Development of a novel, concentric micro-ECoG array enabling simultaneous detection of a single location by multiple electrode sizes.

OBJECTIVE: Detection of the epileptogenic zone is critical, especially for patients with drug-resistant epilepsy. Accurately mapping cortical regions exhibiting high activity during spontaneous seizure events while detecting neural activity up to 500 Hz can assist clinicians' surgical decisions and improve patient outcomes. APPROACH: We designed, fabricated, and tested a novel hybrid, multi-scale micro-electrocorticography (micro-ECoG) array with a unique embedded configuration. This array was compared to a commercially available microelectrode array (Neuronexus) for recording neural activity in rodent sensory cortex elicited by somatosensory evoked potentials and pilocarpine-induced seizures. Main results Evoked potentials and spatial maps recorded by the multi-scale array ("micros", "mesos", and "macros" refering to the relative electrode sizes, 40 micron, 1 mm, and 4 mm respectively) were comparable to the Neuronexus array. The SSEPs recorded with the micros had higher peak amplitudes and greater signal power than those recorded by the larger mesos and macro. Seizure onset events and high-frequency oscillations (∼450 Hz) were detected on the multi- scale, similar to the commercially available array. The micros had greater SNR than the mesos and macro over the 5-1000 Hz frequency range during seizure monitoring. During cortical stimulation experimentation, the mesos successfully elicited motor effects. SIGNIFICANCE: Previous studies have compared macro- and microelectrodes for localizing seizure activity in adjacent regions. The multi-scale design validated here is the first to simultaneously measure macro- and microelectrode signals from the same overlapping cortical area. This enables direct comparison of microelectrode recordings to the macroelectrode recordings used in standard neurosurgical practice. Previous studies have also shown that cortical regions generating high-frequency oscillations are at an increased risk for becoming epileptogenic zones. More accurate mapping of these micro seizures may improve surgical outcomes for epilepsy patients.

Community established best practice recommendations for tephra studies-from collection through analysis.

Tephra is a unique volcanic product with an unparalleled role in understanding past eruptions, long-term behavior of volcanoes, and the effects of volcanism on climate and the environment. Tephra deposits also provide spatially widespread, high-resolution time-stratigraphic markers across a range of sedimentary settings and thus are used in numerous disciplines (e.g., volcanology, climate science, archaeology). Nonetheless, the study of tephra deposits is challenged by a lack of standardization that inhibits data integration across geographic regions and disciplines. We present comprehensive recommendations for tephra data gathering and reporting that were developed by the tephra science community to guide future investigators and to ensure that sufficient data are gathered for interoperability. Recommendations include standardized field and laboratory data collection, reporting and correlation guidance. These are organized as tabulated lists of key metadata with their definition and purpose. They are system independent and usable for template, tool, and database development. This standardized framework promotes consistent documentation and archiving, fosters interdisciplinary communication, and improves effectiveness of data sharing among diverse communities of researchers.

Minimally Invasive, Endoscopic-Assisted Device for Subdural Electrode Implantation in Epilepsy.

BACKGROUND: Subdural grids and strip electrodes provide wide coverage of the cerebral cortex, precise delineation of the extent of the seizure onset zone, and improved spatial sampling to perform functional mapping for eloquent cortex. OBJECTIVE: To describe a novel device that allows for a minimally invasive approach to implantation of subdural grid and strip electrodes. METHODS: A skull mounted device was created to allow for implantation of subdural electrodes through a keyhole craniotomy with direct visualization using the aid of a flexible neurovideoscope. The initial studies in preparation for grid development performed on cadaveric skulls were analyzed to determine the size of craniotomy required for deployment, maximal distance of strip electrode deployment from center of craniotomy, and visual inspection of the cortex was performed for any underlying damage. RESULTS: The device allowed for the placement of subdural electrodes through a 40-mm craniotomy. Subdural electrodes were deployed in multiple directions to a distance of a 70-mm radius from the center of the craniotomy. There was no visual damage to the underlying cortex after the procedures were completed. CONCLUSION: Large craniotomies are typically desired to provide direct visualization of the implantation of subdural electrodes, but can increase the risk of subdural hemorrhages and infections. This study describes a novel minimally invasive endoscopically assisted device for the implantation of subdural strip electrodes under direct visualization. With this device, we are able to limit the size of the craniotomy, avoid incision through the temporalis muscle, and implant subdural electrodes with visualization of the cortex.

Tephra from ice- A simple method to routinely mount, polish, and quantitatively analyze sparse fine particles.

A method involving a graphite substrate has been developed for the mounting and analysis of sparse, fine particles from a liquid suspension to enable improved study of volcanic ash (tephra) and atmospheric dust preserved in glacial ice. Unpolished grains may be studied by scanning electron microscope-energy dispersive spectrometry (SEM-EDS) at full vacuum without the need for a conductive coating due to the close proximity of the underlying graphite. The same grains in the same relative positions may be subsequently examined in polished mounts by a variety of methods including SEM-EDS, electron probe microanalysis, laser ablation-inductively coupled plasma-mass spectroscopy, secondary ion mass spectrometry, and optical microscopy. Particles as small as 3-5 microm may be routinely and easily prepared for analysis as polished grains, and particles of significantly different sizes may be exposed simultaneously. The general approach also offers significant flexibility, including both single- and multiple-sample mounts, and may be adjusted to suit a variety of samples and analytical methods.