A Neural Implant Design Toolbox for Nonhuman Primates.

This paper describes an in-house method of 3D brain and skull modeling from magnetic resonance imaging (MRI) tailored for nonhuman primate (NHP) neurosurgical planning. This automated, computational software-based technique provides an efficient way of extracting brain and skull features from MRI files as opposed to traditional manual extraction techniques using imaging software. Furthermore, the procedure provides a method for visualizing the brain and craniotomized skull together for intuitive, virtual surgical planning. This generates a drastic reduction in time and resources from those required by past work, which relied on iterative 3D printing. The skull modeling process creates a footprint that is exported into modeling software to design custom-fit cranial chambers and headposts for surgical implantation. Custom-fit surgical implants minimize gaps between the implant and the skull that could introduce complications, including infection or decreased stability. By implementing these pre-surgical steps, surgical and experimental complications are reduced. These techniques can be adapted for other surgical processes, facilitating more efficient and effective experimental planning for researchers and, potentially, neurosurgeons.

Time and frequency domain analysis of physiological features during autonomic dysreflexia after spinal cord injury.

Introduction: Autonomic dysreflexia (AD) affects about 70% of individuals with spinal cord injury (SCI) and can have severe consequences, including death if not promptly detected and managed. The current gold standard for AD detection involves continuous blood pressure monitoring, which can be inconvenient. Therefore, a non-invasive detection device would be valuable for rapid and continuous AD detection. Methods: Implanted rodent models were used to analyze autonomic dysreflexia after spinal cord injury. Skin nerve activity (SKNA) features were extracted from ECG signals recorded non-invasively, using ECG electrodes. At the same time, blood pressure and ECG data sampled was collected using an implanted telemetry device. Heart rate variability (HRV) features were extracted from these ECG signals. SKNA and HRV parameters were analyzed in both the time and frequency domain. Results: We found that SKNA features showed an increase approximately 18 seconds before the typical rise in systolic blood pressure, indicating the onset of AD in a rat model with upper thoracic SCI. Additionally, low-frequency components of SKNA in the frequency domain were dominant during AD, suggesting their potential inclusion in an AD detection system for improved accuracy. Discussion: Utilizing SKNA measurements could enable early alerts to individuals with SCI, allowing timely intervention and mitigation of the adverse effects of AD, thereby enhancing their overall well-being and safety.

Acclimation Protocol to Minimize Stress in Immobilized Rats During Non-Invasive Multimodal Sensing of the Autonomic Nervous System.

INTRODUCTION: Rodent models are often used in spinal cord injury investigations to measure physiological parameters but require rats to be restrained during data collection to prevent motion and stress-induced artifacts. MATERIALS AND METHODS: A 4-week acclimation protocol was developed to reduce sympathetic activity during experimentation to collect clean data. Physiological parameters were analyzed throughout the acclimation protocol using surface-based electrodes and an implanted sensor. The sensor was used to extract systolic blood pressure, skin nerve activity, and heart rate variability parameters. RESULTS: Our protocol exposed a minimal increase in sympathetic activity during experimentation despite long periods of restraint. The data suggest that the acclimation protocol presented successfully minimized changes in physiological parameters because of prolonged restraint. CONCLUSIONS: This is necessary to ensure that physiological recordings are not affected by undue stress because of the process of wearing the sensor. This is important when determining the effects of stress when studying dysautonomia after spinal cord injury, Parkinson's disease, and other neurological disorders.