Contradictory Stimuli Research Articles

Multiscale integration of environmental stimuli in plant tropism produces complex behaviors

Plant tropism refers to the directed movement of an organ or organism in response to external stimuli. Typically, these stimuli induce hormone transport that triggers cell growth or deformation. In turn, these local cellular changes create mechanical forces on the plant tissue that are balanced by an overall deformation of the organ, hence changing its orientation with respect to the stimuli. This complex feedback mechanism takes place in a three-dimensional growing plant with varying stimuli depending on the environment. We model this multiscale process in filamentary organs for an arbitrary stimulus by explicitly linking hormone transport to local tissue deformation leading to the generation of mechanical forces and the deformation of the organ in three dimensions. We show, as examples, that the gravitropic, phototropic, nutational, and thigmotropic dynamic responses can be easily captured by this framework. Further, the integration of evolving stimuli and/or multiple contradictory stimuli can lead to complex behavior such as sun following, canopy escape, and plant twining.

Mechanistic Investigation on Oxidative Degradation of ROS-Responsive Thioacetal/Thioketal Moieties and Their Implications

Summary Thioacetal/thioketal moieties have been identified as responsive to reactive oxygen species (ROS). Despite its utility in a broad range of applications, the mechanism that underlies the ROS-induced cleavage of these moieties is not well understood. In this work, through a series of structure-property relationship studies such as Hammett correlation, we propose a mechanism or the oxidative cleavage of thioacetals and thioketals, where the thiolate components are converted to the corresponding disulfide product along with the formation of the respective aldehydes and ketones. The mechanism proposed here involves thioether oxidation that leads to the formation of a thionium intermediate, hydrolysis of which leads to the aldehyde/ketone product. In addition, we also show a preliminary demonstration of the utility of such an understanding, as it offers to sequentially release two distinct small molecules caged in a substrate using two contradictory stimuli, viz. oxidative and reductive conditions.

Contradiction processing in schizophrenia

ABSTRACTIntroduction: Patients with schizophrenia present clinically with difficulties in manipulating contradictory information in the form of loose associations, surface contradictions and delusional beliefs. It is to date unclear whether patients can detect and process information that contradicts their beliefs and prior knowledge and whether this capacity is related to their symptoms and the nature of contradictory stimuli (e.g., personally significant information, emotional information).Methods: We probed contradiction processing in patients with schizophrenia and healthy controls using sentence verification tasks that involve self-referential judgements (Experiment 1) and general knowledge (Experiment 2), while manipulating the emotional content of the stimuli.Results: We found no differences between patients and controls either on reaction time (Experiment 1 & 2) or accuracy measures (Experiment 1).Conclusions: Our results show no general impairment in contradiction processing in schizophrenia. Rather, failures to detect and correct contradictions in symptoms such as formal though disorder or delusions could arise through a complex interplay between executive dysfunctions, stress and the emotional content of the information.

Signal integration in the (m)TORC1 growth pathway.

The protein kinase Target Of Rapamycin (TOR) is a nexus for the regulation of eukaryotic cell growth. TOR assembles into one of two distinct signalling complexes, TOR complex 1 (TORC1) and TORC2 (mTORC1/2 in mammals), with a set of largely non-overlapping protein partners. (m)TORC1 activation occurs in response to a series of stimuli relevant to cell growth, including nutrient availability, growth factor signals and stress, and regulates much of the cell's biosynthetic activity, from proteins to lipids, and recycling through autophagy. mTORC1 regulation is of great therapeutic significance, since in humans many of these signalling complexes, alongside subunits of mTORC1 itself, are implicated in a wide variety of pathophysiologies, including multiple types of cancer, neurological disorders, neurodegenerative diseases and metabolic disorders including diabetes. Recent years have seen numerous structures determined of (m)TOR, which have provided mechanistic insight into (m)TORC1 activation in particular, however the integration of cellular signals occurs upstream of the kinase and remains incompletely understood. Here we have collected and analysed in detail as many as possible of the molecular and structural studies which have shed light on (m)TORC1 repression, activation and signal integration. A molecular understanding of this signal integration pathway is required to understand how (m)TORC1 activation is reconciled with the many diverse and contradictory stimuli affecting cell growth. We discuss the current level of molecular understanding of the upstream components of the (m)TORC1 signalling pathway, recent progress on this key biochemical frontier, and the future studies necessary to establish a mechanistic understanding of this master-switch for eukaryotic cell growth.

The postmodern in music

“Postmodern” is an elusive concept that embraces a wide range of critical theories and attitudes. To borrow the assessment that the American poet Walt Whitman offered of himself, the concept is large and contains multitudes, various aspects of which often seem to be at odds with one another. Postmodern art likewise contains multitudes; indeed, it would seem that one of postmodern art's chief characteristics is the comfortable integration of apparently contradictory stimuli that, importantly, are sited less in the “work” itself than in the eye/ear/mind of the beholder. Grounded on the idea that postmodern music is defined not by composers but by listeners, this essay challenges musicological writing that since the early 1990s has sought both to illuminate an ideology of postmodernism and to identify elements of a postmodernist style. In particular, it counters the much-repeated statement that the first, and perhaps quintessential, example of musical postmodernism is the eclectic yet thoroughly linear and discursive 1972 Third String Quartet of the late American composer George Rochberg; the essay suggests that, if a prototype of the postmodern in music must be named, a better candidate would be Rochberg's palimpsest-like 1965 Music for the Magic Theater.

Remembering the Art of Communism: Analysis of Contradiction: Approaches and Transgressions

The author’s intention in this article is to question the relations of ‘modernism’ and ‘Communism’ in specific cultural texts, ie, artworks and artistic paradigms. In Cold War Western literature we usually find authors who write about the difference and distance between modernism in the West and Communism in the East of Europe, in other words, about the East–West divide in the world. Today it seems as if these differences and distances vaporise and – in memory or in erased cultural traces – we recognise behind them different modes of modernism. Modernism and Communism are no longer seen as relatively different (’for modernism’ and ‘against modern’), but as relatively different answers to similarly contradictory stimuli.

Spatial orientation of postrotatory nystagmus during static roll tilt in cats

While the stimulation of otolith inputs reduces the duration of postrotatory nystagmus (PRN), there is still room for dialogue about the effect of static tilt on the orientation of PRN. We studied one possible influence of static roll tilt on the spatial orientation of PRN in cats. The animal was rotated about an earth-vertical axis (EVA) at a constant velocity of 100 deg/s with an acceleration and deceleration of 120 deg/s2. Within two seconds after stopping EVA rotation, the animal was passively tilted at 45 deg/s about its longitudinal axis by as much as +/- 90 deg in steps of 15 deg. Eye movements were measured with magnetic search coils. The angle of the PRN plane and its slow phase eye velocity were measured. The time constant of PRN decreased with an increase in roll tilt. The PRN plane remained earth horizontal within a range of +/- 30 deg roll tilt. Beyond this range, the velocity of PRN decreased too rapidly to measure any change in orientation. Our results indicate a spatially limited and temporally short interaction of the semicircular canal and otolith signals in the velocity storage mechanism of cat PRN. Our data, along with previous studies, suggest that different species show different solutions to the problem of the imbalance and spatial disorientation during contradictory stimuli.

Gcn2 Mediates Gcn4 Activation in Response to Glucose Stimulation or UV Radiation Not via GCN4 Translation

In mammalian cells transcription factors of the AP-1 family are activated by either stress signals such as UV radiation, or mitogenic signals such as growth factors. Here we show that a similar situation exists in the yeast Saccharomyces cerevisiae. The AP-1 transcriptional activator Gcn4, known to be activated by stress signals such as UV radiation and amino acids starvation, is also induced by growth stimulation such as glucose. We show that glucose-dependent Gcn4 activation is mediated through the Ras/cAMP pathway. This pathway is also responsible for UV-dependent Gcn4 activation but is not involved in Gcn4 activation by amino acid starvation. Thus, the unusual phenomenon of activation of mitogenic pathways and AP-1 factors by contradictory stimuli through Ras is conserved from yeast to mammals. We also show that activation of Gcn4 by glucose and UV requires Gcn2 activity. However, in contrast to its role in amino acid starvation, Gcn2 does not increase eIF2alpha phosphorylation or translation of GCN4 mRNA in response to glucose or UV. These findings suggest a novel mechanism of action for Gcn2. The finding that Gcn4 is activated in response to glucose via the Ras/cAMP pathway suggests that this cascade coordinates glucose metabolism with amino acids and purine biosynthesis and thereby ensures availability of both energy and essential building blocks for continuation of the cell cycle.

Associative memory properties of multiple cortical modules

The existence of recurrent collateral connections between pyramidal cells within a cortical area and, in addition, reciprocal connections between connected cortical areas, is well established. In this work we analyse the properties of a tri-modular architecture of this type in which two input modules have convergent connections to a third module (which in the brain might be the next module in cortical processing or a bi-modal area receiving connections from two different processing pathways). Memory retrieval is analysed in this system which has Hebb-like synaptic modifiability in the connections and attractor states. Local activity features are stored in the intra-modular connections while the associations between corresponding features in different modules present during training are stored in the inter-modular connections. The response of the network when tested with corresponding and contradictory stimuli to the two input pathways is studied in detail. The model is solved quantitatively using techniques of statistical physics. In one type of test, a sequence of stimuli is applied, with a delay between them. It is found that if the coupling between the modules is low a regime exists in which they retain the capability to retrieve any of their stored features independently of the features being retrieved by the other modules. Although independent in this sense, the modules still influence each other in this regime through persistent modulatory currents which are strong enough to initiate recall in the whole network when only a single module is stimulated, and to raise the mean firing rates of the neurons in the attractors if the features in the different modules are corresponding. Some of these mechanisms might be useful for the description of many phenomena observed in single neuron activity recorded during short term memory tasks such as delayed match-to-sample. It is also shown that with contradictory stimulation of the two input modules the model accounts for many of the phenomena observed in the McGurk effect, in which contradictory auditory and visual inputs can lead to misperception.

Effects of Confirmatory and Contradictory Stimuli and Development on Children's Intergroup Attribution

Intergroup attributional differences were investigated among Canadian children at three developmental levels who received confirmatory and contradictory stimuli about ingroup and outgroup individuals. Participants were 83 public school students divided into three levels of social attribution development. An intergroup attribution questionnaire assessed the degree of internality of participants' explanations of the success and failure of ingroup and outgroup members. Results indicated that the participants responded differently to stimuli that confirmed ethnocentric assumptions than they responded to stimuli that contradicted these assumptions. The precise nature of the responses, however, depended on the developmental level of the participant: Whereas younger children tended to use attributions that favored the ethnic ingroup, older children actually used attributions that favored the outgroup.