Eyal Y. Kimchi

Dysregulation of sodium channel expression in cortical neurons in a rodent model of absence epilepsy

Due to the involvement of cortical neurons in spike-wave discharge (SWD) initiation, and the contribution of voltage-gated sodium channels (VGSCs) to neuronal firing, we examined alterations in the expression of VGSC mRNA and protein in cortical neurons in the WAG/Rij absence epileptic rat. WAG/Rij rats were compared to age-matched Wistar control rats at 2, 4, and 6 months. Continuous EEG data was recorded, and percent time in SWD was determined. Tissue from different cortical locations from WAG/Rij and Wistar rats was analyzed for VGSC mRNA (by quantitative PCR) and protein (by immunocytochemistry). SWDs increased with age in WAG/Rij rats. mRNA levels for sodium channels Nav1.1 and Nav1.6, but not Nav1.2, were found to be up-regulated selectively within the facial somatosensory cortex (at AP +0.0, ML +6.0 mm). Protein levels for Nav1.1 and Nav1.6 were up-regulated in layer II-IV cortical neurons in this region of cortex. No significant changes were seen in adjacent regions or other brain areas, including the pre-frontal and occipital cortex. In the WAG/Rij model of absence epilepsy, we identified a specific region of cortex, in layer II-IV neurons on the lateral convexity of the cortex in the facial somatosensory area, where mRNA and protein expression of sodium channel genes Nav1.1 and Nav1.6 are up-regulated. This region of cortex approximately matches the electrophysiologically determined region of seizure onset. Changes in the expression of Nav1.1 and Nav1.6 parallel age-dependent increases in seizure frequency and duration.

Postoperative Delirium in Older Adults: Best Practice Statement from the American Geriatrics Society

Disclosure Information: Disclosures for the members of t Geriatrics Society Postoperative Delirium Panel are listed in Support: Supported by a grant from the John A Hartford Fou to the Geriatrics-for-Specialists Initiative of the American Geri (grant 2009-0079). This article is a supplement to the American Geriatrics Soci Practice Guidelines for Postoperative Delirium in Older Adu at the American College of Surgeons 100 Annual Clinic San Francisco, CA, October 2014.

Redundancy and Synergy of Neuronal Ensembles in Motor Cortex

We examined the ability of neuronal ensembles from rat motor cortex to predict behavioral performance during a reaction time task. We found that neurons that were the best individual predictors of task performance were not necessarily the neurons that contributed the most predictive information to an ensemble of neurons. To understand this result, we applied a framework for quantifying statistical relationships between neurons (Schneidman et al., 2003) to all possible combinations of neurons within our ensembles. We found that almost all neurons (96%) contributed redundant predictive information to the ensembles. This redundancy resulted in the maintenance of predictive information despite the removal of many neurons from each ensemble. Moreover, the balance of synergistic and redundant interactions depended on the number of neurons in the ensemble. Small ensembles could exhibit synergistic interactions (e.g., 23 ± 9% of ensembles with two neurons were synergistic). In contrast, larger ensembles exhibited mostly redundant interactions (e.g., 99 ± 0.1% of ensembles with eight neurons were redundant). We discuss these results with regard to constraints on interpreting neuronal ensemble data and with respect to motor cortex involvement in reaction time performance.

American Geriatrics Society abstracted clinical practice guideline for postoperative delirium in older adults

The abstracted set of recommendations presented here provides essential guidance both on the prevention of postoperative delirium in older patients at risk of delirium and on the treatment of older surgical patients with delirium, and is based on the 2014 American Geriatrics Society (AGS) Guideline. The full version of the guideline, American Geriatrics Society Clinical Practice Guideline for Postoperative Delirium in Older Adults is available at the website of the AGS. The overall aims of the study were twofold: first, to present nonpharmacologic and pharmacologic interventions that should be implemented perioperatively for the prevention of postoperative delirium in older adults; and second, to present nonpharmacologic and pharmacologic interventions that should be implemented perioperatively for the treatment of postoperative delirium in older adults. Prevention recommendations focused on primary prevention (i.e., preventing delirium before it occurs) in patients who are at risk for postoperative delirium (e.g., those identified as moderate‐to‐high risk based on previous risk stratification models such as the National Institute for Health and Care Excellence (NICE) guidelines, Delirium: Diagnosis, Prevention and Management. Clinical Guideline 103; London (UK): 2010 July 29). For management of delirium, the goals of this guideline are to decrease delirium severity and duration, ensure patient safety and improve outcomes.

Dynamic encoding of action selection by the medial striatum.

Successful foragers respond flexibly to environmental stimuli. Behavioral flexibility depends on a number of brain areas that send convergent projections to the medial striatum, such as the medial prefrontal cortex, orbital frontal cortex, and amygdala. Here, we tested the hypothesis that neurons in the medial striatum are involved in flexible action selection, by representing changes in stimulus–reward contingencies. Using a novel Go/No-go reaction-time task, we changed the reward value of individual stimuli within single experimental sessions. We simultaneously recorded neuronal activity in the medial and ventral parts of the striatum of rats. The rats modified their actions in the task after the changes in stimulus–reward contingencies. This was preceded by dynamic modulations of spike activity in the medial, but not the ventral, striatum. Our results suggest that the medial striatum biases animals to collect rewards to potentially valuable stimuli and can rapidly influence flexible behavior.

Streamlined, Inexpensive 3D Printing of the Brain and Skull

Neuroimaging technologies such as Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) collect three-dimensional data (3D) that is typically viewed on two-dimensional (2D) screens. Actual 3D models, however, allow interaction with real objects such as implantable electrode grids, potentially improving patient specific neurosurgical planning and personalized clinical education. Desktop 3D printers can now produce relatively inexpensive, good quality prints. We describe our process for reliably generating life-sized 3D brain prints from MRIs and 3D skull prints from CTs. We have integrated a standardized, primarily open-source process for 3D printing brains and skulls. We describe how to convert clinical neuroimaging Digital Imaging and Communications in Medicine (DICOM) images to stereolithography (STL) files, a common 3D object file format that can be sent to 3D printing services. We additionally share how to convert these STL files to machine instruction gcode files, for reliable in-house printing on desktop, open-source 3D printers. We have successfully printed over 19 patient brain hemispheres from 7 patients on two different open-source desktop 3D printers. Each brain hemisphere costs approximately

Impaired auditory discrimination learning following perinatal nicotine exposure or β2 nicotinic acetylcholine receptor subunit deletion

3–4 in consumable plastic filament as described, and the total process takes 14–17 hours, almost all of which is unsupervised (preprocessing = 4–6 hr; printing = 9–11 hr, post-processing = <30 min). Printing a matching portion of a skull costs

Seizures at the scale of individual neurons.

1–5 in consumable plastic filament and takes less than 14 hr, in total. We have developed a streamlined, cost-effective process for 3D printing brain and skull models. We surveyed healthcare providers and patients who confirmed that rapid-prototype patient specific 3D models may help interdisciplinary surgical planning and patient education. The methods we describe can be applied for other clinical, research, and educational purposes.

Clinical Reasoning: A 44-year-old woman with headache followed by sudden neurologic decline

Maternal smoking during pregnancy can impair performance of the exposed offspring in tasks that require auditory stimulus processing and perception; however, the tobacco component(s) responsible for these effects and the underlying neurobiological mechanisms remain uncertain. In this study, we show that administration of nicotine during mouse perinatal development can impair performance in an auditory discrimination paradigm when the exposed animals are mature. This suggests that nicotine disrupts auditory pathways via nicotinic acetylcholine receptors (nAChRs) that are expressed at an early stage of development. We have also determined that mice which lack nAChRs containing the β2 subunit (β2* nAChRs) exhibit similarly compromised performance in this task, suggesting that β2* nAChRs are necessary for normal auditory discrimination or that β2* nAChRs play a critical role in development of the circuitry required for task performance. In contrast, no effect of perinatal nicotine exposure or β2 subunit knockout was found on the acquisition and performance of a differential reinforcement of low rate task. This suggests that the auditory discrimination impairments are not a consequence of a general deficit in learning and memory, but may be the result of compromised auditory stimulus processing in the nicotine-exposed and knockout animals.

Transient aqueductal occlusion in intracerebral haemorrhage

This scientific commentary refers to ‘Single unit action potentials in humans and the effect of seizure activity’ by Merricks et al. (doi:10.1093/brain/awv208). Seizures are commonly accepted to be events characterized by brief periods of abnormal neuronal firing. However, the basic physiology of what occurs during a seizure remains poorly understood. This significant shortfall prevents us from developing new treatments for the one-third of patients with epilepsy who do not obtain substantial control of their seizures with maximal medical therapy. Beginning in the 1950s, researchers began to address the physiology gap with recordings in models of seizures, including recordings of neural activity in small numbers of individual neurons. First in animal models and now more recently in human patients, studies of individual neurons have described how neural activity changes as seizures start, spread and terminate. These studies, however, have also fuelled additional questions about how seizures can be defined, characterized and ultimately brought under control. The canonical view of a typical seizure is that it represents excessive or ‘hypersynchronous’ activity in a large group of neurons. This textbook model is a satisfactory shorthand for the overall process of a seizure, but neglects noteworthy heterogeneity and important unknowns. In the last decade or so, work from many groups using a …