IEEE Technology and Society Magazine - March 2017 - 14

This experimentation continued
into the late 1970s in various animal models (including primates),
but did not progress to human
trials [6].

Modern Day Electrical
Brain Stimulation
Nevertheless, the idea of using implanted electrodes to modify brain
function in humans did not end
there. Concurrent with Delgado's
work, Medtronic developed the first
"neural pacemaker," which was first
used by Hosobuchi et al. in 1973 to
treat chronic pain by stimulating the
thalamus [7]. This technique came
to be called deep brain stimulation
(DBS). However, this application
of DBS was never approved by the
FDA. It was not until 1997 that DBS
was approved as a treatment for
the tremors characteristic of Parkinson's disease. Clinical development efforts are currently underway
for numerous conditions including
chronic pain, major depression,
obsessive compulsive disorder, and
post traumatic stress disorder [7].

Therapeutic Uses
According the statistics released
by the U.S. Veterans Association,
PTSD affects 30% of U.S. veterans,
and treatment of PTSD relies heavily on compliance with psychotherapy and medications such as
selective serotonin reuptake inhibitors (SSRIs) and antimanic agents
like lithium [8]. However, medication
compliance is often low, which can
hinder recovery. Additionally, PTSD
is often comorbid with other mental health problems including substance abuse [9]. This can further
decrease compliance, especially in
cases where all other interventions
are ineffective. In these cases, DBS
may provide an alternative course of
treatment, helping those who suffer
from PTSD alleviate their symptoms
without the overhead of taking daily

medication. One of the DBS protocols being investigated for PTSD
treatment involves drilling two small
holes in the skull, and implanting
very thin electrodes (approximately 1.27 mm) into the amygdala
on both sides of the brain. This is
the region of the brain that, among
other things, mediates the emotional strength of memories and is
known to be overly active in those
who suffer from PTSD. In 2015, following several years of animal trials,
DBS was successfully used to help
manage the symptoms of treatmentresistant PTSD in a human. The person who underwent the procedure
reports that they have experienced
a marked decline in the severity of
nightmares that were previously preventing them from sleeping more
than a few hours per night [10]. A
clinical trial, headed by doctors Langevin and Koek is currently underway to determine the effectiveness
of this treatment in the broader
population [11].
Memory problems also have debilitating effects on veterans suffering
from TBI [12]. The RAM program
was created by DARPA with a goal
of developing an implantable device
that can be used to treat memory problems in patients with TBI.
One of teams funded by this initiative is led by Drs. Michael Kahana
and Daniel Rizzuto at the University of Pennsylvania (http://memory
.psych.upenn.edu/RAM). Their lab
studies human memory using a variety of techniques, including closedloop brain stimulation. As part of the
RAM effort Rizzuto's lab has created
an open database of the brain signals associated with memory tasks.
So far, all of the recordings have
been done in patients with epilepsy
who already have both recording and
stimulating electrodes implanted for
the purpose of mapping brain function prior to brain resection surgery.
In order to identify the neural corIEEE Technology and Society Magazine

relates of memory, Rizzuto and his
team had participants perform free
recall tasks - for example, looking
at a list of words and asking them
to remember as many as possible.
These tasks were performed for
an hour at a time, sometimes several times per day. By analyzing the
data from the recording electrodes,
Rizzuto's lab was able to predict
which words would be remembered
and which would be forgotten.
Additionally, by applying electrical stimulation at specific times,
they were able to increase the percentage of recalled words. This is
now being refined into a closed loop
brain computer interface system
where brain stimulation is applied
whenever the system detects that
the recorded activity looks more
like a word that will be forgotten than one that will be remembered. As part of the RAM program
Medtronic has been developing a
low-latency, closed-loop stimulation
system that is capable of precisely
stimulating the memory circuits
of the brain. The first subject data
using this device is scheduled to be
collected in February of this year.

Beyond Electricity
Electrical brain stimulation has limitations. In certain cases stimulating electrodes affect not only
the cells in the region where they
were implanted, but cause electrical stimulation to spread through
the fiber pathways to other brain
regions as well. Depending on
where electrodes are implanted
and their specific use case, this
spread has the potential to cause
unwanted short and long term side
effects. Optogenetics, an emerging
field of research that uses light to
stimulate neurons that have been
modified to express light sensitive
genes, may someday provide a way
to circumvent these limitations.
In rats, researchers were able to
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march 2017

http://memory http://psych.upenn.edu/RAM

Table of Contents for the Digital Edition of IEEE Technology and Society Magazine - March 2017