Swammerdam Institute for Life science

Amsterdam, Netherlands

Swammerdam Institute for Life science

Amsterdam, Netherlands
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Lopes da Silva F.,Swammerdam Institute for Life science | Lopes da Silva F.,University of Lisbon
Neuron | Year: 2013

To understand dynamic cognitive processes, the high time resolution of EEG/MEG is invaluable. EEG/MEG signals can play an important role in providing measures of functional and effective connectivity in the brain. After a brief description of the foundations and basic methodological aspects of EEG/MEG signals, the relevance of the signals to obtain novel insights into the neuronal mechanisms underlying cognitive processes is surveyed, with emphasis on neuronal oscillations (ultra-slow, theta, alpha, beta, gamma, and HFOs) and combinations of oscillations. Three main functional roles of brain oscillations are put in evidence: (1) coding specific information, (2) setting and modulating brain attentional states, and (3) assuring the communication between neuronal populations such that specific dynamic workspaces may be created. The latter form the material core of cognitive functions.

Engel J.,Brain Research Institute | da Silva F.L.,Swammerdam Institute for Life science | da Silva F.L.,University of Lisbon
Progress in Neurobiology | Year: 2012

High-frequency oscillations (HFOs) are EEG field potentials with frequencies higher than 30. Hz; commonly the frequency band between 30 and 70. Hz is denominated the gamma band, but with the discovery of activities at frequencies higher than 70. Hz a variety of terms have been proposed to describe the latter (Gotman and Crone, 2011). In general we may consider that the term HFO encompasses activities from 30 to 600. Hz. The best practice is to indicate always explicitly the frequency range of the HFOs in any specific study. There are numerous types of HFOs: those in normal brain appear to facilitate synchronization and information transfer necessary for cognitive processes and memory, while a particular class of HFOs in the brain of animals and people with epilepsy appears to reflect fundamental mechanisms of epileptic phenomena and could serve as biomarkers of epileptogenesis and epileptogenicity in abnormal conditions such as epilepsy. A better understanding of the significance of HFOs depends on a deeper analysis of the mechanisms of generation of different kinds of HFOs, that typically are at the crossroads between intrinsic membrane properties and neuronal interactions, both chemical and electrical. There is still a lack of understanding of how specific information is carried by HFOs and can be operational in normal cognitive processes such as in working and long-term memory and abnormal conditions such as epilepsy. The complexity of these processes makes the development of relevant computational models of dynamical neuronal networks most compelling. © 2012 Elsevier Ltd.

Buzsaki G.,New York University | Silva F.L.D.,Swammerdam Institute for Life science | Silva F.L.D.,University of Lisbon
Progress in Neurobiology | Year: 2012

High frequency oscillations (HFOs) constitute a novel trend in neurophysiology that is fascinating neuroscientists in general, and epileptologists in particular. But what are HFOs? What is the frequency range of HFOs? Are there different types of HFOs, physiological and pathological? How are HFOs generated? Can HFOs represent temporal codes for cognitive processes? These questions are pressing and this symposium volume attempts to give constructive answers. As a prelude to this exciting discussion, we summarize the physiological high frequency patterns in the intact brain, concentrating mainly on hippocampal patterns, where the mechanisms of high frequency oscillations are perhaps best understood. © 2012 Elsevier Ltd.

Pennartz C.M.A.,Swammerdam Institute for Life science | Ito R.,University of Oxford | Ito R.,University of Toronto | Verschure P.F.M.J.,University Pompeu Fabra | And 3 more authors.
Trends in Neurosciences | Year: 2011

The hippocampal formation and striatum subserve declarative and procedural memory, respectively. However, experimental evidence suggests that the ventral striatum, as opposed to the dorsal striatum, does not lend itself to being part of either system. Instead, it may constitute a system integrating inputs from the amygdala, prefrontal cortex and hippocampus to generate motivational, outcome-predicting signals that invigorate goal-directed behaviors. Inspired by reinforcement learning models, we suggest an alternative scheme for computational functions of the striatum. Dorsal and ventral striatum are proposed to compute outcome predictions largely in parallel, using different types of information as input. The nature of the inputs to striatum is furthermore combinatorial, and the specificity of predictions transcends the level of scalar value signals, incorporating episodic information. © 2011 Elsevier Ltd.

Timmermans W.,Swammerdam Institute for Life science | Xiong H.,Swammerdam Institute for Life science | Hoogenraad C.C.,University Utrecht | Krugers H.J.,Swammerdam Institute for Life science
Neuroscience | Year: 2013

Individuals are exposed to stressful events in their daily life. The effects of stress on brain function ranges from highly adaptive to increasing the risk to develop psychopathology. For example, stressful experiences are remembered well which can be seen as a highly appropriate behavioral adaptation. On the other hand, stress is an important risk factor, in susceptible individuals, for depression and anxiety. An important question that remains to be addressed is how stress regulates brain function and what determines the threshold between adaptive and maladaptive responses. Excitatory synapses play a crucial role in synaptic transmission, synaptic plasticity and behavioral adaptation. In this review we discuss how brief and prolonged exposure to stress, in adulthood and early life, regulate the function of these synapses, and how these effects may contribute to behavioral adaptation and psychopathology. © 2013 IBRO.

Scala A.,Swammerdam Institute for Life science | Allmann S.,Swammerdam Institute for Life science | Mirabella R.,Swammerdam Institute for Life science | Haring M.A.,Swammerdam Institute for Life science | Schuurink R.C.,Swammerdam Institute for Life science
International Journal of Molecular Sciences | Year: 2013

Plants cannot avoid being attacked by an almost infinite number of microorganisms and insects. Consequently, they arm themselves with molecular weapons against their attackers. Plant defense responses are the result of a complex signaling network, in which the hormones jasmonic acid (JA), salicylic acid (SA) and ethylene (ET) are the usual suspects under the magnifying glass when researchers investigate host-pest interactions. However, Green Leaf Volatiles (GLVs), C6 molecules, which are very quickly produced and/or emitted upon herbivory or pathogen infection by almost every green plant, also play an important role in plant defenses. GLVs are semiochemicals used by insects to find their food or their conspecifics. They have also been reported to be fundamental in indirect defenses and to have a direct effect on pests, but these are not the only roles of GLVs. These volatiles, being probably one of the fastest weapons exploited, are also able to directly elicit or prime plant defense responses. Moreover, GLVs, via crosstalk with phytohormones, mostly JA, can influence the outcome of the plant's defense response against pathogens. For all these reasons GLVs should be considered as co-protagonists in the play between plants and their attackers. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Schaefer A.,Swammerdam Institute for Life science | Reinhard N.R.,Swammerdam Institute for Life science | Hordijk P.L.,Swammerdam Institute for Life science
Small GTPases | Year: 2014

Cell adhesion and migration are regulated through the concerted action of cytoskeletal dynamics and adhesion proteins, the activity of which is governed by RhoGTPases. Specific RhoGTPase signaling requires spatio-temporal activation and coordination of subsequent protein-protein and protein-lipid interactions. The nature, location and duration of these interactions are dependent on polarized extracellular triggers, such as cell-cell contact, and intracellular modifying events, such as phosphorylation. RhoA, RhoB, and RhoC are highly homologous GTPases that, however, succeed in generating specific intracellular responses. Here, we discuss the key features that contribute to this specificity. These not only include the well-studied switch regions, the conformation of which is nucleotide- dependent, but also additional regions and seemingly small differences in primary sequence that also contribute to specific interactions. These differences translate into differential surface charge distribution, local exposure of amino acid side-chains and isoform-specific post-translational modifications. The available evidence supports the notion that multiple regions in RhoA/B/C cooperate to provide specificity in binding to regulators and effectors. These specific interactions are highly regulated in time and space. We therefore subsequently discuss current approaches means to visualize and analyze localized GTPase activation using biosensors that allow imaging of isoform-specific, localized regulation. © 2014 Taylor & Francis Group, LLC.

Ament K.,Swammerdam Institute for Life science | Krasikov V.,Swammerdam Institute for Life science | Allmann S.,Max Planck Institute for Chemical Ecology | Rep M.,Swammerdam Institute for Life science | And 2 more authors.
Plant Journal | Year: 2010

The role of methyl salicylate (MeSA) production was studied in indirect and direct defence responses of tomato (Solanum lycopersicum) to the spider mite Tetranychus urticae and the root-invading fungus Fusarium oxysporum f. sp. lycopersici, respectively. To this end, we silenced the tomato gene encoding salicylic acid methyl transferase (SAMT). Silencing of SAMT led to a major reduction in SAMT expression and MeSA emission upon herbivory by spider mites, without affecting the induced emission of other volatiles (terpenoids). The predatory mite Phytoseiulus persimilis, which preys on T. urticae, could not discriminate between infested and non-infested SAMT-silenced lines, as it could for wild-type tomato plants. Moreover, when given the choice between infested SAMT-silenced and infested wild-type plants, they preferred the latter. These findings are supportive of a major role for MeSA in this indirect defence response of tomato. SAMT-silenced tomato plants were less susceptible to a virulent strain of F. oxysporum f. sp. lycopersici, indicating that the direct defense responses in the roots are also affected in these plants. Our studies show that the conversion of SA to MeSA can affect both direct and indirect plant defence responses. © 2010 Blackwell Publishing Ltd.

Diezel C.,Max Planck Institute for Chemical Ecology | Allmann S.,Max Planck Institute for Chemical Ecology | Allmann S.,Swammerdam Institute for Life science | Baldwin I.T.,Max Planck Institute for Chemical Ecology
Journal of Integrative Plant Biology | Year: 2011

To defend themselves against herbivore attack, plants produce secondary metabolites, which are variously inducible and constitutively deployed, presumably to optimize their fitness benefits in light of their fitness costs. Three phytohormones, jasmonates (JA) and their active forms, the JA-isoleucine (JA-Ile) and ethylene (ET), are known to play central roles in the elicitation of induced defenses, but little is known about how this mediation changes over ontogeny. The Optimal Defense Theory (ODT) predicts changes in the costs and benefits of the different types of defenses and has been usefully extrapolated to their modes of deployment. Here we studied whether the herbivore-induced accumulation of JA, JA-Ile and ET changed over ontogeny in Nicotiana attenuata, a native tobacco in which inducible defenses are particularly well studied. Herbivore-elicited ET production changed dramatically during six developmental stages, from rosette through flowering, decreasing with the elongation of the first corollas during flower development. This decrease was largely recovered within a day after flower removal by decapitation. A similar pattern was found for the herbivore-induced accumulation of JA and JA-Ile. These results are consistent with ODT predictions and suggest that the last steps in floral development control the inducibility of at least three plant hormones, optimizing defense-growth tradeoffs. © 2011 Institute of Botany, Chinese Academy of Sciences.

Allmann S.,Max Planck Institute for Chemical Ecology | Halitschke R.,Max Planck Institute for Chemical Ecology | Halitschke R.,Cornell University | Schuurink R.C.,Max Planck Institute for Chemical Ecology | And 2 more authors.
Plant, Cell and Environment | Year: 2010

Lipoxygenases (LOXs) are key enzymes in the biosynthesis of oxylipins, and catalyse the formation of fatty acid hydroperoxides (HPs), which represent the first committed step in the synthesis of metabolites that function as signals and defences in plants. HPs are the initial substrates for different branches of the oxylipin pathway, and some plant species may express different LOX isoforms that supply specific branches. Here, we compare isogenic lines of the wild tobacco Nicotiana attenuata with reduced expression of NaLOX2 (irlox2) or NaLOX3 (irlox3) to determine the role of these different LOX isoforms in supplying substrates for two different pathways: green leaf volatiles (GLVs) and jasmonic acid (JA). Reduced NaLOX2 expression strongly decreased the production of GLVs without influencing the formation of JA and JA-related secondary metabolites. Conversely, reduced NaLOX3 expression strongly decreased JA biosynthesis, without influencing GLV production. The temporal expression of NaLOX2 and NaLOX3 also differed after elicitation; NaLOX3 was rapidly induced, attaining highest transcript levels within 1 h after elicitation, whereas NaLOX2 transcripts reached maximum levels after 14 h. These results demonstrate that N. attenuata channels the flux of HPs through the activities of different LOXs, leading to different direct and indirect defence responses mediating the plant's herbivore resistance. © 2010 Blackwell Publishing Ltd.

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