Biomedical Engineering Reference
In-Depth Information
(Villringer et al. 1993). NIRS is currently being used to investigate a wide variety of
scientific questions such as the effects of exercise and alcohol, semantic processing
in learning disorders, and the measurement of oxygen saturation in preterm infants
(Tsujii et al. 2011; Sela et al. 2012; Thompson et al. 2013; Tsujii et al. 2013).
NIRS can only be used on cortical tissue in the brain so it is unable to provide
the same type, quantity, or quality of data as other scanning technologies such as
functional magnetic resonance imaging (fMRI), but it has other advantages that
make it the best candidate for remote scanning. It is far more portable and it can
be used to gather data from patients that are not amenable to functional scans like
premature infants or patients engaged in physical activity such as exercise. NIRS
can also be a wireless system, increasing its convenience and ease of use. In theory,
once the technology becomes advanced enough, NIRS could be administered to an
individual without their knowledge because the equipment could be in a neighbor-
ing room.
With access to an individual's brain activity comes the potential to control. It may
become possible to manipulate individuals' brain activity and consequently their
thoughts, behaviors, or both. Two techniques are relevant in this area, transcranial
magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS).
Both techniques are becoming increasingly popular methods to study—including
by the military—because they are noninvasive and inexpensive compared to other
treatment interventions and they have amazing potential to affect change in the brain
and therefore behavior. The possible military applications of these techniques are to
enhance soldiers' performance by increasing memory and learning, altering mood
states, or by reducing fatigue as well as inducing different types of behavioral change
in individuals besides our own soldiers (Tennison and Moreno 2012).
TMS is currently used in research and to treat depression and other neurologi-
cal conditions (Welberg 2007). TMS causes depolarization or hyperpolarization of
neurons in the brain by placing an electricity-generating magnetic coil above the
head that induces currents in the cortex of the brain (Allen et al. 2007). TMS can
be used to induce activity in specific or large areas of the brain. How TMS currents
actually affect neuronal processing has been a question under study for a number of
years (Allen et al. 2007). TMS lasts for anywhere from seconds to minutes, and it
has the potential to be used as a type of mind, or more aptly, behavioral control. The
military benefits of such a technology, especially one that can be applied remotely,
are significant. It could allow for the peaceful control of hostile individuals, allowing
them to be subdued and disarmed, as well as potential crowd control during riots or
other situations where predictably violent or unpredictable crowds may compromise
safety of all involved in a particular mission. The civilian applications of such a tech-
nology are numerous as well, although the motivation behind some applications may
be suspect as it is not hard to imagine uses driven solely by the prospect of financial
gain. What if TMS could be used to reduce inhibition for a short period of time?
What retailer—from grocery stores to car dealerships—would not like to be able to
apply this to customers walking into and around their stores? By reducing their inhi-
bition, it may increase the likelihood that they will not only purchase something but
perhaps purchase far more than they normally would. More sinister uses can easily
be conjured up as well.
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