Intra-Operative Behavioral Tasks in Awake Humans Undergoing Deep Brain Stimulation Surgery

Abstract

Deep brain stimulation (DBS) is a surgical procedure that directs chronic, high frequency electrical stimulation to specific targets in the brain through implanted electrodes. Deep brain stimulation was first implemented as a therapeutic modality by Benabid et al. in the late 1980s, when he used this technique to stimulate the ventral intermediate nucleus of the thalamus for the treatment of tremor 1 . Currently, the procedure is used to treat patients who fail to respond adequately to medical management for diseases such as Parkinson's, dystonia, and essential tremor. The efficacy of this procedure for the treatment of Parkinson's disease has been demonstrated in well-powered, randomized controlled trials 2 . Presently, the U.S. Food and Drug Administration has approved DBS as a treatment for patients with medically refractory essential tremor, Parkinson's disease, and dystonia. Additionally, DBS is currently being evaluated for the treatment of other psychiatric and neurological disorders, such as obsessive compulsive disorder, major depressive disorder, and epilepsy. DBS has not only been shown to help people by improving their quality of life, it also provides researchers with the unique opportunity to study and understand the human brain. Microelectrode recordings are routinely performed during DBS surgery in order to enhance the precision of anatomical targeting. Firing patterns of individual neurons can therefore be recorded while the subject performs a behavioral task. Early studies using these data focused on descriptive aspects, including firing and burst rates, and frequency modulation 3 . More recent studies have focused on cognitive aspects of behavior in relation to neuronal activity 4,5 . This article will provide a description of the intra-operative methods used to perform behavioral tasks and record neuronal data with awake patients during DBS cases. Our exposition of the process of acquiring electrophysiological data will illuminate the current scope and limitations of intra-operative human experiments. patient's information is reviewed in order to determine if he/she meets the criteria for the intra-operative study (Defined in an Institutional Review Board approved protocol at the Massachusetts General Hospital). 2. If it is determined that the subject meets the study criteria, a physician member of the study group (not the operating surgeon) approaches the patient to discuss the possibility of participation in the study. 3. The consent form for participating in the study is then reviewed and explained to the subject. Importantly, the explanation of the study stresses that participation in the study is voluntary and that at any point he/she has the option to withdraw from participation. Moreover, it is then emphasized that their discussion to participate or to withdraw in the study has no impact on the medical care he/she will receive. 4. If it is determined that the subject understands and agrees to participate in the study, he/she signs the approved informed consent and is enrolled i...

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