An open source 3-d printed modular micro-drive system for acute neurophysiology.

Current, commercial, electrode micro-drives that allow independent positioning of multiple electrodes are expensive. Custom designed solutions developed by individual laboratories require fabrication by experienced machinists working in well equipped machine shops and are therefore difficult to disseminate into widespread use. Here, we present an easy to assemble modular micro-drive system for acute primate neurophysiology (PriED) that utilizes rapid prototyping (3-d printing) and readily available off the shelf-parts. The use of 3-d printed parts drastically reduces the cost of the device, making it available to labs without the resources of sophisticated machine shops. The direct transfer of designs from electronic files to physical parts also gives researchers opportunities to easily modify and implement custom solutions to specific recording needs. We also demonstrate a novel model of data sharing for the scientific community: a publicly available repository of drive designs. Researchers can download the drive part designs from the repository, print, assemble and then use the drives. Importantly, users can upload their modified designs with annotations making them easily available for others to use.

Single-neuron responses in the human nucleus accumbens during a financial decision-making task.

Linking values to actions and evaluating expectations relative to outcomes are both central to reinforcement learning and are thought to underlie financial decision-making. However, neurophysiology studies of these processes in humans remain limited. Here, we recorded the activity of single human nucleus accumbens neurons while subjects performed a gambling task. We show that the nucleus accumbens encodes two signals related to subject behavior. First, we find that under relatively predictable conditions, single neuronal activity predicts future financial decisions on a trial-by-trial basis. Interestingly, we show that this activity continues to predict decisions even under conditions of uncertainty (e.g., when the probability of winning or losing is 50/50 and no particular financial choice predicts a rewarding outcome). Furthermore, we find that this activity occurs, on average, 2 s before the subjects physically manifest their decision. Second, we find that the nucleus accumbens encodes the difference between expected and realized outcomes, consistent with a prediction error signal. We show this activity occurs immediately after the subject has realized the outcome of the trial and is present on both the individual and population neuron levels. These results provide human single neuronal evidence that the nucleus accumbens is integral in making financial decisions.

Prospective assessment of stereotactic ablative surgery for intractable major depression.

BACKGROUND: Despite therapeutic advances for major depression, a subset of patients with this disorder does not respond to conventional treatment. Stereotactic ablative procedures such as anterior cingulotomy have been performed in severely affected, treatment-resistant patients, but the long-term results of such procedures are not fully understood. METHODS: Findings are reported for 33 patients with severe treatment-resistant major depression who underwent ablative stereotactic procedures (dorsal anterior cingulotomy followed if necessary by subcaudate tractotomy). Preoperative and long-term postoperative Beck Depression Inventory scores were obtained along with postoperative Clinical Global Improvement values. Both were analyzed to evaluate patients' responses to the surgical procedure(s). RESULTS: At mean follow-up of 30 months after one or more stereotactic ablative procedures, 11 patients (33.3%) were classified as responders, 14 (42.4%) were partial responders, and 8 (24.2%) did not respond to the surgical procedure(s). Among those (17) who underwent only one procedure, seven (41.2%) responded, whereas six (35.3%) and four (23.5%) showed partial or no response, respectively. Among patients who required multiple surgical procedures, four patients (25%) responded, whereas eight (50%) and four (25%) patients demonstrated partial or no responses, respectively, at long-term follow-up evaluations. CONCLUSIONS: Approximately 75% of depression patients previously resistant to antidepressant therapies received partial or substantial benefit from stereotactic ablative procedures. Those requiring only a single anterior cingulotomy tended to demonstrate more pronounced responses than patients who underwent multiple surgical procedures.

Surgery for Parkinson disease in the United States, 1996 to 2000: practice patterns, short-term outcomes, and hospital charges in a nationwide sample.

OBJECT: The surgical treatment of Parkinson disease (PD) has undergone a dramatic shift, from stereotactic ablative procedures toward deep brain stimulaion (DBS). The authors studied this process by investigating practice patterns, mortality and morbidity rates, and hospital charges as reflected in the records of a representative sample of US hospitals between 1996 and 2000. METHODS: The authors conducted a retrospective cohort study by using the Nationwide Inpatient Sample database; 1761 operations at 71 hospitals were studied. Projected to the US population, there were 1650 inpatient procedures performed for PD per year (pallidotomies, thalamotomies, and DBS), with no significant change in the annual number of procedures during the study period. The in-hospital mortality rate was 0.2%, discharge other than to home was 8.1%, and the rate of neurological complications was 1.8%, with no significant differences between procedures. In multivariate analyses, hospitals with larger annual caseloads had lower mortality rates (p = 0.002) and better outcomes at hospital discharge (p = 0.007). Placement of deep brain stimulators comprised 0% of operations in 1996 and 88% in 2000. Factors predicting placement of these devices in analyses adjusted for year of surgery included younger age, Caucasian race, private insurance, residence in higher-income areas, hospital teaching status, and smaller annual hospital caseload. In multivariate analysis, total hospital charges were 2.2 times higher for DBS (median dollar 36,000 compared with dollar 12,000, p < 0.001), whereas charges were lower at higher-volume hospitals (p < 0.001). CONCLUSIONS: Surgical treatment of PD in the US changed significantly between 1996 and 2000. Larger-volume hospitals had superior short-term outcomes and lower charges. Future studies should address long-term functional end points, cost/benefit comparisons, and inequities in access to care.