"It's alive. ALIVE!" The mad scientist howls as his creation, well, comes to life. That potent mixture of neuronal connections and lightning are all it takes for the monster to arise once more. If you're anything like me, and since you're here I'll assume that you are, this iconic scene from Frankenstein will be the first thing your brain primes when somebody mentions electrodes in the brain. Or perhaps your hardwired to conjure up a more Hitchcock-esque scene involving electroshock therapy in action. Regardless of your imaginative leanings however, there's no denying that the notion of applying direct electrical stimulation to the brain, is once again back in the spotlight thanks to new research published in the Archives of General Psychiatry. But we'll get to that in a moment.
A truly shocking history
The idea of applying electricity directly to the human brain is by no means a new idea. In fact we've been doing it since way back in 1874, when Robert Bartholow first peeled back those cranial curtains to apply electrodes to the brain of Mary Rafferty, a woman with basal cell carcinoma (that's skin cancer for those playing at home). Bartholow found that the introduction of a small electrical current to the left hemisphere of Mary's brain resulted in visible muscular contractions in her right arm and leg, surprisingly all of which occurred with not so much as a headache. However when Bartholow, who in hindsight was perhaps a touch too excitable himself, decided to increase the current he was applying, Mary became distressed before succumbing to seizures and falling into a coma. Sadly, she died just four days later.
However despite this somewhat grim introduction, direct electrical stimulation (DES) of the brain had arrived, and at the hands of more reserved physicians of the time it was able to reveal some truly remarkable things. Perhaps the most famous research of the time was that performed by German neurosurgeon Fredor Krause, who used DES to map the motor cortex in the brains of patients with epilepsy, whilst trying to discover their epileptogenic sweet spots (or the regions of the cortex which were generating the seizures). Interestingly the use of electrodes to map epileptogenic regions is still in use today. In fact it's considered the "gold standard" method for cordoning off those epilepsy inducing sections before they can be carefully removed. Very carefully indeed. However it is not just epilepsy that has benefited from treatments involving DES, with neurological conditions from obsessive compulsive disorder to dystonia, Parkinson's to Tourette's also reaping the rewards. However it is the treatment of depression which has recently bought DES back into the limelight.
It's time we dove a little deeper
Thus far in this tale we have merely been skimming the surface of the applications that DES has in the clinic. The cortical surface as it were. So to gain a better understanding of the new research I was telling you about earlier, perhaps it's time we dove a little deeper. Deep down into our minds. Down to the subcallosal cingulate. It was here, in the subcallosal cingulate white matter, to be precise, that clinicians implanted deep brain stimulation (DBS) electrodes into 17 individuals with either bipolar disorder or major depressive disorder. The treatment involves the use of high-frequency electrical stimulation to a specific brain region, in this case bilaterally to the subcallosal cingulate. The implant, consisting of a thin wire electrode on each side of the brain, connects to a pulse generator, similar to a pacemaker, which is implanted into the patient's chest. Participants in the study initially received four weeks of single-blind stimulation from the implants, meaning they were never sure if the implant had been activated or not, followed by 24 weeks of active stimulation. After this 24 week period, three of the participants had gone into remission, meaning their depression had lifted, whilst seven participants were said to be responding well. More importantly though after two years of active stimulation a total of 92% of the participants were said to be responding to the treatment, with 58% of the participants enjoying the greener grass on the remission side. Most importantly however were the findings that none of the patients achieving remission experienced spontaneous relapse and the chronic treatment was safe and well-tolerated by those involved.
However the success of the study doesn't mean that everything is all rosy for the participants just yet. After years of social isolation they still face the challenge of reintegration back into society, which the authors are helping them through. Not to mention the hassle of constantly having to explain why they keep setting off those airport metal detectors. But one thing's for sure, despite these new found hurdles, there's little doubt that from now on they'll be greeting their days with a smile on their face just like the rest of us. Once we've all had our morning coffee that is.
- Borchers S, Himmelbach M, Logothetis N, & Karnath HO (2011). Direct electrical stimulation of human cortex - the gold standard for mapping brain functions? Nature reviews. Neuroscience, 13 (1), 63-70 PMID: 22127300
- Holtzheimer, P., Kelley, M., Gross, R., Filkowski, M., Garlow, S., Barrocas, A., Wint, D., Craighead, M., Kozarsky, J., Chismar, R., Moreines, J., Mewes, K., Posse, P., Gutman, D., & Mayberg, H. (2012). Subcallosal Cingulate Deep Brain Stimulation for Treatment-Resistant Unipolar and Bipolar Depression Archives of General Psychiatry DOI: 10.1001/archgenpsychiatry.2011.1456