al., 1993; Wasserman et al., 1996b). The risk of seizure
is related to the parameters of stimulation (magnetic intensity, pulse frequency,
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