Serendip is an independent site partnering with faculty at multiple colleges and universities around the world. Happy exploring!
Zapping the Brain
Recently, a new type of neurosurgery,
Deep Brain Stimulation, has been emerging. DBS involves inserting electrodes
into the brain that send constant electrical signals. The procedure is
reversible, the device can be turned off or on, and the frequency of the
electrical pulses can be adjusted. Deep Brain Stimulation has been successfully
used to treat Parkinson's disease. Interestingly, this method has been
experimentally used to treat psychiatric diseases such as OCD, and may
be a viable option for treating depression and addiction as well. The
possibility of treating psychiatric disorders with this new method raises
several questions, both scientifically and ethically.
In a recent study researchers
found that stimulation of the sub-thalamic nucleus may
reduce the symptoms of severe OCD. Researchers believe that this stimulation “may
modify the maintenance of a decision deferring process...and therefore decrease
OCD symptoms”. While successfully reducing symptoms, the procedure proved to be
risky. Eleven of the seventeen participants experienced severe adverse events
during the trial. Some of these events were related to the surgery itself, and
others were behavioral and occurred during the active stimulation phase of the
trial (Mallet et.al.). An earlier study applied DBS to the anterior capsules of
four patients with severe OCD. Three of the four experienced a decrease in
symptoms (Ainsworth).
To many the possibility of
treating severe depression with Deep Brain Stimulation seems promising. Reports
of relief from depression in Parkinson’s disease patients being treated with
DBS in the subthalamic nucleus are encouraging and are prompting more research
into the area. Since relatively little is known about the neurobiology of
depression, multiple regions of the brain are possible targets for DBS. The
STN, the cerebellum, and the thalamus are among the current possibilities. A
2005 study of six patients with treatment-resistant depression found that
patients improved significantly after being treated with DBS in the subgenual
cingulate, a part of the brain that may be
overactive in people with depression (Juckel). Another region of the brain, the
nucleus accumbens, is involved in processing reward and pleasure and in
regulating emotional behavior. When DBS was applied to this region in three
severely depressed patients, their symptoms improved immediately (Ainsworth).
Using
DBS to treat severe depression not only offers hope to desperate patients, but
also could help researchers to better understand the neurological causes of
depression by comparing the results of stimulation of various brain regions on
mood and neuro-chemical levels. Since currently both the exact mechanisms of
how DBS works and the neurological causes of depression are poorly understood,
the potential for discovery is enormous. The number of areas of the brain to
which DBS can be applied as a successful treatment of depression testifies to
the complexity of the disorder. It might also be possible that the list of
symptoms associated with depression actually have multiple pathologies. There
does not seem to be a direct or consistant corralation between stimulation of
certain brain regions and mood, as some Parkinson’s disease patients have
reported increases in levels of depression after DBS to the subthalamic nucleus
rather than decreases.
Though no direct experiments
have been done on the affects of DBS on addictions the result of treatment with
DBS in the STN of Parkinson’s disease patients suffering from DDS, a dopamine
addiction, show that DBS strongly reduces DDS. One patient suffering from both
Parkinson’s disease and alcoholism was treated with DBS and subsequently
recorded abusing alcohol only one time in the following two-year period.
Another patient being treated with DBS in the nucleus accumbens for depression
and anxiety disorder also experienced substance abuse problems. Although he
showed little reduction in his depression and anxiety symptoms, his substance
abuse symptoms decreased significantly. In the Parkinson’s disease patients
researchers cannot be entirely certain that the reduction in dopamine and
alcohol abuse resulted directly from the DBS or as a by-product of the decrease
in their Parkinson’s symptoms. The authors of the study suggest, however, that
the loss of addiction was due to direct DBS affects on the reward seeking
circuit of the brain (Stelten). If DBS does directly affect the reward seeking
area of the brain, does it affect a person’s desire to engage in other
rewarding activities as well? There is evidence that this may be
the case. A Chinese neurosurgeon, Bomin Sun,
found that destroying areas of the nucleus accumbens relieves heroin addicts of
their drug cravings, but also causes apathy and inactivity. Sun
has also experimented with DBS of the same area, and in an unpublished study
apparently had success in treating two patients for addiction with few side
effects (Ainsworth). As it seems that each area of the brain has multiple or
yet unknown functions, and that behaviors result not from just one part of the
brain but, it would seem almost impossible to modify one element of a person’s
behavior in isolation of all other elements.
Knowing the risks and the possibility of side effects and unforseen personality changes, it is understandable that there are ethical concerns surrounding the use of DBS in the treatment of psychiatric disorders. DBS might also seem uncomfortably similar to early practices of psychsurgeries. However, unlike these earlier procedures, DBS is reversable and ajustable; and does seem to offer a viable, if somewhat risky, option for people suffering from dibilitating psychiatric disorders.
Works Cited:
Ainsworth, Claire. “Wireheads.” New Scientist, Jan. 5, 2008.
Juckel, Georg; Uhl, Idun; Padberg, Frank; Brune, Martin; and Winter, Christine. “Psychosurgery and deep brain stimulation as ultima ratio treatment for refractory depression.” Eur Arch Psychiatry Clin Nuerosci. 2009. 259:1-7
Mallet, Luc; Polosan, Mircea; Jaafari, Nematollah; and Baup, Nicolas et. Al. “Subthalamic Nucleus Stimulation in Secere Obsessive Disorder.”The New England Journal of Medicine. Boston: Nov. 13, 2008. Vol. 359, Iss 20; pg. 2121
Stelten, Bianca; Noblese, Lieke; Ackermans, Linda; Temel, Yasmin; and Visser-Vandewalle, Veerle. “The nuerosurgical treatment of addiction.”Neurosurg. Vol. 25. July, 2008.
Comments
Deep brain stimulation