Frontal and temporal white matter pathways play key roles in language processing, but the specific computations supported by different tracts remain a matter of study. A role in speech planning has ...been proposed for a recently described pathway, the frontal aslant tract (FAT), which connects the posterior inferior frontal gyrus to the pre-SMA. Here, we use longitudinal functional and structural MRI and behavioral testing to evaluate the behavioral consequences of a lesion to the left FAT that was incurred during surgical resection of a frontal glioma in a 60-year-old woman, Patient AF. The pattern of performance in AF is compared, using the same measures, with that in a 37-year-old individual who underwent a left anterior temporal resection and hippocampectomy (Patient AG). AF and AG were both cognitively intact preoperatively but exhibited specific and doubly dissociable behavioral deficits postoperatively: AF had dysfluent speech but no word finding difficulty, whereas AG had word finding difficulty but otherwise fluent speech. Probabilistic tractography showed that the left FAT was lesioned postoperatively in AF (but not AG) whereas the inferior longitudinal fasciculus was lesioned in AG (but not AF). Those structural changes were supported by corresponding changes in functional connectivity to the posterior inferior frontal gyrus: decreased functional connectivity postoperatively between the posterior inferior frontal gyrus and pre-SMA in AF (but not AG) and decreased functional connectivity between the posterior inferior frontal gyrus and the middle temporal gyrus in AG (but not AF). We suggest from these findings that the left FAT serves as a key communicative link between sentence planning and lexical access processes.
Sentence production involves mapping from deep structures that specify meaning and thematic roles to surface structures that specify the order and sequencing of production ready elements. We propose ...that the frontal aslant tract is a key pathway for sequencing complex actions with deep hierarchical structure. In the domain of language, and primarily with respect to the left FAT, we refer to this as the 'Syntagmatic Constraints On Positional Elements' (SCOPE) hypothesis. One prediction made by the SCOPE hypothesis is that disruption of the frontal aslant tract should disrupt sentence production at grammatical phrase boundaries, with no disruption of articulatory processes. We test this prediction in a patient undergoing direct electrical stimulation mapping of the frontal aslant tract during an awake craniotomy to remove a left frontal brain tumor. We found that stimulation of the left FAT prolonged inter-word durations at the start of grammatical phrases, while inter-word durations internal to noun phrases were unaffected, and there was no effect on intra-word articulatory duration. These results provide initial support for the SCOPE hypothesis, and motivate novel directions for future research to explore the functions of this recently discovered component of the language system.
Understanding the neural mechanisms that support spontaneous recovery of cognitive abilities can place important constraints on mechanistic theories of brain organization and function, and holds ...potential to inform clinical interventions. Connectivity-based MRI measures have emerged as a way to study how recovery from brain injury is modulated by changes in intra- and inter-hemispheric connectivity. Here we report a detailed and multi-modal case study of a 26 year-old male who presented with a left inferior parietal glioma infiltrating the left arcuate fasciculus. The patient underwent pre- and post-operative functional MRI and Diffusion Tensor Imaging, as well as behavioral assessments of language, motor, vision and praxis. The surgery for removal of the tumor was carried out with the patient awake, and direct electrical stimulation mapping was used to evaluate cortical language centers. The patient developed a specific difficulty with repeating sentences toward the end of the surgery, after resection of the tumor and partial transection of the arcuate fasciculus. The patient recovered from the sentence repetition impairments over several months after the operation. Coincident with the patient's cognitive recovery, we document a pattern whereby intra-hemispheric functional connectivity was reduced in the left hemisphere, while inter-hemispheric connectivity increased between classic left hemisphere language regions and their right hemisphere homologues. These findings suggest that increased synchrony between the two hemispheres, in the setting of focal transection of the left arcuate fasciculus, can facilitate functional recovery.
In our prior work, we conducted a field trial of the mobile application DocCHIRP (Crowdsourcing Health Information Retrieval Protocol for Doctors), designed to help clinicians problem-solve at the ...point of care by crowdsourcing their peers. Here, we present the results of our post-trial survey that investigated the impressions of participating clinicians regarding the use of medical crowdsourcing and to identify factors influencing adoption of the technology. In all, 72 valid surveys were received from 85 registered users (85% response rate). The majority of clinicians (>80%) felt crowdsourcing would be useful to diagnose unusual cases, facilitate patient referrals, and problem-solve at the point of care. Perceived barriers to adoption included interruptions in workflow and the reluctance to publicly expose knowledge gaps. While considered a useful alternative to existing methods, future studies are needed to investigate whether the approach and application can be modified to effectively address these barriers, and to determine whether crowdsourcing will enhance provider performance and the quality of care delivered.
As the pace of medical discovery widens the knowledge-to-practice gap, technologies that enable peer-to-peer crowdsourcing have become increasingly common. Crowdsourcing has the potential to help ...medical providers collaborate to solve patient-specific problems in real time. We recently conducted the first trial of a mobile, medical crowdsourcing application among healthcare providers in a university hospital setting. In addition to acknowledging the benefits, our participants also raised concerns regarding the potential negative consequences of this emerging technology. In this commentary, we consider the legal and ethical implications of the major findings identified in our previous trial including compliance with the Health Insurance Portability and Accountability Act, patient protections, healthcare provider liability, data collection, data retention, distracted doctoring, and multi-directional anonymous posting. We believe the commentary and recommendations raised here will provide a frame of reference for individual providers, provider groups, and institutions to explore the salient legal and ethical issues before they implement these systems into their workflow.
Technology can translocate traditional art into interactive, immersive experiences. At the Asian Art Museum of San Francisco, the authors transformed Tibetan Buddhist mandalas into a 3D virtual ...reality mandala installation. Furthering this project, they externalized an analog of the meditative experience by recording electroencephalograms that dynamically modulated the visual scene. The use of neurofeedback allowed fluctuations in the alpha power to drive the intensity of the fog obscuring the mandala. This aimed to give a sense of clearing the fog with one’s mind in a meditation-like state. The collaboration demonstrated how technology intended for scientific use may be adapted to an artistic installation that enriches the visitor experience.
Cerebral ischemia triggers a cascade of neuroinflammatory and peripheral immune responses that contribute to post-ischemic reperfusion injury. Prior work conducted in CNS ischemia models underscore ...the potential to harness non-antibiotic properties of tetracycline antibiotics for therapeutic benefit. In the present study, we explored the immunomodulatory effects of the tetracycline derivative 9-tert-butyl doxycycline (9-TB) in a mouse model of transient global ischemia that mimics immunologic aspects of the post-cardiac arrest syndrome. Pharmacokinetic studies performed in C57BL/6 mice demonstrate that within four hours after delivery, levels of 9-TB in the brain were 1.6 and 9.5-fold higher than those obtained using minocycline and doxycycline, respectively. Minocycline and 9-TB also dampened inflammation, measured by reduced TNFα-inducible, NF-κβ-dependent luciferase activity in a microglial reporter line. Notably, daily 9-TB treatment following ischemia-reperfusion injury in vivo induced the retention of polymorphonuclear neutrophils (PMNs) within the spleen while simultaneously biasing CNS PMNs towards an anti-inflammatory (CD11bLowYm1+) phenotype. These studies indicate that aside from exhibiting enhanced CNS delivery, 9-TB alters both the trafficking and polarization of PMNs in the context of CNS ischemia-reperfusion injury.
Anthropocene Baselines KOPF, R. KELLER; FINLAYSON, C. MAX; HUMPHRIES, PAUL ...
BioScience/Bioscience,
08/2015, Letnik:
65, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Global ecosystems have shifted from historical conditions, but it is unclear from what baselines change should be assessed. Scientists and managers have increasingly accepted the impossibility of ...returning ecosystems to a “pristine” state; however, historical conditions remain the cornerstone for restoration and management. We explore the rationale behind the application of historical baselines to ecosystem management and propose Anthropocene baselines as a concept to provide an improved basis for the management of human-dominated ecosystems. The Anthropocene baselines concept emphasizes the conservation value of the remnants of historical ecosystems but confronts the reality that many ecosystems cannot—or will not—be restored to historical ranges of variability. In order to prevent further unwanted changes to biodiversity and ecosystem services, we suggest that the management of human-dominated ecosystems must move beyond historical constraints toward new points of reference dictated by social–ecological sustainability.
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