| 1. |
- Yannuzzi, M., et al.
(författare)
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TEFIS: A Single Access Point for Conducting Multifaceted Experiments on Heterogeneous Test Facilities
- 2014
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Ingår i: Computer Networks. - : Elsevier BV. - 1389-1286 .- 1872-7069. ; 63, s. 147-172
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Tidskriftsartikel (refereegranskat)abstract
- A few years ago, an experimental facility composed of networking gear and simulation tools was sufficient for testing the main features of a prototype before the final product could be launched to the Internet market. This paradigm has certainly changed, but the lack of platforms enabling the realistic assessment of the different facets of a product, including cross-cutting trials across different testbeds, poses strong limitations for researchers and developers. In light of this, we present an open platform that offers a versatile combination of heterogeneous experimental facilities called “TEstbed for Future Internet Services” (TEFIS). TEFIS provides a single access point for conducting cutting-edge experiments on testbeds that supply different capabilities, including testbeds dedicated to network performance, software performance, grid computing, and living labs. We shall show that TEFIS covers the entire life-cycle of a multifaceted experiment, with the advantage that a single testrun can seamlessly execute across different experimental facilities. In order to demonstrate the potential and versatility of the TEFIS platform, we describe the deployment of four distinct experiments and provide a set of results highlighting the benefits of using TEFIS. The experiments described in this article cover: i) the experimentation with an open API called OPENER (which is an open and programmable environment for managing experimentation with SDN applications); ii) an application for skiers and tourists at the Megève ski resort in France; iii) an application that can dynamically adapt the Quality of Experience (QoE) of multimedia services for mobile users; and iv) an augmented reality workspace for remote education and learning purposes based on videoconferencing.
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| 2. |
- Guitart-Masip, Marc, et al.
(författare)
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Differential, but not opponent, effects of L-DOPA and citalopram on action learning with reward and punishment
- 2014
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Ingår i: Psychopharmacology. - : Springer Science and Business Media LLC. - 0033-3158 .- 1432-2072. ; 231:5, s. 955-966
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Tidskriftsartikel (refereegranskat)abstract
- Decision-making involves two fundamental axes of control namely valence, spanning reward and punishment, and action, spanning invigoration and inhibition. We recently exploited a go/no-go task whose contingencies explicitly decouple valence and action to show that these axes are inextricably coupled during learning. This results in a disadvantage in learning to go to avoid punishment and in learning to no-go to obtain a reward. The neuromodulators dopamine and serotonin are likely to play a role in these asymmetries: Dopamine signals anticipation of future rewards and is also involved in an invigoration of motor responses leading to reward, but it also arbitrates between different forms of control. Conversely, serotonin is implicated in motor inhibition and punishment processing. To investigate the role of dopamine and serotonin in the interaction between action and valence during learning. We combined computational modeling with pharmacological manipulation in 90 healthy human volunteers, using levodopa and citalopram to affect dopamine and serotonin, respectively. We found that, after administration of levodopa, action learning was less affected by outcome valence when compared with the placebo and citalopram groups. This highlights in this context a predominant effect of levodopa in controlling the balance between different forms of control. Citalopram had distinct effects, increasing participants' tendency to perform active responses independent of outcome valence, consistent with a role in decreasing motor inhibition. Our findings highlight the rich complexities of the roles played by dopamine and serotonin during instrumental learning.
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| 3. |
- Balazs, J, et al.
(författare)
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INTRODUCING THE SUPREME PROJECT
- 2012
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Ingår i: INTERNATIONAL JOURNAL OF BEHAVIORAL MEDICINE. - 1070-5503. ; 19, s. S148-S148
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 4. |
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| 5. |
- Bach, Dominik R., et al.
(författare)
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Human Hippocampus Arbitrates Approach-Avoidance Conflict
- 2014
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 24:5, s. 541-547
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Tidskriftsartikel (refereegranskat)abstract
- Animal models of human anxiety often invoke a conflict between approach and avoidance [1, 2]. In these, a key behavioral assay comprises passive avoidance of potential threat and inhibition, both thought to be controlled by ventral hippocampus [2-6]. Efforts to translate these approaches to clinical contexts [7, 8] are hampered by the fact that it is not known whether humans manifest analogous approach-avoidance dispositions and, if so, whether they share a homologous neurobiological substrate [9]. Here, we developed a paradigm to investigate the role of human hippocampus in arbitrating an approach-avoidance conflict under varying levels of potential threat. Across four experiments, subjects showed analogous behavior by adapting both passive avoidance behavior and behavioral inhibition to threat level. Using functional magnetic resonance imaging (fMRI), we observe that threat level engages the anterior hippocampus, the human homolog of rodent ventral hippocampus [10]. Testing patients with selective hippocampal lesions, we demonstrate a causal role for the hippocampus with patients showing reduced passive avoidance behavior and inhibition across all threat levels. Our data provide the first human assay for approach-avoidance conflict akin to that of animal anxiety models. The findings bridge rodent and human research on passive avoidance and behavioral inhibition and furnish a framework for addressing the neuronal underpinnings of human anxiety disorders, where our data indicate a major role for the hippocampus.
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| 6. |
- Chowdhury, Rumana, et al.
(författare)
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Dopamine restores reward prediction errors in old age
- 2013
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Ingår i: Nature Neuroscience. - : Springer Science and Business Media LLC. - 1097-6256 .- 1546-1726. ; 16:5, s. 648-653
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Tidskriftsartikel (refereegranskat)abstract
- Senescence affects the ability to utilize information about the likelihood of rewards for optimal decision-making. Using functional magnetic resonance imaging in humans, we found that healthy older adults had an abnormal signature of expected value, resulting in an incomplete reward prediction error (RPE) signal in the nucleus accumbens, a brain region that receives rich input projections from substantia nigra/ventral tegmental area (SN/VTA) dopaminergic neurons. Structural connectivity between SN/VTA and striatum, measured by diffusion tensor imaging, was tightly coupled to inter-individual differences in the expression of this expected reward value signal. The dopamine precursor levodopa (L-DOPA) increased the task-based learning rate and task performance in some older adults to the level of young adults. This drug effect was linked to restoration of a canonical neural RPE. Our results identify a neurochemical signature underlying abnormal reward processing in older adults and indicate that this can be modulated by L-DOPA.
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| 7. |
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| 8. |
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| 9. |
- Economides, Marcos, et al.
(författare)
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Anterior Cingulate Cortex Instigates Adaptive Switches in Choice by Integrating Immediate and Delayed Components of Value in Ventromedial Prefrontal Cortex
- 2014
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Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 34:9, s. 3340-3349
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Tidskriftsartikel (refereegranskat)abstract
- Actions can lead to an immediate reward or punishment and a complex set of delayed outcomes. Adaptive choice necessitates the brain track and integrate both of these potential consequences. Here, we designed a sequential task whereby the decision to exploit or forego an available offer was contingent on comparing immediate value and a state-dependent future cost of expending a limited resource. Crucially, the dynamics of the task demanded frequent switches in policy based on an online computation of changing delayed consequences. We found that human subjects choose on the basis of a near-optimal integration of immediate reward and delayed consequences, with the latter computed in a prefrontal network. Within this network, anterior cingulate cortex (ACC) was dynamically coupled to ventromedial prefrontal cortex (vmPFC) when adaptive switches in choice were required. Our results suggest a choice architecture whereby interactions between ACC and vmPFC underpin an integration of immediate and delayed components of value to support flexible policy switching that accommodates the potential delayed consequences of an action.
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| 10. |
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