Aperiodic neural activity is a biomarker for depression severity.

A reliable physiological biomarker for Major Depressive Disorder (MDD) is necessary to improve treatment success rates by shoring up variability in outcome measures. In this study, we establish a passive biomarker that tracks with changes in mood on the order of minutes to hours. We record from intracranial electrodes implanted deep in the brain - a surgical setting providing exquisite temporal and spatial sensitivity to detect this relationship in a difficult-to-measure brain area, the ventromedial prefrontal cortex (VMPFC). The aperiodic slope of the power spectral density captures the balance of activity across all frequency bands and is construed as a putative proxy for excitatory/inhibitory balance in the brain. This study demonstrates how shifts in aperiodic slope correlate with depression severity in a clinical trial of deep brain stimulation for treatment-resistant depression (TRD). The correlation between depression severity scores and aperiodic slope is significant in N=5 subjects, indicating that flatter (less negative) slopes correspond to reduced depression severity, especially in the ventromedial prefrontal cortex. This biomarker offers a new way to track patient response to MDD treatment, facilitating individualized therapies in both intracranial and non-invasive monitoring scenarios.

NeuroDAC: an open-source arbitrary biosignal waveform generator.

Objective.Researchers are developing biomedical devices with embedded closed-loop algorithms for providing advanced adaptive therapies. As these devices become more capable and algorithms become more complex, tasked with integrating and interpreting multi-channel, multi-modal electrophysiological signals, there is a need for flexible bench-top testing and prototyping. We present a methodology for leveraging off-the-shelf audio equipment to construct a biosignal waveform generator capable of streaming pre-recorded biosignals from a host computer. By re-playing known, well-characterized, but physiologically relevant real-world biosignals into a device under test, researchers can evaluate their systems without the need for expensivein vivoexperiments.Approach.An open-source design based on the proposed methodology is described and validated, the NeuroDAC. NeuroDAC allows for 8 independent channels of biosignal playback using a simple, custom designed attenuation and buffering circuit. Applications can communicate with the device over a USB interface using standard audio drivers. On-board analog amplitude adjustment is used to maximize the dynamic range for a given signal and can be independently tuned for each channel.Main results.Low noise component selection yields a no-signal noise floor of just 5.35 ± 0.063. NeuroDAC's frequency response is characterized with a high pass -3 dB rolloff at 0.57 Hz, and is capable of accurately reproducing a wide assortment of biosignals ranging from EMG, EEG, and ECG to extracellularly recorded neural activity. We also present an application example using the device to test embedded algorithms on a closed-loop neural modulation device, the Medtronic RC+S.Significance.By making the design of NeuroDAC open-source we aim to present an accessible tool for rapidly prototyping new biomedical devices and algorithms than can be easily modified based on individual testing needs.ClinicalTrials.gov Identifiers: NCT04281134, NCT03437928, NCT03582891.

Decoding hindlimb kinematics from primate motor cortex using long short-term memory recurrent neural networks.

Recent machine learning techniques have become a powerful tool in a variety of tasks, including neural decoding. Deep neural networks, particularly recurrent models, leverage the temporal evolution of neural ensemble activity to decode complex movement and sensory signals. Using single-unit recordings from microelectrode arrays implanted in the leg area of primary motor cortex in non-human primates, we decode the positions and angles of hindlimb joints during a locomotion task using a long short-term memory (LSTM) network. The LSTM decoder improved decoding over traditional filtering methods, such as Wiener and Kalman filters. However, dramatic improvements over other machine learning (e.g. XGBoost) and latent state-space methods were not observed.

Active microelectronic neurosensor arrays for implantable brain communication interfaces.

We have built a wireless implantable microelectronic device for transmitting cortical signals transcutaneously. The device is aimed at interfacing a cortical microelectrode array to an external computer for neural control applications. Our implantable microsystem enables 16-channel broadband neural recording in a nonhuman primate brain by converting these signals to a digital stream of infrared light pulses for transmission through the skin. The implantable unit employs a flexible polymer substrate onto which we have integrated ultra-low power amplification with analog multiplexing, an analog-to-digital converter, a low power digital controller chip, and infrared telemetry. The scalable 16-channel microsystem can employ any of several modalities of power supply, including radio frequency by induction, or infrared light via photovoltaic conversion. As of the time of this report, the implant has been tested as a subchronic unit in nonhuman primates ( approximately 1 month), yielding robust spike and broadband neural data on all available channels.

Isolated calf lengthening in cerebral palsy. Outcome analysis of risk factors.

We assessed the medium-term outcome of three methods of isolated calf lengthening in cerebral palsy by clinical examination, observational gait analysis and, where appropriate, instrumented gait analysis. The procedures used were percutaneous lengthening of tendo Achillis, open Z-lengthening of tendo Achillis and lengthening of the gastrosoleus aponeurosis (Baker's procedure). We reviewed 195 procedures in 134 children; 45 had hemiplegia, 65 diplegia and 24 quadriplegia. We established the incidence of calcaneus and recurrent equinus and identified 'at-risk' groups for each. At follow-up, 42% had satisfactory calf length, 22% had recurrent equinus and 36% calcaneus. The incidence of calcaneus in girls at follow-up was significantly higher (p = 0.002) while boys had an increased rate of recurrent equinus (p = 0.012). Children with diplegia who had surgery when aged eight years or younger had a 44% risk of calcaneus, while those over eight years had a 19% risk (p = 0.046). Percutaneous lengthening of tendo Achillis in diplegia was the least predictable, only 38% having a satisfactory outcome compared with 50% in the other procedures. The incidence of recurrent equinus in hemiplegic patients was 38%. Only 4% developed calcaneus. The type of surgery did not influence the outcome in patients with hemiplegia or quadriplegia. Severity of involvement, female gender, age at operation of less than eight years and percutaneous lengthening of tendo Achillis were 'risk factors' for calcaneus. Hemiplegia, male gender, and an aponeurosis muscle lengthening increased the risk of recurrent equinus.

Long-term osteoarthritic changes in anterior cruciate ligament reconstructed knees.

To consolidate the indications for anterior cruciate ligament reconstruction and clarify the long-term prognosis associated with current surgical and rehabilitation techniques, the incidence of osteoarthritis in arthroscopically anterior cruciate ligament reconstructed knees requires investigation. Seventy-two patients with anterior cruciate ligament ruptures who were active in sports requiring sidestepping and pivoting, or who had recurrent episodes of giving way, underwent arthroscopic bone-patellar tendon-bone anterior cruciate ligament reconstruction. These patients were evaluated for meniscal damage and osteoarthritic changes at the time of surgery and followed up for 7 years. Fifty-three patients underwent radiographic evaluation at 7 years, which included anteroposterior, lateral, skyline, and 30 degrees posteroanterior weightbearing views. Radiographic evaluation was performed by three independent surgeons and graded as per International Knee Documentation Committee criteria. Results revealed that knees with chronic anterior cruciate ligament deficiency, even those with intact menisci before reconstruction, suffered early osteoarthritic changes. More severe changes were seen with meniscectomy. Acute anterior cruciate ligament reconstruction with meniscal preservation was shown to have the lowest incidence of degenerative change. Controversy exists regarding the timing of anterior cruciate ligament reconstruction. This study supports early reconstruction of anterior cruciate ligament deficient knees before episodes of giving way occur in individuals intent on continuing activities that involve sidestepping and pivoting.

Operative reconstruction after transverse rupture of the tendons of both peroneus longus and brevis. Surgical reconstruction by transfer of the flexor digitorum longus tendon.

Rupture of the tendons of both peroneus longus and peroneus brevis results in considerable disability. We have performed transfer of flexor digitorum longus (FDL) to peroneus brevis in two patients with lateral instability of the hindfoot due to chronic transverse tears of both tendons for which end-to-end repair was not possible. Both patients had excellent function when reviewed after eight and six years, respectively, with no symptoms. CT showed a normal appearance of the FDL in both patients, but the peroneal muscles looked abnormal. Transfer of the FDL provides a reliable solution to lateral instability of the hindfoot resulting from loss of function of both peronei.

Participation in sports after total knee replacement.

Return to regular sports activity was evaluated in a retrospective review of 160 patients who had undergone total knee replacement surgery by a single surgeon (208 knee replacements). Mean age of the patients was 68 years (range, 27 to 87) at surgery and 73 years (range, 33 to 91) at review at a mean follow-up of 5 years (range, 3 to 7). Seventy-nine patients regularly participated in sports, at least once per week, before surgery, and 51 patients regularly participated in sports after surgery. Only eight patients took up sports after surgery who were not regularly involved in sports in the year before surgery. Patients were more likely to return to low-impact activities such as bowls (29 of 32, or 91%) than to high-impact activities such as tennis (6 of 30, or 20% returned). Forty-three of 56 patients (77%) who had participated in regular exercise in the year before surgery returned to sports. Eighty patients did not participate in sports before surgery and 54 of these had coexisting disease that prevented sports. None of these patients returned to sports.

Pigmented villonodular synovitis in the first metatarsophalangeal joint: arthroscopic treatment of an unusual condition.

Pigmented nodular synovitis is an uncommon condition of the foot. In this case history, we report a case of pigmented nodular synovitis in the first metatarsophalangeal joint, treated by arthroscopic synovectomy. Pigmented nodular synovitis to our knowledge has not been described in the first metatarsophalangeal joint. We report successful treatment of the condition by arthroscopic removal of the tissue, with the patient being asymptomatic 2 years after surgery.

Tear of the plantar calcaneonavicular (spring) ligament causing flatfoot. A case report.

Acquired flatfoot deformity after injury is usually due to partial or complete tearing of the tendon of tibialis posterior, with secondary failure of the other structures which maintain the medial longitudinal arch. We describe a patient in whom the rupture of the plantar calcaneonavicular (spring) ligament resulted in a clinical picture similar to that of rupture of the tendon of tibialis posterior. Operative repair of the ligament and transfer of the tendon of flexor digitorum gave an excellent result at four years with the patient returning to full sporting activities.

Distal forearm fractures in children: the role of hand dominance.

A survey of 426 children with unilateral distal forearm fractures was performed to examine the role of hand dominance. Results showed a significant preponderance of fractures occurring in the non-dominant arm (p < .01). This finding has implications for possible preventive strategies in these common injuries.