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  • Berger, Thomas  (1,037)
Year
  • 1
    Language: English
    In: The European journal of neuroscience, July 2011, Vol.34(1), pp.22-30
    Description: Persistent spiking activity is thought to be a cellular process involved in working memory. We have been interested in whether persistent activity also exists in cortical areas which are not involved in this memory process. To study the possible presence and the mechanisms of persistent activity in layer 5 pyramidal cells of the mouse primary somatosensory, visual and motor cortices, we used patch-clamp and calcium imaging techniques. A combination of cholinergic receptor activation and suprathreshold depolarization or sufficient extracellular stimulation leads to either a subthreshold afterdepolarization or suprathreshold persistent activity in these cortices. There is a continuum of response amplitudes depending on depolarization size. To initiate persistent activity, spikes have to be induced at a frequency of at least 20 Hz, if tested for 1 s. Acetylcholine muscarinic, but not nicotinic, receptors are important for initiating persistent activity. Persistent activity is an intrinsic cellular, not a network, phenomenon as it persists under blockade of ionotropic glutamate and GABA receptors. A rise in intracellular calcium concentration through voltage-gated calcium channels is needed for persistent activity initiation, while intracellular calcium stores are not crucial. The increased intracellular calcium concentration leads to the activation of calcium-sensitive nonspecific cationic channels. This study for the first time describes the presence and the underlying mechanisms of persistent activity in pyramidal cells of three primary sensory and motor cortex areas. These results thereby suggest that persistent activity may be a general capability of deep layer cortical pyramidal cells.
    Keywords: Acetylcholine -- Pharmacology ; Action Potentials -- Physiology ; Cerebral Cortex -- Cytology ; Pyramidal Cells -- Drug Effects
    ISSN: 0953816X
    E-ISSN: 1460-9568
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 2011, Vol.108(13), pp.5419-5424
    Description: Neuronal circuitry is often considered a clean slate that can be dynamically and arbitrarily molded by experience. However, when we investigated synaptic connectivity in groups of pyramidal neurons in the neocortex, we found that both connectivity and synaptic weights were surprisingly predictable. Synaptic weights follow very closely the number of connections in a group of neurons, saturating after only 20% of possible connections are formed between neurons in a group. When we examined the network topology of connectivity between neurons, we found that the neurons cluster into small world networks that are not scale-free, with less than 2 degrees of separation. We found a simple clustering rule where connectivity is directly proportional to the number of common neighbors, which accounts for these small world networks and accurately predicts the connection probability between any two neurons. This pyramidal neuron network clusters into multiple groups of a few dozen neurons each. The neurons composing each group are surprisingly distributed, typically more than 100 μm apart, allowing for multiple groups to be interlaced in the same space. In summary, we discovered a synaptic organizing principle that groups neurons in a manner that is common across animals and hence, independent of individual experiences. We speculate that these elementary neuronal groups are prescribed Lego-like building blocks of perception and that acquired memory relies more on combining these elementary assemblies into higher-order constructs. ; p. 5419-5424.
    Keywords: Neocortex ; Animals ; Probability ; Neurons ; Memory
    ISSN: 0027-8424
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  • 3
    Language: English
    In: American Journal of Agricultural Economics, 2015, Vol.97(3), pp.833-854
    Keywords: Agricultural Productivity – Growth ; Climate Change – Analysis ; Economic Conditions – Forecasts and Trends
    ISSN: 0002-9092
    Source: Cengage Learning, Inc.
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  • 4
    In: Nature, 2011, Vol.472(7342), p.197
    Description: Coronal cavities are large low-density regions formed by hemispheric-scale magnetic flux ropes suspended in the Sun's outer atmosphere. They evolve over time, eventually erupting as the dark cores of coronal mass ejections. Although coronal mass ejections are common and can significantly affect planetary magnetospheres, the mechanisms by which cavities evolve to an eruptive state remain poorly understood. Recent optical observations of high-latitude 'polar crown' prominences within coronal cavities reveal dark, low-density 'bubbles' that undergo Rayleigh-Taylor instabilities to form dark plumes rising into overlying coronal cavities. These observations offered a possible mechanism for coronal cavity evolution, although the nature of the bubbles, particularly their buoyancy, was hitherto unclear. Here we report simultaneous optical and extreme-ultraviolet observations of polar crown prominences that show that these bubbles contain plasma at temperatures in the range (2.5-12)10 super(5) kelvin, which is 25-120 times hotter than the overlying prominence. This identifies a source of the buoyancy, and suggests that the coronal cavity-prominence system supports a novel form of magneto-thermal convection in the solar atmosphere, challenging current hydromagnetic concepts of prominences and their relation to coronal cavities.
    Keywords: Solar Convection ; Corona ; Coronal Observations ; Coronal Studies ; Solar Prominences ; Coronal Mass Ejections ; Convection Development ; Rayleigh-Taylor Instabilities ; Buoyancy ; Temperature ; Convection ; Plumes ; Atmosphere ; Sun ; Solar Prominences (523.987);
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 5
    Language: English
    In: Neuron, 2011, Vol.72(6), pp.991-1000
    Description: In classical tetrameric voltage-gated ion channels four voltage-sensing domains (VSDs), one from each subunit, control one ion permeation pathway formed by four pore domains. The human Hv1 proton channel has a different architecture, containing a VSD, but lacking a pore domain. Since its location is not known, we searched for the Hv permeation pathway. We find that mutation of the S4 segment's third arginine R211 (R3) compromises proton selectivity, enabling conduction of a metal cation and even of the large organic cation guanidinium, reminiscent of Shaker's omega pore. In the open state, R3 appears to interact with an aspartate (D112) that is situated in the middle of S1 and is unique to Hv channels. The double mutation of both residues further compromises cation selectivity. We propose that membrane depolarization reversibly positions R3 next to D112 in the transmembrane VSD to form the ion selectivity filter in the channel's open conformation. ► R3 in the S4 of the hHv1 proton channel is part of its cation selectivity filter ► Mutation of R3 allows conduction of Gu , as seen in K and Na channel omega pores ► D112 in S1 interacts with R3 in the open channel and contributes to selectivity ► Thus, gating of hHv1 involves the formation of its selectivity filter
    Keywords: Biology ; Anatomy & Physiology
    ISSN: 0896-6273
    E-ISSN: 1097-4199
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  • 6
    Language: English
    In: World Development, February 2016, Vol.78, pp.572-586
    Description: Rural producer organizations (RPOs) are currently seen as mechanisms of reducing transaction costs and improving market access of smallholder farmers. Yet little is known about the determinants of RPO effectiveness, especially in Sub-Saharan African countries. In this article we assess functioning of Ugandan RPO using a combination of participatory research and survey methods. We recommend areas for development interventions that would enhance the positive impact of RPO on livelihoods of their members. The proposed interventions refer to monetary transactions between RPO and their members, information channels within RPO, access to inputs and finance, member knowledge capacity and motivation of leaders.
    Keywords: Rural Producer Organizations ; Participatory Methods ; Agricultural Development ; Rural Networks ; Coffee Farmers ; Sub-Saharan Africa ; Economics
    ISSN: 0305-750X
    E-ISSN: 1873-5991
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  • 7
    Language: English
    In: Behaviour Research and Therapy, March 2011, Vol.49(3), pp.158-169
    Description: Internet-based self-help for social phobia with minimal therapist support via email have shown efficacy in several controlled trials by independent research teams. The role and necessity of therapist guidance is, however, still largely unclear. The present study compared the benefits of a 10-week web-based unguided self-help treatment for social phobia with the same intervention complemented with minimal, although weekly, therapist support via email. Further, a third treatment arm was included, in which the level of support was flexibly stepped up, from no support to email or telephone contact, on demand of the participants. Eighty-one individuals meeting diagnostic criteria for social phobia were randomly assigned to one of the three conditions. Primary outcome measures were self-report measures of symptoms of social phobia. Secondary outcome measures included symptoms of depression, interpersonal problems, and general symptomatology. Measures were taken at baseline, post-treatment, and at 6-month follow-up. Data from a telephone-administered diagnostic interview conducted at post-treatment were also included. Results showed significant symptom reductions in all three treatment groups with large effect sizes for primary social phobia measures (Cohen’s  = 1.47) and for secondary outcome measures (  = 1.16). No substantial and significant between-groups effects were found on any of the measures (Cohen’s  = 00–.36). Moreover, no difference between the three conditions was found regarding diagnosis-free status, clinically significant change, dropout rates, or adherence measures such as lessons or exercises completed. These findings indicate that Internet-delivered treatment for social phobia is a promising treatment option, whether no support is provided or with two different types of therapist guidance.
    Keywords: Internet Treatment ; Social Anxiety Disorder ; Guided Self-Help ; Randomized Controlled Trial (Rct) ; Medicine ; Psychology
    ISSN: 0005-7967
    E-ISSN: 1873-622X
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  • 8
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 29 March 2011, Vol.108(13), pp.5419-24
    Description: Neuronal circuitry is often considered a clean slate that can be dynamically and arbitrarily molded by experience. However, when we investigated synaptic connectivity in groups of pyramidal neurons in the neocortex, we found that both connectivity and synaptic weights were surprisingly predictable. Synaptic weights follow very closely the number of connections in a group of neurons, saturating after only 20% of possible connections are formed between neurons in a group. When we examined the network topology of connectivity between neurons, we found that the neurons cluster into small world networks that are not scale-free, with less than 2 degrees of separation. We found a simple clustering rule where connectivity is directly proportional to the number of common neighbors, which accounts for these small world networks and accurately predicts the connection probability between any two neurons. This pyramidal neuron network clusters into multiple groups of a few dozen neurons each. The neurons composing each group are surprisingly distributed, typically more than 100 μm apart, allowing for multiple groups to be interlaced in the same space. In summary, we discovered a synaptic organizing principle that groups neurons in a manner that is common across animals and hence, independent of individual experiences. We speculate that these elementary neuronal groups are prescribed Lego-like building blocks of perception and that acquired memory relies more on combining these elementary assemblies into higher-order constructs.
    Keywords: Cerebral Cortex -- Cytology ; Nerve Net -- Anatomy & Histology ; Pyramidal Cells -- Cytology ; Synapses -- Ultrastructure
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 9
    Language: English
    In: Expert Review of Neurotherapeutics, 01 February 2013, Vol.13, pp.3-7
    Description: Multiple sclerosis (MS) is a distressing and debilitating disease, which often leads to a state of progressive deterioration for the individual. Spasticity is a common and disabling neurological feature with increasing presence and severity throughout the progression of MS. Management of this spasticity is a key component of day-to-day care for patients with MS. Data from recent epidemiological studies in Spain (the '6E' and '5E' studies) and Germany (the 'MOVE 1' study) confirm the frequent occurrence of spasticity symptoms in patients with MS. Despite the difficulties experienced by MS patients with spasticity, the condition is largely undertreated because current treatment options do not provide adequate control of MS spasticity. With worsening MS spasticity there is an increase in individual patient symptoms, worsening of quality of life and impairment of daily living. From a healthcare/societal perspective, MS spasticity has been shown to be associated with substantial costs. Many of these costs relate to the increased disability (and consequent need for rehabilitation and caregiver support) that are associated with moderate-to-severe spasticity. Consequently, newer drugs that can provide better symptomatic relief and may slow progression to more severe forms of disability will be a step forward in the level of care that we can provide for MS patients.
    Keywords: Disease Burden ; Epidemiology ; Multiple Sclerosis ; Spasticity ; Treatment ; Pharmacy, Therapeutics, & Pharmacology
    ISSN: 1473-7175
    E-ISSN: 1744-8360
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  • 10
    Language: English
    In: Cognitive Therapy and Research, 2012, Vol.36(5), pp.522-536
    Description: Several studies suggest that computer-based attention modification programmes can be a promising new approach for the treatment of various anxiety disorders, including social anxiety disorder (SAD). The current study investigates the efficacy of a four-week Internet-delivered version of an attentional training for SAD in a randomized controlled double-blind study. Sixty-eight individuals seeking treatment for SAD were randomly assigned to either an attention training group (ATG, N  = 33) or a control group (CG, N  = 35). Participants of the ATG completed modified dot-probe tasks designed to facilitate attentional disengagement from threat. Participants in the CG completed control dot-probe tasks. At post-assessment, participants in both groups showed significant symptom reductions with medium to large within-group effect sizes on social anxiety measures (ATG: Cohen’s d  = .47–.80; CG: d  = .56–.63). However, no significant differences between groups were found at post-treatment for any outcome measure. These findings will be discussed along with the results of a 4-months follow-up assessment.
    Keywords: Internet-based ; Web-based ; Attention bias modification training ; Social anxiety disorder ; Randomized controlled trial
    ISSN: 0147-5916
    E-ISSN: 1573-2819
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