The subthalamic nucleus is a key site controlling motor function in humans. Deep brain stimulation of the subthalamic nucleus can improve movements in patients with Parkinson's disease; however, for unclear reasons, it can also have cognitive effects. Here, we show that the human subthalamic nucleus is monosynaptically connected with cognitive brain areas such as the prefrontal cortex. Single neurons and field potentials in the subthalamic nucleus are modulated during cognitive processing and are coherent with 4-Hz oscillations in medial prefrontal cortex. These data predict that low-frequency deep brain stimulation may alleviate cognitive deficits in Parkinson's disease patients. In line with this idea, we found that novel 4-Hz deep brain stimulation of the subthalamic nucleus improved cognitive performance. These data support a role for the human hyperdirect pathway in cognitive control, which could have relevance for brain-stimulation therapies aimed at cognitive symptoms of human brain disease.awx300media15660002226001.

OBJECTIVE Craniectomy is often performed to decrease intracranial pressure following trauma and vascular injuries. The subsequent cranioplasty procedures may be complicated by surgical site infections (SSIs) due to prior trauma, foreign implants, and multiple surgeries through a common incision. Several studies have found that intrawound vancomycin powder (VP) is associated with decreased risk of SSIs after spine operations. However, no previously published study has evaluated the effectiveness of VP in cranioplasty procedures. The purpose of this study was to determine whether intrawound VP is associated with decreased risk of SSIs, to evaluate VP's safety, and to identify risk factors for SSIs after cranioplasty among patients undergoing first-time cranioplasty. METHODS The authors conducted a retrospective cohort study of adult patients undergoing first-time cranioplasty for indications other than infections from January 1, 2008, to July 31, 2014, at an academic health center. Data on demographics, possible risk factors for SSIs, and treatment with VP were collected from the patients' electronic health records. RESULTS During the study period, 258 patients underwent first-time cranioplasties, and 15 (5.8%) of these patients acquired SSIs. Ninety-two patients (35.7%) received intrawound VP (VP group) and 166 (64.3%) did not (no-VP group). Patients in the VP group and the no-VP group were similar with respect to age, sex, smoking history, body mass index, and SSI rates (VP group 6.5%, no-VP group 5.4%, p = 0.72). Patients in the VP group were less likely than those in the no-VP group to have undergone craniectomy for tumors and were more likely to have an American Society of Anesthesiologists physical status score > 2. Intrawound VP was not associated with other postoperative complications. Risk factors for SSI from the bivariable analyses were diabetes (odds ratio [OR] 3.65, 95% CI 1.07-12.44), multiple craniotomy procedures before the cranioplasty (OR 4.39, 95% CI 1.47-13.18), prior same-side craniotomy (OR 4.73, 95% CI 1.57-14.24), and prosthetic implants (OR 4.51, 95% CI 1.40-14.59). The multivariable analysis identified prior same-side craniotomy (OR 3.37, 95% CI 1.06-10.79) and prosthetic implants (OR 3.93, 95% CI 1.15-13.40) as significant risk factors for SSIs. After adjusting for potential confounders, patients with SSIs were more likely than those without SSIs to be readmitted (OR 7.28, 95% CI 2.07-25.60). CONCLUSIONS In this study, intrawound VP was not associated with a decreased risk of SSIs or with an increased risk of complications. Prior same-side craniotomy and prosthetic implants were risk factors for SSI after first-time cranioplasty.

We describe a novel spinal cord (SC) stimulator that is designed to overcome a major shortcoming of existing stimulator devices: their restricted capacity to selectively activate targeted axons within the dorsal columns. This device overcomes that limitation by delivering electrical stimuli directly to the pial surface of the SC. Our goal in testing this device was to measure its ability to physiologically activate the SC and examine its capacity to modulate somatosensory evoked potentials (SSEPs) triggered by peripheral stimulation. In this acute study on adult sheep (n = 7), local field potentials were recorded from a grid placed in the subdural space of the right hemisphere during electrical stimulation of the left tibial nerve and the spinal cord. Large amplitude SSEPs (>200 µV) in response to SC stimulation were consistently obtained at stimulation strengths well below the thresholds inducing neural injury. Moreover, stimulation of the dorsal columns with signals employed routinely by devices in standard clinical use, e.g., 50 Hz, 0.2 ms pulse width, produced long-lasting changes (>4.5 h) in the SSEP patterns produced by subsequent tibial nerve stimulation. The results of these acute experiments demonstrate that this device can be safely secured to the SC surface and effectively activate somatosensory pathways.

Spinal cord stimulation (SCS) currently relies on extradural electrode arrays that are separated from the spinal cord surface by a highly conducting layer of cerebrospinal fluid. It has recently been suggested that intradural placement of the electrodes in direct contact with the pial surface could greatly enhance the specificity and efficiency of stimulation. The present computational study aims at quantifying and comparing the electrical current distributions as well as the spatial recruitment profiles resulting from extraand intra-dural electrode arrangements. The electrical potential distribution is calculated using a 3D finite element model of the human thoracic spinal canal. The likely recruitment areas are then obtained by using the potential as input to an equivalent circuit model of the pre-threshold axonal response. The results show that the current threshold to recruitment of axons in the dorsal column is more than an order of magnitude smaller for intradural than extradural stimulation. Intradural placement of the electrodes also leads to much higher contrast between the stimulation thresholds for the dorsal root entry zone and the dorsal column, allowing better focusing of the stimulus.

The efficacy of spinal cord stimulators is dependent on the ability of the device to functionally activate targeted structures within the spinal cord, while avoiding activation of near-by non-targeted structures. In theory, these objectives can best be achieved by delivering electrical stimuli directly to the surface of the spinal cord. The current experiments were performed to study the influence of different stimulating electrode positions on patterns of spinal cord electrophysiological activation. A custom-designed spinal cord neurostimulator was used to investigate the effects of lead position and stimulus amplitude on cortical electrophysiological responses to spinal cord stimulation. Brain recordings were obtained from subdural grids placed in four adult sheep. We systematically varied the position of the stimulating lead relative to the spinal cord and the voltage delivered by the device at each position, and then examined how these variables influenced cortical responses. A clear relationship was observed between voltage and electrode position, and the magnitude of high gamma-band oscillations. Direct stimulation of the dorsal column contralateral to the grid required the lowest voltage to evoke brain responses to spinal cord stimulation. Given the lower voltage thresholds associated with direct stimulation of the dorsal column, and its possible impact on the therapeutic window, this intradural modality may have particular clinical advantages over standard epidural techniques now in routine use.