39 research outputs found

    Electrocorticography is superior to subthalamic local field potentials for movement decoding in Parkinson’s disease

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    Brain signal decoding promises significant advances in the development of clinical brain computer interfaces (BCI). In Parkinson's disease (PD), first bidirectional BCI implants for adaptive deep brain stimulation (DBS) are now available. Brain signal decoding can extend the clinical utility of adaptive DBS but the impact of neural source, computational methods and PD pathophysiology on decoding performance are unknown. This represents an unmet need for the development of future neurotechnology. To address this, we developed an invasive brain-signal decoding approach based on intraoperative sensorimotor electrocorticography (ECoG) and subthalamic LFP to predict grip-force, a representative movement decoding application, in 11 PD patients undergoing DBS. We demonstrate that ECoG is superior to subthalamic LFP for accurate grip-force decoding. Gradient boosted decision trees (XGBOOST) outperformed other model architectures. ECoG based decoding performance negatively correlated with motor impairment, which could be attributed to subthalamic beta bursts in the motor preparation and movement period. This highlights the impact of PD pathophysiology on the neural capacity to encode movement vigor. Finally, we developed a connectomic analysis that could predict grip-force decoding performance of individual ECoG channels across patients by using their connectomic fingerprints. Our study provides a neurophysiological and computational framework for invasive brain signal decoding to aid the development of an individualized precision-medicine approach to intelligent adaptive DBS

    Methanogenic activity and biomass in Holocene permafrost deposits of the Lena Delta, Siberian Arctic and its implication for the global methane budget

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    Permafrost environments within the Siberian Arctic are natural sources of the climate relevant trace gas methane. In order to improve our understanding of the present and future carbon dynamics in high latitudes, we studied the methane concentration, the quantity and quality of organic matter, and the activity and biomass of the methanogenic community in permafrost deposits. For these investigations a permafrost core of Holocene age was drilled in the Lena Delta (72°22′N, 126°28′E). The organic carbon of the permafrost sediments varied between 0.6% and 4.9% and was characterized by an increasing humification index with permafrost depth. A high CH4 concentration was found in the upper 4 m of the deposits, which correlates well with the methanogenic activity and archaeal biomass (expressed as PLEL concentration). Even the incubation of core material at −3 and −6°C with and without substrates showed a significant CH4 production (range: 0.04–0.78 nmol CH4 h−1 g−1). The results indicated that the methane in Holocene permafrost deposits of the Lena Delta originated from modern methanogenesis by cold-adapted methanogenic archaea. Microbial generated methane in permafrost sediments is so far an underestimated factor for the future climate development

    Methane fluxes in permafrost habitats of the Lena Delta: effects of microbial community structure and organic matter quality

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    For the understanding and assessment of recent and future carbon dynamics of arctic permafrost soils the processes of CH4 production and oxidation, the community structure and the quality of DOM were studied in two soils of a polygonal tundra. Activities of methanogens and methanotrophs differed significantly in their rates and distribution patterns among the two investigated profiles. Community structure analysis showed similarities between both soils for esterlinked PLFAs and differences in the fraction of unsaponifiable PLFAs and PLELs. Furthermore, a shift of the overall composition of the microbiota with depth at both sites was indicated by an increasing portion of iso- and anteiso-branched fatty acids related to the amount of straight chain fatty acids. Although permafrost soils represent a large carbon pool, it was shown, that the reduced quality of organic matter leads to a substrate limitation of the microbial metabolism. It can be concluded from our and previous findings firstly that microbial communities in the active layer of an Arctic polygon tundra are composed by members of all three domains of life, with a total biomass comparable to temperate soil ecosystems. And secondly that these microorganisms are well adapted to the extreme temperature gradient of their environment

    Small incision iris tumour biopsy using a cavernous sampling forceps

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    The aim of this retrospective report is to describe our experience with the Essen-23G biopsy forceps (Akgül forceps) for biopsies of pigmented iris tumours

    Unusual bilateral traumatic maculopathy following whiplash injury

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    An unusual extensive bilateral macular oedema (MO) with spontaneous resolution occurred following a car crash accident. Qualitative and quantitative analysis of the macular region using spectral domain optical coherence tomography (SD-OCT) and multifocal electroretinogram (mfERG) was performed daily during the first 7 days, as well as at 3 and 6 months following the accident. SD-OCT examination demonstrated extensive MO accompanied by neurosensory detachment and subretinal fluid. During the 7 days following the accident there was gradual resolution of the oedema accompanied by visual recovery. One year later no anatomical changes were observed, the mfERG showed complete recovery and visual acuity returned to normal level. Although whiplash is a common injury in motor vehicle accidents, whiplash maculopathy (WMP) is rarely reported, most likely due to underdiagnosis. Here we describe the spontaneous resolution of a severe MO after whiplash injury in a car crash accident